Biology Courses – 第 3 页

Illustrations of wild animals [insect 6 Homoptera 1]

同翅目 HOMOPTERA

Order Hemiptera
suborder Heteroptera *	Bugs
suborder Homoptera *	Cicadas, Hoppers, Psyllids, Whiteflies, Aphids, and Scale insects

Most people tend to call anything with lots of legs a “bug.” However, to an entomologist, a “bug” is one of the 35,000 or so species of the order Hemiptera.

Hemiptera means “half wing” and refers to the fact that part of the first pair of wings is toughened and hard, while the rest of the first pair and the second pair are membranous. Hemipterans also have modified piercing and sucking mouthparts; some suck plant juices and are plant pests, while others can bite painfully.

A possibly paraphyletic group of insects known as the Homoptera is sometimes included within the Hemiptera, even though they lack the toughened areas on the first pair of wings.

Some entomologists group both Hemiptera and Homoptera within the group Heteroptera; others use the name Heteroptera for what we have called the Hemiptera and use Hemiptera for the Heteroptera.

Confused? So are we. Anyway, the Homoptera have the dubious distinction of being probably the most destructive insects of all. They include aphids, leafhoppers, cicadas, and scale insects: 45,000 species in all.

↑Quoted from University of California Museum Paleontology>arthropoda>uniramia>hemiptera

Hemiptera

Suborder Homoptera

Leafhoppers, Planthoppers, Treehoppers, Cicadas, Aphids, Psyllids, Whiteflies, Scale Insects

The name Homoptera, derived from the Greek “homo-“meaning uniform and “ptera” meaning wings, refers to the uniform texture of the front wings.

Classification & Distribution

Hemimetabola

incomplete development (egg, nymph, adult)

Hemipteroid

closely related to Thysanoptera and Psocoptera

Distribution: Abundant worldwide. All species are terrestrial herbivores.

	North America	Worldwide
Number of Families	38	60
Number of Species	6359	>32,000

Physical Features

Adults:

Antennae slender or bristle-like
Proboscis short, arising near lower back margin of head
Front wings, when present, uniform in texture; at rest, wings fold tent-like over the abdomen
Tarsi 1- to 3-segmented

Immatures:

Structurally similar to adults
Always lacking wings

Major Families

Cicadidae (Cicadas) — Nymphs live underground where they feed on the roots of trees and shrubs. Adults are the largest members of the Homoptera. Males produce loud songs to attract a mate.
Cicadellidae (Leafhoppers) — This is the largest family of Homoptera and includes many pests of cultivated plants. Leafhoppers are important carriers of plant diseases — especially mycoplasmas.
Membracidae (Treehoppers) — Ecologically similar to leafhoppers, these insects have a large pronotum that extends over most of the body. They often resemble thorns or small twigs.
Cercopidae (Spittlebugs or Froghoppers) — Nymphs live on plant stems and produce a frothy defensive secretion around themselves. Adults are similar to leafhoppers in size and general appearance.
Fulgoridae (Planthoppers) — This is one of eleven families classified as planthoppers (superfamily Fulgoroidea). These insects are ecologically similar to leafhoppers and treehoppers. Many species are oddly shaped and cryptically colored.
Psyllidae (Psyllids or Jumping Plant Lice) — Small, aphid-like insects with 3-segmented beaks and 10 segmented antennae. Many species are covered with a woolly layer of wax.
Aleyrodidae (Whiteflies) — Body and wings of adults are covered with a white powdery wax. Nymphs attach to the undersides of leaves and become immobile, resembling scale insects.
Aphididae (Aphids, Plantlice) — Second largest family in the suborder Homptera. Many of these insects are pests of cultivated plants. Aphids are considered the most important carriers of viral plant diseases.
Coccidae (Soft Scale insects) — This is one of 17 families that make up the superfamily Coccoidea (scale insects and mealybugs). Most species are sedentary during most of their life cycle and secreate a protective covering over their bodies. These insects are among the most common pests of cultivated plants.

====================================================↑Quoted from the General Entomology course at North Carolina State University >Resource Library > Compendium > Homoptera (© 2009 by John R. Meyer; Last Updated: 8 April 2009)

>Learn more about homoptera (www.insectsexplained.com)

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蝉科 Cicadidae

1. 草蝉 Mogannia sp.

2. 绿草蝉 Mogannia hebes

3. 蒙古寒蝉 Meimuna mongocica

4. 螗蝉Tanna japonensis

5. 鸣鸣蝉 Oncotympana maculaticollis

6. 蟪蛄Platypleura kaempferi

叶蝉科 Cicadellidae

1. 丽叶蝉 Calodia sp.

2. 华凹大叶蝉 Bothrogonia sinica

3. 条大叶蝉Atkinsoniella

4. 显脉叶蝉Paramesus sp.

5. 槽胫叶蝉Drabescus sp.

6. 窗耳叶蝉Ledra auditura

7. 隐纹大叶蝉Tettigoniella thalia

8. 横脊叶蝉Evacanthus sp.

9.白边拟大叶蝉Ishidaella albomarginata

Illustrations of wild animals [insect 5 Hemiptera]

半翅目 HEMIPTERA

Most people tend to call anything with lots of legs a “bug.” However, to an entomologist, a “bug” is one of the 35,000 or so species of the order Hemiptera.

A possibly paraphyletic group of insects known as the Homoptera is sometimes included within the Hemiptera, even though they lack the toughened areas on the first pair of wings.

Some entomologists group both Hemiptera and Homoptera within the group Heteroptera; others use the name Heteroptera for what we have called the Hemiptera and use Hemiptera for the Heteroptera.

↑Quoted from University of California Museum Paleontology>arthropoda>uniramia>hemiptera

Hemiptera(/heteroptera)
Suborder Heteroptera (/hemiptera)

True Bugs

The name Heteroptera, derived from the Greek “hetero-“em> meaning different and “ptera” meaning wings, refers to the fact that the texture of the front wings is different near the base (leathery) than at the apex (membranous).

Classification & Distribution

Hemimetabola
- incomplete development (egg, nymph, adult)
Orthopteroid
- closely related to Thysanoptera and Psocoptera
Distribution: Abundant worldwide. Found in most terrestrial and freshwater habitats.

North America
Worldwide

Number of Families
40

73

Number of Species
3587

>50,000
Life History & Ecology

Members of the suborder Heteroptera are known as “true bugs”.

They have very distinctive front wings, called hemelytra, in which the basal half is leathery and the apical half is membranous. At rest, these wings cross over one another to lie flat along the insect’s back.

These insects also have elongate, piercing-sucking mouthparts which arise from the ventral (hypognathous) or anterior (prognathous) part of the head capsule.

The mandibles and maxillae are long and thread-like, interlocking with one another to form a flexible feeding tube (proboscis) that is no more than 0.1 mm in diameter yet contains both a food channel and a salivary channel. These stylets are enclosed within a protective sheath (the labium) that shortens or retracts during feeding.

The Heteroptera include a diverse assemblage of insects that have become adapted to a broad range of habitats — terrestrial, aquatic and semi-aquatic.

Terrestrial species are often associated with plants. They feed in vascular tissues or on the nutrients stored within seeds. Other species live as scavengers in the soil or underground in caves or ant nests. Still others are predators on a variety of small arthropods. A few species even feed on the blood of vertebrates.

Bed bugs, and other members of the family Cimicidae, live exclusively as ectoparasites on birds and mammals (including humans). Aquatic Heteroptera can be found on the surface of both fresh and salt water, near shorelines, or beneath the water surface in nearly all freshwater habitats. With only a few exceptions, these insects are predators of other aquatic organisms.

Physical Features

Adults:

Antennae slender with 4-5 segments
Proboscis 3-4 segmented, arising from front of head and curving below body when not in use
Pronotum usually large, trapezoidal or rounded
Triangular scutellum present behind pronotum
Front wings with basal half leathery and apical half membranous (hemelytra). Wings lie flat on the back at rest, forming an “X”.
Tarsi 2- or 3-segmented

Immatures:

Structurally similar to adults
Always lacking wings

Major Families

The three largest families of Heteroptera are:
- - Miridae (Plant Bugs) — Most species feed on plants, but some are predaceous. This family includes numerous pests such as the tarnished plant bug (Lygus lineolaris).
  - Lygaeidae (Seed Bugs) — Most species are seed feeders, a few are predatory. This family includes the chinch bug, Blissus leucopterus a pest of small grains, and the bigeyed bug, Geocoris bullatis, a beneficial predator.
  - Pentatomidae (Stink Bugs) — Shield-shaped body with large, triangular scutellum. Most species are herbivores, some are predators. All have scent glands which can produce an unpleasant odor.
Other families of terrestrial herbivores include:
- - Tingidae (lace bugs)
  - Coreidae (squash bugs and leaffooted bugs)
  - Alydidae (broadheaded bugs)
  - Rhopalidae (scentless plant bugs)
  - Berytidae (stilt bugs)
Other families of terrestrial predators include:
- - Reduviidae (assassin bugs)
  - Phymatidae (ambush bugs)
  - Nabidae (damsel bugs)
  - Anthocoridae (minute pirate bugs)
The major families of aquatic predators include:
- - Corixidae (water boatmen)
  - Gerridae (water striders)
  - Nepidae (water scorpions)
  - Belostomatidae (giant water bugs)
  - Naucoridae (creeping water bugs)
  - Notonectidae (backswimmers)
Bug Bytes
- Two families of Heteroptera are ectoparasites. The Cimicidae (bed bugs) live on birds and mammals (including humans). The Polyctenidae (bat bugs) live on bats.
- Water striders in the genus Halobates (family Gerridae) are the only insects that are truly marine. They live on the surface of the Pacific Ocean.
- Unlike other insects, male bedbugs do not place their sperm directly in the female’s reproductive tract. Instead, they puncture her abdomen and inject the sperm into her body cavity. The sperm swim to the ovaries where they fertilize the eggs. This unusual type of reproductive behavior is appropriately known as “traumatic insemination”.
- Some members of the family Largidae resemble ants. They live as social parasites in ant nests, mimicking the ants’ behavior to get food

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>Learn more about heteroptera (www.insectsexplained.com)

====================================================

蝽科 Pentatomidae

1. 全蝽Homalogonia sp.

2.双峰疣蝽 Cazira verrucosa

3. 庐山珀蝽Plautia lushanica

4.弯角蝽Lelia decem punctata

5. 斑须蝽 Dolycoris baccarum

6.梭蝽Megarrhamphus sp.

7. 绿岱蝽 Dalpada amaragdina

8. 金绿曼蝽Menida metalica

9. 谷蝽Gonopsis affinis

10. 麻皮蝽Erthesns fullo

盲蝽科 Miridae

1. 中黑苜蓿盲蝽 Adelphocoris situralis

2. 后丽盲蝽 Apolygus sp.

3. 斑胸树丽盲蝽Lygocoris pronotalis

长蝽科 Lygaeidae

1. 小长蝽Nysius ericae

2. 红脊长蝽 Tropidothorax elegans

盾蝽科 Scutelleridae

1. 金绿宽盾蝽Poecilocoris lewisi

2.斜纹宽盾蝽 Poecilocoris dissimilis

The blueprint of life [4]: Tertiary Structure of DNA

Finally, we come to the last part of the molecular structure of DNA.

4. Tertiary Structure of DNA – superhelix structure

Advanced folding and intertwining of DNA molecules over the secondary structure .

DNA topology

1. Linear DNA:

Commonly seen in eukaryotes,
with extreme length,
complementary sequence
included in the chromatin (the combination or complex of DNA and proteins that make up the contents of the nucleus of a cell)
interacting with other cellular components.

2. Circular DNA:

(DNA frequently occurs in nature as closed-circular molecules, where the two single strands are each circular and linked together. The number of links is known as the linking number(Lk).)

Usually seen in prokaryotes, e.g. plasmid (质粒), circular bacterial chromosomes and many viral DNA molecules
cccDNA (covalently closed circular DNA) → supercoiled or Relaxed; ncDNA (nicked circular DNA): a nick (缺刻)formed by breaking one phosphodiester bond
two complementary single strands are each joined into circles, 5′ to 3′, and are twisted around one another by the helical path of DNA.
The molecule has no free ends and the two single strands are linked together a number of times corresponding to the number of double-helical turns in the molecule.

cccDNA Topology

Supercoiled DNA

Negative superhelix: natural status of cccDNA with less intra- molecular tension (underwound effect)

Positive superhelix: unnatural status with higher tension (overwound effect)

Relaxed circular DNA: intermediate between negative superhelix and positive superhelix

Topological Equation of cccDNA

L = T + W

L=Linking number=total number of times one strand of the double helix links the other

T=Twisting number= the number of times one strand completely wraps around the other strand

W=Writhing number= the number of times that the long axis of the double helical DNA crosses over itself in 3-D space

Features

1. The linking number of a closed-circular DNA is a topological property, that is one which cannot be changed without breaking one or both of the DNA backbones. (A molecule of a given linking number is known as a topoisomer. Topoisomers differ only in their linking number)

2. Twisting number

For B DNA, T>0(10 bp per turn)

For A DNA, T>0(10.5 bp per turn)

For Z DNA, T<0 (12 bp per turn)

3. Writhing number

Relaxed: W=0

Negative supercoils: W<0

Positive supercoils: W >0

TWIST &WRITHE, from Instant Notes in Molecular Biology(3rd edition)

Topoisomerases (enzymes used to regulate the level of supercoiling of DNA molecules)

To alter the linking number of DNA, the enzymes must transiently break one or both stands. There are two classes of topoisomerases:

Type I Topoisomerase nick one strand of the DNA, changing 1 Linking-number at a time(+/-1 Lk)

Type II Topoisomerase, which requires the hydroloysis of ATP, break two strands of DNA, changing 2 Linking-number at a time(+/-2Lk); also able to unlink DNA molecules.

Most topoisomerases reduce the level of positive or negative supercoiling, that is, they operate in the energetically favorable direction. (However, DNA gyrase, a bacterial type II enzyme, uses the energy of ATP hydrolysis to introduce negative supercoiling into hence removing positive supercoiling generated during replication.)

Topoisomerases are essential enzymes in all organisms; they are involved in replication, recombination and transcription.

Both type I and II enzymes are the target of anti-tumor agents in humans.

DNA superhelix

Biological significance of Superhelix:

DNA packing:

Eg.

This is a famous electron micrograph of an E. coli cell that has been carefully lysed, then all the proteins were removed, and it was spread on an EM grid to reveal all of its DNA.

DNA functioning:

Negative supercoils serve as a store of free energy that aids in processes requiring strand separation, such as DNA replication and transcription; Strand separation can be accomplished more easily in negatively supercoiled DNA than in relaxed DNA.

1. DNA in cells is negatively supercoiled;

2.(-)supercoiling introduced by a topoisomerase II (gyrase 促旋酶) in prokaryotes and by nucleosome (核小体)in eukaryotes

3.Cruciform or bubble structures introduced by (-) supercoiling are potential protein-binding sites

Mendel’s Genetics [4]: examples of mutiple alleles

All the examples used in last classes have employed genes with only two alternative alleles. But the majority of genes exist in several different forms, multiple alleles. This is caused by the mutations of bases at different sites within the same gene, thus affecting different amino acids in the encoded protein.

examples of multiple-allele traits/diseases:

the human β-globin gene where a specific mutation at one site of the gene results in an allele responsible for the hereditary syndrome sickle cell (picture)anaemia, while mutations at several other sited sites in the gene cause a different syndrome, β-thalassemia(beta地中海贫血),
A SICKLE CELL,image from the Internet

Beta-thalassemia, inherited blood disorder caused by reduced or absent synthesis of the beta chains of hemoglobin, resulting in variable phenotypes ranging from severe anemia to clinically asymptomatic individuals.

Although they are alterations of the same gene, the changes are to different codons(a specific sequence of three consecutive nucleotides that is part of the genetic code and that specifies a particular amino acid in a protein or starts or stops protein synthesis). The resulting proteins have variant beta-globins with discrete differences in amino acid sequence and so behave differently.

—————————————————————————

In rabbits, multiple alleles of one gene are responsible for a number of different coat color phenotypes.

Here we go, a little confusing but, interesting:

There are four members of the allelic series: agouti, chinchilla, Himalayan and albino. When homozygous, each series produces a distinct coat pattern. When heterozygous, there is a clear pattern of dominance. Agouti is dominant over all the alleles, chinchilla is dominant over Himalayan and albino, while Himalayan is dominant over albino, which fails to produce any pigment and hence is recessive to the others…Hope your mind is still clear!

1, Agouti rabbit: the wild rabbit.

genetics 4 an agouti rabbit — AN AGOUTI RABBIT, image form the Internet

If you blow into the fur of an Agouti rabbit, you will see “bandings” of different colors along the shaft of the hair, being blue, black, tan, fawn. The Agouti also has light tan coloring around the nostrils and at the back of the neck. The belly is cream.(http://rabbit.wikia.com/wiki/Agouti)

2, Chinchilla rabbit: soft, grey fur.

genetics 4 A five-week-old Chinchilla rabbit — A FIVE-WEEK-OLD CHINCHILLA RABBIT, image from the Internet

Chinchilla Rabbits originated in France and were bred to standard by M. J. Dybowski. They were introduced to the United States in 1919. (wikipedia)

3. Himalayan rabbit: white body with colored points, recognized colors are black, blue, chocolate and lilac.

A HIMALAYAN RABBIT, image from the Internet

red eyes; posed stretched out, body to be 3.5 head lengths. They are the ancestors of Californians, one of the most common meat rabbits.(wikipedia: Himalayan_rabbit)

4. Albino rabbit: completely white since it’s missing the melanin which determines the color of their skin, eyes, and fur.

genetics 4 albino rabbits — AN ALBINO RABBIT, image from the Internet

Not all white rabbits are albinos, so you’ll need to check their eyes. If their eyes are red or pink and their hair is totally white, they would be considered an albino. They are not rare.

An albino rabbit may not have the greatest eyesight due to their lack of eye pigment. Since their eyesight is not the best, they should be caged or kept inside since they may not be able to see predators.(http://www.ask.com/question/albino-rabbits)

Having seen so much about rabbits, hope you haven’t forgotten what we were doing before those cute bunnies. We were learning about examples of multiple alleles of one gene.

the human ABO blood group system.

(all form wikipedia: ABO blood group system:)

The ABO blood type is controlled by a single gene (the ABO gene) with three types of alleles inferred from classical genetics: i, I^A, and I^B. The gene encodes a glycosyltransferase— an enzyme that modifies the carbohydrate content of the red blood cell antigens.

The I^A allele gives type A, I^B gives type B, and i gives type O.

Both I^A and I^B are dominant over i, so only ii people have type O blood. Individuals with I^AI^A or I^Ai have type A blood, and individuals with I^BI^B or I^Bi have type B.

I^AI^B people have both phenotypes, because A and B express a special dominance relationship: codominance(we talked about it last class), which means that type A and B parents can have an AB child.

A type A and a type B couple can also have a type O child if they are both heterozygous (I^Bi,I^Ai)

Hope your mind is still clear!

NOTE: the concept of multiple alleles of one gene is totally different from multiple-gene inheritance.

A polygene, multiple factor, multiple gene inheritance, or quantitative gene is a group of, non-allelic, genes that together influence a phenotypic trait.

The blueprint of life [3] secondary and some special structures of DNA

Let’s pick up where we dropped, the secondary structure of DNA.

IN FACT, a number of different forms of nucleic acid double-helix have been observed and studied, all having the basic pettern of two helically-wound antiparallel strands.

Polymorphism （多样性）of DNA Secondary Structure

―due to conformational changes of sugar-ring on the nucleotide chain.

1. B-form:

right-handed
the structure identified by Watson and Crick,
the most common form,
believed to be the idealized form of the structure adopted by virtually all DNAin vivo (in the living body of a plant or animal), or, at physiological (characteristic of or appropriate to an organism’s healthy or normal functioning) pH and salt concentration.

characterized by:

a helical repeat of 10bp/turn (although now it is known that ‘real’ B-DNA has a repeat closer to 10.5bp/turn);
the presence of base pairs lying on the helix axis and almost perpendicular to it;
having well-defined, deep major and minor grooves.

2. A-form:

right handed
adopted by DNA in vivo under unusual circumstances, (conversed from B-form in low moisture (<75%))
presents in certain DNA-protein complexes

characterized by:

a helical repeat of 11 bp/turn.
the presence of base pairs tilted with respect to the helix axis, and actually lying off the axis.
being the helix formed by RNA and DNA-RNA hybrids. (Similar to some RNA-DNA duplex or RNA-RNA duplex.)

3. Z-form:

left-handed
formed by stretches of alternating pyrimidine-purine sequence, e.g. GCGCGC, especially in negatively supercoiled DNA in high saline (盐) solution.
not easily form even in DNA regions of repeating GCGCGC, since the boundaries between the left-handed Z-form and the surrounding B-form would be very unstale

characterized by:

a zigzag (锯齿型) pattern where its name comes from
12 bp/turn

(1)

A. B, Z-DNA — slide shown by prof.Dong,COMPARISON AMONG A-,B-,Z-DNA

(2)

picture from Instant Notes in Molecular Biology (3rd Edtion)

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Some special structures of DNA

1. Inverted repeats and direct repeats

Inverted Repeat is functionally important as recognition sites on the DNA for the binding of a variety of proteins (e.g. restriction and modification enzymes)

Inverted Repeat is either discontinuous or continuous,

Continuous → palindromic structure (回文结构:inverted repetitions of base sequence over the two strands form a symmetric structure )

Discontinuous→ hairpin & cruciform (发卡、十字结构:self complementary within each of the strands )

hairpin structure & cruciform structure — hairpin structure & cruciform structur

2. DNA triplex (The intramolecular triplex (H-DNA) as an example)

• AG-rich strand vs. CT-rich strand with Hoogsten hydrogen bond

(a quick glance at Hoodsten hydrogen bond:

• Mirror inverted repeat

• a barrier for different DNA and RNA polymerases, and so it is a negative regulator for gene expression.

3. G-quadruplex structure

G-rich sequence(s) to form 4-stranded structure by unusual G-G

H-bonds

Mendel’s Genetics[3]: Variations of the 3:1ratio

Variations of the 3:1 ratio

The simple 3-to-1 monohybrid ratio is not always observed in instances where only one gene is responsible for a particular phenotype.

A number of factors:

Partial or incomplete dominance

Complete dominance means the phenotype of first filial generation(heterozygous) is exactly identical to that of one of the parents(both homozygous). Partial or incomplete dominance means the first filial has phenotype somewhere between that of both parents.

For example, When two pure-bred snapdragons, with white and red petals respectively, cross, their first filial generation has pink petal rather than red or white.

In this case, the homozygous phenotypes are red, or white petals while heterozygous one is between white and red: pink petal.

Thus, it is conceivable that when it comes to the second filial generation, which was produced by the self fertilization of the heterozygous F1, F2 should have three different phenotypes, white, pink, and red. And we can also deduce the ratio of them is 1:2:1.

Codominance

Codominance is similar to incomplete dominance, but here the heterozygote displays both alleles(两种等位基因均被表达).

For example, in humans the MN blood group is controlled by a single gene.

In humans the main blood group systems are the ABO system, the Rh system and theMN system.

Only two alleles exist, M and N. Children whose father is an NN homozygote with N blood and whose mother is a MM homozygote with group M blood are MN heterozygotes and have group MN blood.Both phenotypes are identifiable in the hybrid. And the ratio also switches from 3:1 to 1:2:1.

Lethal alleles

Some alleles affect the viability of individuals that carry them.

In most cases the homozygous recessive does not survive but the heterozygotes may have a normal lifespan.

The best-known example of lethal alleles is the inheritance of yellow coat color in mice.

Yellow fur can arise in strain of mice with different colors, or instance, black. Yellow coat color is dominant to black coat. Mice with BB alleles are back, with BB^yare yellow, with B^yB^y alleles are supposed to be yellow as well, but B^yB^y alleles are lethal and any mice with this genotype die in utero(in the uterus : before birth).

SO it is conceivable that when two yellow mices are mated ratio of the different phenotypes of their first generation is 2 : 1, rather than 3 : 1 or 1 : 2 :1.

NOTE: The allele B^yis recessive in its relation to its effect on viability (only homozygous B^yB^ys die, while the heterozygotes survive ), but dominant in relation to coat color(heterozygotes present in yellow fur in stead of black fur.).

Other examples where alleles are lethal when homozygous but have a dominant effect when heterozygous, include :

tailless Manx cats

genetics — a manx cat, image from the Internet

a breed of domestic cat(Felis catus) originating on the Isle of Man, with a naturally occurring mutation that shortens the tail.

The Manx taillessness gene is dominant and highly penetrant; kittens from two Manx parents are generally born without any tail. Being homozygous for the taillessnees gene is lethal in utero.Thus, tailless cats can only be heterzygous. Because of the danger of having homozygous taillessness gene, breeders avoid breeding two entirely tailless Manx cats together.(wikipedia: Manx (cat))

short-legged Creeper chickens.

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(Annie: If none of the homozygous yellow mice can survive before birth, then where did all the heterozygous yellow mice come from in the first place???????)

Answer: Through mutation. The presence of one mutant allele alters development so as to produce characteristic changes to the animal, but when two of the mutant alleles are present, development is so aberrant as to cause death.

This may occur in utero as described above or resulted in shortened life expectancy as found in several examples in humans, such as Tay-Sachs disease, Huntington’s syndrome（亨丁顿舞蹈症） or sickle-cell anemia（镰刀形红血球病）. (from Instant Notes)

the blueprint of life [2]: primary and secondary structure of DNA

Molecular structure of DNA:

professor Dong first showed us where DNA is:

Then he introduced the molecular structure of DNA with 4 parts:

1. Primary structure of DNA:

Arrangement of nucleotides along a DNA chain.

Annie: So…the primary structure of DNA is a line.

Conventionally, the repeating monomers of DNA are represented by their single letters A, T, G, C.

Professor: There’s a convention to write the DNA sequence with 5′ at the left, that is, in a 5′ to 3′ orientation from left to right.

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2. Secondary structure of DNA—stabilized partial structure formed by polymers of nucleotide

Professor Dong: First, please familiarize yourselves with Chargaff’s Rule:

A+G=T+C & G+T=A+C

↓↓

A=T & G=C

(Chargaff’s Rule)

(Based on analysis of the chemical composition of duplex DNA in the early 1950s, E. Chargaff deduced these rules about the amounts of different nucleotides in DNA.)

Professor: The secondary structure of DNA is a partial structure formed by polymers of nucleotide. The structure is referred to as the double-helix structure.

Two separate chains of DNA are wound around each other, each following a helical (coiling) path, resulting in a right-handed double helix structure.

In 1953, Watson and Click proposed the DNA double-helix structure based on Chargaff’s Rule and DNA Crystallography and X-ray diffraction images of DNA structure by Wilkins and Franklin. (Rosalind Franklin, who was not that well-known as Watson, Click and Wilkins but apparently played a equally significant role in the discovery of the structure.The whole was later nominated Nobel Prize but her, is that even fair?)

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The backbone of duplex DNA is a serious of phosphodiester group (the covalent linkage of a phosphate group between the 5′-hydroxyl of one sugar and the 3′-hydroxyl of the next, that is , repeats of P-sugar unit) linked by phosphodiester bond.

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The strands are joined noncovalently by hydrogen bonding between the bases on opposite strands, to form base pairs.

There are around 10 base pairs per turn in the DNA double-helix. The two strands are oriented in opposite directions in terms of their 5’to3′ direction(the nucleotides in one strand is opposite to their direction in the other strand).

More crucially, the two strands are complementary in terms of sequence. The bases hydrogen-bond to each other as purine-pyrimidine pairs which have very similar geometry and dimensions.

A–T: 2 H-bonds ; C–G: 3 H-bonds

5’- A T G T C -3’

¦¦ ¦¦ ¦¦¦ ¦¦ ¦¦¦

3’- T A C A G -5’

Thus, the sequence of one strand uniquely specifies the sequence of the other, with all that which implies for the mechanism of replication of DNA and its transcription to RNA.

——————————————————————————-

Professor Dong added:

Between the backbone stands run the major and minor grooves.

In a detailed analysis of DNA structure, there are two types of grooves that can be seen; the major groove has the nitrogen and oxygen atoms of the base pairs pointing inward toward the helical axis, while in the minor groove,the nitrogen and oxygen atoms point outwards;

Shown by prof.Dong, MAJOR GROOVE A-T

Shown by prof.Dong, MAJOR GROOVE G-C

Major Groove Minor Groove

Depth: 8.5 Å Depth: 7.5 Å

Width: 11.7 Å Width: 5.7 Å

Å

Definition: Symbol for Ångström, a unit equal to 0.1 nanometer, mainly used in expressing sizes of atoms, lengths of chemical bonds, and wavelengths of electromagnetic radiation.

Supplement: The unit is named after the Swedish physicist, Ångström, Anders Jonas.

picture from Instant Notes in Molecular Biology

Professor: The major groove is more dependent on base composition. and major grooves and minor grooves are also recognition and binding sites for certain protein factors, and are involved in the regulation of gene expression.

——————————————————————————

Professor: Summary of “Double Helix” Model (B-DNA):

Right Handed Double Helix

Outside: P-Sugar backbone

Inside: Base pairing linked by H-bonds

Minor and Major grooves

（note: bp=base pair(s)）

Illustrations of wild animals [insect 4 Praying Mantids]

螳螂目 MANTODEA

Mantodea (Mantids / Praying Mantids)

The name Mantodea is derived from “mantis”, the Greek word for these insects.

Classification & Distribution

Hemimetabola

incomplete development (egg, nymph, adult)

Orthopteroid

closely related to Orthoptera and Blattodea

Distribution: Common in tropical and subtropical climates.

	WORLDWIDE
Number of Families	8
Number of Species	~1800

Life History & Ecology

Mantids have elongate bodies that are specialized for a predatory lifestyle: long front legs with spines for catching and holding prey, a head that can turn from side to side, and cryptic coloration for hiding in foliage or flowers.

Mantids are most abundant and most diverse in the tropics; there are only 5 species commonly collected in the United States and 3 of these have been imported from abroad.

Physical Features

Adults:

Filiform antennae
Head triangular with well-developed compound eyes
Mouthparts mandibulate, hypognathous
Prothorax elongate with large, spiny front legs adapted for catching prey
Front wings thickened, more slender than hind wings
Tarsi 5-segmented
Cerci short, multi-segmented

Immatures:

Structurally similar to adults
Developing wingpads often visible on thorax

Major Families

The name mantid refers only to members of the family Mantidae.

Bug Bytes
- Mantids are the only insects that can turn their head from side to side without moving any other part of the body. Many humans mistakenly interpret this behavior as a sign of intelligence.
- A female mantid may eat her mate while he is still linked with her in copulo. This behavior is probably more common in captivity than in the wild.
- Most mantids are cryptically colored to blend with their environment. A pink Malaysian species spends most of its time hunting for prey on pink orchids.
- Although mantids usually feed on insect prey, they have been known to catch and eat small frogs, lizards, and even birds

====================================================

↑Quoted from the General Entomology course
at North Carolina State University >Resource Library > Compendium > Mantodea (© 2009 by John R. Meyer; Last Updated: 8 April 2009)

>Learn more about pray mantids (mantodearesearch.com)

====================================================

螳科 Mantidae

大刀螳螂Tenodera aridifolia

2. 中华刀螳Tenodera sinensis

3. 短胸大刀螳Tenodera brevicollis

棕静螳 Statilia maculata

广斧螳 Hieroduia patellifera

长颈螳科 Vatidae

中华屏顶螳Kishinouyeum sinensae

the blueprint of life[1]

Of course the blueprint of life is DNA.

DNA is important because it is the genetic material ←contain all the info for the synthesis and functioning of a living form duplicate and passes through to the next generation.

Hearing this Annie questioned herself: DNA is not the genetic for ALL viruses. RNA “blueprints” for the rest of the viruses. Virus, though not even having a cell structure, is a form of life. So why not be fair, and say the blueprint of life are DNA and RNA?

Professor Dong continued,

Proofs:

Bacterial Transformation Experiment

—Griffith, 1928

Professor: So what is the transforming principle?

Annie: It could be a cool type of enzyme that moved the toxic part of S strain onto R strain…

Professor: Well, Enzyme did help a lot in the experiment we’ll talk about later, but it is not the hero of the story.

Annie: So what’s the story?

Professor:

—Avery et al., 1944

slide shown by Prof. Dong ,AVERY REPEATED GRIFFITH’S EXPERIMENT WITH MODIFICATION

Only DNA is responsible for the transformation.

Annie thought: Well, there still existed possibilities that DNA and some other things that were not sugar, lipid or protein cooperated to complete the transformation… The “other things” also contributed to the transformation but could not complete it without DNA? In this case DNA is not the only one that is responsible,

T2 Bacteriophage Infection (Blender Experiment)

—Hershey &Chase, 1952

Experiment 1

Experiment 2

Radioactive labeling of proteins and DNA

The professor continued. So now let’s go deeper and see the chemical composition of DNA.

A 5-carbon sugar , hand in hand with base group and phosphorous group, thought Annie.

It’s not that simple as you learned in high school, said the professor. We need to know the chemical composition of the base group, deoxyribon and phosphorous group as well.

sugar group — slide shown by Prof. Dong,SUGAR GROUP

Professor:

Base — slide shown by Prof. Dong,BASE GROUPS

Annie thought: Pyrimid-ine, Could it have anything to do with the Pyramid in Egypt?

The professor was explaining the structure and Annie didn’t interrupt him with her question.

After class, Annie searched the Internet for an answer, and this is what she found.

The professor continued.

Bonds

P group——phosphester bond–—Sugar—–glycosidic bond—–B group

同翅目 HOMOPTERA

Adults:

Immatures:

Major Families

蝉科 Cicadidae

叶蝉科 Cicadellidae

半翅目 HEMIPTERA

Classification & Distribution

Life History & Ecology

Physical Features

Adults:

Immatures:

Major Families

蝽科 Pentatomidae

长蝽科 Lygaeidae

盾蝽科 Scutelleridae

DNA topology

DNA superhelix

螳螂目 MANTODEA

Life History & Ecology

Physical Features

Adults:

Immatures:

Major Families

Bug Bytes

螳科 Mantidae

长颈螳科 Vatidae