Ch7 Part 1

Question 1

Thomas Hunt

Answer 1

Associated a specific gene with eye colour in flies; however, DNA has proteins and DNA so could not say for certain which carried the hereditary detail.

Question 2

Frederick Griffith

Answer 2

Used two strains of Streptococcus pneumoniae.

One strain killed mice (S), one did not (R). Heat killed (S) and R, if incubated together would result in the death of mice. Additionally, could extract living S strain from dead mouse.

Still unclear how virulence was being transferred.

Question 3

Oswald Avery, Colin MacLeod, Maclyn McCarty

Answer 3

systematically destroyed macromolecules in strains of dead (S) strain.

When DNase was added to S strain extracts, virulence could not be transferred.

Although many scientist remained skeptical.

Question 4

Alfred Hershey and Martha Chase

Answer 4

Model phage T2.

Radiolabeled phosphorous (which is in DNA) and Sulphur (which is in proteins). In separate cultures.

Progeny phases become labeled. Allowed to infect a bacteria.

Cultures (bacteria and phages) were centrifuged. Supernatant contained growth media and phage ghosts (empty capsids). Bacteria cells form at bottom.

Radiation was only seen in the pellet at the bottom of the test tube in the radiolabeled phosphorus.

Question 5

Other evidence that DNA transfers info

Answer 5

DNA total amount is constant across cells and species. (Erwin Chargaff)

DNA replication is semiconservative, DNA is copied during every cell cycle. (Stahl and Meselson)

In quiescent cells macromolecules like proteins are recylced. DNA remains constant

Mutagens cause mutations in DNA

Question 6

Human Chromosomes

Answer 6

24 different chromosomes.

22 are autosomes

2 are sex chromosomes

Non-dentical copies of a chromosome are referred to as homologous.

Question 7

Classical Dominance

Answer 7

Only homozygotes for the recessive gene express the recessive trait.

Question 8

Meiosis

Answer 8

Cell division that reduces the dumber of copies of genes from 2 to 1.

In males. Spermatogonia undergo meiosis.

In females. oogonia.

Question 9

Main difference between Mitosis and Meiosis

Answer 9

Two rounds of cell division in meiosis: Meiosis I and Meiosis II

Question 10

Stages of Meiosis

Answer 10

S - phase before produces 4 copies of the genome.

Prophase I
Metaphase I
Anaphase I
Telophase I

Question 11

Prophase I

Answer 11

Chromosomes condense, nuclear envelope breaks down.

Chromosomes pair with eachother during prophase I in SYNAPSIS - a very specific pairing. In this state chromosomes are called BIVALENT or Tetrad. Allows for crossing over or recombination between homologous chromosomes, not sister chromatids!!

Prophase is the longest stage of meiosis and can take days.

Question 12

synaptonemal complex (SC)

Answer 12

Mediates the process of synapsis. Forms during prophase.

Functions like a zipper.

SYCP2 and SYCP3 form initial complex between homologous chromatin to be paired. These complexes then connect via SYCP1 with additional proteins.

SC formation and recombination are interdependent.

Question 13

Metaphase I

Answer 13

Metaphase plate occurs; however, main difference is that in meiosis tetrads line up at center, not sister chromatids.

Question 14

Anaphase I

Answer 14

Homologous chromosomes separate, but sister chromatids stay together.

Question 15

Telophase I

Answer 15

Divides into two cells.

Cells are considered haploid at this stage!

Question 16

Meiosis II

Answer 16

No additional replication of DNA between Telophase I and Meiosis II.

All proceeds the same afterwards, but as haploid cell.

Sister chromatids however, are not identical as a result of recombination.

Question 17

Non-disjunction

Answer 17

When sister chromatids fail to seperate properly during Meiosis II

Can result in a gamete with either two copies or 0 copies of a given chromosome. Once it bonds with a normal gamete can result in trisomy or monosomy.

Trisomy of Chromosome #21 results in Down Syndrome.

Question 18

Law of segregation

Answer 18

Two alleles of an individual are separated and passed on to the next generation, singly.

ie. only one allele goes into the gamete

Question 19

Law of independent assortment

Answer 19

Alleles of one gene will separate into gamete independently of alleles of another gene.

Not true for LINKAGE.

Question 20

Testcross

Answer 20

When the genotype of an unknown species is crossed with a pure line to determine characteristics.

Progeny are referred to as F1 generation.

Question 21

Incomplete dominance

Answer 21

phenotype of a heterozygote is blended.

Three phenotypes are possible in this situation if two heterozygotes are cross-bred.

Question 22

Codominance

Answer 22

Two alleles are both expressed, but are not blended.

Bood type, ie. antigen expression

Note there is another antigen used to determine blood type: Rh (rhesus) factor. Which has a classic dominant pattern.

Question 23

Pleiotropism

Answer 23

Expression of a gene alters many different, seemingly unrelated phenotypic aspects.

Question 24

Polygenism

Answer 24

Complex traits influenced by many different genes.

Ex. Height

Question 25

Penetrance

Answer 25

Likelihood that a specific genotype will provide a specific phenotype.

Penetrance depends on the allele. Can be altered by age, modifiers, environment etc.

Question 26

Epistasis

Answer 26

Expression of one allele of a gene is dependent upon another gene.

Ex. Can’t have curly hair if you are bald.

Question 27

Recessive Lethal Alleles

Answer 27

Can be lethal when present in homozygous form.

Can be studied by maintaining a ‘stock’ of heterozygotes in diploid organisms.

Haploids are more difficult to study and require an allele that is inducible.

Question 28

Recessive X-chromosome genes in Males?

Answer 28

Always expressed.

Question 29

Linkage

Answer 29

Failure to exhibit independent assortment.

Punnett squares look different for genes on the same allele.

REcombination is the exception to linkage.

Question 30

Recombination Frequency

Answer 30

proportional to distance between genes on the same chromosome.

RF = #recombinants/#offspring

Question 31

Autosomal Dominant

Answer 31

Single copy of allele required for expression

Question 32

Autosomal Recessive

Answer 32

Two copies required for expression

Question 33

Mitochondrial traits

Answer 33

Haploid genome passed along only by mother.

Kids will have it if mother does. Father will not pass on mitochondrial affects.

Example of hemizigosity - where a diploid organism only has one gene copy (occurs for X or Y genes as well)

Note genes encoded by mitochondria indicated by mt (ex. mt-Ap6)

Question 34

Sex-linked traits

Answer 34

Odd patterns of inheritance. Father can only pass y-linked traits to sons.

X-linked traits are observed more frequently. Can be recessive or dominant. Note, males always expressive recessive x-linked traits.

ex. hemophilia or red/green colour blindness (X-chromosome recessive)

X-linked dominant traits are harder to spot as Females will express with one or two copies and males will always express. But these traits do not tend to affect men more than women.

Question 35

Population Genetics

Answer 35

inheritance of traits in population over time.

Note: Population refers to members of a species that mate and reproduce with each other.

Question 36

Hardy-Weinberg Law

Answer 36

Frequencies of alleles in the gene pool or a population will not change over time.

Assumes:
No mutation
No migration
No natural selection
Random mating
Population is large enough to prevent random drift

Question 37

Hadry-Weinberg Math

Answer 37

P + Q = 1

Where p is frequency of dominant allele and q is frequency of recessive allele.

P^2 + 2pq + q^2 = 1

predicting proportion of genotypes in a population.

Question 38

If allele frequencies don’t change over time and genotype frequencies can be calculated from allele frequencies… what happens to phenotype frequencies over time?

Answer 38

Constant. After the first generation that is.

ie. at Hardy-Weinberg Equilibrium

Question 39

Fitness

Answer 39

How successful an organism is at passing on its alleles to future generations.

Question 40

Sources of genetic variation in a population

Answer 40

new alleles and a new combination of existing alleles.

Question 41

Modes of Natural Selection

Answer 41

Directional Selection
Divergent Selection
Stabilizing Selection
Stabilizing Selection
Artificial Selection - human interference
Sexual Selection - sex displays that create non-random selection
Kin Selection - individuals will sacrifice for kin as share alleles

Question 42

Species

Answer 42

Capable of reproducing together and producing sexually viable children. Morphology is used for asexual species.

Members of a population, can and do reproduce together.

Question 43

Reproductive Isolation

Answer 43

Keeps existing species separate.

1. Prezygotic - prevent formation of a hybrid.

ex. environment, temporal, behavioural, mechanical, gametic

2. Postzygotic - prevent survival, development, and reproduction of hybrid individuals.

e. Hybrid inviability (die usually in embryonic stage); hybrid sterility; hybrid breakdown

Question 44

Cladogenesis

Answer 44

Branching of species. ie. all new species come from old species.

Ex. Allopatric isolation (geographic);

Ex. Sympatric isolation - a species gives rise to another species in the same geographical area by divergent selection

Question 45

Anagenesis

Answer 45

One species simply becomes another (does not branch).

Question 46

Homologous Structures

Answer 46

Structures shared by species as a result of a common ancestor.

Question 47

Analogous Structures

Answer 47

Structures that serve the same purpose but do not arise from a common ancestor.

Question 48

Convergent Evolution

Answer 48

When two species come to have many analogous structures.

Opposite - divergent selection

Question 49

Parallel Evolution

Answer 49

Two species go through similar evolutionary processes.

Question 50

8 principal taxonomic categories

Answer 50

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Dumb King Phil Came Over For Great Sex

Question 51

Taxonomy General Categories

Answer 51

Pg. 267 Summary table!

Question 52

Superior

Answer 52

Indicates toward head

or

Cephalad

Question 53

Inferior

Answer 53

Means toward feet

or caudad

Question 54

Early earth atmosphere

Answer 54

A reducing environment.

Question 55

Abiotic Synthesis

Answer 55

Metallic ion mediated spontaneous polymerization of amino acids, carbohydrates, lipids, and ribonucleotides.

Polypeptides made via abiotic synthesis = protenoids.

Question 56

Microspheres

Answer 56

Droplets formed in water by protenoids.

Question 57

Liposomes

Answer 57

Lipids in solution surround protenoids.

Question 58

Coacervate

Answer 58

A complex particle including polypeptides, nucleic acids, and polysaacharides formed during early life development.

Question 59

Protobionts

Answer 59

Umbrella term for Microspheres; Liposomes; Coacervate

Question 60

Protobionts Function

Answer 60

Can in a sense replicate (ie. split when too big); can catalyze reactions; have dividing membrane.

Lacked however, form of heredity