Ch 7: Genetics and Evolution (Princeton Review)

Question 1

The Hardy-Weinberg law states that the __________ of alleles in the gene pool of a population will not ______ ____ ____, provided that the following assumptions are true:

1. ) no mutation
2. ) no migration
3. ) no natural selection
4. ) random mating
5. ) the population is sufficiently large to prevent random drift in allele frequencies (genetic drift)

Answer 1

frequencies
change over time

p. 254

Question 2

A population consists of members of a species that ____ ___ __________ with each other. Even if dispersed over the whole ocean like sea turtles, as long as they meet up and mate, they are a population.

Answer 2

mate and reproduce

p. 253

Question 3

To a population geneticist, each individual is merely a temporary carrier of the _______ in a population. Alleles are examined across the entire population rather than in the individual. The sum total of all genetic information in a population is called the ____ ____.

Answer 3

alleles
gene pool

p. 253

Question 4

For an autosomal gene in a population of 2,000 individuals, how many copies of the gene are present in the gene pool?

Answer 4

2 copies of the gene in each individual, so 4,000 copies total in the gene pool

p. 254

Question 5

What Hardy-Weinberg means at the molecular level is that segregation of alleles, independent assortment, and recombination during meiosis can alter the combinations of alleles in gametes but cannot ________ or ________ the frequency of an allele in the gametes of one individual or the gametes of the population as a whole.

Answer 5

increase or decrease

p. 254

Question 6

If 20% of the population is heterozygous for an allele Q and 10% is homozygous, what will be the frequency of the allele in the population?

Answer 6

0.5 x (20% heterozygotes)

+ 10% homozygotes

= 20%

p. 254

Question 7

If you cross 100 homozygous green pea plants and 100 homozygous yellow pea plants, what will be the frequency of the yellow allele in the gene pool of the progeny?

Answer 7

50%, just as in the parental generation

And if the criteria for Hardy-Weinberg equilibrium are maintained, the frequency will still be 50% after 4 generations.

p. 254

Question 8

If two genes are closely linked on the same chromosome, will Hardy-Weinberg still apply to these genes?

Answer 8

Yes, independent assortment is not a requirement for Hardy-Weinberg, as long as the 5 assumptions hold true.

p. 254

Question 9

State the Hardy-Weinberg law mathematically.

Answer 9

p + q = 1
(p + q)² = 1²

p² + 2pq + q² = 1

p² is the frequency of the GG genotype

2pq is the frequency of the Gg genotype

q² is the frequency of the gg genotype

Question 10

The expected unlinked phenotype ratio from a cross between two double heterozygotes is ______, with 9/16 of the offspring double-dominant, 3/16 dominant/recessive, 3/16 recessive/dominant, and 1/16 double-recessive.

Answer 10

9:3:3:1

(Review of Princeton Review practice exam 1)

Question 11

Due to the extreme complexity of crossing over, meiotic ________ takes the most time in meiosis, days sometimes.

Answer 11

prophase

p. 232

Question 12

In meiosis, during prophase I, homologous chromosomes align themselves with each other in synapsis, with the 2 copies of each gene on two different chromosomes brought closely together. These paired homologous chromosomes are called a ________ or ______.

Answer 12

bivalent or tetrad

p. 232

Question 13

The difference between meiotic metaphase I and mitotic metaphase is….

Answer 13

…..the tetrads are aligned at the metaphase plate, whereas in mitosis, sister chromatids are aligned on the metaphase plate.

p. 234

Question 14

Sometimes during anaphase I of meiosis, homologous chromosomes fail to separate, and sometimes during anaphase II, ______ ________ fail to separate. This is called __________.

Answer 14

sister chromatids

nondisjunction

p. 235

Question 15

If nondisjunction occurs, and the homologous chromosomes do not separate in meiosis I, then one daughter cell from this division will have _ copies of this chromosome and the other cell will have none. In meiosis II, sister chromatids will separate, leaving 2 gametes with _ copies of the chromosome and 2 gametes with no copies of the chromosome.

Answer 15

4

2

p. 235

Question 16

The movements of the chromosomes during meiosis II are identical to the movements in mitosis, with the sole difference being that in meiosis II there is a _______ number of chromosomes, while in mitosis there is a diploid number. The sister chromatids are separated during anaphase II, and after telophase II is complete, ____ ______ _____ have been produced from a single diploid parent cell.

Answer 16

haploid

FOUR haploid cells

p. 234

Question 17

What is the process by which two different species come to possess many analogous structures due to similar selective pressures?

Answer 17

convergent evolution

(e.g. bats and birds; dolphins and sharks)

Bats and dolphins are both mammals, but experience many of the same selective pressures and the other animals in the pairs above.

p. 261

Question 18

What occurs when divergent evolution takes place?

Answer 18

cladogenesis – one species diversifies and becomes two or more new species

p. 261