275-276; 247-249; 251-253

Question 1

discrete traits

Answer 1

traits that are clearly different from each other.

Question 2

quantitative traits

Answer 2

types of continuously varying traits that don’t fall into discrete categories. Common characteristic: when the frequencies of different trait values observed in a population are plotted on a histogram, or frequency distribution, they often form a bell-shaped curve, or normal distribution.

Question 3

If many genes each contribute a small amount to the value of a quantitative trait

Answer 3

then a normal distribution results for the population as a whole.

Question 4

Quantitative traits are produced by the

Answer 4

independent actions of many genes, although it is clear that some genes have much greater effects on the trait in question than other genes do.

Question 5

The transmission of quantitative traits is

Answer 5

said to result from polygenic inheritance.

Question 6

polygenic inheritance

Answer 6

each gene adds a small amount to the value of the phenotype.

Question 7

Weismann’s hypothesis

Answer 7

a reduction in division precedes gamete formation in animals.

Question 8

Changes in chromosome sets occur only during

Answer 8

sexual reproduction – not during asexual reproduction.

Question 9

Asexual reproduction

Answer 9

any mechanism of producing offspring that does not involve the production and fusion of gametes. In eukaryotes, it is based on mitosis. The chromosomes in cells produced by mitosis are identical to the chromosomes in the parental cell.

Question 10

sexual reproduction

Answer 10

the production of offspring through the production and fusion of gametes. Results in offspring that have chromosome complements unlike those of their siblings or their parents.

Question 11

Cells produced by mitosis are

Answer 11

genetically identical to the parent cell, and offspring produced during asexual reproduction are genetically identical to one another as well as their parent.

Question 12

clones

Answer 12

exact copies; offspring of asexual reproduction are clones of their parents.

Question 13

Two aspects of meiosis that create variation among chromosomes:

Answer 13

(1) separation and distribution of homologous chromosomes and (2) crossing over.

Question 14

When pairs of homologous chromosomes line up during meiosis I and the homologs separate

Answer 14

a variety of combinations of maternal and paternal chromosomes can result. Each daughter cell gets a random assortment of maternal and paternal chromosomes.

Question 15

genetic recombination

Answer 15

appearance of new combinations of alleles.

Question 16

A diploid organism can produce

Answer 16

2^n combinations of maternal and paternal chromosomes, where n is the haploid chromosome number.

Question 17

recombination

Answer 17

crossing over produces new combinations of alleles within a chromosome – combinations that did not exist in either parent.

Question 18

self-fertilization

Answer 18

when two gametes produced by the same individual fuse to form a diploid offspring. Offspring are very likely to be genetically different from the parent.

Question 19

outcrossing

Answer 19

gametes from different individuals combine to form offspring.

Question 20

When a sperm and egg come together at fertilization

Answer 20

the number of possible genetic combinations that can result is equal to the product of the numbers od different gametes produced by each parent.

Question 21

Smith

Answer 21

developed a mathematical model showing that because asexually reproducing individuals do not have to produce male offspring, their progeny on average can produce twice as many offspring as individuals that reproduce sexually.

Question 22

Asexual reproduction is much more efficient than sexual reproduction because

Answer 22

no males are produced.

Question 23

Sexual individuals are likely to have some offspring that lack

Answer 23

the deleterious alleles that are present in a parent.

Question 24

Asexual individuals with a deleterious allele are

Answer 24

doomed to transmit the allele to all of their offspring.

Question 25

purifying selection

Answer 25

natural selection against deleterious alleles. Should reduce the numerical advantage of asexual reproduction.

Question 26

If a new strain of disease-causing agent evolves

Answer 26

then all the asexually produced offspring are likely to be susceptible to that new strain. But if the offspring are genetically varied, then it is likely that at least some offspring will have combinations of alleles that enable them to fight off the new strain of pathogen or parasite and produce offspring of their own.

Question 27

sexual reproduction is helpful for two reasons:

Answer 27

(1) Offspring are not doomed to inherit harmful alleles
(2) The production of genetically varied offspring means that at least some may be able to resist rapidly evolving pathogens and parasites.