Exam 2

Question 1

The diploid number of a species is 2n=30. Each diploid nucleus contains 5 ng of DNA in G1. What is the number of chromosomes and the amount of DNA contained each nucleus at the end of the S phase?

Answer 1

30 chromosomes containing 10 ng of DNA

Question 2

A nondisjunction during Meiosis I occurs when the ____ fail to separate, resulting in ____ gametes that are abnormal

Answer 2

Homologous chromosomes, 4

Question 3

When does homologous chromosome pairing and recombination occur?

Answer 3

prophase I

Question 4

If a trait is X-linked recessive, who would express the trait?

Answer 4

Homozygous recessive females and hemizygous recessive males

Question 5

White eye color is an X-linked trait in one line of fruit flies. White eyes is recessive to red eyes. If a red-eyed female and a white eyed male are crossed.

Answer 5

Some of their male progeny may have white eyes

Question 6

Syntenic genes can assort independently when

Answer 6

They are far apart on a chromosome and crossing over occurs frequently between the genes

Question 7

Most combinations of different ABO alleles result in complete dominance of one allele. Which combination results in codominance?

Answer 7

IAIB

Question 8

Independent assortment predicts a 9:3:3:1 ratio with four different phenotypes in the F2 progeny. If the alleles are epistatic, what would you predict?

Answer 8

Fewer than four phenotypes

Question 9

What type of test would you use to determine whether observed data constitute evidence of genetic linkage or are simply a case of chance variation from expected values?

Answer 9

Chi square analysis

Question 10

The tendency of alleles of linked genes to segregate together during meiosis can be broken by _______

Answer 10

recombination

Question 11

An XXX female is a result of _____ during Meiosis

Answer 11

Nondisjunction

Question 12

In meiosis interphase is followed by two successive rounds of cell division, meiosis I and II. Meiosis results in four haploid daughter cells because there is no ___ between these two meiotic cell divisions.

Answer 12

DNA replication

Question 13

Most people with the dominant mutant polydactyly allele have extra digits, but at least 25% have the normal number of digits. This is an example of ___

Answer 13

Incomplete penetrance

Question 14

In an organism with a diploid number of 40: ___ chromosomes move to each pole during anaphase of mitosis, ____ chromosomes move to each pole during anaphase I and ____ chromosomes move to each pole during anaphase II.

Answer 14

40, 20, 20

Question 15

If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?

Answer 15

One gamete will be n+1, one will be n-1, and two will be n

Question 16

In a two-point test cross involving unlinked genes, what phenotypic ratios would be expected from a cross between a dihybrid female and a homozygous recessive male?

Answer 16

1:1:1:1

Question 17

Bob has a genetic condition that affects his skin. Bob’s wife Eleanor has normal skin. No one in Eleanor;s family has ever had the skin condition. Bob and Eleanor have a large family. Of their eleven children, all six sons have normal skin, but all five of their daughters have the same skin condition as bob. What inheritance pattern does the skin condition most likely follow?

Answer 17

X linked dominant

Question 18

Which of the following most closely states what the chi-square test measures?

Answer 18

How well the expected and observed data correlate

Question 19

In humans, the ABO blood type is under the control of autosomal multiple alleles. Color blindness is a recessive X linked trait. If two parents who are both type A and have normal vision, produce a son who is color blind and is type O, what is the probability that their next child will be a female who has normal vision and is type O?

Answer 19

1/8

Question 20

Coat color in dogs depends on action of at least two genes. etc. etc. When dihybrid white dogs are mated, what would be the phenotypic ratio in the offspring

Answer 20

12:3:1

Question 21

If a male is affected with an X linked dominant trait, what proportion of his offspring can be expected to express this trait?

Answer 21

All daughters and no sons

Question 22

Calico cats are always female because

Answer 22

The maternal X chromosome is always heterochromatized into a barr body

Question 23

Turner’s syndrome occurs due to nondisjunction at the sex chromosome resulting in an individual with one X and no Y chromosome. Color-blindness is a sex-linked recessive trait. A color blind man marries a healthy woman. They have two children both with turner’s syndrome. One of the children is color blind, which of the following is true

Answer 23

Nondisjunction occurred in the mother for the color blind child and in the father for the child with normal vision

Question 24

How many barr bodies would be present in cells of an individual of karyotype 44+XXX

Answer 24

2

Question 25

Red green color blindness is due to an x linked recessive allele in humans. A widow’s peak is due to an autosomal dominant allele. Consider the history:
-man with widows peak and normal color vision marries a color blindwoman with a straight hairline
-man’s father had a straight hairline, as did both of the woman’s parents.
If the couple has a child, what is the chance that it will be a son with a widow’s peak?

Answer 25

1/4

Question 26

Given the example provided in widow peak quesion, what is the chance that any daughter the couple has will be color blind with a widow’s peak?

Answer 26

0

Question 27

Lesch-Nyhan is a rare x linked recessive disorder that produces severe mental retardation spastic cerebral palsy and self mutilation. What is the probability that the first son of a woman whose mother’s brother has Lesch Nyhan syndrome will be affected?

Answer 27

1/8

Question 28

King George III of England and other members of royal family afflictid with similar symptoms. It is determined he suffered from porhyria, caused by mutation in a single gene. What is the genetic term descrbing the alteration of multiple, distinct traits of an organism by mutation in a single gene?

Answer 28

Pleiotropy

Question 29

Two alleles of a gene are incompletely dominant. Crossing individuals that are heterozygous for these two alleles will produce the following phenotypic ratio

Answer 29

1:2:1

Question 30

Somatic cells of the red fox normally have 38 chromosomes. During meiosis the number of chromosomes moving towards each pole are ___ in anaphase I and ___ in anaphase II.

Answer 30

19,19

Question 31

A female calico cat mates with a male orange cat, and non-disjunction occurred during meiosis II in the female. The litter of kittens could contain all of the following kittens except

Answer 31

calico female

Question 32

Genetic complementation testing crosses are performed between pure breeding strains for recessive conditions that confer the same mutant phenotype. If the two mutations are in different genes, then what phenotypic ratios would be expected among the progeny?

Answer 32

All fo the F1 progeny would be wild-type