TEST 2

Question 1

Which regions of the X chromosome can recombine during meiosis?

Answer 1

the pseudoautosomal regions

Question 2

In mammals, dosage compensation for X linked genes is achieved by:

Answer 2

Inactivation of one X chromosome during early development

Question 3

An X chromosome that has been inactivated becomes a ______ in female mammals.

Answer 3

Barr body

Question 4

An organism that has only one copy of a gene is called a

Answer 4

Hemizygote

Question 5

A white eyed Drosophila female (white/white) is crossed with a red eyed male. Assuming the trait for eye color is sex-linked. what are the possible phenotypes of the progeny?

Answer 5

Red-eyed females and white-eyed males

Question 6

A color blind male marries a woman who has normal vision. The woman has no history of colorblindness in her family. What percentages of their sons are expected to be colorblind?

Answer 6

0%

Question 7

Assume that a man who carries an X linked gene has children. Assuming normal meiosis and random combination of gametes the man would pass this gene to____

Answer 7

all of his daughters.

Question 8

Sex linked conditions are more common in men than woman bc

Answer 8

men need to inherit only one copy of the recessive allele for the condition to be fully expressed

Question 9

Which of the following is the part of the Y chromosome that is critical for normal male development?

Answer 9

SRY

Question 10

An individuals with 2 kinds of gametes (X bearing and Y bearing) is referred to as

Answer 10

Heterogametic

Question 11

Pedigree

Answer 11

Recessive, autosomal

Question 12

Why is the Y chromosome able to pair with the x chromosome during meiosis?

Answer 12

The X and Y chromosomes share small gene segments that allow them to act like homologues during meiosis.

Question 13

Female mammals that contain 2 types of cell lineages in which the parental X chromosome is inactivated in some cell and the maternal X chromosome is inactivated in others are known as:

Answer 13

Genetic mosaics

Question 14

In some animal species, like humans, sex is determined by:

Answer 14

The presence of the Y chromosome

Question 15

If an X linked disorder is lethal to the affected individual prior to the age at which one reaches reproductive maturation, the lethality will be expressed only in males. Why is this so?

Answer 15

The only sources of the lethal allele in the population are heterozygous females who are carriers and do not express the disorder

Question 16

2 forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their 1st son will have hemophilia?

Answer 16

1/2

Question 17

2 forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their 1st daughter will have hemophilia?

Answer 17

0

Question 18

Which of the following is required to unambiguously link a gene to a chromosome?

Answer 18

The chromosome must be morphologically distinguishable.
The pattern of gene transmission must reflect the chromosome’s behavior during reproduction.
The gene must be defined by a mutant allele.

Question 19

Which organism that was the 1st to be used to relate the behavior of chromosomes during meiosis to Mendel’s principles of Segregation and Independent Assortment?

Answer 19

Drosophila

Question 20

The centimorgan (cM) is a unit named in honor of Thomas Hunt Morgan. To what is it equal?

Answer 20

1% frequency of recombination between 2 genes.

Question 21

You conduct a dihybrid cross. A _____ ratio among the different offspring phenotypes would make you suspect that the genes are linked

Answer 21

12:1:1:4

Question 22

A frequency of recombination that is less than 50% implies:

Answer 22

The genes are linked on the same chromosome.

Question 23

Which of the following most accurately represents how “Hot Dog” Sturtevant created the 1st chromosome map?

Answer 23

He used the data he retrieved from experimental crosses to determine the distance between the genes on the chromosome.

Question 24

Which of the following is a true statement?

ALL TRUE

Answer 24

Genes that are on the same chromosome should be inherited together.
Genes that are on diff chromosomes are not linked.
Genes that are on the same chromosome proceed through meiosis together.

Question 25

Typically, each crossover event produces how many recombinants?

Answer 25

2

Question 26

In a 3 point mapping experiment (means there are 3 linked genes under consideration), how many different classes of offspring are expected?

Answer 26

8

Question 27

The genetic map distance between two loci is roughly equal to

Answer 27

The recombination frequency written as a perecntage.

Question 28

Why doesn’t an exchange between sister chromatids result in the production of a recombinant?

Answer 28

Sister chromatids are genetically identical and therefore an exchange would not show any change in phenotype.

Question 29

There is a gene for flower color in a plant species with wildtype blue and mutant white flowers (f). There is a second gene which determines stalk length (short stalk: wildtype, long stalk: s). 2 plants with genotypes (++fs) are crossed to produce the following offspring:
400 blue, short
400 white, long
100 blue, long
100 white, short
What is the recombination frequency, as shown in the offspring generation?

Answer 29

.20

Question 30

What is a physical map of a chromosome?

Answer 30

Description of the base pair difference between 2 loci

Question 31

What relatively recent scientific advancement has made mapping by linkage or classical genetic mapping approaches virtually obsolete?

Answer 31

the genome sequence of a species

Question 32

What is the concept behind genome wide association sutdies?

Answer 32

Locating genes for particular traits by examining the nonrandom association of a trait with genetic markers from across a genome.

Question 33

What do linkage analysis and genome wide association analysis actually have in common?

Answer 33

Both can give a map showing gene locations in relation to each other.