TEST 2 Flashcards
Which regions of the X chromosome can recombine during meiosis?
the pseudoautosomal regions
In mammals, dosage compensation for X linked genes is achieved by:
Inactivation of one X chromosome during early development
An X chromosome that has been inactivated becomes a ______ in female mammals.
Barr body
An organism that has only one copy of a gene is called a
Hemizygote
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?
Red-eyed females and white-eyed males
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?
0%
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____
all of his daughters.
Sex linked conditions are more common in men than woman bc
men need to inherit only one copy of the recessive allele for the condition to be fully expressed
Which of the following is the part of the Y chromosome that is critical for normal male development?
SRY
An individuals with 2 kinds of gametes (X bearing and Y bearing) is referred to as
Heterogametic
Pedigree
Recessive, autosomal
Why is the Y chromosome able to pair with the x chromosome during meiosis?
The X and Y chromosomes share small gene segments that allow them to act like homologues during meiosis.
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:
Genetic mosaics
In some animal species, like humans, sex is determined by:
The presence of the Y chromosome
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?
The only sources of the lethal allele in the population are heterozygous females who are carriers and do not express the disorder
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?
1/2
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?
0
Which of the following is required to unambiguously link a gene to a chromosome?
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.
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?
Drosophila
The centimorgan (cM) is a unit named in honor of Thomas Hunt Morgan. To what is it equal?
1% frequency of recombination between 2 genes.
You conduct a dihybrid cross. A _____ ratio among the different offspring phenotypes would make you suspect that the genes are linked
12:1:1:4
A frequency of recombination that is less than 50% implies:
The genes are linked on the same chromosome.
Which of the following most accurately represents how “Hot Dog” Sturtevant created the 1st chromosome map?
He used the data he retrieved from experimental crosses to determine the distance between the genes on the chromosome.
Which of the following is a true statement?
ALL TRUE
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.
Typically, each crossover event produces how many recombinants?
2
In a 3 point mapping experiment (means there are 3 linked genes under consideration), how many different classes of offspring are expected?
8
The genetic map distance between two loci is roughly equal to
The recombination frequency written as a perecntage.
Why doesn’t an exchange between sister chromatids result in the production of a recombinant?
Sister chromatids are genetically identical and therefore an exchange would not show any change in phenotype.
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?
.20
What is a physical map of a chromosome?
Description of the base pair difference between 2 loci
What relatively recent scientific advancement has made mapping by linkage or classical genetic mapping approaches virtually obsolete?
the genome sequence of a species
What is the concept behind genome wide association sutdies?
Locating genes for particular traits by examining the nonrandom association of a trait with genetic markers from across a genome.
What do linkage analysis and genome wide association analysis actually have in common?
Both can give a map showing gene locations in relation to each other.
