Exam 2 Flashcards
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?
30 chromosomes containing 10 ng of DNA
A nondisjunction during Meiosis I occurs when the ____ fail to separate, resulting in ____ gametes that are abnormal
Homologous chromosomes, 4
When does homologous chromosome pairing and recombination occur?
prophase I
If a trait is X-linked recessive, who would express the trait?
Homozygous recessive females and hemizygous recessive males
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.
Some of their male progeny may have white eyes
Syntenic genes can assort independently when
They are far apart on a chromosome and crossing over occurs frequently between the genes
Most combinations of different ABO alleles result in complete dominance of one allele. Which combination results in codominance?
IAIB
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?
Fewer than four phenotypes
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?
Chi square analysis
The tendency of alleles of linked genes to segregate together during meiosis can be broken by _______
recombination
An XXX female is a result of _____ during Meiosis
Nondisjunction
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.
DNA replication
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 ___
Incomplete penetrance
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.
40, 20, 20
If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?
One gamete will be n+1, one will be n-1, and two will be n
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?
1:1:1:1
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?
X linked dominant
Which of the following most closely states what the chi-square test measures?
How well the expected and observed data correlate
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?
1/8
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
12:3:1
If a male is affected with an X linked dominant trait, what proportion of his offspring can be expected to express this trait?
All daughters and no sons
Calico cats are always female because
The maternal X chromosome is always heterochromatized into a barr body
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
Nondisjunction occurred in the mother for the color blind child and in the father for the child with normal vision
How many barr bodies would be present in cells of an individual of karyotype 44+XXX
2
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?
1/4
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?
0
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?
1/8
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?
Pleiotropy
Two alleles of a gene are incompletely dominant. Crossing individuals that are heterozygous for these two alleles will produce the following phenotypic ratio
1:2:1
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.
19,19
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
calico female
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?
All fo the F1 progeny would be wild-type
