Exam 3 - Questions Flashcards
c. could affect either sex, but should appear more often in males than females
a number of human diseases/conditions/phenotypes are caused by recessive mutations in genes on the X chromosome. The X-linked recessive traits…
penetrance
what percentage of the individuals with the same genotype will express the phenotype?
expressivity
to what degree is the phenotype expressed in any one individual
A) male, female
In Drosophila, an X0 individual would typically be _______ , while in humans an X0 individual would typically be _______ .
D) is a reversible epigenetic process
X chromosome inactivation _______ .
B) male and female gametes are morphologically distinct
Human gametes are considered anisogamous because _______ .
B) carried on a sex chromosome
If a gene is sex-linked, that means that it is _______ .
A) X and Y are both inactivated as Barr bodies in XXY individuals
Which of the following is not true of the human X and Y chromosomes?
B) 1/4
The ability to taste the chemical phenylthiocarbamide is an autosomal dominant phenotype, and the inability to taste it is recessive. If a taster woman with a non-taster father marries a non-taster man, what is the probability that their first child will be a non-taster girl?
B) 1/4 - Since we know that the woman’s child is a son, in order for him to be affected two things must be true: she must be a carrier (1/2 probability, because her mother was definitely a carrier), and she must pass the DMD allele to her son (1/2 probability).
Duchenne muscular dystrophy (DMD) is X-linked and primarily appears in males. Affected individuals become progressively weaker, starting early in life. A woman whose brother has DMD is pregnant with her first child, a son. What is the probability that this son will be affected with DMD?
B) two - This genotype describes an individual that is heterozygous for five genes (A,B,C,D,E). Genes A,C and D are on the same chromosome, while genes B and E are located on a second chromosome.
How many pairs of homologous chromosomes does the following genotype describe: AcD/aCd; Be/bE ?
D) gene D and gene A - Of the gene pairs presented, only genes D and A are on the same chromosome, which is necessary for genes to exhibit linkage.
Referring again to the genotype described above, which of the following gene pairs could possibly exhibit linkage?
A) occurs during prophase I B) occurs a small number of times per meiotic tetrad C) involves two homologous chromosomes D) is a reciprocal exchange of DNA between non-sister chromatids E) all of the above
Crossing over _______ .
C) 57 red, 57 white, 114 pink - There are 228 total offspring. If the expected 1:2:1 ratio for a dihybrid selfcross with incomplete dominance holds, we expect 1/4 (57) offspring to have red flowers, 1/2 (114) to have pink flowers, and 1/4 (57) to have white flowers.
In snapdragons, the alleles for red flowers (R1) and white flowers (R2) exhibit incomplete dominance, and heterozygotes have pink flowers. From a cross between two pink-flowered plants, you observe the following progeny phenotypes: Red flowers: 70 Whiteflowers: 59 Pink flowers: 99. Based on your understanding of flower color inheritance in snapdragons, how many plants would you expect to observe in each of the three categories?
C) 2 - In this data set, there are three categories (red, white, pink), so df = 3-1 = 2.
In snapdragons, the alleles for red flowers (R1) and white flowers (R2) exhibit incomplete dominance, and heterozygotes have pink flowers. From a cross between two pink-flowered plants, you observe the following progeny phenotypes: Red flowers: 70 Whiteflowers: 59 Pink flowers: 99. How many degrees of freedom are there in your data set?
B) 50% red and 50% pink
In snapdragons, the alleles for red flowers (R1) and white flowers (R2) exhibit incomplete dominance, and heterozygotes have pink flowers. What phenotypes would you expect to observe in the progeny from a cross between a plant with red flowers and a plant with pink flowers?
C) the Curly mutation is homozygous lethal, so curly flies are always heterozygous - This situation is identical to that described for the yellow (AY) allele of the agouti gene in mice, where the AY allele is dominant for yellow fur but displays recessive lethality. A cross between any two yellow mice produces 2/3 yellow and 1/3 agouti, while a cross between any two curly flies produces 2/3 curly and 1/3 non-curly.
In Drosophila, a dominant mutation known as Curly causes a fly’s wings to curl upwards at the tip. Crosses between any two curly-winged flies always produce 2/3 curly and 1/3 non-curly progeny. Which of the following best explains this observation?
C) the phenotypes of both alleles are visible in heterozygotes
In co-dominance, _______ .
E) either B or D are possible for a person with blood type O
A person with blood type O _______ .
E) if two mutations affect the same gene, or different genes
A complementation test is used to determine _______ .
C) 3/16 - This is a dihybrid selfcross, and both parents are IA/IB; H/h. We expect 1/4 of the children to have an IA/IA genotype, but 1/4 of these will have type O blood due to being h/h. To have blood type A, you must be both IA/IA (1/4) and H- (3/4), so the final probability is (1/4) x (3/4) = 3/16.
In a cross between two individuals with AB blood types who are also both carriers of the recessive h allele of the FUT1 gene, what is the probability of one of their children displaying blood type A?
