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5) A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?
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6) Males are more often affected by sex-linked traits than females because
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Bio - ch 15

QuestionAnswer
5) A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype? normal female
6) Males are more often affected by sex-linked traits than females because males are hemizygous for the X chromosome.
7) SRY is best described in which of the following ways? a gene region present on the Y chromosome that triggers male development
1) When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? The gene involved is on the X chromosome.
3) Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early 20th century? Mendelian genes are at specific loci on the chromosome and in turn segregate during meiosis.
4) Thomas Hunt Morgan's choice of Drosophila melanogaster has been proven to be useful even today. Which of the following has/have continued to make it a most useful species? I and IV only (four pairs of chromosomes, short generation time and large number of offspring)
8) In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? tortoiseshell females; black males
9) Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? XCXc and XCY
10) Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? 100%
11) Calico cats are female because a male inherits only one of the two X-linked genes controlling hair color.
12) Bird males are ZZ, females are ZW. A recessive lethal allele that causes death of the embryo is sometimes on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a heterozygous male and a normal female? 2:1 male to female
14) In humans, clear gender differentiation occurs, not at fertilization, but after the second month of gestation. What is the first event of this differentiation? activation of SRY in male embryos and masculinization of the gonads
17) Which of the following statements is true of linkage? The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
18) How would one explain a testcross involving F1 dihybrid flies in which more parental-type
19) What does a frequency of recombination of 50% indicate? The two genes are likely to be located on different chromosomes.
20) What is the reason that linked genes are inherited together? They are located close together on the same chromosome.
3genes at 3loci are being mappedEach has2phenotypes-1 is markedly different from the wild typeThe allele of the 1st gene is inherited with either of the others about 50% of the timeThe unusual alleles of the other2are inherited together 14.4% of the time The first gene is assorting independently from the other two that are linked.
22) The centimorgan (cM) is a unit named in honor of Thomas Hunt Morgan. To what is it equal? 1% frequency of recombination between two genes
25) Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons? The frequency of crossing over varies along the length of the chromosome.
27) If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis? 1/4 of the gametes will be n + 1, 1/4 will be n - 1, and 1/2 will be n.
male-pattern baldness is controlled by autosomal gene that occurs in 2 forms. Allele Hn determines nonbaldness, al Hb det bald. In males, allele Hb is dom over Hn. If man & woman both w/ genotype HnHb have son, what is chance he will b bald? 75%
33) Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse? expression of inappropriate gene products
34) An inversion in a human chromosome often results in no demonstrable phenotypic effect in the individual. What else may occur? Some abnormal gametes may be formed.
35) What is the source of the extra chromosome 21 in an individual with Down syndrome? nondisjunction or translocation in either parent
36) Down syndrome has a frequency in the U.S. population of ~1/700 live births. In which of the following groups would you expect this frequency to be significantly higher? No groups have such higher frequency.
37) A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition? One member of the couple underwent nondisjunction in gamete production.
45) Genomic imprinting is generally due to the addition of methyl (–CH3) groups to C nucleotides in order to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following must be true? Methylation must be reversible in ovarian and testicular cells.
46) Correns described that the inheritance of variegated color on the leaves of certain plants was determined by the maternal parent only. What phenomenon does this describe? chloroplast inheritance
53) The pedigree in Figure 15.3 shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely mitochondrial.
17) Which of the following statements is true of linkage? The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
24) Why does recombination between linked genes continue to occur? New allele combinations are acted upon by natural selection.
Created by: jonnymac07
 

 



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