Quiz 7 Flashcards
Males are more often affected by sex-linked traits than females because
a) male hormones such as testosterone often alter the effects of mutations on the X chromosome.
b) X chromosomes in males generally have more mutations than X chromosomes in females.
c) males are hemizygous for the X chromosome.
d) mutations on the Y chromosome often worsen the effects of X-linked mutations.
c) males are hemizygous for the X chromosome.
Recombination between linked genes comes about for what reason?
a) Mutation on one homolog is different from that on the other homolog.
b) Independent assortment sometimes fails.
c) When genes are linked they always “travel” together at anaphase.
d) Crossovers between these genes result in chromosomal exchange.
d) Crossovers between these genes result in chromosomal exchange.
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?
a) The mother had a chromosomal duplication.
b) The mother carried a translocation.
c) One member of the couple underwent nondisjunction in gamete production.
d) One member of the couple underwent nondisjunction in somatic cell production.
c) One member of the couple underwent nondisjunction in gamete production.
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following information?
a) DNA contains sulfur, whereas protein does not.
b) DNA contains phosphorus, whereas protein does not.
c) DNA contains nitrogen, whereas protein does not.
d) DNA contains purines, whereas protein includes pyrimidines.
b) DNA contains phosphorus, whereas protein does not.
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long) and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent..?
a) leading strands and Okazaki fragments.
b) lagging strands and Okazaki fragments.
c) RNA primers and mitochondrial DNA.
d) RNA primers and leading strands.
a) leading strands and Okazaki fragments.
Which of the following statements is true of histones?
a) Each nucleosome consists of two molecules of histone H1.
b) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
c) The carboxyl end of each histone extends outward from the nucleosome and is called a “histone tail”.
d) Histones are found in mammals, but not in other animals or in plants or fungi.
b) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
Red-green colour blindness is a sex-linked recessive trait in humans. Two people with normal colour vision have a colour-blind son. What are the genotypes of the parents?
a) XCXC and XCY
b) XCXC and XcY
c) XCXc and XCY
d) XcXc and XCY
e) XcXc and XcY
c) XCXc and XCY
A man who is an achondroplastic dwarf with normal vision marries a colour-blind woman of normal height. The man’s father was 6 feet tall, and both the woman’s parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green colour blindness is X-linked recessive.
How many of their daughters might be expected to be colour-blind dwarfs?
a) all
b) three out of four
c) half
d) one out of four
e) none
e) none
How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?
a) The two genes are closely linked on the same chromosome.
b) The two genes are linked but on different chromosomes.
c) Both of the characters are controlled by more than one gene.
d) Recombination did not occur in the cell during meiosis.
e) The testcross was improperly performed.
a) The two genes are closely linked on the same chromosome.
Which of the following statements is true of linkage?
a) Linked genes are found on different chromosomes.
b) Crossing over occurs during prophase II of meiosis.
c) All of the traits that Mendel studied–seed colour, pod shape, flower colour, and others–are due to genes linked on the same chromosome.
d) The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.
e) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
e) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
Which of the following represents the order of increasingly higher levels of organization of chromatin?
a) nucleosome, looped domain, 30-nm chromatin fibre
b) 30-nm chromatin fibre, nucleosome, looped domain
c) nucleosome, 30-nm chromatin fibre, looped domain
d) looped domain, 30-nm chromatin fibre, nucleosome
e) looped domain, nucleosome, 30-nm chromatin fibre
c) nucleosome, 30-nm chromatin fibre, looped domain
Until the mid-1940s, which molecule was favoured as the molecule of inheritance?
a) carbohydrate
b) lipid
c) DNA
d) RNA
e) protein
e) protein
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
a) It catalyzes the lengthening of telomeres.
b) It stabilizes the unwound parental DNA.
c) It synthesizes RNA nucleotides to make a primer.
d) It unwinds the parental double helix.
e) It joins Okazaki fragments together.
e) It joins Okazaki fragments together.
A new DNA strand elongates only in the 5’ to 3’ direction because
a) Okazaki fragments prevent elongation in the 3’ to 5’ direction.
b) DNA polymerase can only add nucleotides to the free 3’ end.
c) the polarity of the DNA molecule prevents addition of nucleotides at the 3’ end.
d) DNA polymerase begins adding nucleotides at the 5’ end of the template.
e) replication must progress toward the replication fork.
b) DNA polymerase can only add nucleotides to the free 3’ end.
The leading and the lagging strands differ in that
a) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.
b) the leading strand is synthesized by adding nucleotides to the 3’ end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5’ end.
c) the leading strand is synthesized at twice the rate of the lagging strand.
d) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
d) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
In his work with pneumonia-causing bacteria and mice, Griffith found that..?
a) the protein coat from pathogenic cells was able to transform nonpathogenic cells.
b) heat-killed pathogenic cells caused pneumonia.
c) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
d) the polysaccharide coat of bacteria caused pneumonia.
c) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
a) The origins of replication occur only at the 5’ end.
b) Helicases and single-strand binding proteins work at the 5’ end.
c) DNA polymerase can join new nucleotides only to the 3’ end of a growing strand.
d) DNA ligase works only in the 3’ -› 5’ direction.
c) DNA polymerase can join new nucleotides only to the 3’ end of a growing strand.
