SEX LINKAGE AND DNA & CHROMOSOME STRUCTURE

Question 1

The term “sex” refers to an organism’s sexual _____.

Answer 1

phenotype

Question 2

Y-linked markers are

Answer 2

DNA sequences on the Y chromosome that vary among individual males.

Question 3

In mammals, each inactivated X chromosome forms a darkly staining body known as a _____ body.

Answer 3

barr

Question 4

Individuals with Turner syndrome most often have which sex chromosomes?

Answer 4

XO

Question 5

A woman who is heterozygous for the sex-linked condition of red–green color blindness marries a man with normal vision. Which of these would you not expect to observe among their possible children?

Answer 5

a son with normal vision and a daughter who is color blind

Question 6

Within each female cell, what is true of X chromosomes that are inactivated?

Answer 6

The X chromosome that is inactivated is random.

Question 7

In XX–XO sex determination, males have which sex chromosomes?

Answer 7

a single X chromosome

Question 8

Studies of rare white-eyed males in Drosophila crosses by _____ demonstrated that the gene for white eyes is on the X chromosome and confirmed the chromosome theory of inheritance.

Answer 8

Bridges

Question 9

Assume that a mutation occurs in the Xist gene of a XY male that makes the gene inactive. What would you expect would be the phenotypic consequences of this mutation for the male?

Answer 9

He would probably have no phenotypic consequences.

Question 10

What is the sexual phenotype for the X:A ratio equal to 1.3?

Answer 10

metafemale

Question 11

How is dosage compensation achieved in fruit flies?

Answer 11

doubling gene activity on the X chromosome of males but not of females

Question 12

In which sex-determining system is the female the heterogametic sex?

Answer 12

ZZ–ZW

Question 13

What does functional hemizygosity mean?

Answer 13

The cells in an individual female are not identical with respect to the expression of the genes on the X chromosome.

Question 14

A eukaryotic diploid cell from an organism with the XX–XO sex determination system has two pairs of autosomes and one X chromosome. One pair of autosomes has a heterozygous locus with alleles A and a. The other pair of autosomes has a heterozygous locus with alleles B and b. What is the probability of a gamete from this individual having this genotype: alleles a and b, without chromosome X?

Answer 14

1/8

Question 15

Fruit flies with XXY sex chromosomes and all other chromosomes normal in number have which sexual phenotype?

Answer 15

female

Question 16

A woman who is homozygous for the sex-linked recessive condition of red–green color blindness marries a man with normal vision. Among their possible children, which of these would you expect not to see?

Answer 16

a boy with normal vision

Question 17

What is the likely proportion of white-eyed and red-eyed flies in a cross between a red-eyed male (X+Y) and a white-eyed female (XwXw)?

Answer 17

50% red-eyed, 50% white-eyed

Question 18

Watson and Crick first proposed that DNA exists as a

Answer 18

double helix.

Question 19

Which enzyme or enzymes destroyed the transforming substance in Avery and colleagues’ experiments?

Answer 19

DNase

Question 20

Please choose the correct answer from the following choices, and then select the submit answer button.

Which of these is not a part of a nucleotide?

a nitrogen-containing base

an -R group

a sugar

a phosphate

Answer 20

an -R group

Question 21

A graduate student hoping to specialize in virology is studying the process of viral DNA integration within host cells by bacteriophages. If they desire to configure a means of mitigating that integration, which of these steps would not help in decreasing bacteriophage replication?

Answer 21

removal of phage head after host attachment

Question 22

Jean is developing a genetics protocol based on base composition. From her sequencing data, she gathered that the ratio of (A + T) to (C + G) is 1:4, respectively. She also noted the RNA strand shown. What is the original DNA strand sequence and structure that is observed?

5’-UAACCUACCGGGGGCCUCGGGCAU-3’

5’-UACGGGCUCCGGGGGCCAUCCAAU-3’; Z-DNA

5’-TAACCTACCGGGGGCCTCGGGCAT-3’; A-DNA

5’-ATGCCCGAGGCCCCCGGTAGGTTA-3; B-DNA

5’-ATGCCCGAGGCCCCCGGTAGGTTA-3’; Z-DNA

Answer 22

5’-ATGCCCGAGGCCCCCGGTAGGTTA-3’; Z-DNA

Question 23

Which of these statements is NOT consistent with Chargaff’s findings about the composition of DNA?

Answer 23

The combined amount of adenine and thymine is equal to the combined amount of guanine and cytosine.

Question 24

If the percentage of cytosine in a sample of DNA is 18%, what is the likely percentage of adenine?

Answer 24

32%

Question 25

The primary structure of DNA can be modified through a process called methylation. Considering nitrogenous bases, which of these sequences is more likely to undergo methylation if found in plant DNA?

Answer 25

5’-CCCCAAACCGTAACCC-3’

Question 26

Each sequence indicates one of two strands of a DNA molecule. The two strands of which molecule would be held together most tightly?

Answer 26

5’-GGGGGGGGGG-3’

Question 27

Chromosomal puffs on polytene chromosomes in Drosophila indicate areas of active

Answer 27

transcription.

Question 28

Most DNA is _____ supercoiled, which eases the separation of the two strands during replication and transcription.

Answer 28

negatively

Question 29

Which statement best describes chromatin associated with actively transcribed genes as compared to chromatin associated with genes which are not being actively transcribed?

Answer 29

more relaxed and more acetylated

Question 30

A stretch of 100 base pairs of DNA contains 15 complete rotations. This DNA molecule is

Answer 30

positively supercoiled.

Question 31

All of these repeated sequences can be found in telomeres EXCEPT

CCGGGG.

TTGGGG.

TTAGGG.

TTAGGC.

Answer 31

CCGGGG.