Deck 11: Chromosome Structure and Dna Sequence Organization

Question 1

What is unusual about the amino acid composition of histones? How is the function of histones related to the amino acid composition? Of which histones are nucleosomes
composed?

Answer 1

Histones contain large amounts of positively charged amino acids such as lysine and arginine. Thus, they can bind electrostatically to the negatively charged
phosphate groups of nucleotides. Nucleosomes are composed of all histones except H1.

Question 2

List the components of a nucleosome.

Answer 2

Histones H2A, H2B, H3, and H4 exist as two types of tetramers: (H2A)2 +
(H2B)2 and (H3)2 + (H4)2.

Question 3

In the formation of nucleosomes, one histone class, H1, is not directly involved, yet it does associate with DNA to form higher -level chromosomal structures. Where does this histone (H1) associate?

Answer 3

in the spaces between nucleosome/DNA complexes

Question 4

How does a polytene chromosome differ from a typical eukaryotic chromosome?

Question 5

Chromatin of eukaryotes is organized into repeating interactions with protein octomers called nucleosomes. Nucleosomes are composed of which class of molecules?

A) lipids
B) nonhistone chromosomal proteins
C) H1 histones
D) glycoproteins
E) histones

Question 6

What are histones, and how are they arranged in nucleosomes?

Question 7

Compare and contrast the chromosome structure of viruses, bacteria, and eukaryotes.

Question 8

What similarities do bacterial chromosomes have with eukaryotic chromosomes?

Question 9

A particular variant of the lambda bacteriophage has a DNA double -stranded genome of 51,365 base pairs. How long would this DNA be?

Question 10

Although mutations have been observed in many different genes, they have not been isolated in histones. Why does this seem reasonable? If one wanted to produce
antibodies to histones, would it be an easy task? Explain your answer.

Question 11

List several configurations that characterize different viral chromosomes.

Question 12

That some organisms contain much larger amounts of DNA than are apparently "needed" and that other relatively closely related organisms may have vastly different amounts of DNA is more typical in _.

A) the alphoid rather than the diphloid family
B) prokaryotes than in eukaryotes
C) RNA viruses than in DNA viruses
D) viruses than in bacteria
E) eukaryotes than in prokaryotes

Question 13

In E. coli, the genetic material is composed of

A) circular, double -stranded RNA
B) linear, double -stranded DNA
C) RNA and protein
D) circular, double -stranded DNA
E) polypeptide chains

Question 14

Viral chromosomes exist in a variety of conformations and can be made up of _.

A) DNA, RNA, or protein
B) protein - or lipid -coding sequences
C) DNA or RNA
D) DNA only
E) RNA only

Question 15

Eukaryotic chromosomes contain two general domains that relate to the degree of
Condensation. These two regions are _.

A) called heterochromatin and euchromatin
B) each void of typical protein -coding sequences of DNA
C) separated by large stretches of repetitive DNA
D) void of introns
E) uniform in the genetic information they contain

Question 16

Describe the basic structure of a nucleosome. What is the role of histone H1?

Question 17

When native chromatin is digested with micrococcal nuclease, what significant result occurs?

Question 18

In addition to highly repetitive and unique DNA sequences, a third category of DNA sequences exists. What is it called, and which types of elements are involved in it?

A) composite DNA; telomeres and heterochromatin
B) multiple gene family DNA; hemoglobin and 5.0S RNA
C) dominant DNA; euchromatin and heterochromatin
D) moderately repetitive DNA; SINEs, LINEs, and VNTRs
E) permissive DNA; centromeres and heterochromatin

Question 19

In human chromosomes, satellite DNA sequences of about 170 base pairs in length are present in tandem arrays of up to 1 million base pairs. Found mainly in centromere regions, these DNA sequences are called _.

A) telomeres
B) euchromatic regions
C) primers
D) alphoid families
E) telomere -associated sequences

Question 20

Describe the chromosomal conformations of $X174 and polyoma viruses.

Question 21

What is the function of a TERRA (telomere repeat -containing RNA)?

Question 22

Viral genomes are always linear, double -stranded DNA.

Question 23

What are minisatellites and microsatellites?

Question 24

How do VNTRs relate to DNA fingerprinting?

Question 25

Approximately how much of the mammalian genome is composed of repetitive DNA?

Question 26

Briefly state what is meant by repetitive DNA.

Question 27

In situ hybridization allows one to "visualize" the location of labeled RNA or DNA in a tissue or cell.

Question 28

Each human contains an identical set of VNTRs.

Question 29

Briefly describe the makeup of VNTRs (variable number tandem repeats).

Question 30

What is meant by SINE in terms of chromosome structure? by LINE? Why are they called "repetitive"?

Question 31

In instances in the eukaryotic genome, DNA sequences represent evolutionary vestiges of duplicated copies of genes. What are such regions called and what are their
characteristics?

Question 32

The E. coli chromosome is circular and double -stranded DNA.

Question 33

Telomerase is an enzyme involved in the replication of the ends of eukaryotic chromosomes.

Question 34

In contrast with euchromatin, heterochromatin contains more genes and is earlier replicating.