Deck 12: DNA Organization in Chromosomes

Question 1

This figure represents supercoiled,circular,double- stranded DNA: If this molecule of DNA originated as a linear molecule with a linking number L of 30,which was then circular unwound,the L for the unwound circular molecule would be_________ .

A)28
B)30
C)18
D)20
E)32

Answer 1

28

Question 2

In which of the following ways do polytene chromosomes differ from other chromosomes?

A)Polytene chromosomes represent uncoiled versions of meiotic chromosomes.
B)Polytene chromosomes are multiple copies of identical single- stranded DNA.
C)Polytene chromosomes can only be found in bacteria.
D)Polytene chromosomes are separated but not replicated.
E)Polytene chromosomes are replicated but not separated.

Answer 2

E

Question 3

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

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

Answer 3

DNA or RNA

Question 4

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

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

Question 5

If relaxed circular DNA is designated R ,supercoiled circular DNA is designated S) and linear DNA is designated L ,arrange these conformations in order of increasing rate of sedimentation during centrifugation.

A)L ,S ,R
B)S ,L ,R
C)S ,R ,L
D)R ,S ,L
E)L),R),S)

Question 6

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

Question 7

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

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

Question 8

Eukaryotic chromosomes contain two general domains that relate to the degree of condensation.These two regions are_________ .

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

Question 9

How was it experimentally determined that "puffs" are transcriptionally active?

Question 10

Chromosomal regions that represent evolutionary vestiges of duplicated copies of genes that have underdone sufficient mutations to render them untranscribable are called_________ .

A)satellites
B)alleles
C)pseudogenes
D)LINEs
E)transposons

Question 11

Type I topoisomerases differ from type II topoisomerases in that the type I enzymes_________ .

A)induce negative supercoiling
B)cleave both strands of a double helix
C)cleave one strand of a double helix
D)decrease the linking number L of a double helix
E)ligate fragments of DNA that have been hydrolyzed

Question 12

In E.coli,the genetic material is composed of _________.

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

Question 13

Describe the chromosomal conformations of ΠX174 and polyomaviruses.

Question 14

Explain how linear DNA can be supercoiled.

Question 15

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

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

Question 16

What is the relationship between topoisomers?

Question 17

Which statement about lampbrush chromosomes is incorrect?

A)More DNA is looped out from the axis than is required for a single gene.
B)They are meiotic chromosomes.
C)Looped out regions are active in RNA synthesis.
D)The loops consist of two DNA helices,whereas the axis consists of a single DNA helix.
E)Instead of being condensed,they are extended.

Question 18

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 19

List several configurations that characterize different viral chromosomes.

Question 20

The condensed areas in polytene and lampbrush chromosomes are referred to as_________ .

A)centromeres
B)chiasmata
C)chromomeres
D)chromatids
E)puffs

Question 21

How do VNTRs relate to DNA fingerprinting?

Question 22

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

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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 28

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

Question 29

What are minisatellites and microsatellites?

Question 30

Briefly state what is meant by repetitive DNA.

Question 31

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?

Question 32

List the components of a nucleosome.

Question 33

What similarities do bacterial chromosomes have with eukaryotic chromosomes?

Question 34

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?

Question 35

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

Question 36

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 37

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