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_________ .

Accepted Answer

A

Question 2

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

Accepted Answer

Polytene chromosomes are characterized by their structure where the DNA is replicated multiple times without separation, leading to thick, visible chromosomes often seen in certain tissues of dipteran insects like fruit flies. This is different from typical chromosomes that undergo replication and separation during cell division.

Question 3

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

Accepted Answer

Viral chromosomes can be made up of either 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?

Accepted Answer

Nucleosomes are composed of histones, which are a class of proteins that package and organize DNA in eukaryotic cells. H1 histones and nonhistone chromosomal proteins may also be involved in chromatin organization, but the primary components of nucleosomes are the core histones (H2A, H2B, H3, H4). Glycoproteins and lipids are not involved in nucleosome formation or chromatin organization.

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.

Accepted Answer

Linear DNA sediments slower than relaxed circular DNA, which in turn sediments slower than supercoiled DNA due to differences in compactness and shape.

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 .

Accepted Answer

Satellite DNA sequences of about 170 base pairs in length are present in tandem arrays of up to 1 million base pairs, and are found mainly in centromere regions. These DNA sequences are called alphoid families. Telomeres are the protective caps at the ends of chromosomes, euchromatic regions are areas of active gene expression in the genome, primers are short nucleotide sequences used in DNA replication and PCR, and telomere-associated sequences are DNA sequences that interact with telomeres. None of these options accurately describe the identified DNA 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 _________.

Accepted Answer

The condition of varying amounts of DNA is more commonly seen in eukaryotes than in prokaryotes. This is due to differences in the way DNA is organized and regulated in these two types of organisms. Prokaryotes typically have a much simpler genome with limited non-coding regions, while eukaryotes have larger and more complex genomes that include regulatory elements and repetitive sequences. Therefore, there is greater potential for variations in DNA content within eukaryotes.

Question 8

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

Accepted Answer

Eukaryotic chromosomes contain two general domains called heterochromatin and euchromatin. Heterochromatin is highly condensed and contains mostly repetitive DNA and few genes, while euchromatin is less condensed and contains most protein-coding genes. The other answer choices are incorrect.

Question 9

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

Accepted Answer

The answer of How was it experimentally determined that "puffs"...

Question 10

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

Accepted Answer

Chromosomal regions that represent evolutionary vestiges of duplicated copies of genes that have undergone sufficient mutations to render them untranscribable are called pseudogenes. Satellites (A) are highly repetitive DNA sequences found in centromeric regions of chromosomes. Alleles (B) are different versions of the same gene. LINEs (D) are retrotransposons that can transpose by using their own reverse transcriptase enzyme to make cDNA copies of themselves that are inserted elsewhere in the genome. Transposons (E) are pieces of DNA that can move from one location to another within the genome.

Question 11

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

Accepted Answer

The answer of Type I topoisomerases differ from type II...

Question 12

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

Accepted Answer

E.coli has a circular, double-stranded DNA as its genetic material. RNA and protein are involved in gene expression, but they are not the main components of the genetic material. Circular, double-stranded RNA is rare in cells and is usually found in viruses. Polypeptide chains are involved in protein synthesis, but they are not the genetic material. Linear, double-stranded DNA is found in eukaryotic cells, but not in bacteria like E.coli.

Question 13

Describe the chromosomal conformations of ΠX174 and polyomaviruses.

Accepted Answer

The answer of Describe the chromosomal conformations of ΠX174 and...

Question 14

Explain how linear DNA can be supercoiled.

Accepted Answer

The answer of 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?

Accepted Answer

The third category of DNA sequences is moderately repetitive DNA, which involves SINEs (short interspersed nuclear elements), LINEs (long interspersed nuclear elements), and VNTRs (variable number tandem repeats). These are DNA sequences that are present in multiple copies throughout the genome but are not as highly repetitive as the first category. The other answer choices are not correct, as they either do not refer to a third category or involve different types of DNA elements.

Question 16

What is the relationship between topoisomers?

Accepted Answer

The answer of What is the relationship between topoisomers?...

Question 17

Which statement about lampbrush chromosomes is incorrect?

Accepted Answer

Lampbrush chromosomes feature loops that are extended regions of chromatin, which are actively involved in RNA synthesis. These loops are not simply two DNA helices; they are more complex structures involving DNA and proteins, and the axis of the chromosome is also not limited to a single DNA helix but is a complex structure. Thus, the statement about the loops consisting of two DNA helices and the axis consisting of a single DNA helix is incorrect.

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?

Accepted Answer

The answer of A particular variant of the lambda bacteriophage...

Question 19

List several configurations that characterize different viral chromosomes.

Accepted Answer

The answer of List several configurations that characterize different viral...

Question 20

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

Accepted Answer

Condensed areas in polytene and lampbrush chromosomes are referred to as chromomeres.

Quiz 12: DNA Organization in Chromosomes

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_________ .