Chapter 11: Chromosome Structure and DNA Sequence Organization

Question 1

True or False. Viral chromosomes can exist as circular structures closed loops), or they can take the form of linear molecules.

Answer 1

True

Question 2

What type of chromosome does X174 bacteriophage have?

Answer 2

Circular single stranded DNA

Question 3

What type of chromosome does polyomavirus have?

Answer 3

Circular double stranded DNA

Question 4

What type of chromosome does Lambda bacteriophage have?

Answer 4

linear double-stranded DNA molecule prior to infection but closes to form a ring upon its infection of the host cell.

Question 5

Generally consist of a double-stranded DNA molecule, compacted into a structure sometimes referred to as the nucleoid.

Answer 5

Bacterial chromosome

Question 6

These are types of DNA-binding proteins associated with bacterial chromosomes. These are small but abundant in the cell and contain a high percentage of positively charged amino acids that can bond ionically to the negative charges of the phosphate groups in DNA. They function to fold and bend DNA.

Answer 6

HU and H-NS (Histone like Nucleoid Structure)

Question 7

True of False. Both mitochondria and chloroplasts are inherited through the maternal cytoplasm

Answer 7

True

Question 8

True or False. Eukaryotic Mitochondrial DNA exists as a double-stranded, closed circle that is free of the chromosomal proteins characteristic of eukaryotic chromosomal DNA. However, an exception is found in some ciliated protozoans, in which the DNA is linear. Nor is there usually much in the way of intergenic spacer DNA. Gene repetitions are seldom present.

Answer 8

True

Question 9

True or False. Chloroplast DNA contains an autonomous genetic system distinct from that found in the nucleus and cytoplasm, which has as its foundation a unique DNA molecule (cpDNA). Fairly uniform in size among different organisms, ranging between 100 and 225 kb in length. Circular and double-stranded, and it is free of the associated proteins characteristic of eukaryotic DNA. Duplications of many DNA sequences are also present.

Answer 9

True

Question 10

They are about 200 to 600 mm long and when they are observed under the light microscope, they reveal a linear series of alternating bands and inter-bands.

Answer 10

Polytene Chromosome

Question 11

A generalized term describing lateral condensations of material along the axis of a chromosome.

Answer 11

Chromomeres

Question 12

Strands present in bands (polytene chromosome) undergo localized uncoiling during genetic activity. Each such uncoiling event results in what is called a ____ because of its appearance. Are visible manifestations of gene activity (transcription that produces RNA) is evidenced by their high rate of incorporation of radioactively labeled RNA precursors, as assayed by autoradiography.

Answer 12

Puff

Question 13

Resembles the brushes used to clean kerosene-lamp chimneys in the nineteenth century. They are meiotic chromosomes and are interpreted as extended, uncoiled versions of the normal meiotic chromosomes.

Answer 13

Lampbrush Chromosome

Question 14

True or False. Studies of precise interactions of histone molecules and DNA in the nucleosomes constituting chromatin show that histones H2A, H2B, H3, and H4 occur as two types of tetramers, (H2A)2 • (H2B)2 and (H3)2 • (H4)2. Each repeating nucleosome unit consists of one of each tetramer (creating an octamer) in association with about 200 bp of DNA.

Answer 14

True

Question 15

When nuclease digestion time is extended, some of the 200 bp of DNA are removed from the nucleosome, creating what particle consisting of 147 bp.

Answer 15

nucleosome core

Question 16

11-nm-diameter fiber is further packed into a thicker, 30-nm-diameter structure that was initially called?

Answer 16

Solenoid

Question 17

It is this structure that is characteristic of an uncoiled chromatin fiber in interphase of the cell cycle.

Answer 17

Solenoid

Question 18

30-nm structures are folded into a series of what structure, which further condense the chromatin fiber into a structure that is 300 nm in diameter

Answer 18

Looped domain

Question 19

A _____ is one of the longitudinal subunits of the metaphase chromosome.

Answer 19

Chromatid

Question 20

The chromatin is induced to change its structure to accommodate protein–DNA interactions. This process is called?

Answer 20

Chromatin remodeling

Question 21

A chromatin remodeling process that involves the addition of an acetyl group to the positively charged amino group present on the side chain of the amino acid lysine effectively changes the net charge of the protein by neutralizing the positive charge.

Answer 21

Acetylation

Question 22

Acetylation is a histone modification by the action of the what enzyme?

Answer 22

histone acetyltransferase (HAT)

Question 23

True or False. High levels of acetylation open up, or remodel, the chromatin fiber, an effect that increases in regions of active genes and decreases in inactive regions.

Answer 23

True

Question 24

Chromatin remodeling that involves the addition of methyl group to both arginine and lysine residues of histones, and these changes can either increase or decrease transcription depending on which amino acids are methylated.

Answer 24

Methylation

Question 25

Chromatin remodeling that involves the addition of phosphate group to the hydroxyl groups of the amino acids serine and histidine, introducing a negative charge on the protein.

Answer 25

Phosphorylation

Question 26

Phosphorylation is a histone modification by the action of the what enzyme?

Answer 26

kinase

Question 27

Methylation is a histone modification by the action of the what enzyme?

Answer 27

histone methyltransferase

Question 28

It is usually negatively correlated with gene activity (the operation of this chromatin remodeling leads to gene heterochromatinization) and occurs most often when the nucleotide cytidylic acid is next to the nucleotide guanylic acid, forming what is called a CpG island.

Answer 28

Cytosine methylation

Question 29

Cytosine methylation occurs most often when the nucleotide cytidylic acid is next to the nucleotide guanylic acid, forming what is called?

Answer 29

CpG island

Question 30

Parts of chromosomes that are uncoiled.

Answer 30

Euchromatin

Question 31

True or False. Heterochromatin replicates later during the S phase of the cell cycle than euchromatin does.

Answer 31

True

Question 32

Genetically active areas sometimes become genetically inert if they lie adjacent to the translocated heterochromatin. This is an example of a genetic phenomenon called?

Answer 32

Position effect (position of a gene or group of genes relative to all other genetic material may affect their expression)

Question 33

Parts of chromosomes that remain condensed.

Answer 33

Heterochromatin

Question 34

Made it possible to distinguish such chromosomes from one another as a result of differential staining along the longitudinal axis of mitotic chromosomes.

Answer 34

Chromosome banding

Question 35

This cytogenetic technique involves the digestion of the mitotic chromosomes with the proteolytic enzyme trypsin, followed by Giemsa staining.

Answer 35

G-banding

Question 36

G banding stains regions of the DNA that is rich in what specific base pairs?

Answer 36

A-T base pairs

Question 37

This cytogenetic technique uses chromosome preparations that are heat denatured. Subsequent Giemsa staining reveals only the heterochromatic regions of the centromeres.

Answer 37

C-banding

Question 38

Rapid reassociation was characteristic of multiple DNA fragments composed of identical or nearly identical nucleotide sequences. This process results to DNA structure called?

Answer 38

Repetitive DNA

Question 39

True or False. While some functional genes are present in more than one copy (repetitive), the majority of repetitive sequences are non-genic, and in fact, most serve no known function.

Answer 39

True

Question 40

These repetitive DNA structures are found in the heterochromatic centromeric regions of chromosomes.

Answer 40

Satellite DNA

Question 41

True or False. Satellite DNA falls in the category of highly repetitive DNA.

Answer 41

True

Question 42

These repetitive DNA structures are known to consist of relatively short sequences repeated a large number of times. These sequences are present as tandem repeats clustered in very specific chromosomal areas known to be heterochromatic—the regions flanking centromeres.

Answer 42

highly repetitive DNA.

Question 43

Minimal region of the centromere that supports the function of chromosomal segregation.

Answer 43

CEN region

Question 44

The most recognized satellite DNA sequences found mainly in the centromere regions of the eukaryotic chromosome.

Answer 44

Alphoid family

Question 45

In alphoid family, H3 histone, a normal part of most all eukaryotic nucleosomes, is substituted by a variant histone designated as?

Answer 45

CENP-A

Question 46

15 to 100 bp long and are found within and between genes. Many such clusters are dispersed throughout the genome and are often referred to as minisatellites. BNumber of tandem copies of each specific sequence at each location varies from one individual to the next

Answer 46

Variable number tandem repeats

Question 47

Repeated sequences consist of di-, tri-, tetra-, and pentanucleotides. Dispersed throughout the genome and vary among individuals in the number of repeats present at any site.

Answer 47

Microsatellites or Short tandem repeats

Question 48

Alu family is a type of repetitive transposed sequences called?

Answer 48

Short Interspersed Elements

Question 49

Some members of this sequence family are transcribed into RNA, although the specific role of this RNA is not certain. The consequence is their potential for transposition within the genome, which is related to chromosome rearrangements during evolution.

Answer 49

Alu family (short interspersed elements)

Question 50

Members of this sequence family are about 6400 base pairs long and are present up to 500,000 times. Their 5′-end is highly variable, and their role within the genome has yet to be defined. Are also referred to as retrotransposons because of the similarity of the process through which they get transposed to the process of infection of retrovirus

Answer 50

L1 family (long interspersed elements)

Question 51

L1 family is a type of repetitive transposed sequences called?

Answer 51

Long Interspersed Elements

Question 52

These are DNA sequences representing evolutionary vestiges of duplicated copies of genes that have undergone significant mutational alteration. Only a very small part of the genome actually codes for proteins.

Answer 52

Pseudogenes