12. DNA organization in Chromosomes

Question 1

Genetic information in viruses, bacteria, mitochondria,
and chloroplasts, with some exceptions, is contained in
a what shape

Answer 1

circular DNA molecule relatively free of associated proteins

Question 2

in contrast to viruses and bacteria,
contain large amounts of DNA that during most of the
cell cycle is organized into nucleosomes and is present
as either uncoiled chromatin fibers or more condensed
structures.

Answer 2

eukaryotic cells

Question 3

in contrast to viruses and bacteria,
contain large amounts of DNA that during most of the
cell cycle is organized into ___and is present
as either uncoiled chromatin fibers or more condensed
structures.

Answer 3

nucleosomes

Question 4

The uncoiled chromatin fibers characteristic of __coil up and condense into chromosomes during
the stages of eukaryotic cell division.

Answer 4

interphase

Question 5

Whereas ___genomes consist of mostly unique
DNA sequences coding for proteins, ___
genomes contain a mixture of both unique and
repetitive DNA sequences.

Answer 5

bacterial
eukaryotic

Question 6

Eukaryotic genomes consist mostly of ___DNA
sequences.

Answer 6

noncoding

Question 7

are largely devoid of associated proteins and contain relatively less genetic information.

Answer 7

bacterial chromosomes

Question 8

dna of X174 bacteriophage

Answer 8

single stranded

Question 9

possesses a linear doublestranded DNA molecule prior to infection, but it closes
to form a ring upon infection of the host cell.

Answer 9

bacteriophage lambda

Question 10

They always consist of a double-stranded DNA molecule, compacted into a structure sometimes referred to as
the

Answer 10

nucleoid

Question 11

DNA in bacterial chromosomes is found to be associated with several types of DNA-binding proteins.
Two, called

Answer 11

HU and H-NS proteins

Question 12

which is particularly characteristic of closed-circular molecules.

was first proposed as a result of a study of double-stranded
DNA molecules derived from the polyoma virus, which
causes tumors in mice

Answer 12

supercoiled DNA

Question 13

to contort in a certain way, in order to retain normal base pairing.

Answer 13

supercoil

Question 14

In 1963, it was observed that when
the polyoma DNA was subjected to high-speed centrifugation, it was resolved into three distinct components, each of
different density and compactness. The one that was least
dense and thus least compact was subsequently proposed
by

Answer 14

Jerome Vinograd

Question 15

Consider a double-stranded linear molecule
existing in the normal Watson–Crick right-handed helix
[Figure 12.4(a)]. This helix contains 20 complete turns,
which means the ___ of the molecule is 20

Answer 15

linking number

Question 16

Two otherwise identical molecules that differ only in
their linking number are said to be ___of one
another

Answer 16

topoisomers

Question 17

First discovered by Martin Gellert and
James Wang, these catalytic molecules are known as either
type I or type II, depending on whether they cleave one or
both strands in the helix, respectively

Answer 17

topoisomerases

Question 18

who discovered topoisomerases

Answer 18

martin gellert
james wang

Question 19

serves to reduce the number of negative supercoils
in a closed-circular DNA molecule.

Answer 19

topoisomerase I

Question 20

introduces negative supercoils into DNA. This latter enzyme
is thought to bind to DNA, twist it, cleave both strands,
and then pass them through the loop that it has created

Answer 20

topoisomerase II

Question 21

are found in various tissues
(salivary, midgut, rectal, and malpighian excretory tubules)
in the larvae of some flies, as well as in several species of
protozoans and plants. They were first observed by
E. G. Balbiani in 1881

Answer 21

polytene chromosomes

Question 22

chromosomes that can be seen in the nuclei of interphase cells

Answer 22

polytene chromosomes

Question 23

The banding pattern is distinctive for each
chromosome in any given species. Individual bands
are sometimes called

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

Answer 23

chromomeres

Question 24

Each such uncoiling event results
in a bulge called a __, so named because of its appearance
under the microscope

Answer 24

puff

Question 25

so named because it resembles the brushes used to clean kerosene lamp chimneys in the nineteenth century

Answer 25

lampbrush chromosome

Question 26

They are now known to be characteristic of most vertebrate oocytes as well as the spermatocytes of some insects. Therefore, they are meiotic chromosomes. Most of the experimental work on them has been done with material taken from amphibian oocytes

Answer 26

lampbrush chromosome

Question 27

who discovered lampbrush chromosome

Answer 27

Walther Flemming J. Ruckert

Question 28

However, after chromosome separation and cell division, cells enter the interphase stage of the cell cycle, at which time the components of the chromosome uncoil and decondense into a form referred to as

Answer 28

chromatin

Question 29

The associated proteins can be categorized as either positively charged __ or less positively charged nonhistone proteins. O

Answer 29

hisotnes

Question 30

To accommodate these protein–DNA interactions, chromatin must be induced to change its structure, a process now referred to as

Answer 30

chromatin remodelling

Question 31

the study of modifications of an organism’s genetic and phenotypic expression that are not attributable to alteration of the DNA sequence making up a gene

Answer 31

epigenetics

Question 32

the parts of chromosomes that are uncoiled a

Answer 32

euchromatin

Question 33

part of chromosome that remain condensed

Answer 33

heterochromatin

Question 34

the position of a gene or group of genes relative to all other genetic material may affect their expression.

Answer 34

position effect

Question 35

cytological procedures were developed that made possible differential staining along the longitudinal axis of mitotic chromosomes.

Answer 35

chromosomal banding techniques

Question 36

one of the first chromosome banding techniques was devised by

Answer 36

Mary Lou Pardue Joe Gall

Question 37

Only the centromeric regions of mitotic chromosomes took up the stain! The staining pattern was thus referred to as

Answer 37

C-banding

Question 38

Other chromosome-banding techniques were developed at about the same time. The most useful of these techniques produces a staining pattern differentially along the length of each chromosome. This method, producing

Answer 38

G-bands

Question 39

Some functional genes are present in more than one copy referred to as

Answer 39

multiple-copy genes

Question 40

However, one or more additional peaks indicate the presence of DNA that differs slightly in density. This component, called

Answer 40

satellite DNA

Question 41

his was discovered in 1969 when several researchers, including Mary-Lou Pardue and Joe Gall, applied the technique of i___ ___to the study of satellite DNA

Answer 41

in situ hybridization

Question 42

described cytologically in the late nineteenth century as the primary constrictions along eukaryotic chromosomes

Answer 42

centromeres

Question 43

The minimal region of the centromere that supports the function of chromosomal segregation is designated the

Answer 43

CEN region

Question 44

Within this heterochromatic region of the chromosome, the DNA binds a platform of proteins, which in multicellular organisms includes the ___that binds to the microtubules making up the spindle fiber during division

Answer 44

kinetochore

Question 45

In humans, one of the most recognized satellite DNA sequences is the ___ family, found mainly in the centromere regions

Answer 45

alphoid

Question 46

each about 170 bp in length, are present in tandem arrays of up to 1 million base pairs. It is now believed that such repetitive DNA in eukaryotes is transcribed and that the RNA that is produced is ultimately involved in kinetochore function

Answer 46

alphoid family

Question 47

These repeating DNA sequences may be 15–100 bp long and are found within and between genes. Many such clusters are dispersed throughout the genome, and they are often referred to as minisatellites

Answer 47

variable number tandem repeats (VNTRs)

Question 48

the variation in size (length) of these regions between individual humans was originally the basis for the forensic technique referred to as

Answer 48

DNA fingerprinting

Question 49

Another group of tandemly repeated sequences consists of di-, tri-, tetra-, and pentanucleotides, also referred to as

Answer 49

microsatellites or short tandem repeats

Question 50

which are mobile and can potentially move to different locations within the genome.

Answer 50

transposable sequences

Question 51

are less than 500 base pairs long and may be present 1,500,000 times or more in the human genom

Answer 51

short interspersed elements (SINEs)

Question 52

The best characterized human SINE is a set of closely related sequences called the the name is based on the presence of DNA sequences recognized by the restriction endonuclease Alu I). Members of this DNA family, also found in other mammals, are 200–300 base pairs long and are dispersed rather uniformly throughout the genome, both between and within genes

Answer 52

alu family

Question 53

represents yet another category of repetitive transposable DNA sequences.

Answer 53

long interspersed elements (LINEs)

Question 54

The new L1 copy then integrates into the DNA of the chromosome at a new site. Because of the similarity of this transposition mechanism to that used by retroviruses, LINEs are referred to a

Answer 54

retrotransporoons

Question 55

These are DNA sequences representing evolutionary vestiges of duplicated copies of genes that have undergone significant mutational alteration

Answer 55

pseudogenes