chapter 5

Question 1

proteins _: they _

Answer 1

perform most of the cell’s functions:
serve as building blocks for cell structures; they form the enzymes that catalyze the cell’s chemical reactions; they regulate the activity of genes; and they enable cells to move and to communicate with one another.

Question 2

chro- mosomes contain both _ and _

Answer 2

DNA
protein

Question 3

DNA, after all, is simply a _ composed of _, which are _.

Answer 3

long polymer
only four types of nucleotide subunits
chemically very similar to one another

Question 4

DNA=

Answer 4

deoxyribonucleic acid (DNA)

Question 5

the two strands are held together by _ bonds

Answer 5

hydrogen

Question 6

With the exception of the _ (_) and highly special- ized cells that _ (such as _), human cells each contain two copies of every chromosome, one inherited from the mother and one from the father.

Answer 6

gametes
sperm and eggs
lack DNA entirely
mature red blood cells

Question 7

Each chromosome can be “_” a different color using _

Answer 7

painted
_
sets of chromosome-specific DNA molecules coupled to different fluorescent dyes.

Question 8

An earlier and more traditional way of distinguishing one chromosome from another involves _.

Answer 8

staining the chromosomes with dyes that bind to certain types of DNA sequences
_
These dyes mainly distin- guish between DNA that is rich in A-T nucleotide pairs and DNA that is G-C rich, and they produce a predictable pattern of bands along each type of chromosome. The resulting patterns allow each chromosome to be identified and numbered.

Question 9

An ordered display of the full set of _ human chromosomes is called the human _

Answer 9

46
karyotype

Question 10

_ analyze karyotypes to detect chromosomal abnormalities that are associated with some _ (Figure 5–9) and with certain types of _

Answer 10

Cytogeneticists
inherited disorders
cancer

Question 11

A gene is often defined as a _

Answer 11

segment of DNA that contains the instructions for making a particular protein or RNA mol- ecule.

Question 12

Together, the total genetic information carried by a complete set of the chromosomes present in a cell or organism constitutes its _.

Answer 12

genome

Question 13

the total number of genes is about _ for the simplest bacterium and about _ for humans.

Answer 13

500
24,000

Question 14

However, chromosomes from many eukaryotes—includ- ing humans—contain, in addition to genes and the specific nucleotide sequences required for normal gene expression, a large _

Answer 14

excess of interspersed DNA

Question 15

DNA must be able to be replicated, and the replicated copies must be separated and partitioned equally and reliably into the two daughter cells at each cell division. These processes occur through an ordered series of events, known collectively as the _.

Answer 15

cell cycle

Question 16

_, when chro- mosomes are duplicated, and _, the much more brief stage when the duplicated chromosomes are distributed, or segregated, to the two daughter nuclei.

Answer 16

interphase
mitosis

Question 17

One type of nucleotide sequence, called a _, is where DNA replication begins; eukaryotic chromosomes contain _ to _

Answer 17

replication origin
many replication origins
allow the long DNA molecules to be replicated rapidly

Question 18

Another DNA sequence forms the _ that mark the ends of each chromosome. Telomeres contain _ that are required for the ends of chromosomes to be _.

Answer 18

telomeres
repeated nucleotide sequences
fully replicated

Question 19

telomeres also serve as a _ that keeps the chromosome tips from _.

Answer 19

protective cap
_
being mistaken by the cell as broken DNA in need of repair.

Question 20

Eukaryotic chromosomes also contain a third type of specialized DNA sequence, called the _, that allows duplicated chromosomes to be separated during M phase (see Figure 5–14). During this stage of the cell cycle, the DNA coils up, adopting a more and more compact structure, ultimately forming highly compacted, or condensed, mitotic chromosomes

Answer 20

centromere

Question 21

The proteins that bind to DNA to form eukaryotic chromosomes are traditionally divided into two general classes: the _ and the _ chromosomal proteins.
The complex of both classes of protein with nuclear DNA is called _.

Answer 21

histones
nonhistone
chromatin

Question 22

Histones are responsible for the first and most fundamental level of chromatin packing: the formation of the _.

Answer 22

nucleosome

Question 23

The interphase nucleus is the _

Answer 23

nucleus of a cell when it is not dividing

Question 24

Eukaryotic cells have several ways to adjust rapidly the local structure of their chromatin. One way takes advantage of a set _. These protein machines use the energy of ATP hydrolysis to change the position of the DNA wrapped around _

Answer 24

of ATP-dependent chromatin-remodeling complexes
_
nucleosomes

Question 25

Interphase chromatin is not uniformly packed. Instead, regions of the chromosome containing genes that are being actively expressed are generally more _, whereas those that contain silent genes are more _.

Answer 25

extended condensed

Question 26

The most highly condensed form of interphase chromatin is called _

Answer 26

heterochromatin

Question 27

Heterochromatin typically makes up about 10% of an interphase chromosome, and in mammalian chromosomes, it is concentrated around the _ region and in the _ DNA at the chromosome ends

Answer 27

centromere telomeric

Question 28

we use the term euchromatin to refer to _

Answer 28

chromatin that exists in a less condensed state than heterochromatin

Question 29

In female mammals, one X chromosome is _ to prevent _ of X-linked genes. This inactivation occurs randomly in early embryonic development by _

Answer 29

inactivated overexpression the X chromatin being highly condensed forming heterochromatin --> inactivation

Question 30

Life depends on the _, _, and _ of genetic information.

Answer 30

stable storage maintenance inheritance

Question 31

Genetic information is carried by _ and is encoded in _.

Answer 31

very long DNA molecules _ the linear sequence of four nucleotides: A, T, G, and C

Question 32

Each molecule of DNA is a _ composed of _, _, which are held together by _ between _.

Answer 32

double helix a pair of antiparallel complementary DNA strands hydrogen bonds G-C and A-T base pairs

Question 33

The genetic material of a eukaryotic cell—its _—is contained in _, each formed from _.

Answer 33

genome _ a set of chromosomes _ a single, enormously long DNA molecule that contains many genes

Question 34

When a gene is expressed, part of _ is _, most of which are _.

Answer 34

its nucleotide sequence transcribed into RNA molecules translated to produce a protein

Question 35

The DNA that forms each eukaryotic chromosome contains, in addition to _, many _, one _, and _. These special DNA sequences ensure that, before cell division, each chromosome can be _, and that the resulting daughter chromosomes can be parceled out _.

Answer 35

genes replication origins centromere two telomeres duplicated efficiently equally to the two daughter cells

Question 36

In eukaryotic chromosomes, the DNA is tightly folded by _. This complex of DNA and protein is called _.

Answer 36

binding to a set of histone and nonhistone chromosomal proteins _ chromatin

Question 37

Histones _–protein particles called _, which further _.

Answer 37

pack the DNA into a repeating array of DNA _ nucleosomes _ fold up into even more compact chromatin structures

Question 38

A cell can regulate _—temporarily _ or _ particular regions of its chromosomes—using _ and _ in various ways.

Answer 38

its chromatin structure decondensing condensing chromatin-remodeling complexes enzymes that covalently modify histone tails

Question 39

The loosening of chromatin to a more decondensed state allows proteins involved in _, _, and _ to gain _

Answer 39

gene expression DNA replication DNA repair access to the necessary DNA sequences.

Question 40

Some forms of chromatin have a pattern of _ that causes the DNA to become so highly condensed that its genes _; a high degree of condensation occurs on all chromosomes during _ and in the _.

Answer 40

histone tail modification cannot be expressed to produce RNA mitosis heterochromatin of interphase chromosomes

Question 41

The 5' end of the sugar has a _ attached to the _.

Answer 41

phosphate group 5th carbon

Question 42

The 3' end of the sugar has a _ (-OH) attached to the _. This is the site where _ during the _.

Answer 42

hydroxyl group 3rd carbon new nucleotides are added elongation of the DNA/RNA strand

Question 43

DNA is made of four _

Answer 43

nucleotide building blocks.

Question 44

Each nucleotide is composed of _

Answer 44

a sugar phosphate covalently linked to a base

Question 45

The nucleotides are _ linked together into _, with a _ from which the _—_, _, _, and _ (A, C, G, and T)—extend.

Answer 45

covalently polynucleotide chains sugar-phosphate backbone bases adenine cytosine guanine thymine

Question 46

A DNA molecule is composed of _ polynucleotide chains (DNA strands) held together by _

Answer 46

two _ hydrogen bonds between the paired bases.

Question 47

polarity at the _ end

Answer 47

3'

Question 48

_ hydrogen bonds form between A and T, whereas _ form between G and C

Answer 48

two three

Question 49

The bases can pair in this way only if the two polynucleotide chains that contain them are _

Answer 49

antiparallel

Question 50

DNA has at chemical _; that is, _

Answer 50

polarity its two ends are chemically different

Question 51

Most genes contain information to make _.

Answer 51

proteins

Question 52

Note that for a minority of genes, the final product is the _. In these cases, _ is complete once the nucleotide sequence of the DNA has been transcribed into the _.

Answer 52

RNA molecule itself gene expression nucleotide sequence of its RNA

Question 53

Chromosome painting is done by exposing the _ tagged with _. The labeled DNA probes can only bind to their matching sequences on the chromosome (hybridization).

Answer 53

chromosomes to single-stranded DNA molecules _ fluorescent dyes

Question 54

each “gene” is considered to include both _

Answer 54

the “coding strand” and its complement.

Question 55

_ DNA sequence elements are needed to produce a eukaryotic chromosome that can be duplicated and then segregated at mitosis. Each chromosome has _, one _, and two _.

Answer 55

Three multiple origins of replication centromere telomeres

Question 56

The DNA replicates in _, beginning at the _ and proceeding _along the chromosome.

Answer 56

interphase origins of replication bidirectionally from each origin

Question 57

In M phase, the _ attaches the _ to the _ so that one _.

Answer 57

centromere _ compact, duplicated chromosomes _ mitotic spindle _ copy will be distributed to each daughter cell when the cell divides

Question 58

Prior to cell division, the centromere also helps to hold the _.

Answer 58

duplicated chromosomes together until they are ready to be pulled apart

Question 59

Telomeres contain _ that allow for the _.

Answer 59

DNA sequences complete replication of chromosome ends

Question 60

The nucleolus is the most prominent structure in the _

Answer 60

interphase nucleus.

Question 61

The _ is the most prominent structure in the interphase nucleus.

Answer 61

nucleolus

Question 62

Heterochromatin contains _ genes and is located _ of the nucleus, immediately under the _.

Answer 62

few mainly around the periphery nuclear envelope

Question 63

The large, dark region within the nucleus is the _, which contains the _

Answer 63

nucleolus genes for ribosomal RNAs.

Question 64

Nucleosomes contain _.

Answer 64

DNA wrapped around a protein core of eight histone molecules

Question 65

When the DNA around each isolated nucleosome core particle is released, its length is found to be _ nucleotide pairs

Answer 65

147

Question 66

“beads-on-a-string” form of _

Answer 66

chromatin

Question 67

The chromatin in human chromosomes is folded into looped domains. These loops are established by _ that bind to specific DNA sequences, creating a clamp at the base of each loop.

Answer 67

special nonhistone chromosomal proteins

Question 68

after DNA packing, EACH DNA MOLECULE HAS BEEN PACKAGED INTO A _ THAT IS _ SHORTER THAN ITS FULLY EXTENDED LENGTH

Answer 68

MITOTIC CHROMOSOME 10,000-FOLD

Question 69

_ locally reposition the DNA wrapped around nucleosomes. This large complex contains _ subunits, including one that _ and four that recognize _.

Answer 69

Chromatin-remodeling complexes 15 hydrolyzes ATP specific covalently modified histones

Question 70

Chromatin-remodeling complexes use _ to loosen the _ and push it along the _. the enzyme can _ a sequence of DNA, controlling its availability to other _

Answer 70

energy derived from ATP hydrolysis nucleosomal DNA histone octamer expose or hide DNA-binding proteins.

Question 71

The pattern of modification of histone tails can determine _.

Answer 71

how a stretch of chromatin is handled by the cell

Question 72

most modifications occur on the _, for which _ amino acids are shown.

Answer 72

N-terminal tail 36

Question 73

Acetylation of lysines, for instance, can reduce the _ of the tails for adjacent nucleosomes, thereby _ chromatin structure and _ particular nuclear proteins.

Answer 73

affinity loosening allowing access to

Question 74

Both ATP-dependent chromatin-remodeling complexes and _ are tightly regulated.

Answer 74

histone-modifying enzymes

Question 75

Histone-modifying enzymes work in concert with the chromatin-remodeling complexes to _, allowing local chromatin structure to change rapidly according to the needs of the cell.

Answer 75

condense and relax stretches of chromatin

Question 76

_ work in concert with the _ to condense and relax stretches of chromatin, allowing local chromatin structure to change rapidly according to the needs of the cell.

Answer 76

Histone-modifying enzymes chromatin-remodeling complexes

Question 77

_ allow heterochromatin to form and to spread.

Answer 77

Heterochromatin-specific histone modifications

Question 78

histone modifications attract _ that reproduce the same histone modifications on neighboring _. In this manner, heterochromatin can spread until it encounters a _ that blocks further propagation into regions of euchromatin.

Answer 78

heterochromatin-specific proteins nucleosomes barrier DNA sequence

Question 79

HETEROCHROMATIN-SPECIFIC PROTEINS, INCLUDING _

Answer 79

HISTONE-MODIFYING ENZYMES

Question 80

X chromosome inactivation is _. Some genes on the inactivated X chromosome _.

Answer 80

not entirely complete "escape" this process and remain active

Question 81

The X chromosome contains several genes associated with the _, including _, which plays an important role in detecting and fighting _.

Answer 81

immune system TLR7 (Toll-Like Receptor 7) viral infections

Question 82

Griffith showed that heat-killed infectious bacteria can transform _ into _.

Answer 82

harmless live bacteria pathogens

Question 83

Griffith found that a _ in the pathogenic S strain could _, the nonlethal R strain into the deadly S strain.

Answer 83

substance present permanently change, or transform