CHAP 5

Question 1

Which of the following is false?
A. A gene is a unit of heredity
B. Gene is transferred from a parent to offspring
C. Gene determines some characteristic of the offspring.
D. Chromosomes consist of proteins only

Answer 1

D

Chromosomes consist of proteins and nucleotides

Question 2

What is the difference between The two forms of pneumococcus?

Answer 2

• S (smooth) which is lethal after infection because it contains polysaccharides, but the heated form is not lethal
• R (rough) which is not lethal after injection

Question 3

Which molecule does this virus inject in the bacteria and remains in the virus particle?

Answer 3

The radioactive DNA entered the bacterial cells, while the radioactive proteins remained outside with the empty virus heads.

Question 4

Which of the following is wrong?
A. All the bases of DNA are on the outside of the double helix, while the sugar–phosphate backbones is on the inside.
B. pyrimidine- U,C,T purine- A, G
C. A DNA molecule is composed of two polynucleotide chains held together by hydrogen bonds between the paired bases.
D. the two strands of DNA run antiparallel to each other.

Answer 4

A. base- inside

sugar-phosphate backbone - outside

Question 5

Which of the following is true about the double helix structure of DNA?
A. DNA helix contains 10 base pairs per helical turn
B. twisting of DNA contributes to the energetically favorable conformation of the DNA double helix.
C. Coiling of the two strands around each other creates two grooves in the double helix.
D. each base pair of DNA has a similar width.
E. All

Answer 5

E

Question 6

Chromosomes can be ordered according to all except:-
A. Size
B. Staining via DNA hybridization using fluorescently tagged DNA molecules that recognize specific Chromosomes
C. Staining methods using dyes that distinguish AT- rich from CG-rich regions and result in reproductive band patterns
D. Volume of DNA strands.

Answer 6

D.

Question 7

An ordered display of the full set of 46 human chromosomes is called…………..

Answer 7

the human karyotype, which is used for o detecting Chromosome abnormalities

Question 8

All cells have two copies of each chromosome except:-
A. sperm cell
B. mature red blood cells
C. eggs cell
D. White blood cell
E. All except D

Answer 8

E.
Mature red blood cells have no chromosomes
germ cells (eggs and sperm) have one copy

Question 9

Which of the following is wrong about the interphase?
A. Replication origin- Where replication of the DNA begins
B. Telomeres- Where chromosome duplication ends
C. Interphase Chromosomes are not randomly distributed within the nucleus
D. Interphase chromosomes are long, thin threads of DNA and can be easily distinguished in the light microscope.
E. Centromere- Allows separation of duplicated Chr. during M phase

Answer 9

D. They can’t be distinguished by light microscope.

Question 10

Which of the following is true related to M phase of mitotic replication?
A. the DNA coils up forming highly compacted, or condensed Chromosomes that can be visualized
B. Each duplicated mitotic chromosome has two identical daughter DNA
C. Mitotic Chromosomes consist of two sister chromatids
D. All

Answer 10

D

Question 11

Which of the following is not true about Nucleosome?
A. Nucleosome core particles consists of a complex of 8 histone proteins
B. Nucleosomes reduces the length of DNA with one-third
C. Nucleosomes provides the first level of DNA packing.
D. Nucleosome core particles consists of a stretch of double-stranded DNA, 147 nucleotide pairs long
E. None

Answer 11

E

Question 12

All four of the histones in chromosome are relatively small proteins, with a high proportion of positively charged amino acids
A. True
B. False

Answer 12

A

Question 13

.........has a long, unstructured N-terminal amino acid “tail” that extends out from the nucleosome core particle.
A. nucleotide
B. histones in the octamer
C. Interfase chromosome
D. nonhistone chromosomal proteins

Answer 13

B.

Question 14

The additional packing of nucleosome depends on a fifth histone called ………

Answer 14

histone H1

Question 15

How is a chromatin fiber folded to produce mitotic chromosomes?

Answer 15

1. chromatin fiber is folded into a series of loops
2. these loops are further condensed to produce the interphase chromosome
3. The interfase chromosome undergoes at least one more level of packing to
   form the mitotic chromosome.

Question 16

Which of the following is not correct?
A. During mitosis, many of the chromatin-remodeling complexes are irreversible chemical modification of the histones.
B. The tails of the core histones are subject to covalent modification
C. Modifications are important for the stability of chromatin fibers
D. Acetylation of lysines can reduce affinity of the tails for adjacent nucleosomes

Answer 16

A

they are reversible

Question 17

Which of the following is true about modification of histones?
A. modifications can serve as docking sites on the histone tails for a variety of regulatory proteins.
B. Different patterns of modifications attract different proteins to particular stretches of chromatin.
C. All of the proteins attracted to histone promote chromatin condensation
D. A and C
E. A and B

Answer 17

E
Some of the proteins attracted to histone promote chromatin condensation, whereas others decondense chromatin and facilitate access to the DNA.

Question 18

Which of the following is not true about histone-modifying enzymes?
A. They are tightly regulated
B. they work in concert with the chromatin-remodeling complexes to condense or decondense stretches of chromatin
C. allow local chromatin structure to change rapidly according to the needs of the cell.
D. None

Answer 18

D

Question 19

Which of the following is not true regarding heterochromatin and euchromatin
A. Heterochromatin-The most highly condensed form of interphase chromatin
B. Heterochromatin- makes up about 10% of an interphase chromosome, and in mammalian chromosomes.
C. Euchromatin-The rest of the interphase chromatin
D. Euchromatin- means different chromatin

Answer 19

D.
Euchromatin means normal or true chromatin
Heterochromatin means different chromatin

Question 20

Where is heterochromatin mostly concentrated?

Answer 20

It is concentrated around the centromere region and in the telomeres at the ends of the chromosomes.

Question 21

Arrange the following in the correct order
1. The modification cause a wave of condensed chromatin to propagate along the chromosome.
2. histone tail modification attract a set of heterochromatin-specific proteins, including
histone-modifying enzymes
3. The heterochromatin will continue to spread until it encounters a barrier DNA sequence that stops the propagation
4. attracted protein create the same histone tail modifications on adjacent nucleosomes.

Answer 21

2, 4, 1, 3

Question 22

Mention an example of disease caused by extended region of heterochromatin

Answer 22

Anemia

• The gene that encodes β-globin—part of the oxygen-carrying hemoglobin molecule—is next to a region of heterochromatin.
• If, because of an inherited DNA deletion, that heterochromatin spreads the β-globin gene is poorly expressed

Question 23

Why are Interfase X Chromosomes inactivated in female mammals?

Answer 23

A double dose of X-chromosome products would be lethal so it permanently inactivate of one random X in each cell. It also becomes highly condensed into heterochromatin (embryo)