Chapter 5

Question 1

Mitotic chromosomes were first visualized with the use of very simple tools: a basic light microscope and some dyes. Which of the following characteristics of mitotic chromosomes reflects how they were named?

Answer 1

Color

Question 2

What chemical groups are used to construct a DNA molecule?

Answer 2

Five-carbon sugar, Phosphate, and Nitrogen-containing base

Question 3

Which of the following DNA strands can form a DNA duplex by pairing with itself at each position?

Answer 3

5′-AAGCGCTT-3′

Question 4

The DNA from two different species can often be distinguished by a difference in the ______

Answer 4

ratio of A + T to G + C.

Question 5

A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes “painted”?

Answer 5

Using fluorescent DNA molecules.

Question 6

Which of the following questions would be answered by karyotype analysis?

Answer 6

-Is the individual genetically female or male?
-Do any of the chromosomes contain pieces that belong to other chromosomes?
-Does the individual have an extra chromosome?

Question 7

Mitotic chromosomes are in the most highly condensed form. Interphase cells contain
chromosomes that are less densely packed and ________

Answer 7

occupy discrete territories in the nucleus.

Question 8

Mitotic chromosomes are __________ times more compact than a DNA molecule in its
extended form

Answer 8

10,000

Question 9

The classic “beads-on-a-string” structure is the most decondensed chromatin structure
possible and is produced experimentally. Which chromatin components are retained
when this structure is generated?

Answer 9

-linker DNA
-nucleosome core particles
-core histones

Question 10

The core histones are small, basic proteins that have a globular domain at the C-terminus and a long, extended conformation at the N-terminus. Which of the following is true of the N-terminal “tail” of these histones?

Answer 10

-It is subject to covalent modifications
-It extends out of the nucleosome core.

Question 11

Stepwise condensation of linear DNA happens in five different packing processes. Which of the following four processes has a direct requirement for histone H1?

Answer 11

Formation of the 30-nm fiber

Question 12

Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the “histone code.” Which of the following patterns will probably lead to gene silencing?

Answer 12

lysine 9 methylation

Question 13

How do changes in histone modifications lead to changes in chromatin structure?

Answer 13

They help recruit other proteins to the chromatin

Question 14

The polarity of a DNA strand results from the polarity of the nucleotide subunits.

Answer 14

True

Question 15

How many DNA nucleotides incorporated into DNA?

Answer 15

Adenine, Thymine, Guanine, and cytosine

Question 16

Consider two different species of yeast that have similar genome sizes. Is it likely that they contain the same number of genes? Is it likely that they contain a similar number
of chromosomes?

Answer 16

No, similar genome size indicates nothing about # of genes and chromosomes.

Question 17

The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. How many telomeres are in each cell? What is the main function of telomeres?

Answer 17

92 telomers per cell, two on each chromosome

-Protect ends of chromosomes and enable complete replication of the DNA of each chromosome

Question 18

Origins of replication typically have a relatively high number of A-T base pairs. How does this sequence feature relate to the function of these DNA regions?

Answer 18

A-T rich regions thermodynamically easier to open due to two H bonds, instead of the three H bonds between G-C

Question 19

Describe the mechanism by which heterochromatin can spread, once it has been established in one region of the chromosome.

Answer 19

Specific set of proteins & enzymes attracted which create the same modifications on adjacent chromosomes…Occurs in “wave”

Question 20

Explain the reason why the cell requires a mechanism for identifying specific sequences of DNA.

Answer 20

Specific sequences of DNA contain important information for gene expression and DNA packaging.
-Where gene starts/ends
-Where transcription starts
-Where to assemble specific protein complexes

Question 21

If given three strands of DNA to be separated by heat, which would melt first?

Answer 21

A-T bonds contain 2 H Bonds
C-G bonds contain 3 H Bonds

The more the H bonds, the more stable, the less to melt

Question 22

Each eukaryotic chromosome must contain the following DNA sequence elements: multiple origins of replication, two telomeres, and one centromere.

Answer 22

True

Question 23

How wide are nucleosome core particles?

Answer 23

11nm in diameter