Chapter 12, Problem 1P

For each of the terms in the left column, choose the beast matching phrase in the right column

a. telomere	1. protein complex that keeps sister chromatids together until anaphase
b. G-bands	2. origin of replication in yeast
c. kinetochore	3. repetitive DNA found near centromere in higher eukaryotes
d. nucleosome	4. specialized structure at the end of a linear chromosome
e. ARS	5. complexes of DNA, protein and RNA in the eukaryotic nucleus
f. satellite DNA	6. small basic proteins that bind to DNA and form the core of the nucleosome
g. chromatin	7. complex of DNA and proteins where spindle fibers attach to a chromosome.
h. cohesion	8. beadlike structure consisting of DNA wound around histone proteins
i. histones	9. protein complex that protects telomeres from degradation and end-to-end fusions
j. shelterin	10. regions of a chromosome that are distinguished by staining differences.

Summary Introduction

a.

To determine:

The phrase that describes “telomere”.

Answer to Problem 1P

Correct answer:

Telomere: specialized structure at the end of a linear chromosome.

Explanation of Solution

Telomeres are the structures that are present at the end of the chromosomes and have a repetitive sequence of nucleotides and are responsible for the growth or mitosis that takes place in the cell. The telomere shortens with age that implies the loss of power of division for the cell.

Summary Introduction

b.

To determine:

The phrase that describes “G-bands.”

Answer to Problem 1P

Correct answer:

G-bands: regions of chromosome that are distinguished by staining difference

Explanation of Solution

G-bands are present in the chromosome as alternating structures and are stained by specific dyes to distinguish them from the other regions of the chromosome. The G in the G-bands stands for Giemsa based on the type of strain that is used to visualize them.

Summary Introduction

c.

To determine:

The phrase that describes “kinetochore.”

Answer to Problem 1P

Correct answer:

Kinetochore: complex of DNA and protein where spindle fibers attach to a chromosome.

Explanation of Solution

Kinetochores are the spherical structures that are present near the centromere and attach the spindle fibers along with the centromere during the cell division cycle. These are made up of complex of proteins that are associated with the centromeres.

Summary Introduction

d.

To determine:

The phrase that describes “nucleosome.”

Answer to Problem 1P

Correct answer:

Nucleosome: beadlike structures consisting of DNA wound around histone proteins.

Explanation of Solution

Nucleosomes are the rounded bead-like structures that are made up tightly coiled DNA and the histone proteins that wound the DNA and connect them through linker DNA or H1 histone protein. These nucleosomes then further condense to form chromosomes.

Summary Introduction

e.

To determine:

The phrase that describes “ARS.”

Answer to Problem 1P

Correct answer:

ARS: origin of replication in yeast.

Explanation of Solution

Origin of replication in yeast is different than other eukaryotes. It consists of autonomously replicating sequences (ARS) that are present at the origin once the yeast has entered into START phase. This phase is permanent, and the proteins are formed for the replication of DNA.

Summary Introduction

f.

To determine:

The phrase that describes “satellite DNA.”

Answer to Problem 1P

Correct answer:

Satellite DNA: repetitive DNA found near the centromere in higher eukaryotes.

Explanation of Solution

Satellite DNA is only present in the higher eukaryotes like vertebrates. These are usually present near the end of the chromosome and have repetitive sequences of nucleotides. The satellite DNA is very crucial for identification purpose during DNA fingerprinting analysis.

Summary Introduction

g.

To determine:

The phrase that describes “chromatin.”

Answer to Problem 1P

Correct answer:

Chromatin: complexes of DNA, protein, and RNA in the eukaryotic nucleus.

Explanation of Solution

Chromatin is the structure that resembles small threads and are widely distributed inside the nucleus of the cell. The chromatin condenses during cell division to form chromosomes that divide into separate cells at the time of formation of daughter cells.

Summary Introduction

h.

To determine:

The phrase that describes “cohesin.”

Answer to Problem 1P

Correct answer:

Cohesin: the protein complex that keeps sister chromatids together until anaphase.

Explanation of Solution

Cohesins are the proteins that are very crucial during cell division as it prevents the chromosomes from separating before the anaphase. The chromosomes stick together till the metaphase where they can attach to the spindle fibers and then get correctly distributed to the respective daughter cells. Cohesin prevents the separation of chromosomes before this phase.

Summary Introduction

i.

To determine:

The phrase that describes “histones.”

Answer to Problem 1P

Correct answer:

Histones: small basic proteins that bind to DNA and form the core of the nucleosome.

Explanation of Solution

Histones are the basic proteins that are rich in arginine and lysine and participate in forming nucleosomes that further condense to form chromosomes. The histones are of five types that are H1, H2a, H2b, H3, and H5.

Summary Introduction

j.

To determine:

The phrase that describes “shelterin.”

Answer to Problem 1P

Correct answer:

Shelterin: the protein complex that protects telomeres from degradation and end-to-end fusions.

Explanation of Solution

Shelterin belong to the class of protein that perform protective functions during cell divisions. These proteins prevent the degradation of the protein complexes from the action of different types of proteases that are present inside the nucleus. These also function to inhibit the end-to-end fusion of two adjacent chromosomes.