Chromosome Structure

Question 1

What proteins determine chromosome structure and regulate gene expression?

Answer 1

Histones.

Question 2

What are the two function of centromeres during cell division?

Answer 2

1) Hold sister chromatids together

2) Serve as an attachment site for spindle fibers

Question 3

What structure mediates the attachment of the centromere to the spindle fibers?

Answer 3

The kinetochore

Question 4

What type of DNA is the centromere made of?

Answer 4

Alpha satellite DNA

Question 5

What is the name for a chromosome whose centromere is at the center? just off of center? near the end? at the end?

Answer 5

Metacentric, submetacentric, acrocentric, and telocentric (doesn’t exist in human chromasomes)

Question 6

What specific signal ques anaphase, and what prevents this signal from happenings?

Answer 6

Centromere division signals anaphase to begin, and if ALL the chromosomes aren’t attached to the spindle fibers yet, NONE of the centromeres will divide.

Question 7

Define kinetochore.

Answer 7

The kinetochore is the centromeric DNA and all the proteins associated with it. The proteins consist of inner, central, and outer leaflets (the outer leaflet is closest to the spindle fibers).

Question 8

Birth defects and somatic cell carcinomas result from what mistake in meiosis/mitosis?

Answer 8

Aneuploidy.

Question 9

True or false: During mitosis, microtubules are strewn all around the cell, but will disassemble and reassemble in preparation for interphase.

Answer 9

False: the microtubules are spread all over during interphase, and will and reassemble for mitosis.

Question 10

What protein gets the credit for causing chromosomal movement towards the poles during anaphase?

Answer 10

Kinetochore- it produces a force that depolymerizes the microtubule in the forward direction and polymerizes the microtubule behind it.

Question 11

What three errors can occur to prevent proper segregation of chromosomes?

Answer 11

Mutations that prevent kinetochores from generating force. Mutations that disrupt proper connections of the spindle fibers to the centromere. Bad attachments of spindle fibers to the proper end of the centromere.

Question 12

An improper spindle fiber attachment that results in a lagging chromatid that has not been pulled to either pole will result in what consequence?

Answer 12

One of the daughter cells will not have that chromosome.

Question 13

An improper spindle fiber attachment that results in unsegregated chromatids that get pulled to the same pole will result in what consequence?

Answer 13

One daughter cell will have an aneuploidy (with one extra chromosome) and the other will be devoid of that chromosome.

Question 14

New strands of DNA are synthesized in what direction?

Answer 14

5’->3’ (because template strand is read 3’->5’… recall that replication requires the 3’ hydroxyl to lay down the next nucleotide)

Question 15

In order for DNA Pol to begin replication, what must first be laid down?

Answer 15

RNA primer

Question 16

Which end of the template DNA strand is lost when no telomerase is present to elongate it?

Answer 16

3’ end (because DNA Pol reads 3’->5’ and must have an RNA primer laid down there first. So when you remove the primer that was placed on the 3’ end of the strand, nothing can fill in the missing nucleotides).

Question 17

What is the tandem repeat sequence that comprises the telomere?

Answer 17

TTAGGG in mammals

Question 18

What does telomerase use as its template for adding nucleotides to the leading strand?

Answer 18

It uses a guide RNA template

Question 19

True or false: Telomerase elongates the lagging strand, which would otherwise be shortened with each round of replication.

Answer 19

False: Telomerase elongates the leading strand’s TEMPLATE strand.