Lecture 14 - Specialized Chromosome Structures

Question 1

What is the telomere, what is its sequence, and what unique characteristic does this give the teleomere?

L14 S3-5

Answer 1

Repetitive, protective sequence located at the end of chromosomes.

Sequence is TTAGGG and there are roughly 2500 repeats at birth.

This sequence allows the telomere to form a loop with itself.

Question 2

What are the centromere and kinetochore?

L14 S14

Answer 2

Centromere:

• repetitive region of DNA located on every chromosome that serves as attachment site for kinetochore
• unique, repetitive 171 bp sequence called alpha satellite DNA

Kinetochore:
-complex of proteins that connects the chromosome, via centromere, to microtubules of mitotic spindle

Question 3

What is the function of cohesin?

L14 S18

Answer 3

Functions to hold sister chromatids together during mitosis.

Question 4

What affect does acetylation and methylation have on chromatin structure?

L14 S24

Answer 4

Acetylation:

• open histone structure
• more active transcription

Methylation

• tight histone structure
• less active transcription

Question 5

What is a nucleosome?

L14 S26

Answer 5

Basic unit of DNA histone packaging.

consists of histone octamer with ~166 bp of DNA wound around it

Question 6

Differentiate between euchromatin and heterochromatin.

L14 S29

Answer 6

Euchromatin:

• less condensed
• chromosome arms
• many genes
• transcription is common

Heterochromatin:

• more condensed
• located at repetitive regions
• few genes
• transcription is infreqent

Question 7

What does DNase sensitivity indicate about a region of DNA?

L14 S32;34

Answer 7

It indicates gene activity. If the gene is active it is loosely packed and vulnerable to DNase.

Question 8

How can repetitive sequences be useful for forensic analysis?

L14 S40

Answer 8

Each individual will have a unique pattern of repetitive sequences at different locations. Can be used as a genetic “fingerprint”.