Lecture I - Specialized Chromosome Structure/Sequence

Question 1

What is the function of a Telomere?

Answer 1

Protecting the end of a chromosome from damage during replication or fusion from neighboring chromosome.

Question 2

What is a Telomere’s structure?

Answer 2

TTAGGG repeats. (5’->3’) AATCCC (3’->5’)

Question 3

What is the structure of a centromere?

Answer 3

constricted region of a chromosome where spindle fibers attach, surrounded by heterochromatin.

Question 4

What is a centromere essential for?

Answer 4

chromosome separation and site of assembly of the kinetochore

Question 5

What forms a t-loop?

Answer 5

The G-rich strand, which is longer than the c-rich strand, folds over and pairs with a short stretch of DNA. Forming a t-loop.

Question 6

Increased blood lead levels in children lead to shorter telomere length. What is a result of shorter telomeres?

Answer 6

increased incidence of disease and a shorter lifespan

Question 7

Short Leukocyte Telomere Length (LTL) increases the probability of what?

Long LTLs increase the risk of what?

Answer 7

Short LTLs - Cardiovascular disease

Long LTLs - developing major cancers.

Question 8

A complex of proteins associated with the centromere of a chromosome, to which the microtubules of the spindle attach during cell division is what?

Answer 8

Kinetochore

Question 9

This is a small cylindrical cell organelle located near the nucleus in the cytoplasm of most eukaryotic cells that divides in perpendicular fashion during mitosis.

Answer 9

Centriole

Question 10

This kinetochore protein is mutated in human ciliopathy and microcephaly phenotypes.

Answer 10

CENPF

Question 11

This enzyme is responsible for positive and negative supercoiling of DNA

Answer 11

Topoisomerase

Question 12

Describe the basic chromatin structure from smallest unit all the way down to a chromosome.

Answer 12

Consists of a nucleosome (smallest level), which is a basic unit of DNA packaging in eukaryotes consisting of a histone octamer and a segment of DNA wound in sequence around it.

The next level is a chromatosome, which is a nucleosome with a linker histone (H1) and 166 bp of DNA.

Finally there is linker DNA - which is DNA in between two nucleosome cores that in association with the linker histone hold the two nucleosomes together.

These linked nucleosomes are folded onto one another into a 30 nm fiber that form 300 nm long loops. These loops are then folded onto one another to produce a 250 nm fiber that is then folded into a chromosome.

Question 13

This type of chromatin is more condensed, contains fewer genes, and is replicated late in S phase.

Answer 13

Heterochromatin

Question 14

This type of chromatin is Less condensed, contains many genes, and is replicated throughout S phase.

Answer 14

Euchromatin

Question 15

Histones carry a __ Charge and DNA carries a __ charge

Answer 15

Positive; Negative

Question 16

What is a polytene chromosome?

Answer 16

chromosome created by repeated rounds of DNA replication with no cell division. Contain chromosome puffs where chromatin is relaxed and active transcription is taking place. Often found in insect salivary glands.

Question 17

What is DNase I sensitivity correlated with?

Answer 17

The transcription of globin genes in chick embryos, **TLDR of the study suggests that chromatin structure changes in the course of transcription. **

Question 18

What is epigenetics?

Answer 18

Heritable alteration of phenotype because of altered chromatin structure via histone modification/acetylation or DNA methylation.

Question 19

What is microsatellite DNA and how can it be used in forensics?

Answer 19

A track of tandemly repeated DNA motifs that range in length from 2-5 nucleotides and are typically repeated 5-50 times. (Ie, TATATATATA). Microsatellites are used for mapping locations within a genome.

Microsatellite DNA is useful for forensics because each person has a unique fingerprint of microsatellites.

Question 20

What is a gene family?

Answer 20

Similar but not identical copies of unique DNA sequences that arose through duplication of an existing gene.

Question 21

What are the two types classes of moderately repetitive DNA?

Answer 21

Tandem repeat sequences and Interspersed repeat sequences.