Exam 1: Lecture 15 & 16

Question 1

telomere organization:

Answer 1

region of repetitive nucleotide sequences at each end of a chromosome (TTAGGG)n

Question 2

telomere fcn:

Answer 2

protects the end of the chromosome from deterioration or form fusion with neighboring chromosomes (sticky ends can cause breakage)

Question 3

centromere structure/organization:

Answer 3

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

Question 4

centromere fcn:

Answer 4

essential for chromosome separation

Question 5

dna at the ends of euk chromosomes consists of telomeric short repeated sequences. the G-rich strand at the telomere is longer than the C-rich strand. this is relevant for:

Answer 5

T-loop; G-rich strand folds over and pairs with a short stretch of dna to form t-loop

Question 6

shortened telomeres are associated with

Answer 6

shorter life span and increased incidence of disease

Question 7

when telomeres are never shortened, ie able to extend their life span indefinitely, this is associated with

Answer 7

cancer; cells never dying

Question 8

telomere length is inversely associated w/

Answer 8

aging

Question 9

region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division

Answer 9

centromere

Question 10

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

Answer 10

kinetochore

Question 11

a small, cylindrical cell organelle, located near the nucleus in the cytoplasm of most euk cells, that divides in perpendicular fashion during mitosis

Answer 11

centriole

Question 12

the centromere is the chromosomal locus essential for

Answer 12

chromosome inheritance and genome stability

Question 13

the physical role of the centromere is to

Answer 13

act as the site of assembly of the kinetochore

Question 14

the kinetochore is a highly complex multiprotein structure that is responsible for

Answer 14

the actual events of chromosome segregation

• binding microtubules
• signalling to the cell cycle machinery when all chromosomes have adopted correct attachments to the spindle

Question 15

positive supercoiling is for

Answer 15

packaging dna ( no access to dna)

Question 16

negative supercoiling is for

Answer 16

unwinding dna (for the process of transcription)

Question 17

topoisomerase is for

Answer 17

enzyme responsible for adding and removing turns in the coil (supercoiled dna is overwound or underwound, causing it to twist on itself)

Question 18

bacterial have _ dna which is advantageous how?

Answer 18

circular; no tips exposed to nucleases like proks and their need for telomeres

Question 19

define histones

Answer 19

proteins that condense/wrap/package and order dna

Question 20

histones have a _ charge and dna has a _ charge

Answer 20

histones have positive and dna negative charge

Question 21

nucleosome

Answer 21

segment of dna wound in sequence around 8 core histone proteins (histone unit)

Question 22

chromatosome

Answer 22

histone octamer plus linker histone (H1) and 166 bp of dna

Question 23

linker dna

Answer 23

double stranded dna inbtwn two nucleosome cores (holds cores together)

Question 24

what are the 2 main biochemical modifications histones/dna are subjected to?

Answer 24

histone acetylation = de-condense (gene activation)

dna methylation = compact/condensing

Question 25

t/f: the nucleosome is the fundamental repeating unit of a chromosome

Answer 25

false of a CHROMATIN

Question 26

chromatin is

Answer 26

dna plus the proteins that make up a chromosome

Question 27

euchromatin

Answer 27

less condensed; location is on chromosome arms. transcription is often

Question 28

heterochromatin

Answer 28

more condensed; location is at centromeres, telomeres, and other specific places. transcription is infrequent

Question 29

changes in chromatin structure: polytene

Answer 29

created by repeated rounds of dna replication with no cell division

Question 30

changes in chromatin structure: chromosomal puffs

Answer 30

regions of relaxed chromatin where active transcription is taking place

Question 31

changes in chromatin structure: dnase I sensitivity

Answer 31

correlates with gene activity/expression suggesting that chromatin structure changes in the course of transcription

Question 32

is dna methylation reversible?

Answer 32

yes; methylation is often due to environmental factors and folic acid studies have shown reversibility

Question 33

is epigenetics heritable?

Answer 33

yes bc of altered chromatin structure (histone modification, acetylation or dna methylation modification) w/o changing the dna sequence

Question 34

retroviral/transposon origin?

Answer 34

SINEs (Alu) and LINEs (L1)

Question 35

characteristics of moderately repetitive dna

Answer 35

-150-300 bp long
-tandem repeated sequences
interspersed repeat sequences (SINEs/LINEs)

Question 36

characteristics of highly repetitive dna

Answer 36

• less than 10 bp long

- microsatellite dna tandemly/adjacent repeated dna motifs

Question 37

why is microsatellite dna useful in forensics?

Answer 37

each person has a unique “fingerprint” of microsatellites (inherit from mom and dad)

Question 38

neutralizing their positive charges would have which effect on the histone proteins?

Answer 38

they would no longer be attracted to dna