chapter 11

Question 1

Describe the organization of bacterial chromosomes

Answer 1

• haploid with single chromosomes
• circular with genes for survival and reproduction, variable in size
• multiple copies of plasmids
• some have linear or more than one chromosomes

Question 2

nucleoid

Answer 2

bacterial and archaea chromosomes packed in a region

Question 3

how are bacterial chromosomes compacted?

Answer 3

• proteins help organize the DNA into loops that pack the chromosome into the nucleiod
• the circular DNA undergoes supercoiling

Question 4

relaxed circle

Answer 4

least twisted

Question 5

highly supercoiled form

Answer 5

most tightly twisted

Question 6

negative supercoiling

Answer 6

bacteria and archaea, twists DNA in the opposite direction to the helical twist

Question 7

positive supercoiling

Answer 7

in some archaea, twists the DNA in the same direction as the double helix

Question 8

topoisomerases

Answer 8

partially unwind supercoiled DNA to receive torsional stresses that could result from “overwinding”

Question 9

cross section through a nucleosome

Answer 9

cor particle octomer= H2A, H2B, H3 and H4

Question 10

what does H1 do?

Answer 10

linkes regions with DNA + H1 occur between adjacent nucleosomes

Question 11

30-nm fiber

Answer 11

solenoid structure

-10-nm fiber coils into a solenoid structure, w/6-8 nucleosomes per turn and histone H1 stabilizing the solenoid

Question 12

chromosome scaffold

Answer 12

determines chromosome shape

-composed of filamentous nonhistone proteins

Question 13

metaphase chromatin

Answer 13

chromatin is compacted 250x compared to the 300nm fiber

Question 14

active transcription

Answer 14

take place in segments of loops distant form MARS, larger loops have more active transcription than small loops

Question 15

chromatin remodeling

Answer 15

nucleosomes displace to expose promotor and other regulator sequences

Question 16

epigenetic marks or epigenetic modifications

Answer 16

chemical modifications to histones in nucleosomes

-addition or removal of chemical groups such as methyl or acetyl groups

Question 17

methyl groups

Answer 17

tighten DNA packaging- decrease transcription

Question 18

acetyl groups

Answer 18

loosen packaging- increase transcription

Question 19

when are epigenetic modifications of histones transmitted

Answer 19

cell division or reproduction

Question 20

metacentric

Answer 20

middle

Question 21

submetacentric

Answer 21

slightly closer to one end

Question 22

acrocentric

Answer 22

near one end

Question 23

telocentric

Answer 23

end

Question 24

unstable centromere positions

Answer 24

acentric and dicentric

Question 25

acentric

Answer 25

no centromere at all

Question 26

dicentric

Answer 26

two cenromeres

Question 27

ring chromosome

Answer 27

circular chromosome with no telomeres

-stability high variable but can be transmitted to next generation

Question 28

p chromosome

Answer 28

short arm (petit)

Question 29

q chromosome

Answer 29

long arm

Question 30

heterochromatin

Answer 30

compact heavily staining chromosome regions rich in satellite DNA (highly repeated non-coding DNA sequences) and low in gene content

Question 31

euchromatin

Answer 31

less condensed chromosome regions high in gene content

Question 32

Facultative heterochromatin

Answer 32

• exhibits variable levels of condensation,

- related to levels of transcription of resident genes

Question 33

constitutive heterochromatin

Answer 33

-is permanently condensed, found prominently in centromeres and telomeres,
and composed primarily of repetitive DNA sequences

Question 34

telomeres

Answer 34

repetitive sequences at the ends of chromosomes

• get shorter with every division of a differentiated somatic cell
• ensure that incomplete chromosome replication does not affect vital genes

Question 35

what kind of cells are telomerase expressed in?

Answer 35

germ-line cells
stem cells
-over-expressed in cancer cells