lecture 22

Question 1

what is the unit of DNA and histone proteins called?

Answer 1

chromatin

Question 2

what type of chromatin is lightly packed, rich in gene concentration, and is most
often under active transcription?

Answer 2

euchromatin

Question 3

what type of chromatin is tightly packed, mainly genetically inactive sequences; has genetic information that cannot be read?

Answer 3

heterochromatin

Question 4

what are the TWO types of heterochromatin?

Answer 4

facultative and constitutive

Question 5

what is facultative heterochromatin?

Answer 5

can change to become euchromatin
ex. Barr bodies, gene slicing

Question 6

what is constitutive heterochromatin?

Answer 6

always in that configuration that is gene poor
ex. telomeres, centromeres

Question 7

what model, made to explain DNA packaging, can be described as a ball of yarn that is pushed together?

Answer 7

folded fiber model; did NOT include proteins

Question 8

describe the nucleosome model.

Answer 8

DNA is wrapped around histone cores which wraps around itself and gets tighter until it forms a chromosome

Question 9

what is meant by “housekeeping proteins?”

Answer 9

histones as they are always being made

Question 10

what is meant by the idea that histones are highly conserved?

Answer 10

they maintain the same sequence across organisms

Question 11

how many times does DNA wrap around the histone core?

Answer 11

2 times

Question 12

what histones are in the histone core?

Answer 12

2 H2A, 2 H2B, 2H3, 2H4

Question 13

what is the charge of the histone core?

Answer 13

very positive/basic so that the negatively charged DNA will wrap around it

Question 14

describe the H1 histone.

Answer 14

the “linker” histone; bigger than the other histones(around 200 amino acids compared to 120); tissue specific; not highly conserved; part of the nucleosome but not the core

Question 15

what is a helical coiling composed of six nucleosomes called?

Answer 15

solenoid

Question 16

which histone is responsible for packing the six nucleosomes into a solenoid formation in a process known as supercoiling?

Answer 16

H1

Question 17

what is the configuration called that involves opposite nucleosomes being linked so that they can be compacted more tightly?

Answer 17

zig-zag model

Question 18

what is being referred to by “beads on a string?”

Answer 18

nucleosomes being held together by linker DNA

Question 19

what are chromatin loops built around?

Answer 19

a scaffold of topoisomerase II

Question 20

what is the compaction level of euchromatin?

Answer 20

chromatin loops

Question 21

what is the compaction level of heterochromatin?

Answer 21

metaphase chromosome

Question 22

what phase of the cell cycle does DNA excess in a double helix formation or a “beads on a string” formation?

Answer 22

G1 growth phase

Question 23

what phase of the cell cycle does DNA change from a solenoid to chromatin loops?

Answer 23

G2 growth phase

Question 24

what happens to the chromatin loops at the start of prophase in mitosis?

Answer 24

they condense

Question 25

when is the final condensed chromosome formed?

Answer 25

metaphase

Question 26

what phase of the cell cycle does a karotype depict?

Answer 26

metaphase