Chromosome Structure 24-26

Question 1

What chromosome structures are in prokaryotes?

Answer 1

Loop Domains (Supercoiling within)

Question 2

What are Loop Domains?

Answer 2

-each loop held by DNA binding proteins
-related genes

Question 3

What are Supercoils?

Answer 3

within loop domains
more DNA can fit

Question 4

What does topoisomerase do?

Answer 4

cuts sugar-phosphate backbone for adding or removing supercoiling

Question 5

What is
Chromatin
Chromosome

Answer 5

Chromatin - DNA + proteins
Chromosome - highly condensed chromatin

Question 6

What are
heterochromatin
euchromatin

Answer 6

heterochromatin - highly condensed, no gene expression

euchromatin - packaging changes throughout cell cycle, contains expressed genes

Question 7

What is constitutive and facultative heterochromatin?

Answer 7

constitutive - always condensed, centromere/telomere

facultative - some times condensed, inactivated X chromosome

Question 8

What are centromeres?

Answer 8

-part of chromosome attaches to spindle fibers
-required for proper segregation of chromatids
-No genes present, highly repetitive DNA
- # repeats varies

Question 9

What are telomeres?

Answer 9

• POT (protection of telomeres) proteins bind single-stranded overhang
  —- stability
  —- prevents ends from degrading or sticking together
• ends fold over —> triple-stranded structure
• DNA remains tightly packed

Question 10

What are the Beads on a string?

Answer 10

-simplest level chromatin structure
-visible –> low salt conditions

Question 11

What is a Nucleosome?

Answer 11

8 Histones + DNA

Question 12

What are Histone Proteins?

Answer 12

-small, positively charged
- Arg & Lys amino acids
-bind tightly to DNA

Question 13

What are the 5 types of Histones?

Answer 13

H1 - linker histone

Core Histones
H2A - 2
H2B - 2
H3 - 2
H4 - 2