Ch. 7 Chromosomes and Chromatin (Exam 1)

Question 1

What is the job of a chromosome?

Answer 1

To ensure that DNA is replicated and distributed properly during cell division

Question 2

Why are telomeres repetitive sequences?

Answer 2

They do not code for anything, but they do protect the ends of chromosomes

Question 3

What is euchromatin?

Answer 3

Loosely condensed, active gene-rich, transcriptionally active form of chromatin

Question 4

What is heterochromatin?

Answer 4

Highly condensed, gene-poor, transcriptionally inactive form of chromatin

Question 5

What is chromatin?

Answer 5

Mixture of DNA and proteins that form the chromosomes

Question 6

What is constitutive heterochromatin?

Answer 6

Heterochromatin that is always tightly condensed and always heterochromatin

Question 7

What is facultative heterochromatin?

Answer 7

Heterochromatin that’s not always condensed as it is converted from a region of euchromatin

Question 8

What do G-bands allow for each chromosome?

Answer 8

To be identified by its characteristic banding pattern

Question 9

Are genes located in bands with higher or lower G-C content?

Answer 9

Higher

Question 10

What is the centromere responsible for?

Answer 10

Segregation at mitosis and meiosis

Question 11

What enzyme do telomeres use to extend the end of chromosomes to resolve the shortening from replication?

Answer 11

Reverse transcriptase

Question 12

What organisms would lampbrush chromosomes appear in?

Answer 12

Certain amphibians and birds

Question 13

What is the cause of lampbrush chromosomes?

Answer 13

Unusually extended meiosis

Question 14

What is a polytene chromosome, and where are they found?

Answer 14

A large chromosome with thousands of DNA strands found in the salivary of fruit flies

Question 15

What is the fundamental subunit of the chromatin?

Answer 15

Nucleosome

Question 16

How many histone proteins are in a nucleosome?

Answer 16

8

Question 17

What are the histones that form a nucleosome?

Answer 17

H2A, H2B, H3, and H4

Question 18

What are the 3 components of a nucleosome?

Answer 18

1) 200bp DNA
2) 2 copies of each core histone
3) linker histone H1

Question 19

What is the state of chromosomes during interphase?

Answer 19

Loosely condensed

Question 20

What is the state of a mitotic chromosome in terms of how condensed it is?

Answer 20

Tightly condensed

Question 21

What is the general structure of chromatin at the primary level?

Answer 21

“Beads on a string” i.e. very basis DNA compacting

Question 22

What is the general structure of chromatin at the secondary (condensing) level?

Answer 22

30nm solenoid fiber

Question 23

What is the general structure of chromatin at the tertiary level?

Answer 23

3D structures of interphase or mitotic chromosomes

Question 24

What does micrococcal nucleases show about the DNA packaged into each nucleosome?

Answer 24

It can be divided operationally into two regions

Question 25

What are the two types of nucleosomal DNA?

Answer 25

Core and linker

Question 26

Which two amino acids are responsible for the nucleosome’s high affinity for DNA?

Answer 26

Arginine and lysine

Question 27

What important role do linker histones (H1) play in the formation of higher-order chromatin structures?

Answer 27

They help wrap two full turns of DNA around the core

Question 28

These histones are not only the most conserved, but they are also the core histones responsible for DNA packing in all eukaryotes…

Answer 28

H3 and H4

Question 29

What combination of histones makes up the octomer?

Answer 29

2 H2A-H2B dimers and an H3-H4 tetramer

Question 30

Where is the nucleosome’s protein located in terms of its core?

Answer 30

Inside

Question 31

Where is a nucleosome’s DNA located in terms of its core?

Answer 31

Around the surface

Question 32

Does the acetylation of histones activate or deactivate a gene?

Answer 32

Activate

Question 33

What flexible structure on the histone allows for covalent modifications needed for chromosome function (HINT: terminal)?

Answer 33

N-terminal

Question 34

Histone code generally refers to the collective impact of modifications on the chromatin domain. As such, structure determines…

Answer 34

Function

Question 35

Histone variants change the nature of…

Answer 35

Chromatin