Biochemistry

Question 1

How does DNA fit into the nucleus?

Answer 1

Chromatin form

Question 2

What is a nucleosome?

Answer 2

When DNA loops twice around histone octamer

Question 3

Phosphate gives DNA a +/- charge

Answer 3

-

Question 4

What gives histones a + charge?

Answer 4

Lysine and arginine

Question 5

What is the difference between mitochondrial and cellular DNA?

Answer 5

Mitochonddrial is circular and does not utilize histones

Question 6

Heterochromatin looks like?

Answer 6

Highly condensed

Question 7

What chromatin is transcriptionally active?

Answer 7

Eurochromatin, heterochromatin isn’t

Question 8

What does it mean that heterochromatin doesn’t undergo transcription?

Answer 8

Increased methylation and decreased acetylation

Question 9

What bodies may be in heterochromatin?

Answer 9

Barr bodies (inactive X chromosomes)

Question 10

Which chromatin is darker?

Answer 10

Heterochromatin

Question 11

Euchromatin is e

Answer 11

Expressed

Question 12

What is DNA methylation?

Answer 12

Changes in expression of a DNA segment without changing the sequence

Question 13

What is DNA methylation involved in?

Answer 13

Aging, carcinogenesis, genomic imprinting, transposable element repression, and X chromosome inactivation

Question 14

Lyonization

Answer 14

X chromosome inactivation

Question 15

DNA is methylated in

Answer 15

Imprinting

Question 16

Methylation within ____ ______ represses gene transcription

Answer 16

CpG islands

Question 17

Histone methylation causes

Answer 17

Reversible transcriptional suppression, but can also cause activation depending on location of methyl groups

Question 18

Histone acetylation does what?

Answer 18

Removes histones + charge –> relax DNA coiling and increased transcription

Question 19

Histone methylation makes DNA mute/active

Histone acetylation makes DNA mute/active

Answer 19

Mute

Active

Question 20

How do thyroid hormone receptors alter thyroid hormone synthesis?

Answer 20

Acetylation

Question 21

Nucleoside vs nucleotide

Answer 21

Nucleoside: base + deoxyribose (sugar)
Nucleotide: base + deoxyribose + phosphate linked by 3’=5’ phosphodiester bond

Question 22

Purine examples

Answer 22

AG - 2 rings

Question 23

Pyrimidine examples

Answer 23

CUT - 1 ring

Question 24

Deamination reactions (CAG5)

Answer 24

Cytosine –> Uracil
Adenine –> hypoxanthine
Guanine –> xanthine
5-methylcytosine –> thymine

Question 25

Uracil is found in ______
Thymine is found in ______
______ of uracil makes thymine

Answer 25

RNA
DNA
Methylation

Question 26

What end of incoming nucleotide bears the triphosphate ?

Answer 26

5’

Question 27

What is the purpose of the triphosphate?

Answer 27

Energy source for the bond

Question 28

What is the target of 3’ hydroxyl attack

Answer 28

a-Phosphate

Question 29

What has a methyl?

Answer 29

Thymine

Question 30

Is C-G bond weaker or stronger than A-T bond?

Answer 30

CG (3 H bonds)

AT (2 H bonds)

Question 31

Increased CG content does what to DNA?

Answer 31

Increases melting temperature of DNA

Question 32

What are necessary for purine synthesis?

Answer 32

Amino acids (glycine, aspartate, glutamine)

Question 33

What 2 drugs inhibit pyrimidine synthesis?

Answer 33

Leflunomide

5-FU

Question 34

What 2 drugs inhibit purine synthesis?

Answer 34

6-MP

Mycophenolate/ribavirin

Question 35

What drugs inhibit both purine and pyrimidine synthesis?

Answer 35

Hydoxyurea
Methotrexate
Trimethoprim
Pyrimethamine