Molecular

Question 1

heterochromatin

Answer 1

highly dense
darker on EM
transcriptionally inactive

Question 2

euchromatin

Answer 2

less condensed
lighter on EM
transcriptionally active

Question 3

DNA methylation

Answer 3

represses transcription

mutes DNA

Question 4

histone methylation

Answer 4

reversibly represses DNA transcription, but can activate it depending on methylation location

(mutes DNA)

Question 5

histone acetylation

Answer 5

relaxes DNA coiling, allowing for transcription

activates DNA

Question 6

NucleoSide

Answer 6

base + deoxyribose (Sugar)

Question 7

NucleoTide

Answer 7

base + deoxyribose + phosphaTe

Question 8

Purine Nucleotides

Answer 8

A

G

Question 9

amino acids required for purine synthesis

Answer 9

Glycine
Aspartate
Glutamine

Question 10

Pyrimidine Nucleotides

Answer 10

C
T (DNA)
U (RNA)

Question 11

Methotrexate (MTX)

Answer 11

inhibit dihydrofolate reductase (decreasing dTMP - deoxythymidine monophosphate)

(disrupts pyrimidine synthesis)

Question 12

Adenosine deaminase deficiency

Answer 12

ADA is required for degradation of adenosine and deoxyadenosine. In ADA deficiency, increased dATP, leading to toxicity in lymphocytes.

(major cause of SCID)

Question 13

Lesch-Nyhan syndrome

Answer 13

Defective purine salvage due to absent HGPRT

HGPRT:
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)
Retardation (intellectual disability)
DysTonia

Question 14

Unambiguous genetic code

Answer 14

Each codon specifies only 1 amino acid

Question 15

Degenerate/redundant genetic code

Answer 15

Most amino acids are coded by multiple codons.

Wobble—codons that differ in 3rd, “wobble” position may code for the same tRNA/amino acid. Specific base pairing is usually only required in the first 2 nucleotide positions of mRNA codon.

Question 16

Commaless, nonoverlapping genetic code

Answer 16

Read from a fixed starting point as a continuous sequence of bases.

Question 17

Universal genetic code

Answer 17

Genetic code is conserved throughout evolution.

Question 18

DNA replication

Answer 18

5′ to 3′ direction

Question 19

Origin of replication

Answer 19

May be single (prokaryotes) or multiple (eukaryotes).

AT-rich sequences (such as TATA box regions) are found in promoters and origins of replication.

Question 20

Replication fork

Answer 20

Y-shaped region along DNA template where leading and lagging strands are synthesized.

Question 21

Helicase

Answer 21

Unwinds DNA template at replication fork.

Question 22

Single-stranded binding proteins

Answer 22

Prevent strands from reannealing.

Question 23

DNA topoisomerases

Answer 23

Create a single- or double-stranded break in the helix to add or remove supercoils.

Question 24

what inhibits eukaryotic topoisomerase I?

Answer 24

Irinotecan/topotecan

Question 25

what inhibits eukaryotic topoisomerase II?

Answer 25

Etoposide/teniposide

Question 26

what inhibits prokaryotic topoisomerase II (DNA gyrase) & topoisomerase IV?

Answer 26

Fluoroquinolones

Question 27

Primase

Answer 27

Makes an RNA primer on which DNA polymerase III can initiate replication.

Question 28

DNA polymerase III

Answer 28

Prokaryotes only. Elongates leading strand by adding deoxynucleotides to the 3′ end. Elongates lagging strand until it reaches primer of preceding fragment. 3′ to 5′ exonuclease activity “proofreads” each added nucleotide. (5′ to 3′ synthesis and proofreads with 3′ to 5′ exonuclease.)

Question 29

DNA polymerase I

Answer 29

Prokaryotic only. Degrades RNA primer; replaces it with DNA.

Question 30

DNA ligase

Answer 30

Catalyzes the formation of a phosphodiester bond within a strand of double-stranded DNA. Joins Okazaki fragments.

Question 31

Telomerase

Answer 31

Eukaryotes only. An RNA-dependent DNA polymerase that adds DNA to 3′ ends of chromosomes to avoid loss of genetic material with every duplication. Often dysregulated in cancer cells, allowing unlimited replication.

Question 32

Mutations in DNA based on severity

Answer 32

silent << missense < nonsense < frameshift.

Question 33

Silent

Answer 33

Nucleotide substitution but codes for same (synonymous) amino acid; often base change in 3rd position of codon (tRNA wobble).

Question 34

Missense

Answer 34

Nucleotide substitution resulting in changed amino acid example: Sickle cell disease

Question 35

Nonsense

Answer 35

Nucleotide substitution resulting in early stop codon (UAG, UAA, UGA). Usually results in nonfunctional protein.

Question 36

Frameshift

Answer 36

Deletion or insertion of a number of nucleotides not divisible by 3, resulting in misreading of all nucleotides downstream. examples: Duchenne muscular dystrophy, Tay-Sachs disease.

Question 37

Splice site

Answer 37

Mutation at a splice site p retained intron in the mRNA p protein with impaired or altered function. Rare cause of cancers, dementia, epilepsy, some types of β-thalassemia.

Question 38

Lac operon

Answer 38

when glucose is absent and lactose is available, the lac operon is activated to switch to lactose metabolism.