Biochemistry- Molecular

Question 1

Heterochromatin

Answer 1

HeteroChromatin = Highly Condensed.

Barr bodies

Question 2

Euchromatin

Answer 2

Eu = true, “truly transcribed.”

Euchromatin is Expressed

Question 3

DNA methylation

Answer 3

CpG Methylation Makes DNA Mute.

Question 4

Histone acetylation

Answer 4

Histone Acetylation makes DNA Active.

Question 5

Purinas

Answer 5

PURines (A,G)—2 rings

PURe As Gold.

Question 6

Pirimidinas

Answer 6

PYrimidines (C,U,T)—1 ring.

CUT the PY (pie).

Question 7

NucleoSide

NucleoTide

Answer 7

base + (deoxy)ribose (Sugar).

base + (deoxy)ribose + phosphaTe;

Question 8

Amino acids necessary for purine

synthesis:

Answer 8

GAG:
Glycine
Aspartate
Glutamine

Question 9

Leflunomide

Answer 9

pyrimidine synthesis: inhibits dihydroorotate

dehydrogenase

Question 10

Methotrexate (MTX), trimethoprim (TMP),

and pyrimethamine:

Answer 10

pyrimidine synthesis: inhibit dihydrofolate

reductase

Question 11

5-fluorouracil (5-FU)

Answer 11

pyrimidine synthesis: inhibits thymidylate synthase

Question 12

6-mercaptopurine (6-MP) and its prodrug

azathioprine:

Answer 12

inhibit de novo purine synthesis

Question 13

Mycophenolate and ribavirin:

Answer 13

purine synthesis: inhibit inosine

monophosphate dehydrogenase

Question 14

Hydroxyurea:

Answer 14

purine and pyrimidine synthesis: inhibits ribonucleotide

reductase

Question 15

Adenosine deaminase

deficiency

Answer 15

dATP 􀁰 toxicity in lymphocytes. autosomal recessive

Question 16

Lesch-Nyhan

syndrome

Answer 16

Defective purine salvage due to absent HGPRT
HGPRT:
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)
Retardation (intellectual disability)
DysTonia

Question 17

Lesch-Nyhan

syndrome Treatment

Answer 17

allopurinol or febuxostat (2nd line).

Question 18

Most amino acids are coded by multiple codons, Exceptions:

Answer 18

methionine and tryptophan encoded

by only 1 codon (AUG and UGG

Question 19

Genetic code features

Answer 19

Unambiguous
Degenerate/redundant
Commaless, nonoverlapping
Universal

Question 20

DNA replication is

Answer 20

semiconservative, involves both continuous and discontinuous (Okazaki fragment) synthesis, and
occurs in the 5′ 􀁰 3′ direction

Question 21

Origin of

replication A

Answer 21

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

Question 22

Replication fork

Answer 22

Y-shaped region along DNA template where

leading and lagging strands are synthesized.

Question 23

Helicase

Answer 23

Unwinds DNA template at replication fork.

Question 24

Single-stranded

binding proteins

Answer 24

Prevent strands from reannealing.

Question 25

DNA | topoisomerases

Answer 25

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

Question 26

Irinotecan/topotecan Etoposide/teniposide Fluoroquinolones

Answer 26

- inhibit eukaryotic topoisomerase I. - inhibit eukaryotic topoisomerase II. - inhibit prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV.

Question 27

Primase

Answer 27

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

Question 28

DNA ligase

Answer 28

Joins Okazaki fragments

Question 29

Telomerase

Answer 29

Eukaryotes only. An RNA-dependent DNA polymerase that adds DNA to 3′ ends of chromosomes to avoid loss of genetic material with every duplication.

Question 30

DNA polymerase III

Answer 30

DNA polymerase III has 5′ 􀁰 3′ synthesis and | proofreads with 3′ 􀁰 5′ exonuclease.

Question 31

DNA polymerase I

Answer 31

Same functions as DNA polymerase III, also | excises RNA primer with 5′ 􀁰 3′ exonuclease.

Question 32

Mutations in DNA

Answer 32

silent << missense < nonsense < frameshift.

Question 33

􀂃 Transition— 􀂃 Transversion—

Answer 33

purine to purine (eg, A to G) or pyrimidine to pyrimidine (eg, C to T). purine to pyrimidine (eg, A to T) or pyrimidine to purine (eg, C to G).

Question 34

stop codon

Answer 34

(UAG, UAA, UGA)

Question 35

splice site mutation

Answer 35

is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA

Question 36

operón

Answer 36

una unidad genética funcional formada por un grupo o complejo de genes capaces de ejercer una regulación de su propia expresión por medio de los sustratos con los que interactúan las proteínas codificadas por sus genes.

Question 37

DNA repair | Single strand

Answer 37

Nucleotide excision repair Base excision repair Mismatch repair

Question 38

DNA repair | Double strand

Answer 38

Nonhomologous end joining

Question 39

Lynch syndrome

Answer 39

(hereditary nonpolyposis colorectal cancer [HNPCC]). | Mismatch repair is defective

Question 40

xeroderma pigmentosum

Answer 40

Defective Nucleotide excision repair prevents repair of pyrimidine dimers that are formed as a result of ultraviolet light exposure.

Question 41

Defect in ataxia telangiectasia, breast/ovarian cancers with BRCA1 mutation, and Fanconi anemia.

Answer 41

Nonhomologous end joining

Question 42

mRNA start codons

Answer 42

AUG inAUGurates protein synthesis. (methionine)

Question 43

mRNA stop codons

Answer 43

``` UGA = U Go Away. UAA = U Are Away. UAG = U Are Gone. ```

Question 44

Promoter

Answer 44

Site where RNA polymerase II and multiple | other transcription factors bind to DNA

Question 45

Enhancer

Answer 45

Stretch of DNA that alters gene expression by | binding transcription factors

Question 46

Silencer

Answer 46

Site where negative regulators (repressors) bind.

Question 47

RNA polymerase I RNA polymerase II RNA polymerase III makes 5S rRNA, tRNA (smallest RNA, tiny).

Answer 47

``` makes rRNA (most numerous RNA, rampant). makes mRNA (largest RNA, massive). mRNA is read 5′ to 3′. makes 5S rRNA, tRNA (smallest RNA, tiny). ```

Question 48

I, II, and III

Answer 48

are numbered in the same order that their products are used in protein synthesis: rRNA, mRNA, then tRNA.

Question 49

Actinomycin D

Answer 49

inhibits RNA polymerase in | both prokaryotes and eukaryotes.

Question 50

α-amanitin, found in Amanita phalloides (death | cap mushrooms),

Answer 50

inhibits RNA polymerase II. severe hepatotoxicity if ingested.

Question 51

Capped, tailed, and spliced transcript is called...

Answer 51

mRNA.

Question 52

polyadenylation signal.

Answer 52

AAUAAA

Question 53

Splicing of pre-mRNA

Answer 53

1. Primary transcript combines with (snRNPs) form spliceosome. 2. Lariat-shaped (looped) intermediate is generated. 3. Lariat is released to precisely remove intron and join 2 exons.

Question 54

Antibodies to spliceosomal snRNPs (anti- | Smith antibodies)

Answer 54

highly specific for SLE

Question 55

Anti-U1 RNP antibodies

Answer 55

highly associated with mixed connective tissue | disease (MCTD).

Question 56

Introns vs exons

Answer 56

Introns are intervening sequences and stay in the nucleus, whereas exons exit and are expressed.

Question 57

microRNAs

Answer 57

regulate gene expression by targeting the 3′ untranslated region of specific mRNAs for degradation or translational repression

Question 58

tRNA T-arm:

Answer 58

contains the TΨC (ribothymidine, pseudouridine, cytidine. T-arm Tethers tRNA molecule to ribosome.

Question 59

tRNA D-arm:

Answer 59

contains dihydrouridine residues. D-arm Detects the tRNA by aminoacyl-tRNA synthetase.

Question 60

tRNA structure

Answer 60

Have CCA at 3′ end along. The amino acid is covalently bound to the 3′ end of the tRNA. CCA: Can Carry Amino acids

Question 61

Aminoacyl-tRNA synthetase

Answer 61

scrutinizes amino acid before and after it binds to tRNA. Is responsible for accuracy of amino acid selection.

Question 62

Elongation

Answer 62

Think of “going APE”: A site = incoming Aminoacyl-tRNA. P site = accommodates growing Peptide. E site = holds Empty tRNA as it Exits.

Question 63

Ribosome Eukaryotes: PrOkaryotes:

Answer 63

40S + 60S 􀁰 80S (Even). | 30S + 50S 􀁰 70S (Odd).

Question 64

30S + 50S 􀁰 70S (Odd).

Answer 64

Intracellular protein involved in facilitating and/or maintaining protein folding.

Question 65

Covalent alterations

Answer 65

Phosphorylation, glycosylation, hydroxylation, methylation, acetylation, and ubiquitination.

Question 66

wobble phenomenon.

Answer 66

different codons that can be created but they only code for 20 amino acids.