Biochemistry - Molecular

Front 1

this type of chromatin is condensed and transcriptionally inactive

Back 1

heterochromatin

Front 2

this type of chromatin is less condensed and transcriptionally active

Back 2

euchromatin

Front 3

which type of chromatin ties nucleosomes together in a string (30-nm fiber)?

Back 3

H1

Front 4

what histones make up the nucleosome core?

Back 4

H2A, H2B, H3, H4

Front 5

what are the purines, and how many rings do they have?

Back 5

A, G; 2 rings

Front 6

what are the pyrimidines and how many rings do they have?

Back 6

C, T, U; 1 ring (pyramids were CUT)

Front 7

which nucleotide has a ketone?

Back 7

guanine

Front 8

which nuclotide has a methyl?

Back 8

thymine (THYmine has a meTHYl)

Front 9

deamination of cytosine makes what?

Back 9

uracil

Front 10

which bond is stronger: G-C or A-T? why?

Back 10

G-C is stronger because it has 3 H bonds

Front 11

what happens to the melting temperature when you increase the G-C content?

Back 11

increases (b/c more H bonds)

Front 12

what is it called when a purine is substituted for a purine or a pyrimidine is substituted for a pyrimidine?

Back 12

transItion (Identical type)

Front 13

what is it called when a purine is substituted for a pyrimidine or vice versa?

Back 13

transVersion (conVersion between types)

Front 14

what are some exceptions to the universality of the genetic code?

Back 14

mitochonria, archaeobacteria, mycoplasma, some yeasts

Front 15

what is a silent mutation

Back 15

same amino acid - often base change in 3rd position of codon (tRNA wobble)

Front 16

what is a missense mutation?

Back 16

changed amino acid (conservative - new aa is similar in chemical structure)

Front 17

what is a nonsense mutation?

Back 17

change resulting in an early stop codon - stop the nonsense!

Front 18

what are the stop codons?

Back 18

UGA, UAA, UAG

Front 19

what is the mRNA initiation codon and what does it code for in eukaryotes?

Back 19

AUG, methionine (AUG inAUGurates protein synthesis

Front 20

what does the initial AUG code for in prokaryotes?

Back 20

formyl-methionine

Front 21

what do DNA topoisomerases do?

Back 21

create a nick in the helix to relieve supercoils

Front 22

what does primase do?

Back 22

makes an RNA primer on which DNA polymerase III can initiate replication

Front 23

what does DNA polymerase III do?

Back 23

elongates the chain by adding deoxynucleotides to the 3' end until it reaches primer of preceding fragment; 3' -> 5' exonuclease activity proofreads each added nucleotide

Front 24

what does DNA polymerase I do?

Back 24

degrades RNA primer with 5' to 3' exonuclease

Front 25

what does DNA ligase do?

Back 25

seals DNA

Front 26

in which direction does DNA polymerase synthesis occur?

Back 26

5' to 3'

Front 27

in which direction does proofreading with exonuclease occur?

Back 27

3' to 5'

Front 28

after excision repair-specific glycosolase recognizes and removes a damaged base, what does endonuclease do?

Back 28

makes a break several bases to the 5' side and removes a short stretch of nucleotidse - the n DNA polymerase fills gap and DNA ligase seals it

Front 29

the 5' of the incoming nucleotide bears what?

Back 29

the triphosphate/engergy sourse for bond

Front 30

DNA, RNA, and protein synthesis all occur in what direction

Back 30

5' to 3'

Front 31

which is the largest type of RNA?

Back 31

mRNA (massive)

Front 32

which is the most abundant type of RNA?

Back 32

rRNA (rampant)

Front 33

whihc is the smallest type of RNA

Back 33

tRNA (tiny)

Front 34

RNA polymerase I makes what?

Back 34

rRNA

Front 35

RNA polymerase II makes what?

Back 35

mRNA

Front 36

what does RNA polymerase III make?

Back 36

tRNA

Front 37

alpha-amantin, a substance found in death cap mushrooms, inhibits what?

Back 37

RNA polymerase II

Front 38

this is the site where RNA polymerase and multiple other transcription factors bind to DNA upstram from gene locus

Back 38

promoter

Front 39

this is a stretch of DNA that alters gene expression by binding transcription factors

Back 39

enhancer - may be located close to, far from, or even within (in an intron) teh gene whose expression it regulates

Front 40

theis is the site where negative regulators (repressors) bind

Back 40

operator

Front 41

intervening noncoding segments of DNA are called what?

Back 41

introns

Front 42

where are introns spliced out of?

Back 42

primary mRNA transcripts

Front 43

these particles facilitate splicing by binding to primary mRNA transcripts and forming spliceosomes

Back 43

snRNPs

Front 44

where does RNA processing occur?

Back 44

nucleus

Front 45

what three events occur in RNA processing after transcription?

Back 45

(1) capping on 5' end (7-methyl-G)
(2) polyadenylation on 3' end (approx 200 A's)
(3) splicing out of introns

Front 46

what do all tRNAs have at the 3' end?

Back 46

CCA along with a high percentage of chemically modified bases

Front 47

in tRNA, the anticodon end is opposite what?

Back 47

the 3' aminoacyl end

Front 48

what does a mischarged tRNA do?

Back 48

reads the usual codon but inserts wrong amino acid

Front 49

what two things are responsible for the accuracy of amino acid selection?

Back 49

aminoacyl-tRNA synthetase and binding of charged tRNA to the codon

Front 50

during protein synthesis, in which site does Met sit?

Back 50

in the P site - peptidyl

Front 51

during protein synthesis, where does the incoming amino acid bind?

Back 51

A site - aminoacyl; hydrolyzes Met's bond to its tRNA while simultaneously forming a peptidyl bond between the 2 amino acids