Biochemistry Ch 7. RNA and the Genetic Code

Question 1

Central dogma

Answer 1

States that DNA is transcribed to RNA which is translated to protein

Question 2

Degenerate code

Answer 2

Allows multiple codons to encode for the same amino acid

Question 3

Initiation codon

Answer 3

AUG

Question 4

Termination codon

Answer 4

UAA, UGA, UAG

Question 5

Mutations without effects

Answer 5

Redundancy and wobble allows mutations to occur without effects in the protein

Question 6

Wobble

Answer 6

Third base in the codon

Question 7

Point mutation types

Answer 7

Silent mutations, nonsense mutations, and missense mutations

Question 8

Silent mutations

Answer 8

Have no effect on protein synthesis

Question 9

Nonsense mutations

Answer 9

aka truncation, mutations that produce a premature stop codon

Question 10

Missense mutations

Answer 10

Produce a codon that codes for a different amino acid

Question 11

Frameshift mutations

Answer 11

Result from nucleotide addition or deletion and chance the reading frame of subsequent codons

Question 12

RNA vs DNA

Answer 12

RNA substitutes a ribose sugar for deoxyribose, substitution of uracil for thymine, single stranded instead of double stranded

Question 13

Three types of RNA

Answer 13

Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Question 14

Messenger RNA

Answer 14

Carries the messages from DNA in the nucleus via transcription of the gene, it travels into the cytoplasm to be translated

Question 15

Transfer RNA

Answer 15

Brings in amino acids and recognizes the codon on the mRNA using its anticodon

Question 16

Ribosomal RNA

Answer 16

Makes up the ribosome and is enzymatically active

Question 17

Helicase

Answer 17

Unwinds the DNA helix

Question 18

RNA polymerase II

Answer 18

Binds to the TATA box within the promoter region of the gene(25 base pairs upstream from first transcribed base)

Question 19

TATA box

Answer 19

-

Question 20

Prometer region

Answer 20

-

Question 21

hnRNA

Answer 21

Synthesized from the DNA template (antisense) strand

Question 22

Posttranscriptional modifications include

Answer 22

A 7-methylguanylate triphosphate cap is added to the 5’ end

A polyadenosyl (poly-A) tail is added to the 3’ end

Splicing is done by snRNA and snRNPs in the spliceosome, introns are removed in a lariat structure and exons are ligated together

Prokaryotic cells can increase variability of gene products through polycistronic genes while eukaryotic cells use alternative splicing

Question 23

Polycistronic genes

Answer 23

Starting transcription in different sites within the gene leads to different gene products

Question 24

Alternative splicing

Answer 24

Combining different eons in a modular fashion to acquire different gene products

Question 25

Ribosomes

Answer 25

Factories where translation (protein synthesis) occurs

Question 26

Stages of translation

Answer 26

Initiation, elongation, and termination

Question 27

Initiation in prokaryotes

Answer 27

Occurs with 30S ribosome attaches to the Shine-Dalgarno sequence and scans for a start codon, it lays down N-formylmethionine in the P site of the ribosome

Question 28

Shine-Dalgarno sequence

Answer 28

-

Question 29

Initiation in eukaryotes

Answer 29

Occurs when the 40S ribosome attaches to the 5’ cap and scans for a start codon, it lays down methionine in the P site of the ribosome

Question 30

Elongation

Answer 30

Involves the addition of new aminoacyl-tRNA into the A site of the ribosome and transfer of the growing polypeptide chain from the tRNA in the P site of the tRNA in the A site, the now uncharged tRNA pauses in the E site before exiting the ribosome

Question 31

Termination

Answer 31

Occurs when the codon in the A site is a stop codon, uses a release factor to release the protein

Question 32

Release factor

Answer 32

Places a water molecule on the polypeptide chain and thus releases the protein

Question 33

Posttranslational modifications

Answer 33

Folding by chaperones
Formation of quaternary structure
Cleavage of proteins or signal sequences
Covalent addition of other biomolecules (phosphorylation, carboylatvon, glycosylation, prenylation)

Question 34

Jacob-Monod model

Answer 34

Model of repressors and actors that explains how operons work

Question 35

Operons

Answer 35

Inducible or repressible clusters of genes transcribed as a single mRNA

Question 36

Inducible systems

Answer 36

Bonded to a repressor under normal conditions, they can be turned on by an inducer pulled the repressor from the operator site, example is the lac operon

Question 37

Chaperones

Answer 37

-

Question 38

Repressor

Answer 38

-

Question 39

Operator site

Answer 39

=

Question 40

Inducer

Answer 40

-

Question 41

Repressible systems

Answer 41

Are transcribed under normal conditions, can be turned off by a corepressor coupling with the repressor and the binding of this complex to the operator site, example is the trp operon

Question 42

Transcription factors

Answer 42

Search for promoter and enhancer regions in the DNA

Question 43

Promoters

Answer 43

Within 25 base pairs of the transcription start site

Question 44

Enhancers

Answer 44

Are more than 25 base Paris from the transcription start site

Question 45

Modification of chromatin structure

Answer 45

Affects the ability of transcriptional enzymes to access the DNA through histone acetylation (increased accessibility) or DNA methylation (decreased accessibility)