RNA and The Genetic Code

Question 1

Initiation Codon

Answer 1

AUG (methionine)

Question 2

Stop Codons

Answer 2

UAG UAA UGA

Question 3

Silent Mutations

Answer 3

no effect on protein synthesis, usually occurs in the wobble position

Question 4

Nonsense (trunction) Mutations

Answer 4

produces a premature stop codon

Question 5

Missence Mutations

Answer 5

produce a codon that codes for a different amino acid

Question 6

Frameshift Mutations

Answer 6

results from nucleotide deletion or insertion and change the reading frame for subsequent codons

Question 7

Structural Differences between DNA and RNA

Answer 7

Deoxyribose vs Ribose sugars
Substitution of Uracil for Thymine
Single stranded vs double stranded

Question 8

mRNA

Answer 8

carries the message from DNA in the nucleus via transcription of the gene; travels to cytoplasm to be translated

Question 9

tRNA

Answer 9

brings amino acids; recognizes the codon on the mRNA using its anticodon

Question 10

rRNA

Answer 10

makes up much of the ribosome; enzymatically active

Question 11

rRNA

Answer 11

makes up much of the ribosome; enzymatically active

Question 12

Steps in Transcription in RNA

Answer 12

Helicase and topoisomerase unwind DNA
RNA polymerase II binds to TATA box within promotor region
hnRNA synthesized from DNA strand
Post-transcriptional modifications

Question 13

Post Transcriptional Modifications to RNA

Answer 13

5’ Cap added
3’ Poly-A Tail added
Splicing by spliceosome to remove introns and splice together exons

Question 14

Translation Stages in RNA

Answer 14

Initiation
Elongation
Termination

Question 15

Posttranslational Modifications

Answer 15

Folding by chaperones
Formation of quaternary structure
Cleavage of proteins or signal sequences
Covalent addition of other biomolecules

Question 16

Control of Gene Expression in Prokaryotes

Answer 16

Operons (Jacob Monod Model) are inducible or repressible clusters of genes transcribed as a single mRNA

Question 17

Control of Gene Expression in Eukaryotes

Answer 17

Transcription factors search for promotor and enhancer regions in DNA
Promoters: within 25 base pairs of he transcription start site
Enhancers: more than 25 base pairs away from the transcription start site

Question 18

Small and Large subunit of ribosome

Answer 18

40S and 60S

Question 19

A-Site

Answer 19

holds the incoming aminoacyl-tRNA complex

Question 20

P-Site

Answer 20

holds tRNA that carries the growing polypeptide chain

Question 21

E-Site

Answer 21

where the inactivated tRNA pauses transiently before exiting the ribosome

Question 22

Chaperone Proteins

Answer 22

assis in protein folding

Question 23

Inducible Systems

Answer 23

repressor tightly bonded to operator system and acts as a roadblock, binding of a protein reduces transcriptional activity and to remove the block an inducer must bind the repressor protein

Question 24

Repressible Systems

Answer 24

allow constant production of a product, the repressor is inactive until it binds to a corepressor and they tend to work in negative feedback loops with the product serving as the corepresser

Question 25

Histone Acetylation

Answer 25

histone acetylases acetylate lysine residues and weakens the interactions of the histone with DNA, which opens the DNA chromatin formation therefore increasing gene expression levels

Question 26

DNA Methylation

Answer 26

DNA methylases add methyl groups to cytosine and adenine which can silence genes