Chapter 7 - RNA And The Genetic Code

Question 1

Start codon

Answer 1

MET

Question 2

Stop codons

Answer 2

UGA You Go Away
UAG. You Are Gross
UAA. You are Ugly

Question 3

What is a degenerate genetic code?

Answer 3

More than one codon can specific a singly amino acid

Question 4

Wobble position of codon

Answer 4

Third base in the codon can wobble and you can still have same AA

Question 5

Silent mutation

Answer 5

Goes unseen, usually because of wobble

Question 6

Point mutation

Answer 6

One codon swapped out for another

Either:

• missense (expressed mutation)
• nonsense. (Expressed mutation)
• silent

Question 7

Missense mutation

Answer 7

One amino substitute for another

Question 8

Nonsense mutation

Answer 8

Codon now encodes for premature stop codon

***STOP this nonsense!

Question 9

Frameshift mutations

Answer 9

Caused by addition or deletion of a nucleotide causing a shift in reading frame

Question 10

What is the main player in transcribing mRNA in Eukareotes ?

Answer 10

RNA Polymerase II

Question 11

What is the promoter region on eukaryotes called?

Answer 11

TATA box

Question 12

Différence b/w DNA polymerase III and RNA polymerase II

Answer 12

DNA polymerase III: needs a primer

RNA poly II doesn’t

Question 13

Three types of RNA polymerase in eukaryotes

Answer 13

RNA polymerase I : in nucléolus, synthesizes rRNA

RNA polymerase II: in nucleus, synthesizes hnRNA (preprocessed mRNA)

RNA polymerase III: synthesizes tRNA and some rRNA

Question 14

What is hnRNA?

Answer 14

Preprocessed mRNA

Question 15

What direction do RNA polymerase II transcribe DNA?

Answer 15

5’ to 3’ ..just like DNA synthesis

Question 16

What is the spliceosome?

Answer 16

Small nuclear RNA (snRNA) binds with small nuclear ribonucleoproteins (snRNPs)

Question 17

Tell me about the 5’ cap

Answer 17

Put at the end of the hnRNA molecule

• recognized by ribosome as the binding site
• protects mRNA from degradation

Question 18

Tell me a bout the 3’ Poly-A Tail

Answer 18

Protects the message against rapid degradation

*its like a fuse for a time bomb, instead of black powder it is adenine

Question 19

What is alternative splicing?

Answer 19

When hnRNA is spliced together to produce multiple variants of proteins encoded by the same original gene

Question 20

What are the three phases of translation?

Answer 20

Initiation, elongation, termination

Question 21

What is the order of elongation pieces in the ribosomes

Answer 21

APE :

Question 22

What are the three A,P, and E parts of translation?

Answer 22

A site: mRNA binds first to this site

P: polypeptide grows here

• met is first placed their
• GTP is used!!

E: inactivated tRNA gets bumped off

Question 23

Is lacoperon indicible or répressible?

Answer 23

Indicible…we don’t need lactose unless we ain’t got glucose (we as in prokaryotes)

Question 24

What is an indicible system

Answer 24

Repressor is bound to operator and so the RNA polymerase can’t plow though

Negative control

*useful because allows gene products to only be produced when they are needed

Question 25

What is a negative inducible and negative répressible system ?

Answer 25

Inducible: its turned off but can be turned on

Répressible: turned on but can be turned off

***negative pertains to the binding to the operator that turns transcription off

Question 26

Example of positive control mechanisms for gene expression

Answer 26

CAP “catabolic activator protein” assists the lac Opéron: when Glucose is low…they are like “hey we need to use something else for energy”

CAP binds to cAMP which binds to promoter of operon and increases transcription of lactase gene

Question 27

What are the two recognizable domains on transcription factors?

Answer 27

DNA binding domain

Activation domain

Question 28

What is DNA binding domain?

Answer 28

Binds to a specific nucleotide sequence in the promoter region to help in recruitment of transcriptional machinery

Question 29

What is the activation domain (TFs)

Answer 29

Allows for binding of several TFs and other important regulatory proteins

Question 30

What is an enhancer?

Answer 30

Used to enhance transcription levels

• group of response elements

Learn more about this if you have time

Question 31

What is histone acetylation and why is it used?

Answer 31

Acetylation of histone proteins decreases the + charge on lysine residues and weakens the interaction of histone with DNA

*** Results in the chromatin opening up for easier access

Question 32

What is DNA methylation?

Answer 32

Chromatin remodeling and regulation of genes expression in cell

DNA methylases add methyl group to cytosine and adenine

**methylation often linked with silencing expression

Question 33

Chat with mihai about :
Response elements
TFs
Enhancers
The domains

Answer 33

Mihai or maybe Eugene?