Molecular Genetics

Question 1

Where is the growing polypeptide chain transferred to during the formation of a new peptide bond?

Answer 1

The growing polypeptide moves from the P site to the A site

Question 2

What catalyzes the peptide bond between the polypeptide chain and incoming amino acid on the aminoacyl-tRNA

Answer 2

The ribosome

Question 3

capsomeres

Answer 3

Series of protein subunits that make up a viral coat (capsid)
Capsomeres come together to form a protective protein coat called the capsid

Question 4

Lytic cycle

Answer 4

Virus takes over host cell to replicate and causes harm to the host

Question 5

What occurs during the lytic cycle?

Answer 5

Breaking apart the host genome and replicating many copies of viral nucleic acid
Many rounds of transcription and translation occur, allowing the viral genome to make many viral proteins
The copies of the viral nucleic acid can then be packaged into viral proteins to make new virus particles
The particles can then lyse (break apart) the host cell and go on to infect other cells

Question 6

Silent mutation

Answer 6

Change in the DNA code that results in no change in what amino acid the codon codes for
This is due to degeneracy: several different condones code for the same amino acid

Question 7

Proteins that play a role in DNA replication:

Answer 7

DNA helicase
Single strand binding protiens
Topoisomerase (DNA gyrase)
Primase
DNA polymerase
DNA sliding clamp
DNA ligase
Telomerase

Question 8

Alternative splicing

Answer 8

Where different mRNA molecules are produced from the same pre-mRNA primary transcript

Question 9

What does alternative splicing allow for?

Answer 9

Increased genetic diversity without increasing the size of the genetic code

Question 10

DNA replication: initiation

Answer 10

The process of creating the origin of replication

Question 11

DNA replication: initiation steps

Answer 11

1. initiator proteins bind to specific sequences on DNA
2. Recruitment of other proteins to the AT rich sequence
   › helicase: breaks down hydrogen bonds between DNA strands and separates the strands
   › single-stranded binding proteins: attach to DNA strands and keep the origin of replication open
3. Recruitment of other enzymes to synthesize daughter strands

Question 12

RNAi molecules

Answer 12

• RNA interference
• interfere with mRNA via complementary base pairing to silence certain genes and prevent translation
• block gene expression using siRNA

Question 13

What is the signal to end transcription in a eukaryotic cell?

Answer 13

The terminator sequence is the sequence in the DNA that signals the end of transcription and causes RNA polymerase to dissociate from the DNA

Question 14

What mutations can result in frameshifts?

Answer 14

Insertions and deletions

Question 15

Where does transcription occur in prokaryotes?

Answer 15

In the cytosol simultaneously with transcription because prokaryotes do not have membrane-enclosed nuclei

Question 16

What is transcription?

Answer 16

The process of converting a sequence of DNA to mRNA before it can be translated into proteins

Question 17

Steps of transcription:

Answer 17

1) Initiation: transcription factors on a promoter sequence (aka the promoter) attracts RNA polymerase to specific genes on the DNA strand
2) Elongation: begins after RNA polymerase has aligned and the transcription bubble has formed
3) Termination: RNA polymerase transcribed the terminator sequence (aka the terminator) which signals RNA polymerase to stop transcribing

Question 18

In which direction does RNA polymerase travel during elongation step of transcription?
In which direction is the mRNA strand extended?

Answer 18

3’ —> 5’ direction on the template strand
Extends mRNA strand in the 5’ —> 3’ direction

Question 19

Coding, non-coding and mRNA strand:

Answer 19

Coding (sense/anti-template strand): 5’ —> 3’ direction and is identical to the mRNA strand (T replaced with U)

Non-coding (antisense/template strand): 3’ —> 5’ complementary to both coding and mRNA strands. The strand in which RNA polymerase binds to and transcribes the mRNA strand

mRNA strand: 5’ —> 3’, identical to coding strand

Question 20

What must occur before prokaryotic transcription can take place?

Answer 20

A sigma factor combined with prokaryotic core RNA polymerase to form the RNA polymerase holoenzyme, giving it the ability to target specific DNA promoter regions

Question 21

Prophage

Answer 21

• viral genomes that integrate into bacterial genomes: bacteriophage infects a bacterial cell –> DNA is incorporated into the host genome –> considered a prophage
• host + viral genome = prophage

Question 22

DNA polymerase extends the complementary strand in the ____________ direction

Answer 22

5’ —> 3’

Question 23

DNA polymerase reads the template strand in the _________ direction

Answer 23

3’ —> 5’

Question 24

Post transcriptional modifications:

Answer 24

The conversion of pre-mRNA into processed mRNA which leaves the nucleus —> 3 main types:

1) 5’ capping
2) polyadenylation of the 3’ end
3) splicing out introns

Question 25

5’ capping

Answer 25

7-methylguanosine cap is added to the 5’ end of the mRNA during elongation
Protects the mRNA from degradation, provides stability to the mRNA and acts as a point of attachment for ribosomes during translation

Question 26

Missense mutations

Answer 26

Occurs when the change in the DNA code results in the codon now coding for a different amino acid
This can sometimes lead to detrimental effects in protein folding (and therefore function) depending on the properties of the new amino acid
There are two types: conservative and non-conservative

Question 27

Conservative missense mutation

Answer 27

Mutations that make small impacts on protein folding because the mutated amino acid has the same properties as the unmuted amino acid

Question 28

Non-conservative missense mutations

Answer 28

Can lead to the protein folding incorrectly because the mutated amino acid does not share the same properties as the unmuted amino acid

Question 29

helicase

Answer 29

• unzips DNA to form replication fork

Question 30

what is the least abundant RNA molecule?

Answer 30

mRNA- due to its high turnover rate

Question 31

histone acetylation

Answer 31

• acetyl group binds to histone tail
• promotes transcription by decondensing the chromatin structure

Question 32

transcription factors

Answer 32

• proteins bind to control elements and manage the transcription of DNA