Module 4: Nucleic Acid And Protein Synthesis And Their Regulation

Question 1

How are the proteins and nucleic acids of a cell produced and maintained?

Answer 1

4 basic genetic processes that help: protein synthesis, DNA replication, DNA repair, and genetic recombination

Question 2

Why do cells need proteins?

Answer 2

Proteins are extremely important for the minute-by-minute, day-by-day functions of all cells

Question 3

What steps are involved in protein synthesis?

Answer 3

Includes DNA transcription, mRNA translation, ribosomal assembly

Question 4

Transcription

Answer 4

First step in protein synthesis
Takes the genetic info from DNA and transcribes it into the form of mRNA → the immature mRNA is modified by RNA splicing to remove its introns (non-coding regions)
Done by the enzyme RNA polymerase

Question 5

RNA polymerase in transcription

Answer 5

Can recognize a promoter sequence in DNA → binds to this sequence with the help of transcription factors → then initiate the transcription of the downstream genes
Once it reaches the termination sequence → dissociates from the template DNA strand → releases the newly synthesized immature mRNA to be modified by splicing

Question 6

Methods of gene expression

Answer 6

Gene regulatory protein
Histone acetylation and deacetylation
Methylation

Question 7

Types of RNA involved in protein synthesis

Answer 7

mRNA
rRNA
tRNA

Question 8

rRNA aka ribosomal RNA

Answer 8

Makes up the structure of the ribosome

Question 9

Role of the ribosome in protein synthesis

Answer 9

Ribosome= the enzyme that catalyzes the formation of peptide bonds in a protein

Question 10

Peptide bonds

Answer 10

Connections between each amino acid

Question 11

tRNA aka transfer RNA

Answer 11

The RNA that carries specific amino acids based on the genetic code to the ribosome that then creates peptide

Question 12

How does the tRNA know which amino acid it needs to take to the ribosome to make protein?

Answer 12

It contains an anticodon → used when a tRNA transfers an amino acid corresponding to the genetic code → it tells the tRNA which amino acid is next in the polypeptide sequence

Question 13

Codons in the DNA

Answer 13

Are 3-nucleotide sequences that correspond to specific amino acids
A group of 3 nucleotides = a reading frame → when protein synthesis occurs, the DNA code is read by 3 nucleotides

Question 14

Anticodon

Answer 14

Complementary to the codon present in DNA
Tells the tRNA which amino acid is next in the polypeptide sequence

Question 15

Prokaryotic ribosomes vs. Eukaryotic ribosomes

Answer 15

Prokaryotes and eukaryotes have different ribosomes
Prokaryotes → the 70S ribosome = made of a 30S and a 50S subunit
Eukaryotes → the 80S ribosome = made of a 40S and a 60S subunit

Question 16

Structure of ribosomes

Answer 16

All ribosomes have an A site, a P site, and an E site
A site = part where the tRNA delivers the amino acid
P site = part where the formation of the peptide bond is catalyzed
E site = where the peptide chain exits the ribosome as it’s being synthesized

Question 17

Stop codons

Answer 17

Three codons within the code thatcorrespond to the stoppage of translation
They are UAG, UAA, and UGA

Question 18

Start codon

Answer 18

A codon that signals the start of translation
It is AUG → corresponds to the amino acid methionine
Prokaryotes → this amino acid has a formyl group attached = fMet/ formyl-methionine

Question 19

Codons corresponding to the 20 essential amino acids

Answer 19

UUU, UUC = Phe
UUA, UUG, CUU, CUC, CUA, CUG =Leu
UCU, UCC, UCA, UCG =Ser
UAU, UAC = Tyr
UAA, UAG, UGA =STOP
UGU, UGC =Trp

Question 20

DNA repair mechanisms

Answer 20

The cells use these to maintain DNA in its optimal state → to fix lesions in DNA that may occur spontaneously or through exposure to harmful substances

Question 21

Mutations in DNA

Answer 21

Constantly occur spontaneously
Can be disease-causing or not
Cells try to repair but if not repaired, they can get passed throughout generations
Natural selection usually eliminates disease-causing mutations → only present at low rates
Different types: point mutations, frameshift mutations

Question 22

Point mutations

Answer 22

Caused by a single base pair change
Includes silent, missense, and nonsense mutations

Question 23

Frameshift mutations

Answer 23

Result in a shift in the reading frame → causes production of a short (truncated) protein or can add the wrong amino acid, changing the protein structure entirely

Question 24

Common types of DNA repair mechanisms

Answer 24

Base excision repair, double-stranded break repair, and mismatch repair

Question 25

Base excision repair

Answer 25

Only the damage nucleotide is removed and then replaced
Everything is then glued back together using the enzyme DNA ligase → like a hot glue gun

Question 26

Mismatch repair

Answer 26

Mis-paired buses are removed from the DNA strand
1. A number of proteins recognize the mismatched area →2. They cut out that whole patch of DNA → 3. DNA polymerase puts in the new and correct bases → 4. DNA ligase glues the pieces back together

Question 27

Double-stranded break repair

Answer 27

Used when DNA has been damaged and a double-stranded break was created
This type of damage can occur when exposed to high-energy radiation or other factors
This repair is done via 2 mechanisms: non-homologous end joining (NHEJ) and homologous recombination (HR)

Question 28

Non-homologous end joining (NHEJ)

Answer 28

The DNA is just glued back together at the breakage point
Not the best repair method → the cell can lose some DNA or have an addition of DNA at the breakage point
Result = usually a small mutation at the breakage site

Question 29

Homologous recombination (HR)

Answer 29

The information of the damaged chromosome is found in the homologous sister chromosome/chromatid → this info is used to repair the DNA