Biology

Question 1

What is an operon?

Answer 1

An operon is a unit of genetic function found in bacteria consisting of a promoter and an operator and a cluster of genes

Question 2

Differenciate a repressible and inducible operon

Answer 2

> repressible operon are usually on and can be deactivated
inducible operon are usually of and can be activated

Question 3

Sort the stage form precursor to essential product

Answer 3

1. increase tryptophan
2. trp repressor activated
3. transcription by polymerase II
4. tryptophan pathway enzyme
5. tryptophan synthesis
   This process is anabolic

Question 4

Sort the stage from nutrient to simpler molecule

Answer 4

1. high lactose
2. high allolactose
3. active lac repressor
4. transcription by polymerase II
5. lactose pathway
6. hydrolysis

Question 5

Contrast positive and negative regulation

Answer 5

positive regulation enable gene expression while negative regulation prevent it

Question 6

Explain the negative regulation of the trp operon

Answer 6

The presence of tryptophan acts as a co-repressor, leading to repression of the trp operon. (ensure that tryptophan is only produce when needed)

Question 7

Explain the negative regulation of the lac operon

Answer 7

the presence of lactose alleviates the repression of the lac operon. enabling the bacterium to use lactose as a carbon source.

Question 8

Explain the positive regulation of the lac operon

Answer 8

-cAMP bind allosterically to a regulatory protein
- CRP binds to promoter
- This binding facilitate the binding of RNA polymerase
-This stimulate the transcription of the lac operon gene

Question 9

List the stages in which gene expression can be regulated.

Answer 9

Transcription, RNA processing, translation, degradation and protein modification

Question 10

Define epigenetic inheritance

Answer 10

Trait transmitted by mechanism not linked to the nucleotide sequence

Question 11

Differentiate the role of general transcription and specific transcription

Answer 11

General transcription initiate transcription by binding a component protein to the TATA box while specific transcription initiates gene expression by acting as a promoter or enhancer

Question 12

Describe the role of control elements

Answer 12

They serves as a binding site for transcription factor and help recruit transcription initiators.

Question 13

provide example of post-transcriptional factor

Answer 13

Ex. alternative RNA splicing, reversible phosphorylation, protein modified post-translation,

Question 14

Sort genetic material from lower to higher level

Answer 14

DNA < histone < nucleosome < chromatin < Chromosome

Question 15

Why do thermophilic organisms have a higher GC content?

Answer 15

Because GC are more thermally stable, so they act better in high temp

Question 16

Define semi-conservative DNA replication.

Answer 16

Each new DNA molecules conserve half of the origin molecule

Question 17

Differentiate lagging strand synthesis from leading strands synthesis

Answer 17

Leading strand- same direction as replication fork, use 1 RNA primer, continuous
Lagging strand- away from replication fork direction, use multiple primer, discontinuous

Question 18

List the step of PCR

Answer 18

1. Denaturation of parental DNA
2. Annealing of DNA primer
3. elongation

Question 19

Define telomere

Answer 19

sequence of dna that can be repeated over 1000 time. (protect the organism from being eroded during successive round of replication

Question 20

Provide counter example of gene hypothesis

Answer 20

One gene = one enzyme- tubulin, insulin ( not all genes code for enzyme)
One gene = one protein- hemoglobin (many protein are made of multiple subunit)
One gene = one polypeptide- mRNA, tRNA

Question 21

contrast transcription and translation in eukaryotes and prokaryotes

Answer 21

in prokaryotes, transcription occur immediately and in cytoplasm while transcription occurs in nucleus, in eukaryotes. Translation occurs in cytoplasm in eukaryotes.

Question 22

Contrast to two types of mutation

Answer 22

Synonymous: change codon but doesn’t affect amino acids
Non-Synonymous: change codon and amino acids

Question 23

explain effects of mutation

Answer 23

> Missense: affect the primary, secondary and tertiary structure of protein
Non-conservative missense: lead to amino acid with very different chemical properties
Point-mutation: change in a single base pair within the dna molecule
indels: cause loss of protein function

Question 24

differentiate between anabolic and catabolic pathway

Answer 24

Catabolic pathway breakdown complex molecule to smaller molecule while anabolic builds complex molecule