Regulation Of Genetic Expression

Question 1

What is the reason people having the same cells, creating different types of proteins, and phenotypic appearance ?

Answer 1

Bcuz of the regulation of genetic expression. Even twins have the different phenotypes . According to which gene is being transcribed by which cell and how is it regulated

Question 2

Gene expression site in prokaryotic and eukaryotic level

Answer 2

Pro- transcription only bcuz of the lack of compartmentalization , everything occurs spontaneously

Eu- different level different time eg, epigenetic gene transcription , post transcriptional modification , transition and translational modification

Question 3

Eukaryotic DNA can be found in the cytoplasm

Answer 3

False. Only in the nucleus. Only prokaryotic DNA can be spotted in the cytoplasm

Question 4

Is every gene being transcribed in the cell?

Answer 4

No. The DNA is a compact struture with histones. If every cell is being transcribed ——> messy asa histones need to be unwounded

Question 5

The promoter sequence activity difference in pro and eu

Answer 5

In eukaryotes, each gene has their own promoter sequence.

Question 6

What is an operon?

Answer 6

Genes that work together is known as an operon

Question 7

In prokaryotes, if specific sequence of genes do not need to be transcribed , what will they do ?

Answer 7

There is an operator sequence on DNA where repressors bind to inhibit the transcription of that specific genes

Question 8

What if the bacteria wants to enhance the gene transcription ?

Answer 8

The small macromolecules binds to activator site

Question 9

Operons are present only in prokaryotes

Answer 9

False. Although very rare and uncommon, operons are present in some eukaryotic organisms

Question 10

Lac operon’s structure

Answer 10

Lac Z- breakdown of lactose into small macromolecules
Lac Y - cellular transport of lactose into the cell
Lac A- transacetylase enzyme activity

Question 11

Lac operon only operates when ———

Answer 11

Lactose is present . Otherwise, the func of LacZ, LacY and LacZ ka tone ma ya tot wuh

Question 12

When the lactose in present, ———— can bind to ———

Answer 12

Allolactose is present and it can bind to repressor ——> so that repressor cannot bind to operator ===> lactose trancription (+)

When lactose is absent ——> vice versa——> allolactose (-) , repressor binds to the operator and lactose transcription is not
present

Question 13

When glucose is absent, but lactose is present, how is the activity of lac operon?

Answer 13

Generally thinking, ——> glucose is absent so the cell needs energy and demand for glucose. Lac operon gene can transcribe lactose——> lactose is the dipolyssacharide of glucose and galactose. So lac operon must be activated. Since lactose is also present, the lac gene can operate.

Low level of glucose ——> increased cAMP molecule——> binds to CAP===> CAP binds to CAP binding site ——> activation of transcription

+

Lactose present - allolactose present - binds to repressor protein - repressor cannot bind to operator- the trancription (+)
Combing two, lactose trancription will be very active

Question 14

How is the trancription of lac operon when both glucose and lactose are presnt

Answer 14

Lactose is present so transcription will be present

But glucose is present so camp conc will be low, camp cannot bind to CAP, CAP cannot bind to CAP binding site——> the lac gene will not be activated,

Summary, the transcription will be present but not be very active

Generally thinking, since glucose is present, the energy is sufficient, it does not need to transcribe more glucose for energy

Question 15

Lac operon is ——— operon.

Answer 15

Indicible

Lactose shi mha transcribe ml ma shi yin ma transcribe boo

Question 16

How is the operation of the TRP operon ?

Is it an inducible operon as well like lac-operon?

Answer 16

Tryp operon operates on negative feedback mechanism. Tryptophan present ——> try operon is repressed

Tryptophan absent ——> the tryp operon transcribe .

Tryp operon is the repressible operon . ( it represses when the tryptophan is present.

When tryptophan is present , it binds to repressor protein——> the repressor binds to operator sequence ——> the transcription is inhibited

When tryptophan is absent, the repressor protein is not bound with anything , cannot bind to operator, the transcription proceeds

Question 17

How can we regulate the epigenetic gene expression of eukaryotes?

Answer 17

Methylation and acteylation of the DNA molecules

Methylation - chromosomes tightly packed together
Acetylation- causes nucleosomes in loose packaging

Temporary- does not chane the DNA base sequence

Question 18

Epigenetic gene expression is before the ———

Answer 18

Transcription processes

Question 19

Regulation of transcriptional modification

Answer 19

Eu transcription
- Transcriptional factors
- enhancer regions
- silencer region
- activator proteins
- repressor proteins

When TF 2B binds to the DNA——> DNA bends ——> enhancer regions far away from the promoter region get closer and associate with the TF and promoter regions

Question 20

Regulation of post transcriptional gene expression

Answer 20

1. Splicing ====> splicing introns to produce proteins encoded by specific genes. The alternative splicing ——> different proteins ===> regulation
2. Capping and tailing are for stability and to prevent breakdown(stability)

The time RNA spend on cytoplasm is directly proportional to the protein synthesis

Decay rate fast——> less time in the cytoplasm ——> protein synthesis reduced

Decay rate slow——-> more time in cytoplasm——> protein synthesis more

3. Micro RNAs and stability —> micro RNA breakdown the RNA and reduce their stability —> less pr-
4. Binding of proteins to untranslated regions of the RNAs——> may increase or decrease stability

Question 21

Addition of ubiquitin group leads to ———

Answer 21

Protein degradation

Addition of uniquitin indicates that protein lifespan is completed ——> those proteins move to proteosomes to be degraded