Molecular Basis of Inheritance — Page 19 | NEET Biology

Q181

Jacob and Monod studied lactose metabolism in E.coli and proposed operon concept. Operon concept is applicable for

A all prokaryotes

B all prokaryotes and some eukaryotes

C all prokaryotes and all eukaryotes

D all prokaryotes and some protozoans

Correct Answer

Option B

Solution

(b) Gene regulation of eukaryotes is complex as compared to that of prokaryotes.

Q182

In a DNA percentage of thymine is

20 \%

then what will be the percentage of guanine?

A

20 \%

B

40 \%

C

30 \%

D

60 \%

Correct Answer

Option C

Solution

(c) According to Chargaff rule, the ratio of purine bases to pyrimidine bases is equal.

$A=T, C=G$ .

If T is 20% then A is 20% and C and G are 30%, 30%.

Q183

In E.coli during lactose metabolism repressor binds to operator

A regulatory gene

B operator gene

C structural gene

D promoter region

Correct Answer

Option B

Solution

(b) Regulator gene forms a biochemical substance for suppressing the activity of operator gene.

Promoter gene is the gene which provides point of attachment to RNA polymerase required for transcription of structural genes.

Structural genes are genes which transcribe mRNA for polypeptide synthesis.

Q184

During transcription, the DNA site at which RNA polymerase binds is called

A enhancer

B promoter

C regulator

D receptor

Correct Answer

Option B

Solution

(b) Regulator is a gene which forms a biochemical for suppressing the activity of operator gene.

Promoter is the gene which provides the point of attachment to RNA polymerase required for transcription of structural genes.

Q185

What does "lac" refer to in what we call the lac operon?

A The number

1,00,000

B Lactose

C Lactase

D Lac insect

Correct Answer

Option B

Solution

(b) Lactose operon in E.coli is a catabolic pathway in which the structural genes remain switched off unless the inducer (Lactose) is present in the medium.

Q186

In transgenics, expression of transgene in target tissue is determined by regulatory sequences

A enhancer

B transgene

C promoter

D reporter

Correct Answer

Option D

Solution

(d) Transgenic organisms are genetically modified organisms.

Q187

Which one of the following makes use of RNA as a template to synthesize DNA?

A DNA polymerase

B RNA polymerase

C Reverse transcriptase

D DNA dependant RNA polymerase

Correct Answer

Option C

Solution

(c) Reverse transcriptase (RNA dependent DNA polymerase) is present in some retroviruses e.g., HIV virus.

Q188

Transformation experiment was first performed on which bacteria?

A E.coli

B Diplococcus pneumoniae

C Salmonella

D Pasteurella pestis

Correct Answer

Option B

Solution

(b) Transformation is change in genetic material of an organism by obtaining genes from outside.

Q189

Semi-conservative replication of DNA was first demonstrated in:

A Escherichia coli

B Streptococcus pneumoniae

C Salmonella typhimurium

D Drosophila melanogaster

Correct Answer

Option A

Solution

(a) Meselson and Stahl demonstrated semi-conservative replication in E. coli.

Q190

During transcription holoenzyme RNA polymerase binds to a DNA sequence and the DNA assumes a saddle like structure at that point. What is that sequence called?

A AAAT box

B TATA box

C GGTT box

D CAAT box

Correct Answer

Option B

Solution

(b) About 28 base pairs from transcription start site are TATA boxes.

After 40 bases from TATA boxes appears LAAT boxes.

Both of these sequence serve as recognition site in eukaryotic promoters (Transcription in eukaryotic genes in a far more complicated process than in prokaryotes)