Molecular Basis of Inheritance — Page 20 | NEET Biology

Q191

Which form of RNA has a structure resembling clover leaf?

A rRNA

B hn RNA

C m RNA

D t RNA

Correct Answer

Option D

Solution

(d) rRNA occurs inside ribosomes. mRNA carries information from DNA to polypeptides. hnRNA are heterogenous nuclear RNA. tRNA has clover leaf structure.

Q192

Select the correct option: Direction of RNA synthesis Direction of reading the template DNA strand

A

5 - 3

B

3-5

C

5^{\prime}-3^{\prime}

D

3^{\prime}-5^{\prime}

Correct Answer

Option A

Solution

(a) Synthesis of RNA exhibits several features that are synonymous with DNA replication.

RNA synthesis requires accurate and efficient initiation, elongation proceeds in the $5^{\prime} \to 3^{\prime}$ direction (i.e. the polymerase moves along the template strand of DNA in the $3^{\prime} \to 5^{\prime}$ , direction), and RNA synthesis requires distinct and accurate termination.

Q193

Extranuclear inheritance occurs in

A peroxisome and ribosome

B chloroplast and mitochondria

C mitochondria and ribosome

D chloroplast and lysosome

Correct Answer

Option B

Solution

(b) In eukaryotic cells, two cytoplasmic organelles, mitochondria and chloroplast of green plants, contain their own genetic materials.

Q194

DNA template sequence of CTGATAGC is transcribed over mRNA as

A GUCTUTCG

B GACUAUCG

C GAUTATUG

D UACTATCU

Correct Answer

Option B

Solution

(b) During transcription, from the DNA template complementary mRNA is formed and thymine is replaced by uracil.

Q195

The following ratio is generally constant for a given species:

A

(A+G)/(C+T)

B

(T+C)/(G+A)

C

(G+C)/(A+T)

D

(A+C)/(T+G)

Correct Answer

Option C

Solution

(c) According to Chargaff purines and pyrimidines are in equal amounts.

Purine (adenine) is equimolar with pyrimidine (thymine) and purine (guanine) is equimolar with pyrimidine (cytosine).

Base ratio $(A+T)/(C+G)$ is specific for species.

Q196

Gene regulation governing lactose operon of E.coli that involves the lac I gene product is :

A Negative and inducible because repressor protein prevents transcription

B Negative and repressible because repressor protein prevents transcription

C Feedback inhibition because excess of b-galactosidase can switch off trascription

D Positive and inducible because it can be induced by lactose

Correct Answer

Option A

Solution

(a) Lac operon under control of repressor shows a negative regulation. Operon has inducible nature.

Q197

Which antibiotic inhibits interaction between ribosomal RNA and mRNA during bacterial protein synthesis?

A Neomycin

B Streptomycin

C Tetracycline

D Erythromycin

Correct Answer

Option A

Solution

(a) Neomycin is the antibiotic which inhibits the translation of bacterial protein so that it can not affect the host cell.

Q198

The two polynucleotide chains in DNA are

A discontinuous

B antiparallel

C semi-conservative

D parallel.

Correct Answer

Option B

Solution

(b) The two chains are antiparallel, one aligned in $5^{\prime} \to 3^{\prime}$ direction the other in $3^{\prime} \to 5^{\prime}$ direction.

Q199

During transcription, RNA polymerase holoenzyme binds to a gene promoter and assumes a saddle-like structure, what is its DNA-binding sequence?

A AATT

B CACC

C TATA

D TTAA

Correct Answer

Option C

Solution

(c) The DNA binding sequence for RNA polymerase is called TATA box.

Q200

E.coli cells with a mutated

z

gene of the lac operon cannot grow in medium containing only lactose as the source of energy because:

A the lac operon is constitutively active in these cells

B they cannot synthesize functional betagalactosidase

C in the presence of glucose, E.coli cells do not utilize lactose

D they cannot transport lactose from the medium into the cell

Correct Answer

Option B

Solution

(b) Operons are segments of genetic material which function as regulated unit or units that can be switched on and switched off.

An operon consists of one to several structural genes.

(Three in lac operon) These are genes which produce mRNAs for forming polypeptides / proteins / enzymes. $Z$ (produces enzyme $\beta$ galactosidase for splitting lactose into glucose and galactose).

Y (produces enzyme galactoside permease required for entry of lactose) and $A$ (produces enzyme thiogalactoside trans-acetylase).

The three structural genes of the operon produce a single polycistronic mRNA.