NEET Biology Molecular Basis of Inheritance MCQs Set 19

Answer: (b) mRNA

Explanation:
1. The codons in mRNA specify the order of amino acids.
2. So the correct choice is option (b).

Teacher's Note:
1. mRNA carries the code.
2. tRNA reads it.

Answer: (d) Beadle and Tatum

Explanation:
1. Beadle and Tatum worked on Neurospora mutants and proposed that each gene controls one enzyme.
2. So the correct choice is option (d).

Teacher's Note:
1. Garrod: inborn errors of metabolism.
2. Neurospora experiments.

Answer: (c) 3.4 nm

Explanation:
1. A turn contains 10 base pairs at 0.34 nm each.
2. So the correct choice is option (c).

Teacher's Note:
1. 10 x 0.34 nm.
2. 2 nm is the diameter.

Answer: (a) rye

Explanation:
1. Triticale is an amphidiploid of wheat (Triticum) and rye (Secale).
2. So the correct choice is option (a).

Teacher's Note:
1. Triticum + Secale.
2. Combines wheat yield with rye hardiness.

Answer: (c) UAG, UGA, UAA

Explanation:
1. UAA, UAG and UGA are stop (nonsense) codons.
2. So the correct choice is option (c).

Teacher's Note:
1. They code for no amino acid.
2. Release factors bind.

Answer: (a) 5-methyl uracil

Explanation:
1. Thymine is uracil with a methyl group on carbon 5.
2. So the correct choice is option (a).

Teacher's Note:
1. DNA uses T for stability.
2. RNA uses U.

Answer: (b) differential expression of genes

Explanation:
1. All cells have the same genes but different sets are switched on in different tissues.
2. So the correct choice is option (b).

Teacher's Note:
1. Gene regulation.
2. Cells do not lose genes.

Answer: (c) transcription factors

Explanation:
1. Transcription factors control whether RNA polymerase transcribes a gene.
2. So the correct choice is option (c).

Teacher's Note:
1. Regulation at transcription.
2. Not by ribosomes.

Answer: (c) antiparallel

Explanation:
1. One chain runs 5' to 3' and the other 3' to 5'.
2. So the correct choice is option (c).

Teacher's Note:
1. Opposite polarity.
2. Semiconservative is about replication.

Answer: (d) n = 21 and x = 7

Explanation:
1. Hexaploid wheat is 2n = 42. Basic number x = 7 and gametes carry three sets, so n = 21.
2. So the correct choice is option (d).

Teacher's Note:
1. 6 sets of x = 7.
2. n is the gamete number.

Answer: (d) uracil

Explanation:
1. Uracil occurs in RNA, not in DNA.
2. So the correct choice is option (d).

Teacher's Note:
1. DNA: A, T, G, C.
2. RNA: A, U, G, C.

Answer: (c) several ribosomes attached to a single mRNA

Explanation:
1. Many ribosomes translate one mRNA at the same time, forming a polysome.
2. So the correct choice is option (c).

Teacher's Note:
1. Increases protein output.
2. Seen as beads on a string.

Answer: (b) adenine, thymine - purines

Explanation:
1. Adenine is a purine but thymine is a pyrimidine.
2. So the correct choice is option (b).

Teacher's Note:
1. Pu: A, G.
2. Py: C, T, U.

Answer: (b) all mutations, dominant or recessive, are expressed in haploids

Explanation:
1. With a single allele of each gene there is no second allele to mask a recessive mutation.
2. So the correct choice is option (b).

Teacher's Note:
1. No masking by a dominant allele.
2. Used in microbial genetics.

Answer: (b) splicing

Explanation:
1. Splicing joins exons after removing introns from hnRNA.
2. So the correct choice is option (b).

Teacher's Note:
1. Capping adds 5' methyl guanosine.
2. Tailing adds poly A.

Answer: (c) Escherichia coli

Explanation:
1. Meselson and Stahl used E. coli grown in 15N medium and density gradient centrifugation.
2. So the correct choice is option (c).

Teacher's Note:
1. Heavy nitrogen 15N.
2. CsCl gradient.

Answer: (c) a change in a single base pair

Explanation:
1. A point mutation alters one base pair of DNA, as in sickle cell anaemia.
2. So the correct choice is option (c).

Teacher's Note:
1. Single base change.
2. Deletion or insertion can cause frameshift.

Answer: (a) forensic science

Explanation:
1. Satellite DNA is highly repetitive and varies between people, so it is the basis of DNA fingerprinting.
2. So the correct choice is option (a).

Teacher's Note:
1. VNTR polymorphism.
2. Does not code for protein.

Answer: (b) HIV

Explanation:
1. HIV is a retrovirus that copies RNA into DNA (reverse transcription), reversing the usual flow.
2. So the correct choice is option (b).

Teacher's Note:
1. Reverse transcription: RNA to DNA.
2. DNA to RNA to protein is the standard flow.

Answer: (b) genetic fingerprinting

Explanation:
1. Both reveal DNA variations used for genetic fingerprinting.
2. So the correct choice is option (b).

Teacher's Note:
1. DNA profiling.
2. VNTR analysis.

Answer: (b) satellite DNA occurring as highly repeated short segments

Explanation:
1. Repeated sequences (VNTRs) differ in number between individuals, producing unique band patterns.
2. So the correct choice is option (b).

Teacher's Note:
1. Not fingertips.
2. Inherited bands.

Answer: (d) electrophoresis

Explanation:
1. Gel electrophoresis separates the negatively charged DNA fragments by size.
2. So the correct choice is option (d).

Teacher's Note:
1. Smaller fragments move farther.
2. Agarose gel.

Answer: (b) BAC and YAC

Explanation:
1. Bacterial and yeast artificial chromosomes carry large inserts.
2. So the correct choice is option (b).

Teacher's Note:
1. Used in the Human Genome Project.
2. Large DNA inserts.

Answer: (d) c, b, a, e, d

Explanation:
1. DNA is isolated, cut, separated by electrophoresis, transferred to a membrane (Southern blot) and then hybridised with a labelled probe.
2. So the correct choice is option (d).

Teacher's Note:
1. Isolate, digest, run, blot, probe.
2. Probe goes last.

Answer: (b) G 17%, A 33%, T 33%

Explanation:
1. G = C = 17%, so A + T = 66%, and A = T = 33%.
2. So the correct choice is option (b).

Teacher's Note:
1. G = C, A = T.
2. Sum to 100.