Question

Read the following four statements $(A-D)$:
(A) In transcription, adenosine pairs with uracil.
(B) Regulation of lac operon by repressor is referred to as positive regulation.
(C) The human genome has approximately $50,000$ genes.
(D) Haemophilia is a sex-linked recessive disease.
How many of the above statements are right?

• A. Four
• B. One
• C. Two
• D. Three

Answer 1

The correct option is D Three

A)
During transcription, small segments of DNA are transcribed into RNA by the enzyme RNA polymerase. The two strands of DNA start separating after recognizing the specific sequence of DNA by the promoter.The RNA polymerase begins copying from a specific point of one strand of the DNA using a special type of sugar-containing nucleosides called ribonucleoside-5- triphosphates to begin growing chain.Each successive ribonucleotide is directed by complementary base pairing rules of DNA. For e.g. C or cytosine in DNA directs incorporation of G or guanine in RNA, likewise Thymine or T into Adenine or A, and A into U or Uracil.

B)

The lac operon uses two-part control mechanism to ensure that cell expends energy producing the enzymes encoded by lac operon only when necessary.In the absence of lactose lac repressor halts production of the enzymes encoded by the lac operon.

C)

The human genome has approximately 19000 to 20000. genes. The estimated number is expected to drop further as the gene finding methods will improve.

D)

Hemophilia is a genetic disorder with deficiency of clotting factor VIII. Haemophilia is inherited in an X linked recessive manner.

Therefore A, B, and D are the correct statement. Answer D is the correct answer.