Biology

Molecular Biology and Genetics

717 Questions

Molecular biology and genetics explore the structure and function of DNA, RNA, genetic mutations, and heredity. Understanding these building blocks of life is essential for most biology examinations. Review these practice questions to test your molecular genetics knowledge.

DNA structure and basesGenetic mutationsNucleic acids compositionDNA sequencing and replication

Molecular Biology and Genetics Questions

Multiple choice

Which among of the following statements regarding DNA is false?

  1. The double helix structure was first discovered by Watson and Crick.

  2. Adenine pairs with uracil.

  3. Cytosine pairs with guanine.

  4. Total amount of purines is equal to total amount of pyrimidines.

  5. Sugar is beta-D-2-deoxyribose.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because in DNA, adenine pairs with thymine. Uracil is not found in DNA.

Multiple choice

As a result of the ground-breaking work of Barbara McClintock, many scientists now believe that all of the information encoded in 50,000 to 100,000 of the different genes found in a human cell are contained in merely three percent of the cell's DNA.

  1. 50,000 to 100,000 of the different genes found in a human cell are contained in merely

  2. 50,000 to 100,000 of the human cell's different genes are contained in a mere

  3. the 50,000 to 100,000 different genes found in human cells are contained in merely

  4. 50,000 to 100,000 of human cell's different genes is contained in merely

  5. the 50,000 to 100,000 different genes found in a human cell is contained in a mere
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The subject here (i.e. the information) is singular, but specific. Hence, option 5 is the correct expression.

Multiple choice

RNA contains

  1. ribose sugar and thymine

  2. ribose sugar and uracil

  3. de-oxyribose sugar and thymine

  4. de-oxyribose sugar and uracil
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

RNA contains ribose sugar and guanine, adenine, cytosine and uracil bases.

Multiple choice

Which among the following does not characterise DNA molecule?

  1. It is composed of nitrogen bases, phosphates and sugars.

  2. It is double helix.

  3. The two polynucleotide chains are antiparallel.

  4. The distance between two successive sugar molecules is 34A0.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

One full turn of the helix, called gyre, measures 34A0 in length. The distance between two successive sugar molecules is 3.4A0. Thus, each gyre accommodates 10 nucleotides.

Multiple choice

The parent double stranded helix will remain unchanged in ________ type of DNA replication.

  1. conservative mode

  2. dispersive mode

  3. semi conservative mode

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Conservative mode is a postulated type of DNA replication in which double-stranded helix remains intact and acts as a template for a new double-stranded DNA helix. This type of DNA replication is disproved model, in this type of replication one-half of the daughters DNA molecules will have both strands composed of newly polymerized nucleotides and the old parent double stranded helix will remain unchanged.

Multiple choice

Which of the following properties helps the DNA in existing like a twisted rope?

  1. Grooves

  2. Base pairing

  3. Sense and antisense

  4. Supercoiling
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

DNA can be twisted like a rope in a process called DNA supercoiling. With DNA in its relaxed state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound.

Multiple choice

Which among the following is not a nitrogenous base?

  1. Adenine

  2. Thymine

  3. Ribose

  4. Guanine

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ribose is an organic compound with formula C5H10O5.It is specifically, a monosaccharide (simple sugar) with linear form H-(C=O)-(CHOH)4-H, which has all the hydroxyl groups on the same side in the Fischer projection.

Multiple choice

Diameter of DNA is constant due to

  1. hydrogen bonds between base

  2. phosphodiester bonds

  3. disulphide bonds

  4. covalnet bonds

  5. -
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Correct Answer: hydrogen bonds between base