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

Assertion (A): DNA shows hypochromicity on heating. Reason (R): Heat denaturation of DNA causes the double helix structure to unwind to form single-stranded DNA.

Directions: In the following question there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answers as under:

1. If A and R both are correct and R is the correct explanation of A.
2. If A and R both are correct and R is not the correct explanation of A.
3. If A is correct and R is incorrect.
4. If A is incorrect and R is correct.
5. If A and R both are incorrect.

  1. 1

  2. 2

  3. 3

  4. 4

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

Correct answer. A is incorrect and R is correct. DNA shows hyperchromicity on heating. Heat denaturation of DNA causes the double helix structure to unwind to form single-stranded DNA. When DNA in solution is heated above its melting temperature, the double-stranded DNA unwinds to form single-stranded DNA. The bases become unstacked and can thus, absorb more light.

Multiple choice

Nucleotides are

  1. nucleoside + phosphoric acid

  2. nucleoside + sulphuric acid

  3. nucleoside + nitric acid

  4. nucleoside + citric acid

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

It is the correct answer as nucleotides are monomeric units of nucleic acids. Each nucletode consists of a nucleoside linked with phosphoric acid. Nucleoside is a combination of a nitrogen base and a pentose sugar.

Multiple choice

ATP contains _______ phosphate molecule/s in its molecule.

  1. 1

  2. 2

  3. 3

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

ATP (Adenosine Triphosphate) contains 3 phosphate molecules in its structure: adenine-ribose-phosphate-phosphate-phosphate. The 'Tri' in Triphosphate means 'three'. Breaking the bond to the third (terminal) phosphate releases energy for cellular work. ADP (Adenosine Diphosphate) has only 2 phosphates.

Multiple choice

Which of the following statements does not characterise the noncoding DNA in the cell?

  1. The noncoding regions are under poor evolutionary pressure and negative selection.

  2. Prevents frameshift mutation.

  3. Controls the flow of transcription.

  4. Acts as genetic switches.

  5. The amount of noncoding DNA varies greatly among species.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Many noncoding DNA sequences have important biological functions as indicated by comparative genomics studies that report some regions of noncoding DNA that are highly conserved, sometimes on time-scales representing hundreds of millions of years, implying that these noncoding regions are under strong evolutionary pressure and positive selection.

Multiple choice

The two strands of DNA are linked by

  1. phosphate-diester bonds

  2. covalent bonds

  3. hydrogen bonds

  4. ionic bonds
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The two strands of DNA are linked by hydrogen bonds formed in between nitrogen bases.

Multiple choice

The mutation due to the insertion or deletion of nucleotides is known as

  1. frameshift mutation

  2. neutral mutation

  3. silent mutation

  4. conditional mutation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Frameshift mutation is a mutation caused by insertion or deletion of a number of nucleotides that is not evenly divisible by three from a DNA sequence. Due to the triplet nature of gene expression by codons, the insertion or deletion can disrupt the reading frame, or the grouping of the codons, resulting in a completely different translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein produced is.

Multiple choice

The process by which extra nucleotides are added into the DNA molecule is known as

  1. point mutation

  2. insertions

  3. deletions

  4. amplifications
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Insertions add one or more extra nucleotides into the DNA. They are usually caused by transposable elements, or errors during replication of repeating elements, e.g. AT repeats. Insertions in the coding region of a gene may alter splicing of the mRNA (splice site mutation), or cause a shift in the reading frame (frameshift), both of which can significantly alter the gene product.