Biology

Molecular Biology and Genetics

985 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

The two strands of the DNA molecule are held together by:

  1. phosphate bond

  2. amino bond

  3. hydrogen bond

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

DNA's double helix structure is maintained by hydrogen bonds between complementary base pairs on opposite strands. Adenine pairs with thymine (2 hydrogen bonds), and guanine pairs with cytosine (3 hydrogen bonds). These bonds are strong enough to hold the strands together but weak enough to separate during DNA replication and transcription.

Multiple choice

In Lysosomal Storage Disorders, which of the following is true?

  1. The lysosomes are deficient in the enzyme hydrolase.

  2. There is a defect in the fusion of lysosomes and phagosomes.

  3. There is a defect in the lysosomal membrane.

  4. None of these

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

Lysosomal Storage Disorders are characterized by deficiency of specific lysosomal hydrolase enzymes, leading to accumulation of substrates within lysosomes. The primary defect is the absence or dysfunction of these hydrolytic enzymes. Options B and C describe other possible lysosomal dysfunctions but are not the defining feature of LSDs. Option D is incorrect because the enzyme deficiency (Option A) is the hallmark of these disorders.

Multiple choice

In Lysosomal Storage Disorders, true is:

  1. The lysosomes are deficient in the enzyme hydrolase

  2. There is a defect in the fusion od lysosomes and phagosomes

  3. There is a defect in the lysosomal membrane

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

Lysosomal storage disorders are caused by deficiency of specific hydrolytic enzymes within lysosomes. This leads to accumulation of substrates that would normally be degraded. The primary defect is not in lysosomal membrane structure or fusion with phagosomes - the core issue is missing or deficient hydrolase enzymes.

Multiple choice

What is true about linkage analysis in familial gene disorders?

  1. Characteristic DNA polymorphism in a family is associated with disorders.

  2. Characteristic DNA polymorphism with a clinical phenotype.

  3. Useful to make pedigree chart to show affected and non-affected family members.

  4. Used to make a pedigree chart to show non-paternity.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Linkage analysis tracks DNA polymorphisms (markers) that co-segregate with a disease phenotype within families. It identifies chromosomal regions harboring disease genes by observing inheritance patterns. It doesn't directly make pedigree charts (that's done separately) or detect non-paternity.

Multiple choice

A molecule of ATP is structurally similar to a molecule of

  1. RNA molecule

  2. DNA molecule

  3. amino acid

  4. fatty acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ATP (Adenosine Triphosphate) is structurally similar to RNA molecules because both contain a ribose sugar (not deoxyribose like DNA) and the nitrogenous base adenine. ATP can be considered a modified RNA nucleotide with three phosphate groups instead of one. DNA contains deoxyribose sugar, amino acids and fatty acids are completely different molecular structures.

Multiple choice

Interdependent genes with related functions form

  1. a coadapted gene complex

  2. an inversion

  3. a fitness set

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

A coadapted gene complex refers to a set of interdependent genes with related functions that have evolved together to work in a coordinated manner. These genes often influence the same trait or set of traits and their effects are interconnected. The other options are incorrect: an inversion is a chromosomal rearrangement, a fitness set refers to possible combinations of traits, and super mutation is not a standard genetic term.

Multiple choice

Prokaryotic genetic system has :

  1. DNA and histone

  2. DNA and no histone

  3. No DNA and histone

  4. No DNA and no histone

  5. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Prokaryotes do not contain DNA packing histones.

Multiple choice

Purines are generally abbreviated as:

  1. R

  2. Y

  3. C

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

In single-letter nucleotide notation, R stands for purines (A and G), while Y stands for pyrimidines (C and T/U). C and U represent specific bases, not base categories.

Multiple choice

Which of the following statements are false?

  1. All T cells originate from haematopoietic stem cells in the bone marrow.
  2. All the blood grouping reactions are precipitation reactions.
  3. Idiotypic determinants of an antibody are associated with the variable region.
  4. The basis for blue-white screening with PUC vectors is intergenic complementation.

  1. Only 1 and 2

  2. Only 1 and 4

  3. Only 2 and 3

  4. Only 2 and 4

  5. Only 3 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Correct answer. Both the statements are false. All the blood grouping reactions are agglutination reactions. The basis for blue-white screening with PUC vectors is intraallelic complementation.

Multiple choice

Which of the following statement is true?

  1. DNA is non-polar due to the highly charged phosphate backbone.

  2. DNA is polar due to the highly charged phosphate backbone.

  3. DNA is polar due to the highly charged sugar backbone.

  4. DNA is non-polar due to the highly charged sugar backbone.

  5. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA is polar due to highly charged phosphate backbone.

Multiple choice

Which of the following statement is true?

  1. One gene code for one protein

  2. Genome size is proportional to the number of genes in eukaryotes.

  3. Genome size may not be proportional to number of genes in eukaryotes

  4. Genetic codes are universal.

  5. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

genome size may not be proportional to number of genes in eukaryotes