All Free Biology MCQs with Answers

• A. Position
• B. Frequency
• C. Copy
• D. Inversion

Explanation: Factual recall; The locus describes the position of the gene on a chromosome, so option A is correct.Option B, frequency, is generally used to describe frequency of alleles, i.e. how frequently one allele occurs relative to the other or the proportions in which each allele of a particular gene occurs.Option C, copy, as the name implies, refers to copies or duplications of a portion of the genetic code, found in the genome of an organism.Option D, inversion, is a mutation, that involves chromosome rearrangement, where one segment of a chromosome is reversed from end to end.

• A. Kinetochore
• B. Locus
• C. Allele
• D. Gene

Explanation: The gene is the basic physical and functional unit of heredity. It consists of a specific sequence of nucleotides at a given position on a given chromosome that codes for a specific protein. A kinetochore is a disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart. In genetics, a locus is a specific, fixed position on a chromosome where a particular gene or genetic marker is located. An allele is one of two, or more, forms of a given gene variant.

• A. TACGGATCCTG
• B. UAGCGAUCCUG
• C. AUGCCUAGGAC
• D. UACCGAUCCUG
• E. GCAUUCGAAGU

Explanation: DNA strand serves as the template for RNA synthesis. The RNA nucleotide sequence is complementary to that of DNA template strand except the presence of uracil in place of thymine. As we know that adenine base pairs with thymine and guanine with cytosine; the RNA sequence of given DNA strand would be UACGGAUCCUG. This makes option D correct answer.

• A. Transcriptase
• B. Polymerase
• C. Reverse transcriptase
• D. Synthetase

Explanation: Option A, transcriptase, is an RNA dependent RNA polymerase, which forms RNA strands by using RNA strands as a template. Option B, polymerase, can either be DNA polymerase or RNA polymerase, resulting in a complementary strand of DNA or RNA from a particular template strand. Option C is the correct answer, as reverse transcriptase is an RNA-dependent DNA polymerase, as it uses RNA as a template to form a DNA copy. This enzyme is the principal enzyme in retroviruses such as HIV. Option D, synthetase, is any enzyme that results in the synthesis of many different compounds, and is not specific to DNA or RNA.

• A. Peptide bond
• B. Phosphodiester bond
• C. Glycosidic bond
• D. Ester bond

Explanation: When nucleotides are incorporated into DNA, adjacent nucleotides are linked by a phosphodiester bond: a covalent bond is formed between the 5' phosphate group of one nucleotide and the 3'-OH group of another. In this manner, each strand of DNA has a "backbone" of phosphate-sugar-phosphate-sugar-phosphate.

• A. DNA polymerase
• B. Ligase
• C. Primase
• D. Endonuclease

Explanation: DNA polymerase adds nucleotides to the three prime (3')-end of a DNA strand, one nucleotide at a time. So option A is incorrect. In DNA replication, ligase's job is to join together fragments of newly synthesized DNA to form a seamless strand. So option B is correct. Primase are enzymes that catalyze the synthesis of short RNA molecules used as primers for DNA polymerases. So option C is incorrect. Restriction endonucleases are enzymes that recognize DNA sequences, scan the sequence and cleave the fragment around or within that sequence. So option D is incorrect.

• A. DNA
• B. Protein
• C. RNA
• D. A and C

Explanation: Mutation can occur in DNA and RNA i.e alteration in bases of DNA and RNA. Mutations can not occur in proteins.

• A. 6th
• B. 5th
• C. 4th
• D. 3rd
• E. 1st

Explanation: The nitrogenous bases are purines or pyrimidines. The nitrogen base is attached to the C-1 of the pentose sugar.

• A. Euchromatin
• B. Heterochromatin
• C. Nucleosome
• D. Super coils
• E. None of these

Explanation: Highly condensed portions of chromatin are called heterochromatin. Euchromatin is the uncondensed portion of DNA. The nucleosome is the fundamental subunit of the chromatin. Super coils refer to the multiple folds the DNA undergoes for it to be compressed enough to be incorporated in the nucleus.

• A. 44 + XX
• B. 44 + XY
• C. 44 + XXY
• D. 44 + XO
• E. 44 + XXX

Explanation: The genotype of a normal male contains 44 autosomes and two sex chromosomes, which are XY.