All Free Biology MCQs with Answers

• A. They are formed during meiosis.
• B. They are held together by centromeres.
• C. They are chromatids of the same chromosome.
• D. They carry both morphologically similar members with same set of genes.

Explanation: The homologous chromosomes are made before meiosis, so option A is incorrect. Early in prophase I, homologous chromosomes come together to form a synapse. The chromosomes are bound tightly together and in perfect alignment by a protein lattice, so option B is incorrect. The question talks about chromosomes, not chromatids, so option C is incorrect. Homologous chromosomes carry the same genes and hence are morphologically similar. So option D is correct.

• A. The genetic component i.e. the genes in an individual for a particular trait
• B. Partner of gene pair
• C. The form of appearance of a trait
• D. The position of a gene on the chromosome

Explanation: A phenotype is an individual's observable traits, such as height, eye color, and blood type.

• A. DNA polymerase
• B. RNA polymerase
• C. DNA transcriptase
• D. RNA transcriptase

Explanation: RNA polymerase is the main transcription enzyme. RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. DNA polymerase is an enzyme that synthesizes DNA molecules from deoxyribonucleotides, which are the building blocks of DNA. The enzymes play an essential role in DNA replication, usually working in pairs to produce two matching DNA stranges from a single DNA molecule. There are no enzymes known as DNA or RNA transcriptase. However, we have Reverse Transcriptase (RT) which is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed as 'reverse transcription'.

• A. Genotype
• B. Phenotype
• C. Karyotype
• D. Allele

Explanation: A karyotype is an individual's collection of chromosomes. Presented below is a karyogram.

• A. Option A
• B. Option B
• C. Option C
• D. Option D
• E. Option E

Explanation: The DNA sequence will bealanine - GCA = CGT arginine - CGA = GCTlysine - AAG = TTCphenylalanine - UUU = AAA

• A. 16%
• B. 18%
• C. 32%
• D. 36%

Explanation: 32% of the nitrogenous bases are cytosine so 32% of the nitrogenous bases are guanine, according to Chargaff's rule. This makes a total of 64%. The remaining percentage is 36%. So, half of this i.e. 18% will be of adenine and 18% will be of thymine in DNA. As Adenine is translated into uracil in mRNA, therefore, uracil is also 18% in mRNA. So, total will be 36%.

• A. 2
• B. 3
• C. 4
• D. 6

Explanation: The number of adenine base pairs on one strand is equal to thymine base pairs on the other strand and the cytosine base pairs are equal to the guanine base pairs on the other strand. According to the given condition, there are 30 base pairs thus;

• A. Mitosis
• B. Meiosis
• C. Geographic distribution
• D. Active transport

Explanation: Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, which results in new allelic combinations in the daughter cells.

• A. Hemophilia
• B. Phenylketonuria
• C. Sickle cell anemia
• D. Down's Syndrome

Explanation: Trisomy 21 i.e. the presence of 3 chromosomes at the 21th pair is the characteristic of Down's syndrome.

• A. Genetic drift
• B. Genotype
• C. Gene pool
• D. Gene mutation

Explanation: The total set of gene copies for all genes in a population is referred to as its gene pool. (A: Genetic drift) is the change in the frequency of an existing gene variant in a population due to random sampling of organisms. (B: Genotype) is an organism's set of heritable genes that can be passed down from parents to offspring. (D: Gene mutation) is a permanent alteration in the DNA sequence that makes up a gene.