All Free Biology MCQs with Answers
Every Biology question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
19844 questions · page 742 of 1985
7411. The actual replication of chromosome is _.
- A. Chromatin
- B. chromatids
- C. centromere
- D. polar dyes
Explanation: A chromatid is one of two identical halves of a replicated chromosome. During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes.
Correct answer: chromatids7412. An animal has 80 chromosomes in its gametes, how many chromosomes will be seen in the animal's muscle cells?
- A. 120
- B. 240
- C. 40
- D. 160
Explanation: If an animal cell has 80 chromosomes in its gametes, it would have double that number in its somatic cells (body cells). Therefore, there would be 160 chromosomes in its muscle cell or any other somatic cell.
Correct answer: 1607413. In humans the sequence TTAGGG is repeated how many times?
- A. 3000
- B. 4000
- C. 2500
- D. 3500
Explanation: In humans the telomere sequence is TTAGGG. This sequence is usually repeated about 3,000 times and can reach up to 15,000 base pairs in length.
Correct answer: 30007414. A trait determines by a gene on the X chromosome is said to be
- A. Pseudoautosomal
- B. Sex linked
- C. Both a & b
- D. None of the above
Explanation: X-linked, as related to genetics, refers to characteristics or traits that are influenced by genes on the X chromosome.
Correct answer: Sex linked7415. Complementary DNA molecule is:
- A. DNA from mRNA
- B. An artificial DNA
- C. Single stranded DNA
- D. A small segment of chromosomal DNA
Explanation: A complementary DNA molecule or cDNA is, by definition, a DNA copy of a messenger RNA or mRNA molecule, produced by reverse transcriptase.
Correct answer: DNA from mRNA7416. Meselson and Stahl transferred few bacteria grown in N15 medium to N14 medium for replicating their DNA. What would be the result after two rounds of replication?
- A. 100% heavy duplex
- B. 100% hybrid duplex
- C. 50% hybrid duplex and 50% heavy duplex
- D. 50% hybrid duplex and 50% light duplex
Explanation: After two rounds of replication, half of the duplexes will be hybrid i.e. contain one N15 strand and one N14 strand, while the other half will contain only N14 or light strands.
Correct answer: 50% hybrid duplex and 50% light duplex7417. If sequence in DNA is CCCTAGAG, then what would be the sequence in messenger RNA after transcription?
- A. GGGAUCUC
- B. GGGATCTC
- C. GGAAUCUC
- D. GGGGTCTC
Explanation: C pairs with G, A pairs with T in DNA while A pairs with U in RNA. The question asks for the corresponding mRNA sequence, after transcription of the DNA sequence. The C bases will correspond to G bases on the mRNA, T will correspond to A, G will correspond to C, whereas A will correspond to U and not T because the transcript is made up of RNA and not DNA, hence U takes the place of T. Option A describes the correct transcript: C C C T A G A G G G G A U C U C
Correct answer: GGGAUCUC7418. Which one is an example of a Nucleotide?
- A. Adenosine
- B. NAD
- C. ATP
- D. Guanine
Explanation: ATP is a nucleotide, as it contains a pentose sugar, an adenine base, and three phosphate groups. A nucleotide may have one or more phosphate groups.
Correct answer: ATP7419. The nitrogen-containing bases in nucleotide are of two types; Purines and Pyrimidines. The purines bases are:
- A. Adenine, Guanine, and Cytosine
- B. Guanine and Cytosine
- C. Adenine and Guanine
- D. Adenine and Thymine
Explanation: Purine bases are adenine and guanine, while pyrimidine bases are thymine, cytosine, and uracil. Option C is the only option that mentions only purine bases, while the others mention a combination of purine and pyrimidine bases.
Correct answer: Adenine and Guanine7420. The process in which a complementary copy of the code from a gene is produced by RNA Polymerase in the nucleus:
- A. Transcription
- B. Translation
- C. Proofreading
- D. DNA Replication
Explanation: Transcription, is when RNA polymerase makes a copy of a gene on a template DNA strand in the nucleus; this copy is messenger RNA.
Correct answer: Transcription