DNA/RNA Structure — Homi Bhabha Exam Biology MCQs with Solutions
Free Homi Bhabha Exam Biology DNA/RNA Structure MCQs with step-by-step solutions (10 questions). Part of Heredity & Genetics. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — DNA/RNA Structure · medium · theory
The molecule that carries the hereditary (genetic) information in most living organisms is:
A. RNA only
B. protein
C. DNA ✓ Correct
D. glucose
Solution: DNA (deoxyribonucleic acid) stores and transmits genetic information.
Q2 — DNA/RNA Structure · hard · theory
The double-helix structure of DNA was proposed by:
A. Darwin
B. Watson and Crick ✓ Correct
C. Mendel
D. Robert Hooke
Solution: James Watson and Francis Crick described the DNA double helix in 1953.
Q3 — DNA/RNA Structure · medium · theory
The four nitrogenous bases found in DNA are adenine, thymine, guanine and:
A. ribose
B. cytosine ✓ Correct
C. glucose
D. uracil
Solution: DNA contains A, T, G and C; uracil occurs in RNA, not DNA.
Q4 — DNA/RNA Structure · hard · theory
In RNA, the base that replaces thymine (found in DNA) is:
A. cytosine
B. guanine
C. uracil ✓ Correct
D. adenine
Solution: RNA uses uracil (U) in place of the thymine found in DNA.
Q5 — DNA/RNA Structure · medium · theory
A segment of DNA that controls a particular trait is called a:
A. ribosome
B. gene ✓ Correct
C. tissue
D. cell
Solution: A gene is a unit of heredity — a stretch of DNA coding for a characteristic.
Q6 — DNA/RNA Structure · hard · theory
In the DNA double helix, adenine (A) always pairs with:
A. uracil (U)
B. cytosine (C)
C. guanine (G)
D. thymine (T) ✓ Correct
Solution: Complementary base pairing: A pairs with T, and G pairs with C.
Q7 — DNA/RNA Structure · medium · theory
The thread-like structures in the nucleus that carry the genes are called:
A. lysosomes
B. chromosomes ✓ Correct
C. vacuoles
D. ribosomes
Solution: Chromosomes, made of DNA and protein, carry the genes.
Q8 — DNA/RNA Structure · hard · theory
Structurally, DNA is usually ______, while RNA is usually ______:
A. both double-stranded
B. both single-stranded
C. single-stranded; double-stranded
D. double-stranded; single-stranded ✓ Correct
Solution: DNA is typically a double-stranded helix; RNA is generally single-stranded.
Q9 — DNA/RNA Structure · hard · theory
A single unit (building block) of DNA, consisting of a sugar, a phosphate and a base, is called a:
A. monosaccharide
B. nucleotide ✓ Correct
C. amino acid
D. fatty acid
Solution: A nucleotide (sugar + phosphate + nitrogenous base) is the monomer of nucleic acids.
Q10 — DNA/RNA Structure · medium · theory
In eukaryotic cells, most of the DNA is located in the:
A. cytoplasm
B. cell wall
C. ribosome
D. nucleus ✓ Correct
Solution: The bulk of a eukaryotic cell's DNA is found in the nucleus (some in mitochondria/chloroplasts).