NEET Genetics and Evolution 1 — Questions and Answers
Question 1: Which of Mendel's laws states that alleles for different traits are inherited independently of each other?
- Law of Dominance
- Law of Segregation
- Law of Independent Assortment (Correct answer)
- Law of Blending
Correct answer: Law of Independent Assortment
The Law of Independent Assortment states that genes for different traits segregate independently during gamete formation, explaining dihybrid cross outcomes.
Question 2: In a monohybrid cross between two heterozygotes (Aa × Aa), what is the expected phenotypic ratio in the offspring?
- 1:2:1
- 3:1 (Correct answer)
- 1:1
- 9:3:3:1
Correct answer: 3:1
The cross Aa × Aa produces a 1:2:1 genotypic ratio (AA:Aa:aa), but since A is dominant, the phenotypic ratio is 3 dominant to 1 recessive.
Question 3: An allele that is expressed in the phenotype only when present in homozygous form is called:
- Dominant
- Codominant
- Recessive (Correct answer)
- Epistatic
Correct answer: Recessive
A recessive allele is only expressed in the phenotype when an individual carries two copies of it, as the dominant allele masks its expression in heterozygotes.
Question 4: A cross between a homozygous dominant (AA) and a homozygous recessive (aa) parent produces offspring that are:
- All dominant phenotype (AA)
- All recessive phenotype (aa)
- Half dominant and half recessive
- All heterozygous (Aa) (Correct answer)
Correct answer: All heterozygous (Aa)
When AA × aa cross, every offspring receives one A allele from the dominant parent and one a allele from the recessive parent, making all offspring heterozygous Aa.
Question 5: Which of the following is the best example of codominance in genetics?
- ABO blood group type AB in humans (Correct answer)
- Blue eyes vs. brown eyes in humans
- Tall vs. short pea plant height
- Sickle cell disease in homozygous individuals
Correct answer: ABO blood group type AB in humans
In blood type AB, both the A and B antigens are fully expressed simultaneously on red blood cells, demonstrating true codominance where neither allele dominates the other.
Question 6: In Mendel's experiments, the trait that was hidden in the F1 generation but reappeared in the F2 generation was called:
- Dominant
- Epistatic
- Recessive (Correct answer)
- Codominant
Correct answer: Recessive
Mendel called the trait that disappeared in the F1 generation 'recessive' because it was masked by the dominant trait but reemerged in one-quarter of F2 offspring.
Question 7: Mendel's Law of Segregation states that:
- Dominant alleles always mask recessive alleles in heterozygotes
- The two alleles of a gene separate during gamete formation so each gamete carries only one allele (Correct answer)
- Genes on different chromosomes always assort independently
- Traits from parents are blended in offspring
Correct answer: The two alleles of a gene separate during gamete formation so each gamete carries only one allele
The Law of Segregation states that the two alleles for each trait separate (segregate) during meiosis so that each gamete receives only one allele, which reunites at fertilization.
NEET Genetics and Evolution 1
Which of Mendel's laws states that alleles for different traits are inherited independently of each other?