Biology

Genetics and Plant Breeding

1,240 Questions

Genetics and Plant Breeding explores the principles of heredity, chromosomal inheritance, and hybridization techniques. It includes key concepts like Mendelian genetics, gene linkage, and polygenic inheritance. This topic is essential for students tackling advanced biology or botany sections in competitive examinations.

Mendelian InheritanceChromosome TheoryGene LinkagePolygenic InheritancePlant HybridizationPopulation Genetics Equilibrium

Genetics and Plant Breeding Questions

Multiple choice

Which among the following statements does NOT characterise sex linkage in mammals?

  1. Sex linkage is the genotypic expression of an allele related to the chromosomal sex of the individual.

  2. Genes on the X or Y chromosome are called sex-linked.

  3. X-linked recessive allele in humans causes hemophilia.

  4. X-linked traits are maternally inherited.

  5. The incidence of recessive X-linked phenotypes in females is the square of that in males.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance.

Multiple choice

Mendel studied seven contrasting characters through the cross breeding experiment with pisum sativum. Which of the following characters he identified as dominant characters?

  1. Yellow colouring of seeds, white colouring of flowers, inflated seed pods

  2. Green colour of unriped pods, axillary position of flowers, round shape of seeds

  3. Tall stem, constricted seed pods, terminal position of flowers

  4. Green colour of seeds, purple colour of flower, inflated seed pods

  5. Yellow colour of unriped pods, axillary position of flowers, round shape of seeds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because all are dominant characters: Green colour of uniped pods: Dominant Axillary position of flowers: Dominant Round shape of seeds: Dominant

Multiple choice

If father has blood group A and mother has blood group O, then which one of the following blood groups may be found in their son?

  1. B

  2. AB

  3. O

  4. B, AB or O
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If father has blood group A (genotype could be AA or AO) and mother has blood group O (genotype OO), their children can inherit either A or O alleles from the father and O from the mother. Possible genotypes are AO (blood group A) or OO (blood group O). Therefore, the son could have blood group O or A, but not B or AB.

Multiple choice

The normal phenotypic ratio of dihybrid cross is

  1. 9: 3: 3: 1

  2. 3: 1

  3. 12: 3: 1

  4. 9: 3: 4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The normal phenotypic ratio for a dihybrid cross (two traits, both heterozygous parents) is 9:3:3:1. This represents 9 dominant for both traits : 3 dominant for first trait only : 3 dominant for second trait only : 1 recessive for both traits. 3:1 is the monohybrid ratio, and 9:3:4 and 12:3:1 are modified ratios seen with epistasis or lethal genes.

Multiple choice

When a heterozygous offspring is crossed with a homozygous recessive parent, the cross is called a:

  1. back cross

  2. test cross

  3. out cross

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A test cross involves crossing an individual with unknown genotype (usually heterozygous) with a homozygous recessive individual to determine the unknown genotype. Back cross is crossing with a parent, out cross is with unrelated individual, making test cross the correct answer.

Multiple choice

A free martin is a/an:

  1. monozygotic twin

  2. infertile female

  3. infertile male

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A freemartin is an infertile female mammal (usually cattle) born as a twin to a male. The placental connection allows male hormones to masculinize the female's reproductive tract, causing infertility. Freemartins are not monozygotic (identical) twins - they are dizygotic (fraternal). They are genetically female but reproductively malformed.

Multiple choice

Parents with blood group O and AB will have children with blood group:

  1. O and A

  2. O and B

  3. A and B

  4. A,B and O
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Parent with blood group O (genotype ii) can only pass i allele. Parent with AB (genotype IAIB) can pass either IA or IB. Children will have genotypes IAi (type A) or IBi (type B). Type O children (ii) are impossible since the AB parent cannot contribute an i allele.

Multiple choice

A cross between a hybrid and its parent is:

  1. test cross

  2. back cross

  3. monohybrid cross

  4. dihybrid cross
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A backcross involves crossing a hybrid offspring with one of its parental types. This differs from a test cross (cross with homozygous recessive), monohybrid cross (single trait heterozygotes), or dihybrid cross (two traits). Backcrossing is used to recover parental genotypes or introgress traits.

Multiple choice

If a man of blood group B marries a woman of blood group AB, then the possible blood groups of their children are

  1. B, AB

  2. A, B, AB

  3. B, A, AB, O

  4. A, B, O
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a man with blood group B (genotype I^Bi or I^Bi^i) marries a woman with AB (genotype I^AI^B), their children can inherit A from the mother and B or i from the father (giving A or AB), or B from the mother and B or i from the father (giving B). If father is I^Bi^i: children can be I^AI^B (AB), I^Ai (A), I^Bi^B (B), or I^Bi (B). Thus possible groups are A, B, AB - matching Option B.

Multiple choice

Genetic recombination is due to

  1. fertilisation and meiosis

  2. mitosis and meiosis

  3. fertilisation and mitosis

  4. Both (2) and (3)

  5. None of the above

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Genetic recombination is due to the process of fertilisation followed by meiosis. 

Multiple choice

Law of Mendel which is not completely applicable is

  1. Co-dominance

  2. Law of segregation

  3. Law of independent assortment

  4. Law of dominance

  5. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Law of independent assortment is not applicable completely. When two genes are closed together on the same chromosome, they do not assort independently and are said to be linked.