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

Two genes are located on the same chromosome and are known to be 12 map units apart. An AABB individual is crossed to an aabb individual to produce AaBb offspring. The AaBb offsprings are then crossed to aabb individuals. If this cross produces 1000 offsprings, what is the predicted number of offsprings with each of the four genotypes: AaBb, Aabb, aaBb and aabb?

  1. 60 Aabb, 440 aaBb, 440 AaBb and 60 aabb

  2. 0 Aabb, 0 aaBb, 440 AaBb and 440 aabb

  3. 440 Aabb, 440 aaBb, 60 AaBb and 60 aabb

  4. 60 Aabb, 60 aaBb, 440 AaBb and 440 aabb
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The genes are 12 map units apart, so the recombination frequency is 12%. Parental gametes (AB and ab) occur 88% of the time (44% each), while recombinant gametes (Ab and aB) occur 12% of the time (6% each). When AaBb is crossed with aabb, we get 440 AaBb, 440 aabb, 60 Aabb, and 60 aaBb.

Multiple choice

In Drosophila melanogaster, cherub wings (ch), black body (b) and cinnabar eyes (cn) are recessive to their corresponding alleles (represented as ch+, b+ and cn+, respectively) and are all located on chromosome 2. Homozygous wild type flies were mated with cherub, black and cinnabar flies and the resulting F1 females were test crossed with cherub, black and cinnabar males. The following progenies were produced from the test cross: ch b+ cn 110 ch+ b+ cn+ 780 ch+ b cn 70 ch+ b+ cn 6 ch b cn 769 ch b+ cn+ 60 ch+ b cn+ 111 ch b cn+ 9 Total 1915 Of these three genes, which one is in the middle?

  1. The locus that determines cherub wings

  2. The locus that determines cinnabar eyes

  3. The locus that determines black body

  4. Cannot be determined

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

In a three-point cross, the double crossover classes have the lowest frequency. Here, ch b+ cn+ (60) and ch+ b cn+ (111) are the double crossovers. Comparing these to the parental types (ch+ b+ cn+ at 780 and ch b cn at 769), we see that cn+ stays with ch+ (parental) and with ch (double crossover), meaning cn is in the middle. The gene order is ch-cn-b.

Multiple choice

Mitochondrial Eve is the woman from whom all living humans are descended matrilineally, and __________________ is the man from whom all living humans are descended patrilineally.

  1. Mitochondrial Adam

  2. Nucleic Adam

  3. X-chromosomal Adam

  4. Y-chromosomal Adam

  5. Somaclonal Adam
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In human genetics, Y-chromosomal Adam (Y-MRCA) is a hypothetical name given to the most recent common ancestor (MRCA) from whom all currently living people are descended patrilineally.

Multiple choice

If a donor A sacrifices C offspring to help recipient B, its cousins to gain D offspring then the percentage relatedness of the donor to recipient is ______________.

  1. 50%

  2. 25%

  3. 30%

  4. 15%

  5. 100%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Hamilton's rule : The relatedness of an offspring to its parents is 0.5. So, with its cousins the relatedness will be (0.5×0.5) = 0.25. Instead of giving birth to its own offspring with relatedness of 0.5 helping other siblings to reproduce will increase the relatedness to 0.5× that number of offsprings.

Multiple choice

The phrase "like begets like" is best analysed in the context of which of the following?

  1. Forward genetics

  2. Classical genetics

  3. Reverse genetics

  4. Cytogenetics

  5. Both forward and classical genetics
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

They deals with phenomenon of like begets like, e.g.,  human babies are like human beings in over all characteristics. As forward genetics is study on the basis of phenotype, study of DNA sequences comprising the gene for this phenotype and classical genetics is also known as transmission genetics, e.g.,: Mendelian genetics, Non-mendelian genetics.