Principles of Inheritance and Variation
- A male human is heterozygous for autosomal genes A and B and is also hemizygous for hemophilic gene h. What proportion of his sperms will be abh?
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Chance of getting a = 1 2 Chance of getting b = 1 2 Chance of getting b = 1 2 Chance of getting sperms with abh = 1 × 1 × 1 = 1 2 2 2 8
Correct Option: A
Chance of getting a = 1 2 Chance of getting b = 1 2 Chance of getting b = 1 2 Chance of getting sperms with abh = 1 × 1 × 1 = 1 2 2 2 8
- In a certain plant, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t) .If a plant with RRTt genotype is crossed with a plant rrtt genotype, what will be the percentage of tall plants with red fruits in the progeny?
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Ratio = 1: 1 red fruit yellow fruitCorrect Option: A
Ratio = 1: 1 red fruit yellow fruit
- A self-fertilizing trihybrid plant forms
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A self-fertilizing trihybrid plant forms 8 different gametes and 64 different zygotes.
The genotype of trihybrid plant is AaBbCc.
Number of gametes formed = 2n = 23 = 8
Here n = no. of heterozygosity = 3 in present case.
No. of zygotes formed = 82 = 64.Correct Option: A
A self-fertilizing trihybrid plant forms 8 different gametes and 64 different zygotes.
The genotype of trihybrid plant is AaBbCc.
Number of gametes formed = 2n = 23 = 8
Here n = no. of heterozygosity = 3 in present case.
No. of zygotes formed = 82 = 64.
- Test cross involves
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A cross of F1 hybrid with its recessive homozygous parent is called the test cross. It is done to determine the genotype of a given plant. If the given plant has homozygous dominant traits then on test cross it gives all dominant trait plants but if it is heterozygous dominant than it gives dominant and recessive phenotypes in 1: 1 ratio.
Correct Option: B
A cross of F1 hybrid with its recessive homozygous parent is called the test cross. It is done to determine the genotype of a given plant. If the given plant has homozygous dominant traits then on test cross it gives all dominant trait plants but if it is heterozygous dominant than it gives dominant and recessive phenotypes in 1: 1 ratio.
- The recessive genes located on X-chromosome in humans are always
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Males have only one X - chromosome. Hence any gene present on the one X - chromosome expresses itself n males. Females have two X- chromosomes. The mutant allele must be present on both the X-Chromosomes to express itself phenotypically. If only one copy of allele present, then the female only becomes a carrier showing no external manifestation of the gene. Sublethal condition can never arise in males.
Correct Option: C
Males have only one X - chromosome. Hence any gene present on the one X - chromosome expresses itself n males. Females have two X- chromosomes. The mutant allele must be present on both the X-Chromosomes to express itself phenotypically. If only one copy of allele present, then the female only becomes a carrier showing no external manifestation of the gene. Sublethal condition can never arise in males.
