Genes which code for a pair of contrasting traits are known as:
Alleles are slightly different forms of the same gene. They are genes that code for a pair of contrasting traits. For example, T (for tall) and t (for dwarf) are alleles of each other.
Question 92 of 519
📘 CLASS XII
If an organism has two identical alleles for a particular gene (e.g., TT or tt), its genotype is described as:
Mendel proposed that in a true-breeding variety, the allelic pair of genes for a trait are identical, or homozygous. TT and tt are examples of homozygous genotypes.
Question 93 of 519
📘 CLASS XII
A pea plant with the genotype Tt is best described as:
Since the Tt plant is heterozygous for genes controlling one character (height), it is a monohybrid. Plants with dissimilar alleles (Tt) are heterozygous.
Question 94 of 519
📘 CLASS XII
Who developed the graphical representation used to calculate the probability of all possible genotypes of offspring in a genetic cross?
The diagram used to understand the formation of zygotes and F1 and F2 plants is called a Punnett Square. It was developed by a British geneticist, Reginald C. Punnett.
Question 95 of 519
📘 CLASS XII
In a Mendelian monohybrid cross, what is the genotypic ratio in the F2 generation?
While the F2 phenotypic ratio is 3:1, the genotypic ratio is 1/4 (TT) : 1/2 (Tt) : 1/4 (tt), which simplifies to 1:2:1.
Question 96 of 519
📘 CLASS XII
A cross between an organism with a dominant phenotype (of unknown genotype) and its recessive parent is called a:
To determine the genotype of a tall plant at F2, Mendel crossed the tall plant with a dwarf plant. This is called a test cross, where an organism with a dominant phenotype is crossed with a recessive parent.
Question 97 of 519
📘 CLASS XII
Which of the following statements is part of Mendel's Law of Dominance?
The Law of Dominance states that: (i) Characters are controlled by discrete units called factors; (ii) Factors occur in pairs; (iii) In a dissimilar pair of factors, one member dominates the other.
Question 98 of 519
📘 CLASS XII
The Law of Segregation is based on the fact that:
The Law of Segregation is based on the fact that the alleles do not show any blending and that both characters are recovered as such in the F2 generation, though one is not seen at the F1 stage.
Question 99 of 519
📘 CLASS XII
In the dog flower (Antirrhinum sp.), a cross between true-breeding red-flowered (RR) and true-breeding white-flowered (rr) plants results in F1 progeny that are all pink. This is an example of:
In the dog flower, the F1 (Rr) from a cross between red (RR) and white (rr) flowered plants was pink. This phenotype is in between the two parents and is a good example of incomplete dominance.
Question 100 of 519
📘 CLASS XII
What is the phenotypic ratio in the F2 generation of a cross showing incomplete dominance, like the flower colour in snapdragons?
When the pink F1 (Rr) was self-pollinated, the F2 resulted in a ratio of 1 (RR) Red : 2 (Rr) Pink : 1 (rr) White. Here the phenotypic ratio is 1:2:1.
