Alleles are alternate forms of a gene found at the same locus on homologous chromosomes, such as T (tall) and t (dwarf).
Question 132 of 519
📘 CLASS XII
The progeny of a cross between two heterozygous parents (AaBb × AaBb) in a Mendelian dihybrid cross will show how many different phenotypes?
A dihybrid cross produces four phenotypic combinations: A_B_, A_bb, aaB_, and aabb.
Question 133 of 519
📘 CLASS XII
Which cross involves crossing two individuals that are heterozygous for one trait (e.g., Rr × Rr)?
A monohybrid cross involves tracking the inheritance of a single character, typically done by crossing two heterozygotes for that trait.
Question 134 of 519
📘 CLASS XII
In the four o'clock plant, the cross of a pink flower with a white flower yields 50% pink and 50% white flowers. This result is characteristic of:
In incomplete dominance, Pink is heterozygous (RW) and White is homozygous recessive (WW or rr). The cross RW × WW yields 1/2 RW (Pink) and 1/2 WW (White), a 1:1 phenotypic ratio.
Question 135 of 519
📘 CLASS XII
The 'factors' mentioned by Mendel that determine phenotype were later termed as:
Mendel's 'factors' are the units of inheritance, which were later identified as genes located on chromosomes.
Question 136 of 519
📘 CLASS XII
If an individual is heterozygous for a trait (Aa), what percentage of their gametes will contain the recessive allele 'a'?
According to the Law of Segregation, the two alleles separate, so 50% of the gametes will carry 'A' and 50% will carry 'a'.
Question 137 of 519
📘 CLASS XII
The phenomenon where the phenotype of the heterozygote is exactly the same as the homozygous dominant is known as:
Complete dominance is the standard Mendelian case where the dominant allele completely masks the recessive allele in the heterozygote.
Question 138 of 519
📘 CLASS XII
When two pure lines (homozygous parents) are crossed, the first generation of offspring is called the:
F1 (First Filial) generation refers to the first generation of offspring produced from the parental (P) generation cross.
Question 139 of 519
📘 CLASS XII
Which term describes the organism's entire genetic makeup?
The genome is the complete set of genetic material (DNA) present in a cell or organism. The genotype refers to the specific alleles for a particular trait.
Question 140 of 519
📘 CLASS XII
Down's syndrome is a genetic disorder caused by the trisomy of which specific chromosome?
Down's syndrome (Trisomy 21) is caused by the presence of an extra copy of chromosome 21, resulting in a total chromosome count of 47.
