Which chromosomal disorder is characterized by short stature, rudimentary ovaries, and lack of secondary sexual characters in females?
Turner’s Syndrome is caused by the absence of one X chromosome (45 with X0). Such females are sterile as their ovaries are rudimentary and they lack other secondary sexual characters.
Question 62 of 519
📘 CLASS XII
The total number of chromosomes in a human with Turner's Syndrome is:
Turner’s Syndrome results from the absence of one of the X chromosomes. This condition is also referred to as monosomy of a chromosome and results in a karyotype of 45 with X0.
Question 63 of 519
📘 CLASS XII
The concept that "the alleles do not show any blending" is a fundamental basis for which of Mendel's laws?
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, even though one is not seen at the F1 stage.
Question 64 of 519
📘 CLASS XII
If two genes on the same chromosome are very tightly linked, they show:
Morgan and his group found that even when genes were on the same chromosome, some were very tightly linked, which meant they showed very low recombination. For example, the genes for yellow body and white eyes in Drosophila showed only 1.3 percent recombination.
Question 65 of 519
📘 CLASS XII
The idea of using recombination frequency between gene pairs to create genetic maps was first implemented by:
T.H. Morgan's student, Alfred Sturtevant, used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome.
Question 66 of 519
📘 CLASS XII
If a single gene can exhibit multiple phenotypic expressions, it is called a:
A gene that can exhibit multiple phenotypic expressions is called a pleiotropic gene. The mechanism is often the effect of the gene on metabolic pathways that contribute to different phenotypes, such as in phenylketonuria.
Question 67 of 519
📘 CLASS XII
How many different genotypes are possible for the human ABO blood groups in the entire population?
Since there are three different alleles (IA, IB, and i) governing the blood group, and each diploid person possesses any two of them, there are a total of six different possible genotype combinations: IAIA, IAi, IBIB, IBi, IAIB, and ii.
Question 68 of 519
📘 CLASS XII
The ability of a pea plant with genotype Tt to be phenotypically tall is explained by the:
According to the Law of Dominance, in a dissimilar pair of factors (like T and t), one member dominates the other. T for tallness is dominant over t for dwarfness, which is why the heterozygote Tt has a tall phenotype.
Question 69 of 519
📘 CLASS XII
A woman has a haemophilic son, but she and her husband are not haemophilic. What is the genotype of the woman?
Haemophilia is an X-linked recessive disease (Xh). For her son (XhY) to be haemophilic, he must have received the Xh allele from his mother. Since the mother herself is not haemophilic, her recessive gene is suppressed by a dominant normal gene, meaning she is a heterozygous carrier (XHXh).
Question 70 of 519
📘 CLASS XII
A person with phenylketonuria accumulates phenylpyruvic acid in the brain, which leads to:
In Phenylketonuria, phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. Accumulation of these in the brain results in mental retardation.
