Let’s compare the characteristics of X-chromosome and Y-chromosome: X-chromosome: 1. It is a straight, rod-like chromosome longer than the Y chromosome and is metacentric. 2. It contains a significant amount of euchromatin and a smaller amount of heterochromatin. 3. With a large DNA content, it is genetically active, housing numerous genes. 4. The non-homologous region is … Read more
Phenylketonuria (PKU) is a genetic condition due to a shortage of the enzyme phenylalanine hydroxylase. This deficiency leads to an accumulation of phenylalanine in the body, disrupting protein balance. Phenylalanine is found in all proteins and certain artificial sweeteners. The enzyme shortage hampers the conversion of phenylalanine into tyrosine, crucial for neurotransmitter production. PKU arises … Read more
Linkage in genetics means genes on the same chromosome tend to be inherited together, affecting how traits are passed down. Humans have 23 pairs of chromosomes. Each chromosome forms a linkage group. Therefore, there are 23 linkage groups in human beings.
In humans, the determination of a child’s sex is based on the combination of sex chromosomes inherited from both parents. However, the father’s contribution is crucial in determining the sex of the child due to the nature of sex chromosomes. The father contributes both an X and a Y chromosome in his sperm. Meanwhile, the … Read more
Mendel’s success in his experiments with pea plants can be attributed to several factors: 1. Choice of Organism: Pea plants (Pisum sativum) were an excellent choice due to their easily observable traits, short generation time, and ability to self-pollinate or cross-pollinate. 2. Controlled Experiments: Mendel meticulously controlled the breeding of the pea plants, ensuring purebred … Read more
Pleiotropy refers to a genetic phenomenon where a single gene influences multiple, seemingly unrelated traits or characteristics. The phenotypic ratio is 1:2 instead of 3:1 because of the death of recessive homozygote. The disease, sickle-cell anaemia, is caused by a gene Hbs . Normal or healthy gene HbA is dominant. The carriers (heterozygotes HbA/Hbs ) … Read more
The Law of Segregation, proposed by Gregor Mendel, states that during the formation of gametes (sex cells), the two alleles for a gene separate (or segregate) from each other into different gametes. As a result, each gamete carries only one allele for each gene. This principle also embodies the idea of the purity of gametes … Read more
This table outlines the dominant and recessive forms of each trait that Mendel studied in pea plants. Trait Dominant Form Recessive Form Seed shape Round Wrinkled Seed color Yellow Green Pod shape Inflated Constricted Pod color Green Yellow Flower position Axial Terminal Plant height Tall Short Flower color Purple White
One classic example of complete sex linkage is the gene for hemophilia, a blood clotting disorder. The gene responsible for hemophilia is located on the X chromosome. Since the gene is recessive and located on the X chromosome, its expression is more prevalent in males. If a male inherits one copy of the hemophilia gene, … Read more
One example of a chromosomal disorder caused by non-disjunction of autosomes is Down syndrome, also known as trisomy 21. This condition arises when there’s an extra copy of chromosome 21, usually due to non-disjunction during the formation of the egg or sperm.