Botany MCQs for NEET — Practice Questions with Answers

To find the different types of gametes produced by a pea plant with the genotype AaBb, it should be crossed with a plant that is homozygous recessive for both traits (genotype aabb). This is known as a test cross. The progeny of this cross will display the different combinations of alleles from the AaBb parent, allowing us to observe the different types of gametes produced. Therefore, the plant should be crossed with a plant with the genotype aabb.

Cretinism is not a hereditary disease. It is a condition arising from a deficiency of thyroid hormone, which is often due to a lack of iodine in the diet. Unlike hereditary diseases such as Cystic Fibrosis, Thalassaemia, and Haemophilia, cretinism is not passed down genetically.

A woman with 47 chromosomes due to 3 copies of chromosome 21 is characterized by Down's Syndrome. This condition is also known as Trisomy 21, where the presence of an extra chromosome 21 leads to the characteristic symptoms of Down's Syndrome.

The disease described in the question is likely inherited in a sex-linked recessive pattern. This is suggested by the fact that the disease affects only the sons (males) and not the daughters (females), indicating that the gene responsible for the disease is located on the X chromosome. Males have only one X chromosome, so a single recessive allele on this chromosome will result in the disease, whereas females have two X chromosomes, so they would need two copies of the recessive allele to express the disease.

Polygenic inheritance refers to the combined effect of multiple genes on a single trait. Skin color in humans is an example of polygenic inheritance because it is controlled by multiple genes, each contributing to the final phenotype. This results in a wide range of skin colors.

The phenotype of an organism is the observable physical or biochemical characteristics determined by both its genotype (genetic makeup) and environmental influences. This means that the same genotype can result in different phenotypes under different environmental conditions.

A test cross involves crossing an individual showing a dominant phenotype but unknown genotype (F₁ hybrid) with an individual that is homozygous recessive for the trait in question. This helps to determine whether the dominant phenotype is homozygous dominant or heterozygous.

Cri-du-chat syndrome is caused by a deletion of a portion of the short arm of chromosome 5. The syndrome gets its name from the characteristic cry of affected infants, which resembles the mewing of a cat. This deletion results in various developmental issues and physical abnormalities.

In hexaploid wheat (Triticum aestivum), the haploid number (n) of chromosomes is 21. The basic chromosome number (X) is 7. This is because hexaploid wheat has six sets of chromosomes (2n = 6x = 42). Hence, n = 21 and X = 7.

Inheritance of skin colour in humans is an example of polygenic inheritance. This means that multiple genes are involved in determining skin colour. Each gene may have several alleles that contribute to the final phenotype, resulting in a wide range of skin tones.