explain the chromosomal theory of inheritance?
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Answer:
hii frnd
Explanation:
Solution :
The chromosome basis was put forth by Sutton and Boveri independently in 1902. Both had concluded that the genes are contained in chromosomes. Allelic genes present in a heterozygote segregate independently because the chromosomes carrying these genes segregate when the *** cells are formed.
In order to accept the conclusion, we have to understand the behavior of chromosomes in the light of Mendel’s assumptions.
Individuality of chromosomes: Every organism has a fixed number of chromosomes. The nuclei of gametes contain haploid (n) and those of zygotes have double the number or diploid (n) number of chromosomes.
Meiosis: At the time of meiosis, for the formation of gametes, the pairs of chromosomes of the diploid sets undergo pairing.
The chromosomes of each pair segregate independently of every other pair during the distribution into gametes. This is similar to Mendel’s law of independent assortment in the segregation of factors.
During the fusion of haploid gametes, the homologus chromosomes from the parents are brought together to form the diploid zygote.
The chromosomes maintain the structure and uniqueness during lifetime of the individual whether observable or not.
From these points it is evident that a clear parallelism exists between Mendel’s factors and chromosomes and there is a firm basis for Mendel’s laws of heredity in the behavior of chromosomes during meiosis and fertilization and therefore the chromosomal theory of inheritance was proposed.
Postulates of Chromosomal Theory of Inheritance:
(i)The factors described by Mendel are the genes that are the actual physical units of heredity.
(ii)The genes are present on the chromosomes in a linear fashion.
(iii)Each organism has a fixed number of chromosomes which occur in two sets referred to as diploid (2n). A pair of similar chromosomes constitute the homologus pair.
(iv)Of this one set is received from the male parent (paternal) and the other from the female parent (maternal).
(v)The maternal and paternal chromosomes are contributed by the egg and the sperm respectively during zygote formation. But only sperm nucleus is involved proving that chromosomes are present within the nucleus.
(vi)The chromosomes and therefore the genes segregate and assort independently at the time of gamete formation as explained in the Mendel’s law of segregation and Law of Independent Assortment.
Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in the changes in the genotype and phenotype of the organisms.
Deletions, insertions, duplications and inversions result in alteration of chromosomes that lead to chromosomal aberrations. They are also observed in cancer cells.
Mutations can also arise due to a change in the base pair of DNA. This is known as point mutation. A classic example is sickle cell anaemia where in glutamic acid is replaced by valine due to the mutation in the codon.
Answer:The Chromosomal Theory of inheritance, proposed by Sutton and Boveri, states that chromosomes are the vehicles of genetic heredity. Neither Mendelian genetics nor gene linkage is perfectly accurate; instead, chromosome behavior involves segregation, independent assortment, and occasionally, linkage.
Explanation: