Question

explain the Chromosome Theory of Inheritance.

Explain how Mendal’s law of segregation and law of independent assortment relate to the above theory.

How does crossing over disrupt these laws?

Please use the term “linkage group” in your answer and explain how that term relates to all of the above

(In own words)

Answer 1

Chromosome theory of inheritance was given by sutton and boveri. Following are the features of this theory -

1. All the organisms are made up of chromosomes and genes which are present in two alternates. Therefore Every cell of the organism is diploid in nature.

2. These two alternate of chromosome are referred to as homologous chromosomes which segregate during meiosis.

3. After meiosis in diploid cells, haploid gametes are formed.

4. Fertilization of two haploid gametes results in the formation of diploid zygote which undergoes mitosis to form extracellular adult.

5. All the chromosomes segregate and show independent assortment during cell division.

As per mendel's law of segregation, homologous pair of chromosomes separate from each other so that each gamete receives one chromosome of a pair. This is related to point number 2 of chromosome theory. During gamete formation, homologous chromosomes separate from each other in anaphase 1 of meiosis 1.

As per mendel's law of independent assortment, alleles for different genes assort independently of each other during gamete formation. This is related to point number 5 of chromosome theory.

Crossing over is an exception to mendel's law of independent assortment. This is because during crossing over there is exchange of genetic material between non sister chromatids of homologous chromosomes so that different genes of these chromosomes do not assort independently of each other during gamete formation.

Linkage is an exception to law of segregation because when genes are linked together they form a linkage group. Due to the process of linkage these are always inherited together, that is, they are not segregated from each Other independently during gamete formation.

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