Q. 143.6( 5 Votes )

How does ga

Answer :

The gain or loss of chromosomes take place in humans due to the failure of segregation of sister chromatids during cell division (non-disjunction) which is called as aneuploidy.

Chromosomal disorder involving Autosomes-


Down’s Syndrome-


This is caused due to the presence of an additional copy of the chromosome number 21. Therefore, it is also known as the trisomy of 21


Symptoms include-


• The affected individual is short statured and has a small head.


• Presence of a furrowed tongue and partially opened mouth.


• Palm is broad and has a characteristic palm crease.


Chromosomal disorder involving sex chromosomes-


Klinefelter’s Syndrome-


This is caused due to the presence of an additional copy of X chromosome which results in the karyotype 47 XXY.


Symptoms are-


• A male with feminine development like the development of breasts (gynaecomastia).


• Sparse body hair


• Long limbs


• The individuals are sterile.


OR


(a) i. In this case, point mutation, i.e., single base substitution has occurred. In the 5th codon, instead of an ‘AAC’, an ‘ATC’ is present.


ii. In this case, point mutation, i.e., single base deletion has occurred. In the 5th codon, A is missing in ‘AC’. Therefore, instead of an ‘AAC’, there is an ‘AC’.


b) 4 amino acids will be translated in both of the above mentioned cases because; one codon is mutated and hence cannot be translated.


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