A. The cells in your body receivehalf their chromosomes from your father and one

Question

A. The cells in your body receivehalf their chromosomes from your father and one half of theirchromosomes from your mother. So for each pair of homologouschromosomes one will be a maternal chromosome and one will be apaternal chromosome.. During meiosis when the haploid gametes areformed, each member of the pair but not both ends up in a gamete.This is the principle of segregation.1. For humans (N =23) how manypossible combinations of maternal and paternal chromosomes arethere? Show your reasoning. Hint: are we dealingwith ordered or unordered events here?

B. How many of thecombinations from part A involve 10 maternal chromosomes and 13paternal chromosomes? Hint are we dealing with an ordered orunordered event here?

Explanation / Answer

1. For a single pair of chromosome, the gamete will have either the maternal or paternal chromosome i.e. there are two possibilities. Therefore, for 23 pairs of homologous chromosomes, the number of possible combinations of maternal and paternal chromosomes are 223.

2. The number of ordered combinations where there are 10 maternal and 13 paternal chromosomes, will be-

N!/[(M!)(N-M)!] . Here N= 23, M= 13

=23!/[(13!)(23-13)!]

=23!/[(13!)(10)!]

= 23x 22x 21x 20x 19x 18x 17x16x 15x 14/ 10x 9x 8x 7x 6x 5x 4x 3x 2x1

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