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It was observed that in a family a woman has only daughters.Analyse on the basis of genetics and give an explaination.(3marks)
Asked by prabal | 27 Feb, 2018, 12:47: PM
answered-by-expert Expert Answer
  • If the family has only daughters, it does not necessarily imply that the mother has the genetical defect.
  • A male has one X chromosome and one Y chromosome (XY). Therefore, half of the male gametes or sperms will have X chromosomes and the other half will have Y chromosomes.
  • A female has both the X chromosomes (XX). Therefore, all the female gametes or ova always have X chromosomes.
  • If a sperm carrying the X chromosome fertilises an ovum which always carries the X chromosome, then the combination of sex chromosomes will be XX and hence the child born will be a female (girl).
  • If a sperm carrying the Y chromosome fertilises an ovum, then the combination of sex chromosomes will be XY and hence the child born will be a male (boy).
  • Thus, the male (father) is responsible for the sex of the baby.
  • Hence, it is a chance event that every time the woman conceived, only the sperm containing the X chromosome fertilised the egg. As a result, only daughters were born.
Answered by Sheetal Kolte | 27 Feb, 2018, 01:07: PM

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