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Sunday, 25 March 2012

Determining Sex of Offspring


Specification:
  • Recall that the sex of a person is controlled by one pair of chromosomes, XX in a female and XY in a male
  • Describe the determination of the sex of offspring at fertilisation, using a genetic diagram

 

Definitions:
Autosomes/Autosomal Chromosomes: Chromosomes in a cell other than the sex chromosomes
Sex chromosomes:
  • Human males have an X chromosome and a much shorter Y chromosome in each somatic cell. The X chromosome contains more genes than the Y chromosome.
  • Females have a pair of X chromosomes.
  • Human somatic cells have 22 pairs of autosomal chromosomes and a pair of sex chromosomes, X and Y.
     
    Determining Sex:
  • During gamete production, the female gametes or eggs contain an X chromosome each.
  • However, the male will produce two types of sperm-one containing an X chromosome, the other, the Y chromosome.
  • When male and female gametes fuse during fertilisation, there is a 50% chance that the offspring could be male or female.
  • A baby girl inherits one X chromosome from her mother and another from her father.
  • A baby boy receives an X chromosome from his mother and a Y chromosome from his father.

     


     

       

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