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.