Inheritance of sex

• How many pairs of chromosomes do humans have?

  23 pairs
• What do the 22 pairs of chromosomes contain?

  Genes determining inherited characteristics
• What are the sex chromosomes in males?

  X and Y chromosomes
• What are the sex chromosomes in females?

  X and X chromosomes
• How are the gametes produced by females characterized?

  All contain the X chromosome
• How are the gametes produced by males characterized?

  Half contain X and half contain Y
• What are the possible sex chromosomes in the offspring from a male and female?

  XX or XY
• What is the ratio of female to male offspring on average?

  1 to 1
• What does the 50% probability of offspring sex indicate?

  It reflects statistical likelihood, not certainty
• Where can students find questions on the inheritance of sex?

  In the revision workbook
• What is the process of sex inheritance in humans?

  • Males have XY chromosomes
  • Females have XX chromosomes
  • Female gametes: all X
  • Male gametes: half X, half Y
  • Offspring: XX (female) or XY (male)
  • Average ratio: 1 female to 1 male