Mother (XX): Always passes on an X chromosome
Father (XY): Can pass on X or Y (50% chance of each)
| X | Y | |
| X | XX (female) | XY (male) |
| X | XX (female) | XY (male) |
Probability: 50% chance of boy, 50% chance of girl
This key facts covers Inheritance of Sex within Sex Determination for GCSE Biology. Sex chromosomes and sex determination mechanisms It is section 2 of 11 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Sex Determination
What determines the sex of a human baby?
Use a genetic diagram to show how sex is inherited in humans.
Quick recall flashcards
What sex chromosomes do females and males have?
Females: XX (two X chromosomes). Males: XY (one X and one Y chromosome). These are the 23rd pair of chromosomes in humans.
How do you remember XX = female and XY = male?
XX: the two X's look like chromosomes that pair up perfectly โ females have a matching pair. XY: the Y looks like a little man standing with arms out โ males have the odd one out. 'Why are boys different? Because of Y!'