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.
Inheritance of Sex
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
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 — females have a matching pair. XY: the Y looks like a little man standing with arms out — males have the odd one out. 'Why are boys different? Because of Y!'