X and Y chromosomes

Question 1

There are [ ] matched pair of chromosomes in every [ ]

Answer 1

22

human cell

Question 2

What are human’s 23rd pair of chromosomes labelled?

What do they decide?

Answer 2

XX or XY

Whether you are male or female

Question 3

Describe the 23rd pair of chromosomes in a male

Answer 3

All men have an X and a Y chromosome: XY

The Y chromosome causes male characteristics

Question 4

Describe the 23rd pair of chromosomes in a female

Answer 4

All women have 2 X chromosomes: XX

The XX combinations allows female characteristics to develop

Question 5

When making sperm, the X and Y chromosomes are drawn apart in the [ ] division in [ ]. (The original cell has 1 X and 1 Y chromosome)
What chance is there of each sperm cell getting an X chromosome? What chance of a Y chromosome?

Answer 5

first
meiosis
50% that it gets and X
50% that it gets and Y

Question 6

A similar process (to sperm) happens when making eggs. But the original cell has [ ], so all the eggs have one X chromosome

Answer 6

2 X chromosomes

Question 7

What do genetic diagrams show?

Answer 7

The possible combinations of gametes

Question 8

Draw a genetic diagram to show the probability of getting a boy or a girl offspring

Answer 8

Eggs: X X
Sperm
Y XY XY

X                  XX     XX 50% chance of a boy (XY) 50% chance of a girl  (XX)

Question 9

Draw a ‘blob and line’ diagram to show the chance of getting a boy or girl offspring

Answer 9

See book:

page 118