Sex Linkage PowerPoint Presentation

Sex Linkage PowerPoint Presentation

2016-09-17 197K 197 0 0

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8.3. Starter. How many chromosome pairs do humans have?. 23 pairs. What are the sex chromosomes and how is it determined if a person is male or female?. X and Y. Male = XY, Female = XX. Do you know any conditions that are sex linked?. ID: 467653

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Presentations text content in Sex Linkage

Slide1

Sex Linkage

8.3

Slide2

Starter

How many chromosome pairs do humans have?

23 pairs

What are the sex chromosomes and how is it determined if a person is male or female?

X and Y

Male = XY, Female = XX

Do you know any conditions that are sex linked?

Red-Green colour blindness

Haemophilia

Slide3

Learning Objectives

Describe how sex is determined genetically

Explain sex linkage

Explain how haemophilia is inherited

Success Criteria

Complete a

punnet

squares for sex determination in humans, red-green colour blindness and haemophilia

Complete sheet/answer questions about pedigree charts

Slide4

How is sex determined in humans?

Draw a Punnet square to show how sex is determined in humansPhenotypes: 1:1 (50% male, 50% female)

Male gametes

X

Y

X

X

Female gametes

XX

XY

XY

XX

Slide5

Sex Linked Diseases

Some conditions are passed on through the sex chromosomesThey are usually on the X, not Y as the X is a bigger chromosomeRed-green colour blindness Passed on the X chromosome. Normal sighted man = XBY Normal sighted woman = XBXB or XBXbColour blind man = XbY Colour blind woman = XbXbA man only needs 1 recessive allele to be colour blind, a woman would need 2

Slide6

Red-Green Colour Blindness

Task: draw a punnet square for a colour blind male and a normal female (homozygous dominant)Phenotypes: All normal sighted (All females are carriers, males are normal sighted)

Male gametes

X

b

Y

XB

XB

Female gametes

X

B

X

b

X

BXb

XBY

X

B

Y

Slide7

Haemophilia

Blood clots slowly (DNA is altered so that proteins required in clotting aren’t coded for) and even then there may still be internal bleedingPotentially lethal, so the gene is relatively rareAlmost always found in malesTASK: draw a punnet square to show the cross between a carrier female and a normal male

Slide8

Answer

Cross = carrier female and normal maleOffspring phenotypes: normal females, half males will be normal and half will have haemophiliaGenotypes: ¼ normal female, ¼ carrier female, ¼ normal male, ¼ haemophiliac male

Male gametes

X

H

Y

XH

Xh

Female gametes

X

H

X

H

X

HXh

XHY

X

h

Y

Slide9

Pedigree Charts

Squares are malesCircles are femalesShading = sufferer of the diseaseDot in the circle = female carrier of the disease

Slide10

Task

Haemophilia sheet

Slide11


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