Sex Linked Inheritance:(why females are superior to males)

(just kidding)(no, but seriously)(ok, I am kidding)

(or am I?)

Warm Up

• What % probability will a child be born a male? Female?

• How could we set up a punnett square to show this?

Cornell Notes

• Read pages 170-171• In the margin of your

paper, define the bold terms.

• In the large portion of your paper, discuss 3 main points.

• On the bottom, summarize in 3 sentences what you read.

The difference between males and females.

• Females have 2 X chromosomes.

• They always give one X to their offspring.

• The X chromosome has more information than the Y. That’s why females are superior to males.

• Males have 1 X chromosome and 1 Y chromosome.

• They can give either to offspring.

Human Genome

Autosomes (1 – 22)

Sex Chromosomes(X and Y)

X Y

Human Y-chromosome

SRy locus

Males have sperm cells which may have an X chromosome or a Y chromosome. Male gametes (sperm) determine the gender of the offspring when the egg is fertilized.

Punnett Square to determine gender.

• A male gamete XY chromosomes fertilizes the egg (XX).

• What is the chance that the offspring will be female?

Punnett Square to determine gender.

• A male gamete XY chromosomes fertilizes the egg.

X Y

X

X

Punnett Square to determine gender.

• A male gamete XY chromosomes fertilizes the egg.

X Y

X

X

XX XYXX XY

X chromosomes have genes that Y chromosomes don’t.

• X Chromosomes can be carriers of certain recessive traits. In females, the other X probably does not have the trait and can over rule the recessive diseased trait.

BaldnessColor BlindnessDuchenne Muscular DystrophyAdrenoleukodystrophyFragile X Syndrome

Punnett Square to determine gender.

• A carrier female for colorblindness, marries a normal man.

• Will their children be color blind?

• B= normal• b= color blind• Y’s don’t have the trait.

XB Y

XB

Xb

Punnett Square to determine gender.

• A carrier female for colorblindness, marries a normal man.

• Will their children be color blind?

• B= normal• b= color blind• Y’s don’t have the trait.

XB Y

XB

Xb

XBXB XBY

XBXb XbY

Punnett Square to determine gender.

• Normal Female• Normal Male• Carrier Female (isn’t

colorblind)• Colorblind Male

XB Y

XB

Xb

XBXB XBY

XBXb XbY

Inheritance patterns:• Sex-linked recessive conditions

The disease is never passed from father to son.

Males are much more likely to be affected than females.

• All affected males in a family are related through their mothers.

Trait or disease is typically passed from an affected grandfather, through his carrier daughters, to half of his grandsons.

PRACTICEOn your pink sheet of paper… practice the following…