Ch. 5.1 and 5.2

Human Inheritance and Human Genetic Disorders

Patterns of Human Inheritance Some human traits are controlled by a

single gene with two alleles, and others by single genes with multiple alleles.

Others are controlled by many genes that act together (polygenetic).

Widow’s Peak Punnett Sqaure

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The Sex Chromosomes

The Sex Chromosomes are one of the 23 pairs of chromosomes.

They carry genes that determine whether a person is a male or a female.

They also carry other traits.

Sex Chromosomes

Sex = are you a Girl or a Boy? Girl = XX Boy = XY▪ The Y is much smaller than the X

Sex-Linked Genes

These are genes that happen to be on the X and Y chromosomes. They don’t always have to do with boys and girls.

Remember, Girls have 2 Xs (XX) Boys only have 1 (XY) Genes on the X and Y can be either

Dominant or recessive.

Colorblindness

Colorblindness is controlled by a recessive allele on the X chromosome (XcXc or XcY)

If you have the Dominant NORMAL gene, you will see in color. (XCXC or XCY)

If you are a girl and have one of each (XCXc) then you are a carrier. You CARRY the gene for colorblindness, but you see in color! Because C is NORMAL color gene.

Colorblindness is more common in boys:

WHY?! Because they only have 1 X (XY) so

therefor they don’t have the option of a back up gene!

Girls do! (XCXc) If you have a backup gene, you are a

carrier!

So, why do boys have colorblindness more often? (you answer!)

Carrier Punnett Square

The Effect of the Environment

Even if your genes say you are to be VERY TALL, you might end up short if you don’t eat right!

It’s like trying to plant a giant pumpkin seed in the dark and never watering it! IT WON’T GROW!

Review:

1. What causes Red/Green color blindness?

2. Why is it more common in males?

3. Are a person’s characteristics determined only by genes?

4. What is the genotype for Female?

5. What is the genotype for Male?

5.2 Human Genetic Disorders

A Genetic Disorder is something PASSED DOWN through the generations.

IT CANNOT BE “Caught” (Diseases are “caught”)

It just means that you have a different trait that makes some things in life more difficult, but most of the time, you can still function like everyone else.

What causes Genetic Disorders?

Some are caused by mutations in the DNA.

Others have to do with the number of chromosomes you get. (Remember, you are supposed to have 23 from MOM and 23 from DAD)

If you don’t get enough, or you get too many, disorders happen.

Cystic Fibrosis

Cause: Recessive allele on one chromosome

Effect: thick mucus that leads to difficulty breathing and can lead to death.

Sickle-Cell Disease

Cause: A Co-dominant gene (yellow plus blue = green)

Effect: The sickle-shape of the blood cell makes it difficult to transport oxygen to the body. It is usually very painful!

SS = Full sickle-cell SB = half sickle-cell, half

normal blood cells BB = Normal blood cells

Hemophilia (sex linked)

Cause: A recessive allele on the X chromosome

Effect: uncontrollable bleeding. The blood does not clot well, and it can lead to death.

Question: Do boys and girls get this equally? Why or why not?

Down Syndrome

Cause: An EXTRA #21 Chromosome. (could be from MOM or DAD)

Pedigrees

Use a Pedigree to track down your genetics from one generation to the next!

Living With Hemophilia

Managing Genetic Disorders Karyotypes are used to detect

Chromosomal Disorders: Q1: Is this

a girl or aboy?

Q2: Whatgenetic disorder does thischild have?