Genetic Disorders : Autosomal & Sex Linked Traits

Genetic Disorders:Autosomal

&Sex Linked

Traits

Karyotype: All of the chromosomes that an individual has in their body

• Autosomes: All chromosomes except your sex chromosomes

• Sex Chromosomes: Determine which gender you will be

Autosomal Recessive Disorders

• Recessive genes found on an autosome that cause a particular disorder.

• DD = Normal

• Dd = Carrier

• dd = Affected by disorder

2 Examples of Autosomal Recessive

Disorders

Tay-Sachs Disease• A genetically caused disease in which the

gene to make the enzyme Hex-A (Hexosaminidase A) is not working.

• Hex-A is an enzyme that breaks down the lipid GM2 ganglioside.

• Without Hex-A this lipid accumulates on nerve cells, specifically in the brain causing severe brain damage.

• Victims of this disorder do not live past age 5

Tay-Sachs Brain

Tay-Sachs Carriers

Offspring:

25% Normal

50% Carriers

25% Tay-Sachs

Common in Eastern European Ashkenazi Jews

• This is a group of people descendent of medieval Jews from the Rhineland area. (Rhineland: near the river Rhine in Germany)

Cystic Fibrosis 7q31

• Thick mucus is produced by the body–Mucus fills lungs causing lung

infections–Mucus blocks pancreas which causes

digestive problems–Mucus can block bile ducts in liver

causing liver failure.

Cystic Fibrosis

Cystic Fibrosis

Effects

1/30 Caucasians

Carriers of Cystic Fibrosis

Offspring:25% Normal50% Carriers25% Cystic Fibrosis

Autosomal Dominant Disorders• Dominant genes found on an

autosome that cause a particular disorder.

• Affects people after their reproductive years

• DD = Affected

• Dd = Affected

• dd = Normal

1 Example

Huntington’s Disease• Genetically programmed

degeneration of brain cells. • Mood swings, loss of muscle control, loss

of memory and inability to learn, death.

• hh = Normal

• HH or Hh = will get and die of this disease

Person with Huntington’s and a person without Huntington’s

Hh x hh

Offspring:

50% Huntington’s

50% Normal

Huntington’s is most common in Venezuela

•An autosomal disorder: person has 3 homologous chromosomes instead of 2 homologous chromosomes-Often die between conception (when sperm

meets egg) and 1 year old.

Trisomy:

1 Example

Down Syndrome:

• Genotype: 3 copies of 21st chromosome

Chances of Getting Downs

• Age 25: 0.076%

• Age 35: 0.27%

• Age 45: 3.3%

Phenotype: Skin folds above the eye, some cardiac deformities, some levels of mental retardation, extra large tongue

Phenotype: Skin folds above the eye, some cardiac deformities, some levels of mental retardation, extra large tongue

Downs Karyotype

Sex Linked Traits

Sex Linked Traits

• Traits that occur on the X or Y chromosome

2) X Linked: A trait that occurs on the X chromosome.

a) More likely to affect men because men only get one X chromosome.

b) Women must get two recessive chromosomes to show the disorder

3) Colorblind

Phenotype: • The affected person does not

have color vision: usually no green or red (men: 8%, women 0.4%)

How to write a Alleles for Sex Linked Traits

• Women:–Normal: XBXB

–Carrier: XBXb

–Colorblind: XbXb • Men:

–Normal: XBY–Colorblind: XbY

Colorblind Test!

• You will be given a colorblind test.

• You will see circles with many colors of dots

• The dot pattern makes up a number

• What number do you see?

With Color Vision:

Color Blind Test

What number do you see?

Color Blind Test

What number do you see?

This what you would see if you were color blind

What number do you see?

Color Blind Test

What number do you see?

Color Blind Test

What number do you see?

Color Blind Test

What number do you see?

Color Blind Test

What number do you see?

With color vision you see this:

But if you were red-green colorblind….

You would see the #:

5

What do the colorblind see?

  NORMALPROTAN:

Red BlindDEUTERAN:Green Blind

TRITAN:Blue Blind

RED        

YELLOW        

GREEN        

CYAN        

BLUE        

MAGENTA        

Types of Colorblindness

http://www.visitliverpool.jp/nature/images/knowsley-wildflower.jpg

Types of Colorblindness –

Normal No color vision

Protanopia: no red Deuteranopia: no green Tritanopia: no blue

Hemophilia • A genetic sex linked gene that affects the

way your blood clots. (affects clotting factor VIII and IX)

• Small cuts, scrapes and bruises can be life threatening

• 1 in 10, 000 males

• 1 in 100,000,000 females

Common amongst royalty in Europe

Queen Victoria = Carrier

i. How many kids did Victoria have? ________

ii. How many kids were carriers?________ # of kids effected? __________

iii. Were any girls affected by the disorder?______ Boys? _____ How many?_____

92 1

no yes 10

Tay-Sachs Pedigree

??

Turner Syndrome

• Genotype: XO

• Phenotype: – Female – Some women are normal– Many are infertile– do not grow/develop normally, are short

statured.

Klinefelter’s Syndrome

• Genotype: XXY

• Phenotype: – Male– Diminished activity of testes– Reduced fertility

Triplo-X

• Genotype: XXX

• Phenotype: Normal

Hermaphrodites ?!?

• Hermaphrodite: An individual that has all female reproductive parts, and all male reproductive parts

• No such thing in Humans

Hermaphrodites ?!?

• However: XY females are as close as you can get

• Genotype: XY

• Phenotype:– Look like women– Do not have uterus, don’t have periods– Some have testes instead of ovaries

Models have a high % of XY women.

Why?

XY women show some “male-like” features that make them good

models

• Taller than most women

• Chiseled Jaw

• Good Muscle definition

• Don’t have as much body fat

Turner syndrome one X Klinefelter syndrome XXY

Triplo-X (normal)

• What is Turner syndrome?• Turner syndrome describes females who have a common constellation of problems

because they are missing all or part of an X chromosome.• Some will have few, if any, noticeable problems, while others may have many. • Some of these problems include:• short stature • lymphedema (a collection of lymph fluid in the tissues; often causing puffiness of the

hands and feet in newborns) • gonadal failure (resulting in delayed or absent sexual development, infertility) • frequent ear infections • progressive nerve hearing loss • strabismus (wandering or crossed eye) • unusual physical features such as a narrow palate, receding jaw, webbed neck, low

hairline, prominent ears, broad chest, and narrow fingernails and toenails that point upwards

• structural abnormalities of the heart and/or the aorta (the main vessel carrying blood away from the heart)

• structural abnormalities of the kidneys • hypothyroidism • multiple moles • non-verbal learning disability

• Patiño is considered by science as an “androgen insensitive.” A fetus of this class develops testes on the eighth week, but the “androgen receptors” are faulty and thus fail to detect the presence of male hormones, even if these are present in the body. In the end, the child is delivered as a girl. Her breasts may enlarge at puberty but she will never menstruate, as her uterus has not developed.

• Approximately one of every 20,000 persons is an androgen insensitive. And about one of every 2,500 females has a single X chromosome. The XY woman, as I shall distinguish her, is actually no different from the XX woman—well, other than she will not physically bear children. There are even a significant number of Western XY women who are into the modeling profession.

• In this new millennium, we must encourage a deeper learning about what determines our gender. A healthy discussion and research on this will aid us in the compassionate understanding of our diversities. Myths that surround gender expression must be set straight all together in the light of scientific explanations. Only by welcoming such evolution in popular beliefs will we be liberated from social condescension.

Turner’s Syndrome Karyotype