Pedigree definition

Pedigree: a family history that shows how a trait is inherited over several generations

Pedigrees are usually used when parents want to know if they are carriers of a particular disorder

Making a Pedigree

Female

Male

Married Couple

Siblings

Filled in symbols indicate individual is affected with a disorder

How do you read a pedigree chart?

• A shape that is not shaded indicates that the person does NOT have the trait.

• A shape that is half-shaded indicates that the person is a “carrier” (has 1 allele).

• A shape that is completely-shaded indicates that the person has the trait

Example of a Pedigree

You

Parents

Aunts, UnclesAunts, Uncles

GrandparentsGrandparents

BrotherDo any disorders run in this family??

Interpreting a Pedigree What can you tell from a pedigree?

Whether a family has an autosomal or sex-linked disease or disorder Autosomal disorder: appears in both

sexes equally Sex-linked disorder: allele is located only

on the X or Y chromosome. Most sex-linked genes are on the X chromosome and are recessive

So who would have an X-linked disorder more often, boys or girls?

Whether a disorder is dominant or recessive

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?

You

Parents

Aunts, UnclesAunts, Uncles

GrandparentsGrandparents

Brother

Sex Linked! (in this case allele is recessive and located on the X chromosome)

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?

You

Parents

Aunts, UnclesAunts, Uncles

GrandparentsGrandparents

Brother

Autosomal dominant!

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?

You

Parents

Aunts, UnclesAunts, Uncles

GrandparentsGrandparents

Brother

Autosomal recessive!

More Practice

http://highered.mheducation.com/sites/0072485949/student_view0/chapter3/interactive_activity.html

Sex Chromosomes: one of the two chromosomes that determine an individual’s sex (XX=female, XY=male)

Autosomal Chromosomes: chromosome that is not a sex chromosome

Sex-linked gene: gene located on a sex chromosome

Common Genetic Disorders

Color blindness Sickle cell anemia Cystic Fibrosis Hemophilia Huntington’s Disease

For more info, go to: http://www.ncbi.nlm.nih.gov/pubmedhealth/

Color Blindness

Deficiency to perceive colors

Problem with color-sensing pigments in certain nerve cells of the eye

About 1 in 10 men have some form of color blindness.

Sex-linked disorder

Sickle Cell Anemia Disorder where

abnormal hemoglobin (a protein inside red blood cells) is produced and warps red blood cells

Sickle cells deliver less oxygen to body’s tissues and can get stuck in small blood vessels

Tends to be seen in people of African or Mediterranean descent

Recessive trait

Cystic Fibrosis Life threatening, causes thick mucus

to build up in various areas of the body (lungs, digestive tract, etc).

Tends to run in Caucasians, of Northern/Central European descent

(1 in 29 Americans carry the allele) Recessive, autosomal disease Average life span in US for people with CF is 37, death usually caused by lung complications

Hemophilia Bleeding disorder, where it takes a

long time for blood to clot (body lacks proteins involved in clotting)

Treatmentinvolves injection with missing clotting protein

Sex-linked (carried on the Xchromosome)

Huntington’s Disease

Deterioration of brain tissue, usually begins between age 30 and 40.

No cure, but have medications to cope with symptoms

People usually die 15-20 years after onset of degeneration

Autosomal, dominant

Chromosomal Disorders

Nondisjunction: error in meiosis in which the homologous chromosomes fail to separate properly

If nondisjunction occurs during meiosis, gametes with an abnormal number of chromosomes may result, leading to a disorder of chromosome numbers.

Examples of nondisjunction: Trisomy: three copies of a chromosome

Trisomy 21: Down Syndrome (characterized by mild to severe mental retardation)

Turner’s Syndrome: Nondisjunction of the X chromosomes. Females usually only inherits one X chromosome. Women are sterile.

Klinefelter’s Syndrome: males inherit an extra X chromosome. Males are sterile.

Karyotype

A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.