Human Heredity

This section explains what scientists know about human chromosomes, as well as the inheritance of certain human traits and disorders.

It also describes how scientists study the inheritance of human traits.

Human Chromosome How do biologists make a karyotype? A karyotype is simply a picture of a

person's chromosomes in mitosis. The chromosomes are isolated in the

WBC, stained, and examined under the microscope.

A picture of the chromosomes is taken through the microscope.

They cut out the chromosomes from the photographs, then group them together in pairs.

Make A Karyotype

Virtual lab: http://learn.genetics.utah.edu/conten

t/chromosomes/karyotype/

http://learn.genetics.utah.edu/content/labs/

Other Virtual Lab:

http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html

The Punnett square below shows how the sex chromosomes segregate during meiosis.

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

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!

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 percieve 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

Recessive trait, tends to be seen in people of African or Mediterranean descent

Cystic Fibrosis Recessive, autosomal disease 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) 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)

Sex-linked (carried on the Xchromosome)

Treatmentinvolves injection with missing clotting protein

Huntington’s Disease

Autosomal, dominant

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