Key Concepts

•What are two major causes of genetic disorders in humans?

•How do geneticists trace the inheritance of traits?

•How are genetic disorders diagnosed and treated?

Key Terms Genetic

disorder Karyotype pedigree

Causes of Genetic Disorders

Genetic disorder – abnormal condition that a person inherits through genes or chromosomes

Some are caused by mutations in the DNA of genes

Others are caused by changes in the overall structure or number of chromosomes

Cystic Fibrosis Body produces abnormally thick

mucus in the lungs and intestines The thick mucus fills the lungs

making it hard to breathe Caused by recessive allele on one chromosome that is the result of a mutation in which 3 base pairs are removed from a DNA molecule

Sickle- Cell Disease Affects hemoglobin, protein in

blood that carries O2 When o2 concentrations are

low blood cells have a sickle shape

The sickle shape can clog blood vessels and cannot carry as much O2 as normal shaped red blood cells

The allele is codominant with normal allele

A person with 2 sickle shaped alleles will have the disease

One allele and the person will produce both normal and sickle shaped cells. These people will not usually have symptoms of the disease

Hemophilia A person’s blood clots very slowly or not at all Do not produce one of the proteins

needed for normal blood clotting Small bumps and bruises may cause

internal bleeding that can’t be controlled

Caused by a recessive allele on the X chromosome

Sex-linked disorder – occurs more frequently in males

Down SyndromeTrisomy 21 Have an extra copy of

chromosome 21 (instead of a pair the person has 3 copies) Most often occurs when

chromosomes fail to separate properly during meiosis

Have some degree of mental retardation.

Heart defects are also common, but can be treated

Pedigrees

Chart used to trace the inheritance of traits in humans

Can track ordinary traits or a genetic disorder

Managing Genetic Disorders Doctors used to only have Punnett

Squares and pedigrees to help predict genetic disorders

Now they have tools such as karyotypes to help diagnose genetic disorders

People with genetic disorders can be helped through medical care, education, job training, and other methods

Karyotypes

Picture of all the chromosomes in a cell

Arranged in pairs Can reveal whether a person has

the correct number of chromosomes

Genetic Counseling

A couple with a family history of a genetic disorder can go to a genetic counselor for advice

Help couples understand their chances of having a child with a

particular genetic disorder

Dealing with Genetic Disorders Medical treatments help people with

some disorders Ex. Physical therapy helps remove

mucus from the lungs of people with cystic fibrosis

Taking Folic Acid helps people with sickle-cell disease make more red blood cells

Education and job training helps people with Down Syndrome find work in a variety of places of employment