Key ConceptsWhat are two major causes of genetic disorders in humans?How do geneticists trace the

inheritance of traits?

How are genetic disorders diagnosed and treated?

Human Genetic Disorders

Key TermsGenetic

disorderKaryotypepedigree

Causes of Genetic DisordersGenetic 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- quick facts

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 Does 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 211 (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

PedigreesChart used to

trace the inheritance of traits in humans

Can track ordinary traits or a genetic disorder

Managing Genetic Disorders

In the past, doctors only had 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

KaryotypesPicture of all the chromosomes in a cell

Arranged in pairsCan reveal whether a person has the correct number of chromosomes

Genetic CounselingA 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