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