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?

 Genetic disorder
 Karyotype
 pedigree

 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

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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
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Affects hemoglobin, protein in blood that carries O
2
When O
2 concentrations are low blood cells have a sickle shape
The sickle shape can clog blood vessels and cannot carry as much O
2 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

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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

 Have an extra copy of chromosome 211
(instead of a pair the person has
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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

 Chart used to trace the inheritance of traits in humans
 Can track ordinary traits or a genetic disorder

 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

 Picture of all the chromosomes in a cell
 Arranged in pairs
 Can reveal whether a person has the correct number of chromosomes

 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

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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