Human Genetic Disorders

1
Human Genetic Disorders

• 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?

2
Key Terms

• Genetic disorder
• Karyotype
• pedigree

3
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

4
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

5
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

6
Hemophilia

• A persons 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 cant be controlled
• Caused by a recessive allele on the X chromosome
• Sex-linked disorder occurs more frequently in
  males

7
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

8
Pedigrees

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

9
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

10
Karyotypes

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

11
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

12
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