Pedigree definition Pedigree: a family history that shows how a trait is inherited over several generations Pedigrees are usually used when parents.
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Pedigree definition
Pedigree: a family history that shows how a trait is inherited over several generations
Pedigrees are usually used when parents want to know if they are carriers of a particular disorder
Making a Pedigree
Female
Male
Married Couple
Siblings
Filled in symbols indicate individual is affected with a disorder
How do you read a pedigree chart?
• A shape that is not shaded indicates that the person does NOT have the trait.
• A shape that is half-shaded indicates that the person is a “carrier” (has 1 allele).
• A shape that is completely-shaded indicates that the person has the trait
Example of a Pedigree
You
Parents
Aunts, UnclesAunts, Uncles
GrandparentsGrandparents
BrotherDo any disorders run in this family??
Interpreting a Pedigree What can you tell from a pedigree?
Whether a family has an autosomal or sex-linked disease or disorder Autosomal disorder: appears in both
sexes equally Sex-linked disorder: allele is located only
on the X or Y chromosome. Most sex-linked genes are on the X chromosome and are recessive
So who would have an X-linked disorder more often, boys or girls?
Whether a disorder is dominant or recessive
Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?
You
Parents
Aunts, UnclesAunts, Uncles
GrandparentsGrandparents
Brother
Sex Linked! (in this case allele is recessive and located on the X chromosome)
Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?
You
Parents
Aunts, UnclesAunts, Uncles
GrandparentsGrandparents
Brother
Autosomal dominant!
Is this disorder 1) autosomal or sex linked, 2) dominant or recessive?
You
Parents
Aunts, UnclesAunts, Uncles
GrandparentsGrandparents
Brother
Autosomal recessive!
More Practice
http://highered.mheducation.com/sites/0072485949/student_view0/chapter3/interactive_activity.html
Sex Chromosomes: one of the two chromosomes that determine an individual’s sex (XX=female, XY=male)
Autosomal Chromosomes: chromosome that is not a sex chromosome
Sex-linked gene: gene located on a sex chromosome
Common Genetic Disorders
Color blindness Sickle cell anemia Cystic Fibrosis Hemophilia Huntington’s Disease
For more info, go to: http://www.ncbi.nlm.nih.gov/pubmedhealth/
Color Blindness
Deficiency to perceive colors
Problem with color-sensing pigments in certain nerve cells of the eye
About 1 in 10 men have some form of color blindness.
Sex-linked disorder
Sickle Cell Anemia Disorder where
abnormal hemoglobin (a protein inside red blood cells) is produced and warps red blood cells
Sickle cells deliver less oxygen to body’s tissues and can get stuck in small blood vessels
Tends to be seen in people of African or Mediterranean descent
Recessive trait
Cystic Fibrosis Life threatening, causes thick mucus
to build up in various areas of the body (lungs, digestive tract, etc).
Tends to run in Caucasians, of Northern/Central European descent
(1 in 29 Americans carry the allele) Recessive, autosomal disease Average life span in US for people with CF is 37, death usually caused by lung complications
Hemophilia Bleeding disorder, where it takes a
long time for blood to clot (body lacks proteins involved in clotting)
Treatmentinvolves injection with missing clotting protein
Sex-linked (carried on the Xchromosome)
Huntington’s Disease
Deterioration of brain tissue, usually begins between age 30 and 40.
No cure, but have medications to cope with symptoms
People usually die 15-20 years after onset of degeneration
Autosomal, dominant
Chromosomal Disorders
Nondisjunction: error in meiosis in which the homologous chromosomes fail to separate properly
If nondisjunction occurs during meiosis, gametes with an abnormal number of chromosomes may result, leading to a disorder of chromosome numbers.
Examples of nondisjunction: Trisomy: three copies of a chromosome
Trisomy 21: Down Syndrome (characterized by mild to severe mental retardation)
Turner’s Syndrome: Nondisjunction of the X chromosomes. Females usually only inherits one X chromosome. Women are sterile.
Klinefelter’s Syndrome: males inherit an extra X chromosome. Males are sterile.
Karyotype
A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.
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