Transcript Genetics-pedigrees

Pedigrees
Human Heredity
What we have covered so far…
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Monohybrid crosses
Simple dominance
Incomplete dominance
Co-dominance
Multiple alleles
Sex-linked recessive
Honors- Dihybrid crosses
But wait there’s more!!
• Pedigrees
• Chromosomes
• Karyotypes
Pedigrees
• In humans, scientist’s study a family history
using a pedigree.
• Pedigree- a diagram that traces the
inheritance of a particular trait through
several generations.
By using boxes,
circles and
connecting lines, it
is possible to
diagram a family
history of a genetic
disease.
How to read a
Pedigree
•Circles=females
•Squares=males
•solid objects= diseased
individuals
•half-solid objects=
carriers
•unfilled objects=
genetically healthy
individuals
• A pedigree also uses a numbering system in which
Roman numerals represent generations and the
individuals are numbered using 1,2,3,4….
Autosomal Inheritance
• affects both men and women
Autosomal Dominant:
- trait usually present in each
generation
Sex-Linked Inheritance
• trait is carried on the
X chromosome
• affects mostly men
• usually recessive
Examples: hemophilia,
color blindness, baldness
Autosomal Recessive:
- trait usually skips generations
- will only show up if homozygous
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How many generations are listed above? 4
Is the trait above autosomal or X-linked? Autosomal
Is the trait above dominant or recessive? Recessive
How did #8 inherit the trait if his parents don’t express it?
His parents must be carriers of the trait (heterozygous)
5. Why do sex-linked traits show up mainly in men?
Men have only one X chromosome, and can’t be carriers
If individual III-2 marries a person with the
same genotype as individual I-1, what is the
chance that one of their children will be
afflicted with hemophilia?