Download Human Inheritance

Human Inheritance
What makes a super model
• The model system for genetic studies:
• What makes a good model system
– The fruit fly
– The meal worm
– The nematode
• Why humans are not good model systems
The human cell
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Review diploid number (46)
Review mitosis especially metaphase
What’s a Karyotype?
Review haploid number and sex
determination
Genes and people
• Human generation is about 20 years so
genetics relies on family and medical
history
• The pedigree analysis
• Many human traits are inherited by the
action of genes that have dominant and
recessive allele.
Classic Inheritance
• Dominant and recessive
• Rh blood group is a Dom/rec condition
Rh pos is dominant, Rh neg is recessive
• Other examples on the class web site
Multiple alleles and co-dominant
alleles
• Multiple alleles: A type of gene determined
by more than two alleles
• ABO blood type example; blood type is
determines by three alleles
• A and B are co-dominant; both alleles can
be expressed
Polygenic traits
• Traits that are determined by more than one
gene
• Height, skin color, eye color
• Environmental conditions can affect the
phenotype of polygenic traits
Incomplete Dominance
• The heterozygous phenotype shows a trait
somewhere in between the two
homozygotes.
• In flowers, heterozygote is pink when one
homozygote is red and the other is white
• In humans, hair curliness is incomplete.
The homozygotes are straight hair and curly
chair; the heterozygote is wavy hair.