Transcript Inheritance - Thornapple Kellogg High School

Inheritance
Types of Inheritance
• Dominant-recessive
– What we have been doing
– One allele is dominant, one is recessive
• If dominant is present, it is expressed
Types of Inheritance
• Intermediate/Incomplete
– Neither allele is dominant
– Heterozygotes have a phenotype that is
intermediate to the homozygotes
• Black Chicken crossed with a White Chicken
– Results in black, white and blue chickens
Types of Inheritance
• Multiple Alleles
– Many alleles for one trait
• Blood Type
• Codominance
– Heterozygote expresses both traits
Types of Inheritance
• Polygenic Inheritance
– Two or more genes affect a single trait
• Height, skin color
Only type of inheritance affects
the trait?
Environment
• Influences certain traits
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Height – nutrition
Build – exercise
Sunlight – skin shade
What others can you
think of?
Tie It Together!
Everything is tied together…
Meiosis and Mendel
• Chromosome Theory of Inheritance
– Genes are located on chromosomes
• What do chromosomes do during Meiosis?
• How would this affect Mendel’s ideas?
Sex-linked Traits
Sex-linked Traits
• Sex-linked Gene
– Located on a sex chromosome
• For us, most are found on the “X”
– Studied fruit flies
• Red eyes are common, white eyes are rare
• Discovered red eyes are dominant
• Flies with white eyes in experiment were male
Sex-linked Traits
• If linked to X –
– Females must have two white-eye alleles, one on
each X, to express the trait
• XrXr
– Males only need one copy to express it
• XrY
Sex-linked Traits
• In Humans
– Color-blindness
– Hemophilia
– Male pattern baldness