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 – 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 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 X r X r – Males only need one copy to express it X r Y

Sex-linked Traits In Humans – Color-blindness – Hemophilia – Male pattern baldness