3.4 Distinguish among observed inheritance patterns caused by several types of genetic traits (dominant, recessive, codominant, sex-linked, polygenic, incomplete dominance, multiple alleles).
Vocabulary
Tier 3
Dominant - one allele is expressed more often than the recessive one
Recessive - the allele that is not expressed as often
Codominant - both alleles are equally dominant
Sex-linked - the trait is carried on a sex chromosome
Polygenic - many genes make up the trait/phenotype
Incomplete dominance - the two alleles blend together and form a third phenotype
Genotype - what the genes alleles look like (BB or Tt or nn)
Phenotype - what the physical trait is (tall, short, brown, long, etc)
Essential Questions
1. What are the different types of inheritance of genes?
Dominant and Recessive
One allele is dominant and written as a capital letter B, T, N
One allele is recessive and written as a lower case letter b, t, n
Dominant alleles always win. See below.
Sex-linked
Sex-linked traits are inherited on the sex chromosomes XX or XY. The issue here is that the Y chromosome in men doesn't really carry any genes, so whatever the a man's X chromosome is, that's what he gets.
Incomplete Dominance
Incomplete dominance is when the two alleles blend together and cause a third phenotype. A red and white rose blend to make a pink rose.
Polygenic
Poly means many...Polygenic means many genes go into making the phenotype, like human skin color or human height. There are SIX genes for human skin color and even more for height.
Codominant
Codominant inheritance is where both alleles are expressed
Pedigree Charts
Keys to a pedigree chart
-squares are males
-circles are females
-half colored are carriers of the trait
-full colored express the trait (have the disease)