How are traits passed from one generation to the next?

Big Idea Genes  RNA  Protein  Traits The inheritance of each trait is determined by genes that are passed on to descendants unchanged. An individual inherits genes from each parent for each trait. A trait may not show up in an individual, but can still be passed on to the next generation.

Genetic Vocabulary Character = something that can be inherited by the next generation, such as flower color or blood type Trait = a variant of a character, such as purple or white flowers, or Type A or B blood Alleles = Alternative forms of a gene – there are 3 versions of blood type gene = A, B, and O

Humans have two copies of EVERY gene, one inherited from the mother and the other from the father B AB

Heterozygous = alleles inherited from mom and dad were different Homozygous = alleles inherited from mom and dad were the same

Phenotype  expression of genes, what you look like. What it looks like (Traits that SHOW) Phenotype  expression of genes, what you look like.

Genotype  the genes that control characteristics What Genes it has (May or may not show)

Dominant – always shows if the individual has this allele (Capital Letter) Recessive- will only show if the individual has two copies of this allele. Trait hides behind the dominant allele (Lower case letter)

Incomplete Dominance One allele is not completely dominant over another allele.

Codominance Both alleles contribute to the phenotype Heterozygous

How to Predict if offspring will inherit and express a trait: Parents must possess the genes for the kids to get them. Genes are independently sorted during gamete formation. XY

Punnett Squares are a tool for predicting the genotype of the offspring! Aa & Aa

Ratios and %’s XX and XY

Blood Types

Codominance in humans Protein that controls cholesterol levels in the blood. Heterozygous form of the gene produce two different forms of the protein, each with a different effect on cholesterol levels.

Polygenic Traits Traits controlled by two or more genes. Having many genes There are at least three genes involved in making the reddish-brown pigment in the eyes of fruit flies.

Polygenic Traits Skin color in humans Often shows a wide range of phenotype Skin color in humans More than 4 genes that control this trait.

Sex Linked Genes Inheritance of genes located on the X and Y chromosomes More than 100 sex linked genetic disorders mapped on the X chromosome. Y chromosome only contains a few genetic disorders.

Colorblindness Most common form of colorblindness; red-green. 1-10 males Male have just 1 X chromosome. Thus, all X-linked alleles are expressed in male, even recessive. 1-100 females has colorblindness

Hemophilia Protein for normal blood clotting is absent. 1-10,000 males

Duchenne Muscular Dystrophy Progressive weakening and loss of skeletal muscle 1-3000 males