Mendelian Inheritance of Human Traits Simple Recessive Heredity

Simple Recessive Heredity • When a person gets two recessive alleles. • Simple Recessive

Simple Dominant Heredity • When a person gets at least one dominant allele. •

Incomplete Dominance • a heterozygote has a different phenotype as the two homozygotes –

Codominant • in a heterozygote individual both phenotypes are expressed equally – Example –

Codominant, cont. – Example: Blood type gene has three different alleles (each person has

Blood Type Genotype Phenotype AA or AO A BB or BO B AB only

Polygenic Inheritance • - the inheritance pattern of a trait that is controlled by

Sex-linked Traits • There are 22 pairs of chromosomes in your body that are

Sex-Linked Traits, cont. • Some human traits are determined by genes carried on the

Environmental Influences • There are many, many environmental factors that affect the way our

• A karyotype is a chart of chromosome pairs. • This technique is

Pedigree Charts A Pedigree chart is a graphic representation of genetic inheritance. – kind

Pedigree Charts, cont. • When you carefully make a pedigree chart you should be

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Mendelian Inheritance of Human Traits

Simple Recessive Heredity • When a person gets two recessive alleles. • Simple Recessive Genetic Disorder – Cystic Fibrosis (thick accumulation of mucus in lungs and digestive tract) – Tay-Sachs (disease of the central nervous system) – Phenylketonuria-PKU (results in damage to central nervous system)

Simple Dominant Heredity • When a person gets at least one dominant allele. • Simple Dominant Traits – Tongue Rolling – Huntingtons Disease (results in a breakdown of certain areas of the brain)

Complex Patterns of Inheritance

Incomplete Dominance • a heterozygote has a different phenotype as the two homozygotes – Example-Red flowers are RR, white are WW, the heterozygous condition, RW produces pink flowers

Codominant • in a heterozygote individual both phenotypes are expressed equally – Example – cross a black chicken (BB) and a white chicken (WW) the heterozygote wouldn’t be grey, the chicken has both black and white feathers.

Codominant, cont. – Example: Blood type gene has three different alleles (each person has two of the three possibilities) • Type A allele is dominant and produces A type protein on red blood cells • Type B allele is dominant and produces B type protein on red blood cells • Type O allele is recessive (defective) allele and produces no protein on red blood cells

Blood Type Genotype Phenotype AA or AO A BB or BO B AB only AB OO only O

Blood Type

Polygenic Inheritance • - the inheritance pattern of a trait that is controlled by two or more genes. – Examples in humans include – hair color (AABBCC) – eye color – skin color

Sex-linked Traits • There are 22 pairs of chromosomes in your body that are called autosomes. • The other pair are called sex chromosomes. They are called “X” and “Y”. • Female genotype = XX • Male genotype = XY

Sex-Linked Traits, cont. • Some human traits are determined by genes carried on the sex chromosomes, most of these genes are on the X chromosome. • Color blindness and hemophilia are examples of sex-linked traits.

Environmental Influences • There are many, many environmental factors that affect the way our genes are expressed.

• A karyotype is a chart of chromosome pairs. • This technique is used to look at the chromosomes and tell if the individual has the normal number and type. Karyotype

Pedigree Charts

Pedigree Charts A Pedigree chart is a graphic representation of genetic inheritance. – kind of like a family tree

Pedigree Charts, cont. • When you carefully make a pedigree chart you should be able to tell which individuals are possible carriers and the probability that future offspring will express the trait shown.