Human Heredity

Human Chromosomes A chromosome is a threadlike structure within the nucleus containing DNA: To analyze chromosomes, biologists photograph cells in mitosis, when the chromosomes are fully condensed and easy to see The biologist then cut out the chromosomes from the photographs and group them together in pairs A picture of chromosomes arranged in this is known as karyotype

Human Chromosomes A typical human body cell contains _______ chromosomes: 2 of those 46 chromosomes are known as sex chromosomes: X and Y chromosome The remaining 44 chromosomes are known as autosomal chromosomes, or autosomes Male: 46 XY Female: 46 XX

Pedigree Chart A pedigree chart shows the distribution of particular traits within a specific family group A circle represents female A square represents male A half shaded circle or square indicates that a person is a carrier of the trait A completely un-shaded circle or square indicates that a person neither express nor carry the trait A completely shaded circle or square indicates that a person express that trait

Human Traits Some human traits are almost impossible to associate with single genes: Some traits are polygenic, meaning they are controlled by many genes: e.g. shape of your eyes or ears Many traits are strongly influenced by environmental factors including nutrition and exercise: e.g. height

Genetic Disorders Many human genes have become known through the study of genetic disorders: -Disorders caused by recessive alleles: You need to inherit 2 copies of the recessive alleles to have these disorders Disorders caused by dominant alleles: You only need to inherit 1 copy of the dominant alleles to have these disorders

Recessive alleles disorder Albinism: lack of pigment in skin, hair, and eyes (video) Cystic fibrosis: Excess mucus in lungs, digestive tract and liver (video) Galactosemia : Accumulation of galactose in tissues; mental retardation, eye and liver damage Phenylketonuria (PKU): Accumulation of phenylalanine (an amino acid); lack of normal skin pigment, mental retardation (video) Tay-Sachs disease: Lipid accumulation in brain cells; mental deficiency, blindness, death in early childhood (video)

Dominant alleles Disorder Achondroplasia: a form of dwarfism Huntington's disease: Mental deterioration and uncontrollable movements, appears in middle age (video)