Human Heredity

Karyotype: picture of chromosomes

Most genetic disorders are caused by RECESSIVE alleles. Cystic fibrosis- large accumulation of muscus due to lack of protein. Phenylketonuria (PKU)- lack enzyme that converts phenylalanine to tyrosine. Tay-Sachs- lack of enzyme that breaks down fat in the CNS Albinism- lack of pigment in skin.

Cystic Fibrosis http://www.youtube.com/watch?v=Twjg7v-pTO4

Cystic Fibrosis- DON’T WRITE Caused by a defect in a protein that results in an overproduction of muscus. Favors bacterial infections. 1 in 20 white Americans are carriers. 1 in every 2000 children born to white americans has this disorder. Without treatments, most children die before age 5. With treatments, can live into 20’s+

Tay-Sachs- DON’T WRITE Lack enzyme breaks down fat in the CNS- fat collects on the brain. No treatment or cure. Most will die before the age of 6. http://www.youtube.com/watch?v=o3yQZp5Rs-o

Albinism

Disorders caused by dominant alleles: Huntington’s Disease Dwarfism Polydactylism

Huntington’s Disease http://www.youtube.com/watch?v=u9XzqreToII&feature=related

Dwarfism http://www.youtube.com/watch?v=eYam_G92g-o

Polydactyl- more than 5 digits on hand or foot

Caused by changes in DNA (mutations): Sickle-cell Anemia: amino acid is changed in hemoglobin to give cells a sickle shape. Blocks the flow of red blood cells.

Sickle Cell Anemia http://www.youtube.com/watch?v=ujf72mjy0Bg

Some genetic disorders are Sex-Linked Most commonly found in males Mostly on X chromosome (recessive) and since males have only one X chromosome they will express the disorder more often. Examples: Colorblindness Hemophilia Muscular Dystrophy

DON’T WRITE Some genes are located on the X chromosome. Females receive two alleles for these genes, but males only receive one. If the parent is a male, the genotype is automatically known. A colorblind male has to be b, since he only has one allele and colorblindness is recessive. A normal male must then be B Females can be heterozygous for the colorblindness trait - they are called carriers. A female can be BB - normal, Bb - carrier, or bb - colorblind

The following shows a cross between a normal man and a woman who is a carrier

colorblindess test

Hemophilia http://www.youtube.com/watch?v=FS64UXi74lY

Chromosomal Disorders Nondisjunction: chromosomes fail to separate properly during meiosis (formation of gametes) Down Syndrome- extra chromosome on #21 (results in total of 47 chrom) Turner’s Klinefelter’s

Down Syndrome- Extra chromosome on #21. Total of 47 chromosomes

Down Syndrome Karyotype

Klinefelter’s Karyotype XXY

Turner’s Karyotype Only One X

Pedigree—graphic representation of genetic inheritance Pedigree—graphic representation of genetic inheritance. - Male= square - Female= circle - Shaded= has the disorder - Half shaded= carrier of disorder.