Sex Linked and Codominant Genes.

Sex Linked and Codominant Genes.

Hitchhiker’s Thumb Attached Earlobe Unattached Earlobe Ear Wax Ear Diagram Tongue Roll Tongue Flip Tongue Fold

Bent Pinky Dimples Hand Fold PTC Tasting Widow’s Peak Mid-digital hair Short Hallux Finger Length Bent Little Finger

female marriage proband male consanguineous marriage diseased Dizygotic twins Affected individuals Extra-marital mating identical (monozygotic) twins ? Female carrier of an x-linked trait Stillborn or abortion Unknown phenotype progeny carrier

PEDIGREE

GENERATIONS Generations are numbered w/Roman numerals. Within each generation, individuals are numbered from oldest to youngest.

More affected males than females. Affected grand-father to grand-son thru carrier female. SEX-LINKED RECESSIVE TRAITS Females do not manifest the disorder.

Examples of sex-linked recessive traits: COLOR BLINDNESS

How it works… • Female XX and Male XY. • Traits can be carried on either the X or Y chromosomes. ( Mostly on the X). • Dominant and recessive laws still apply.

Problems… • Baldness: Mother XBXb x Father XBY • Color Blindness : Mother XbXb x Father XBY • Hemophilia: Mother XBXB x Father XbY X

Sex Linked Traits – Punnett Squares

DOMINANT Allele DISEASES Huntington’s Disease • Woody Guthrie • Arlo Guthrie • Children Lobster Foot Dominant allele -- you have the disease or you don’t

Examples of Simple Dominant Disorders • Dwarfism • Polydactyly and Syndactyly • Hypertension • Hereditary Edema • Chronic Simple Glaucoma – Drainage system for fluid in the eye does not work and pressure builds up, leading to damage of the optic nerve which can result in blindness. • Huntington’s Disease – Nervous system degeneration resulting in certain and early death. Onset in middle age. • Neurofibromatosis – Benign tumors in skin or deeper • Familial Hypercholesterolemia – High blood cholesterol and propensity for heart disease • Progeria – Drastic premature aging, rare, die by age 13. Symptoms include limited growth, alopecia, small face and jaw, wrinkled skin, atherosclerosis, and cardiovascular problems but mental development not affected.

RECESSIVE Allele DISEASE • Albinism • Achondroplasia • Both parents can be carriers to have an affected child • 2 affected parents will usually produce an affected child • Dominant doesn’t necessarily mean commonplace

Examples of Simple Recessive Disorders • Congenital Deafness • Diabetes Mellitus • Sickle Cell anemia • Albinism • Phenylketoneuria (PKU) – Inability to break down the amino acid phenylalanine. Requires elimination of this amino acid from the diet or results in serious mental retardation. • Galactosemia – enlarged liver, kidney failure, brain and eye damage because can’t digest milk sugar • Cystic Fibrosis – affects mucus and sweat glands, thick mucus in lungs and digestive tract that interferes with gas exchange, lethal. • Tay Sachs Disease – Nervous system destruction due to lack of enzyme needed to break down lipids necessary for normal brain function. Early onset and common in Ashkenazi Jews; results in blindness, seizures, paralysis, and early death.

Polygenic Inheritance in Humans • includes skin, eye, and hair color • light-skinned X dark-skinned • F1: offspring have intermediate skin colors • F2: skin color range from light to dark skin color of the grandparents • Children have intermediate skin color.

Polygenic Traits… • Eye color is determined by more than one gene • Thus eye color appears to vary on an almost continuous scale from brown to green to gray to blue • Eye color is determined by two genes, one controls texture of the iris which refracts light to make blue. A second determines relative abundance of melanin. When a small amount of melanin is present, green eyes result while brown and black eyes result from relatively increasing amounts of melanin

Polygenic Traits… • Hair color is determined by more than one gene • Thus hair color appears to vary on an almost continuous scale from black to brown to blond to red • The brown and black pigment is melanin • The red pigment is an iron containing molecule

CHROMOSOME 1 Cataracts Glaucoma Hereditary deafness Retinitis pigmentosa Schizophrenia Migrane Headahes Prostate cancer Acute Leukemia Brain cancer Muscular dystrophy Colon cancer Alzheimer’s disease Fish odor syndrome

CHROMOSOME 2 Colon cancer Obesity Liver cancer Diabetes mellitus Cleft palate Cataracts Epilepsy Parkinson’s disease Muscular dystrophy Pseudohermaphroditism Ovarian cancer Micropenis

CHROMOSOME 4 Huntington’s disease Night blindness Phenylketonuria Parkinson’s disease Alcoholism Red hair Mast cell leukemia Achondroplasia Dopamine receptor Retinitis pigmentosa Hip dysplasia

Blood Type • 4 Types A,B,ABand O

I Am My Own Grandpa • Many, many years ago when I was twenty-three I was married to a widow who was pretty as could be. This widow had a grown-up daughter who had hair of red. My father fell in love with her and soon the two were wed. • This made my dad my son-in-law and changed my very life For my daughter was my mother, 'cause she was my father's wife. To complicate the matter even though it brought me joy I soon became the father of a bouncing baby boy. • My little baby then became a brother-in-law to dad And so he became my uncle though it made me very sad For if he is my uncle then that also makes him brother, To the widow's lovely daughter who, of course, was my step-mother. • Father's wife then had a child which kept them on the run, And he became my grandchild, 'cause he was my daughter's son; My wife she is my mother's mother and it makes me blue, Because although she is my wife, she's my grandmother too. • Now if she is my grandmother than I'm her grandchild And every time I think of it, it nearly drives me wild; For now I have become the strangest case you ever saw As husband of my grandmother I am my own grandpa. • Chorus: Oh, I'm my own grandpa, I'm my own grandpa It sounds funny, I know, but it really is so Oh, I'm my own grandpa. • Below is a link to the song that can be played in class: • http://www.ziplo.com/grandpa.htm

Sex Linked and Codominant Genes.