Sex Linked and Codominant Sex Linked and Codominant Genes.Genes.

Attached Earlobe Unattached Earlobe

Tongue Roll Tongue Flip Tongue Fold Hitchhiker’s Thumb

Ear WaxEar Diagram

Hand Fold

Bent Pinky PTC Tasting Widow’s PeakDimples

Mid-digital hair Bent LittleFinger

Short Hallux Finger Length

carriercarrier

??

UnknownphenotypeUnknown

phenotype

femalefemale

malemale

Affected individualsAffected

individuals

consanguineous marriage

consanguineous marriage

Female carrier of an x-linked trait

Female carrier of an x-linked trait

marriagemarriage

Extra-maritalmating

Extra-maritalmating

probandproband

diseaseddiseased

progenyprogeny

Stillbornor abortion

Stillbornor abortion

identical (monozygotic)

twins

identical (monozygotic)

twins

Dizygotic twinsDizygotic twins

PEDIGREE

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

GENERATIONS

SEX-LINKEDRECESSIVE TRAITS

More affected males than females.

Affected grand-father to grand-son thru carrier female.

Females do not manifest the disorder.

Examples of sex-linked recessive traits:

COLOR BLINDNESS

Examples of sex-linked recessive traits:

COLOR BLINDNESS

How it works…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…Problems…

1. Baldness: Mother XBXb x Father XBY

2. Color Blindness : Mother XbXb x Father XBY

3. Hemophilia: Mother XBXB x Father XbYX

Sex Linked Traits – Punnett Squares

Huntington’s Disease• Woody Guthrie• Arlo Guthrie• Children

DOMINANT Allele DISEASES

Dominant allele -- you have the disease or you don’t

Lobster Foot

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.

• Dominant doesn’t necessarily mean commonplace

• Albinism• Achondroplasia

• Both parents can be carriers to have an affected child

• 2 affected parents will usually produce an affected child

RECESSIVE Allele DISEASE

RECESSIVE Allele DISEASE

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 Polygenic Inheritance in HumansHumans

• 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

CataractsGlaucomaHereditary deafnessRetinitis pigmentosaSchizophreniaMigrane HeadahesProstate cancerAcute LeukemiaBrain cancerMuscular dystrophyColon cancerAlzheimer’s diseaseFish odor syndrome

CHROMOSOME 1

Colon cancerObesityLiver cancerDiabetes mellitusCleft palateCataractsEpilepsyParkinson’s diseaseMuscular dystrophyPseudohermaphroditismOvarian cancerMicropenis

CHROMOSOME 2

Huntington’s diseaseNight blindnessPhenylketonuriaParkinson’s diseaseAlcoholismRed hairMast cell leukemiaAchondroplasiaDopamine receptorRetinitis pigmentosaHip dysplasia

CHROMOSOME 4

Blood TypeBlood Type

• 4 Types A,B,ABand O4 Types A,B,ABand OParent 1 AlleleParent 1 Allele Parent 2 AlleleParent 2 Allele GenotypeGenotype PhenotypePhenotype

AA AA AAAA AA

AA BB ABAB ABAB

AA OO AOAO AA

BB AA ABAB ABAB

BB BB BBBB BB

BB OO BOBO BB

OO OO OOOO OO

I Am My Own GrandpaI Am My Own Grandpa  

• Many, many years ago when I was twenty-three Many, many years ago when I was twenty-three I was married to a widow who was pretty as could be. I was married to a widow who was pretty as could be. This widow had a grown-up daughter who had hair of red. 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.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 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. For my daughter was my mother, 'cause she was my father's wife. To complicate the matter even though it brought me joy To complicate the matter even though it brought me joy I soon became the father of a bouncing baby boy.I soon became the father of a bouncing baby boy.

• My little baby then became a brother-in-law to dad My little baby then became a brother-in-law to dad And so he became my uncle though it made me very sad And so he became my uncle though it made me very sad For if he is my uncle then that also makes him brother, 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.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, 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; 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, My wife she is my mother's mother and it makes me blue, Because although she is my wife, she's my grandmother too.Because although she is my wife, she's my grandmother too.

• Now if she is my grandmother than I'm her grandchild Now if she is my grandmother than I'm her grandchild And every time I think of it, it nearly drives me wild; And every time I think of it, it nearly drives me wild; For now I have become the strangest case you ever saw For now I have become the strangest case you ever saw As husband of my grandmother I am my own grandpa.As husband of my grandmother I am my own grandpa.

• Chorus: Chorus: Oh, I'm my own grandpa, I'm my own grandpa Oh, I'm my own grandpa, I'm my own grandpa It sounds funny, I know, but it really is so It sounds funny, I know, but it really is so Oh, I'm my own grandpa. Oh, I'm my own grandpa. 

• Below is a link to the song that can be played in class:Below is a link to the song that can be played in class:• http://www.ziplo.com/grandpa.htmhttp://www.ziplo.com/grandpa.htm