Honors Biology Ch. 11 Complex Inheritance and Human Heredity Complex Inheritance and Human Heredity

I.Human Inheritance - heredity in humans is the same as in other organisms - most genetic diseases are recessive and rare

A.Recessive Traits -diseases caused by a single defective gene/protein 1.Cystic Fibrosis (CF) 2.Tay-Sachs Disease 3.Albinism 4.Phenylketonuria (PKU) 5.Sickle-Cell Anemia

DISORDER OCCURRENCE IN THE U.S. CAUSEEFFECT CURE- TREATMENT Cystic Fibrosis 1 : 3500 (Mainly people of northern European descent) The gene that codes for a membrane protein is defective. *Excessive Mucus Production *Digestive and Respiratory Failure *No Cure *Daily Cleaning of Mucus from Lungs *Mucus- thinning Drugs Albinism1 : 17,000 Genes do not produce melanin. *No Color in Skin, Eyes & Hair *Prone to Skin Cancer and Cataracts *No Cure *Protect Skin from the Sun Tay-Sachs Disease 1 : 2500 (Affects People of Jewish descent) Absence of a necessary enzyme that breaks down fatty substances *Buildup of Fatty Deposits in The Brain *Mental Disabilities *No Cure or Treatment *Death Occurs by Age 5

B.Dominant Traits 1.Huntington’s Disease -rare, degenerative nervous system disorder Woody Guthrie

2.Achondroplasia -a disorder of bone growth -homozygous dominant condition is fatal

3.Polydactyly

II.Other Inheritance Patterns A.Sex Chromosomes: - pair of chromosomes that determine an individual’s sex XX - female XY - male Autosomes: the other chromosome pairs except the sex chromosomes

Human Chromosomes: 44 Autosomes

Human Chromosomes: 2 Sex Chromosomes

B.Sex-Linked Traits: -trait controlled by a recessive allele on the "X" sex chromosome -more common in males -Ex. Red-green color-blindness, hemophilia

Can you see a number?

Queen Victoria’s Family

Pedigree of Europe’s Royal Families

C.Sex-Influenced Traits: -trait controlled by an allele that is recessive in females and dominant in males -Ex. Male-pattern Baldness

D.Incomplete Dominance: -a trait in which the heterozygote shows a blending of traits -Ex. Carnations and Snap dragons: R - red, W - white, RW - pink

RR Incomplete Dominance: P Homozygous Red Parent Homozygous White Parent R W RWRW RW Pink W W

RW Incomplete Dominance: F 1 Heterozygous Pink Parent R W RWRR WW RedPink White W R

E.Codominance: -a trait in which the heterozygote shows both alleles equally -Ex. Horses: R - red, W - white, RW - roan -Ex. ABO Blood Groups A B AB

E.Codominance: Roan Horses

E.Codominance: ABO Blood Groups

F.Polygenic Inheritance: -traits controlled by more than one pair of genes -Ex. hair, skin, and eye color

AB Ab aB ab ABAbaBab Human Eye Color EGGS SPERM Mother AaBb Father AaBb AABBAABbAaBBAaBb blackdark browndark brownlight brown AAbB dark brown AAbb light brown AabB Aabbblue aABBaABbaaBBaaBb dark brown light brown blue aABbaABbaaBbaabb blueblue light blue

Human Skin Color

G.Epistasis -A gene at one locus alters the phenotypic expression of a gene at a second locus. - Example: black, brown, and white coat in mice

Epistasis: Black, Brown, and White Coat in Mice BC bCBc bc 1⁄41⁄4 1⁄41⁄4 1⁄41⁄4 1⁄41⁄4 BC bC Bc bc 1⁄41⁄4 1⁄41⁄4 1⁄41⁄4 1⁄41⁄4 BBCcBbCc BBcc Bbcc bbcc bbCc BbCc BbCC bbCC BbCc bbCc BBCCBbCC BBCc BbCc 9 ⁄ 16 3 ⁄ 16 4 ⁄ 16 BbCc  Sperm Eggs

H.Multiple Alleles: 1.ABO Blood Groups: - 4 blood types: A, B, AB, O - caused by a protein in the membranes of red blood cells - 3 alleles for this protein: I A, I B, i

-Genotypes for the 4 blood types: Type A: I A I A, I A i Type B: I B I B, I B i Type AB: I A I B Universal Recipient Type O:ii Universal Donor

2.Rh Blood Groups: -an example of multiple alleles -there are about 8 dominant alleles (+) -one recessive allele (-)

III.Nondisjunction: -homologous chromosomes fail to separate during meiosis

III.Nondisjunction: -Down Syndrome (Trisomy 21) -Klinefelter’s Syndrome (XXY) - XYY Syndrome -Turner’s Syndrome (Monosomy X) (X) -Trisomy X (XXX)

Down syndrome (Trisomy 21)

Incidence of Down Syndrome Age of Mother (years) Number per 1000 Births

Turner’s Syndrome (Monosomy X)

XYY Syndrome

Trisomy X (XXX)

Klinefelter’s Syndrome (XXY)

Down Syndrome (Trisomy 21)

Normal Female

Edward’s Syndrome (Trisomy 18)

IV. Fetal Testing: - Amniocentesis -Chorionic Villus Sampling - Ultrasound

Amniocentesis

Ultrasound image Head Body Head Body

Ultrasound Of Fetus

TheThe EndEnd

Human Chromosomes (23 homologous pairs)