Honors BiologyCh. 11

Honors BiologyCh. 11

Complex Inheritanceand Human

Heredity

Complex Inheritanceand Human

Heredity

I. Human InheritanceI. Human Inheritance- heredity in humans is the same as

in other organisms- most genetic diseases are

recessive and rare

A. Recessive TraitsA. Recessive Traits- diseases caused by a single

defective gene/protein1. Cystic Fibrosis (CF)2. Tay-Sachs Disease3. Albinism4. Phenylketonuria (PKU)5. Sickle-Cell Anemia

DISORDEROCCURRENC

E IN THE U.S.

CAUSE EFFECTCURE-

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

Albinism 1 : 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 B.Dominant Traits 1. Huntington’s Disease

- rare, degenerative nervous system disorder

Woody Guthrie

2. Achondroplasia2. Achondroplasia- a disorder of

bone growth- homozygous

dominant condition is fatal

3. Polydactyly3. Polydactyly

II. Other Inheritance Patterns

II. Other Inheritance PatternsA.A. Sex Sex Chromosomes: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:44 Autosomes

Human Chromosomes:

2 Sex Chromosomes

Human Chromosomes:

2 Sex Chromosomes

B.Sex-Linked Traits: 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?

Can you see a number?

Queen Victoria’s Family

Queen Victoria’s Family

Pedigree of Europe’s Royal Families

Pedigree of Europe’s Royal Families

C. Sex-Influenced Traits:

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:

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 RR

Incomplete Incomplete Dominance: PDominance: PIncomplete Incomplete Dominance: PDominance: P

Homozygous Red Parent

Homozygous White Parent RW

RWRW

RW

Pink Pink

Pink Pink

W

W

RR WW

Incomplete Dominance: F1

Incomplete Dominance: F1

HeterozygousPink Parent

Heterozygous Pink Parent RW

RWR R

WW

Red Pink

Pink White

WW

RR

E.Codominance: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:E.Codominance:

Roan HorsesRoan Horses

E.Codominance:E.Codominance:

ABO Blood Groups

ABO Blood Groups

F.F. Polygenic Polygenic Inheritance:Inheritance:

F.F. Polygenic Polygenic Inheritance:Inheritance:- traits controlled by more than

one pair of genes- Ex. hair, skin, and eye color

ABAB

AbAb

aBaB

abab

ABAB AbAb aBaB abab Human Eye Color

Human Eye Color

EGGSEGGS

SP

ER

MS

PE

RM

MotherMother

AaBbAaBb

FatherFather

AaBbAaBb

AABBAABB AABbAABb AaBBAaBB AaBbAaBb

blackblack dark browndark brown dark browndark brown light brownlight brown

AAbBAAbB

dark browndark brown

AAbbAAbb

light brownlight brown

AabBAabB

light brownlight brown

AabbAabb

blueblue

aABBaABB aABbaABb aaBBaaBB aaBbaaBb

dark browndark brown light brownlight brown light brownlight brown blueblue

aABbaABb aABbaABb aaBbaaBb aabbaabb

light brownlight brown blueblue blueblue light bluelight blue

Human Skin ColorHuman Skin Color

G.Epistasis 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

Epistasis: Black, Brown, and White

Coat in Mice

BC bC Bc bc1⁄41⁄41⁄41⁄4

BC

bC

Bc

bc

1⁄4

1⁄4

1⁄4

1⁄4

BBCc BbCc BBcc Bbcc

Bbcc bbccbbCcBbCc

BbCC bbCC BbCc bbCc

BBCC BbCC BBCc BbCc

9⁄163⁄16

4⁄16

BbCc BbCc

Sperm

Eggs

H.H.Multiple Multiple Alleles:Alleles:

H.H.Multiple Multiple Alleles:Alleles:1.1. ABO Blood Groups: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:

IA, IB, i

- Genotypes for the 4 blood types:

Type A: IA IA, IAiType B: IB IB, IBiType AB: IA IB Universal Recipient

Type O: ii Universal Donor

2.Rh Blood Groups:2.Rh Blood Groups:- an example of multiple alleles- there are about 8 dominant alleles

(+)- one recessive allele (-)

III.III. Nondisjunction:Nondisjunction:III.III. Nondisjunction:Nondisjunction:- homologous chromosomes fail to

separate during meiosis

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

(X)- Trisomy X (XXX)

Down Down syndromesyndrome

(Trisomy 21)(Trisomy 21)

Down Down syndromesyndrome

(Trisomy 21)(Trisomy 21)

Incidence of Down Syndrome

Incidence of Down Syndrome

10 20 30 40 500

100

200

300

400

Age of Mother (years)

Nu

mb

er

per

1000 B

irth

s

Turner’s Syndrome (Monosomy X)

Turner’s Syndrome (Monosomy X)

XYY SyndromeXYY Syndrome

Trisomy X (XXX)

Trisomy X (XXX)

Klinefelter’s Syndrome (XXY)

Klinefelter’s Syndrome (XXY)

Down Syndrome (Trisomy 21)

Down Syndrome (Trisomy 21)

Normal FemaleNormal Female

Edward’s Syndrome (Trisomy 18)

Edward’s Syndrome (Trisomy 18)

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

AmniocentesisAmniocentesis

Ultrasound imageUltrasound image

Head

Body

Head

Body

Ultrasound Of FetusUltrasound Of Fetus

TheTheTheThe

EndEndEndEnd

Human Human ChromosomesChromosomes

(23 homologous (23 homologous pairs)pairs)

Human Human ChromosomesChromosomes

(23 homologous (23 homologous pairs)pairs)