Get out:Get out: Ch 12 notes Ch 12 notes

Ch. 12 ReviewCh. 12 Review

Chapter 12.1Chapter 12.1PedigreesPedigrees

I. Making a PedigreeI. Making a Pedigree

A A _____PEDIGREE__________PEDIGREE_____ is a diagram that represents genetic is a diagram that represents genetic inheritance. (kind of like a family tree)inheritance. (kind of like a family tree)II. Symbols of a pedigreeII. Symbols of a pedigree

femalefemale = = male = male =

= female non carrier= female non carrier = male non = male non carriercarrier

= female that shows the trait= female that shows the trait = male that = male that

shows the traitshows the trait

= female carrier =male carrier = female carrier =male carrier

**Carrier – someone who has a recessive allele for a specific **Carrier – someone who has a recessive allele for a specific trait. (heterozygous)trait. (heterozygous)

A A ______HORIZONTAL___________HORIZONTAL_____ line connecting line connecting a circle and square indicates that the a circle and square indicates that the individuals are parentsindividuals are parents

A A _______VERTICAL____________VERTICAL_____ line connects line connects parents with their offspringparents with their offspring

********RomanRoman numerals numerals represent each different represent each different generationgeneration

III – Why Study a Pedigree?III – Why Study a Pedigree? Most Most geneticgenetic disorders are caused by the disorders are caused by the

recessive allele.recessive allele.

By studying pedigrees, the individual will be By studying pedigrees, the individual will be able to determine the likelihood that he/she able to determine the likelihood that he/she carries the carries the alleleallele..

Information on other members of the family Information on other members of the family can also be studied by looking at a pedigree.can also be studied by looking at a pedigree.

Pedigrees illustrate

inheritance

Pedigrees illustrate

inheritance

Male

Female

Affected male

Affected female

Mating

Parents

Siblings

Known heterozygotes for recessive allele

Death

In a pedigree, In a pedigree, a circle a circle

represents a represents a female; a female; a square square

represents a represents a male.male.

Female Male

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Female

Male

Highlighted Highlighted

circles and circles and

squares squares

represent represent

individuals individuals

showing the trait showing the trait

being studied. being studied.

Also, can be Also, can be

shaded in.shaded in.

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Circles and Circles and

squares that are squares that are

not highlighted not highlighted

designate designate

individuals that individuals that

do not show the do not show the

trait. Also, can trait. Also, can

be blank or not be blank or not

shaded in.shaded in.

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A half-shaded A half-shaded

circle or square circle or square

represents a represents a

CARRIERCARRIER, a , a

heterozygous heterozygous

individual.individual.

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A horizontal line A horizontal line

connecting a circle connecting a circle

and a square and a square

indicates that the indicates that the

individuals are individuals are

parents, and a parents, and a

vertical line vertical line

connects parents connects parents

with their offspring.with their offspring.

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The generations The generations

are identified in are identified in

sequence by sequence by

Roman numerals, Roman numerals,

and each and each

individual is given individual is given

an Arabic number.an Arabic number.

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Remember :Remember :

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Question Question 11

What does this What does this pedigree tell you pedigree tell you about those who about those who show the show the recessive recessive phenotype for phenotype for the disease?the disease?

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The pedigree The pedigree indicates that indicates that showing the showing the recessive recessive phenotype for phenotype for the disease is the disease is fatal.fatal.

Question 2Question 2 What must happen for a person to show a recessive What must happen for a person to show a recessive

phenotype?phenotype?

AnswerAnswerThe person must inherit a recessive allele for the trait from both parents.

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Question Question 33

How many How many females are in females are in this pedigree?this pedigree?

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Question Question 44

How many males How many males are in this are in this pedigree?pedigree?

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Question Question 55

How many How many affected females affected females are in this are in this pedigree?pedigree?

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Question Question 66

How many How many affected males affected males are in this are in this pedigree?pedigree?

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Question Question 77

How many How many carriers are in carriers are in this pedigree?this pedigree?

IV. IV. Simple Simple

Recessive Recessive HeredityHeredity

• Most genetic disorders are caused by recessive alleles. Some common genetics disorders caused by recessive alleles are:

•Cystic Fibrosis

•Tay-Sach

•PKU

a. Cystic fibrosis (CF) - • A fairly common genetic disorder among

white Americans.• Approximately one in 28 white Americans

carries the recessive allele, and one in 2500 children born to white Americans inherits the disorder.

• Due to a defective protein in the plasma membrane, cystic fibrosis results in the formation and accumulation of thick mucus in the lungs and digestive tract.

b. Tay-Sachs Disease• Disease is a recessive disorder of the

central nervous system.

• Page 312 – draw in pedigree and label each persons genotype.

• **What is the genotype of individual II-3?

Pedigree-Tay Sachs

Disease

c. Phenylketonuria (PKU)

• is a recessive disorder that results from the absence of an enzyme that converts one amino acid, phenylalanine, to a different amino acid, tyrosine.

• Because phenylalanine cannot be broken down, it and its by-products accumulate in the body and result in severe damage to the central nervous system.

PhenylketonuriaPhenylketonuria

Phenylketonurics: Contains Phenylalanine

V. Simple Dominant Heredity

•traits may be inherited just as the rule of dominance predicts, a single dominant allele inherited from one parent is all that is needed for a person to show the dominant trait.

May include:

•Hitchhickers Thumb

•Widow’s Peak

•Free hanging Earlobes

Huntington’s Disease

•*Huntington’s Disease*Huntington’s Disease - lethal genetic disorder caused by a rare dominant allele. It results in a breakdown of certain areas of the brain.

Pedigree-Huntington

Disease

• _____ recessive disorder that results form the absence of an enzyme required to break down lipids

• _____ lethal genetic disorder caused by a dominant allele

• _____most common genetic disorder among white Americans

• _____recessive disorder that results from the absence of an exzyme that converts one amino acid into another one

• ____ widow’s peak and hitch hiker’s thumb

a.Cystic Fibrosis d. Huntington’s disease

b.Simple dominant traits e. PKU (phenylketonuria

c.Tay-Sachs diseaseCC

DD

AA

EE

BB

Page 314 : draw the pedigree and label each individuals genotype

Predict :(using a Punnett Square) the probability of II – 4 and 5

having children with Huntington’s disease.

Chapter 12.2 & 12.3 notesWhen Heredity Follows

Different Rules

I. Incomplete dominance:

Appearance of a __INTERMEDIATE__ phenotype

Occurs when a heterozygous individual is __________________________ between those of two homozygotes.

Example: red flowers and white flowers = pink flowers or animal coat color

II. Codominance:

Expression of both alleles

Occurs when you have _2_ dominant alleles and both are expressed.

Examples: Black hen (B) x white hen (W) = black and white hen or human blood types (A, B, AB, O)

Disorder in humans: Sickle cell anemia – different size red blood cell can lead to slowing of blood flow, tissue damage, blockage of blood vessels. (p. 324)

III. Multiple alleles

Occurs when ___MORE__ than __ONE__ alleles control a trait. (Can be 3 to 100 alleles per trait)

Examples: Pigeon color (p.317) Use in humans: Blood Typing (important for

blood transfusions)