albinism

Albinism Caused by altered genes, resulting in the

absence of the skin pigment melanin in hair and eyes

White hair Very pale skin Blue Eyes Pink pupils

Albinism Impaired Vision It is vital that people with

albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer

High risk of skin cancer

Tay-Sachs Disease Caused by the absence of

the enzymes (in lysosomes) responsible for breaking down fatty acids called gangliosides

Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration

Tay Sachs Disease Children with Tay-Sachs, a progressive

neurodegenerative disease that attacks nerve cells, usually die before age 5.

Children will go deaf, have seizures, and, ultimately, become unable to swallow or breathe.

Galactosemia Recessive genetic disorder characterized

by the inability of the body to digest galactose.

Lactose = Galactose + Glucose Symptoms: • liver damage or failure

• cataracts• brain damage• infection

Galactosemia Treatment requires the strict exclusion of

lactose/galactose from the diet.

Dominant Genetic Disorders Dominant Gene results in disorder:

Huntington’s Disease Achondroplasia

Achondroplasia is a genetic condition that

causes small body size and limbs that are comparatively short.

Obesity Breathing problems (apnea) Recurrent ear infections

(otitis media). Other health problems

Huntington’s Disease affects the nervous system. Huntington's disease is a progressive,

degenerative disease that causes certain nerve cells in your brain to waste away.

As a result, you may experience uncontrolled movements, emotional disturbances and mental deterioration.

Huntington’s Disease Diminished memory,

immediate and short-term (long-term memory usually remains intact)

Disease usually manifests itself by age 35

Do Now Peter and Lois decide to try for a 4th child. Determine the possible genotype and

phenotype ratios of the following cross:

DdEe X ddEe

D= Brown hair d=red hair E=fluffy hair e=thinning hair

Pedigree Shows history of a trait in a family Allows researchers to analyze traits within

a family

Symbols for Pedigree

Using Pedigrees Inferring Genotypes

Knowing physical traits can determine what genes an individual is most likely to have.

Predicting Disorders Scientists use pedigree analysis to study: inheritance patterns determine phenotypes genotypes.

Sample Pedigree

Think – Pair - Share

Dominant or Recessive Trait?

Dominant or Recessive Trait?

Do Now Fill in the genotypes for the following

pedigree B=brown eyes b = blue eyes

Test Cross When the genotype of an individual is

unknown, cross the individual with a homozygous recessive

The outcome of the cross determine the genotype of the unknown

Do Now Fill in the pedigree for Achondroplasia. Use

the variable A.

11.2 Incomplete Dominance: Heterozygous phenotype is an

intermediate phenotype between the two homozygous phenotypes.

Two alleles are blended Ex) Four O’clock Flowers Red + WhiteWhite = Pink

Codominance Neither trait is dominant instead, both

traits are shown (No Blending) Ex) Roan Cows Red + WhiteWhite = RED AND WHITE

Sickle Cell Disease Affects red blood cells and ability to

transport oxygen.

Homozygous recessive alleles=

Heterozygous=

Homozygous dominant alleles=

Sickle Cell and Malaria People who are

heterozygous for sickle cell, have a higher resistance to malaria.

Multiple Alleles Traits determined by

more than 2 allelesEx. Blood Typing (3 alleles ABO) A and B are dominant

to O

Do Now A parent with the blood type A and one

with B have a child with type O blood. What are the parents genotypes?

Draw out the punnett square.

Universal Donor

Sample Problem Determine the possible offspring of the

following crosses

1. AB and O 2. AA and BO 3. AB and AB

Coat Color of Rabbits Rabbits have a hierarchy of coat color 4 alleles (C, cch, ch, and c) Dominant C > cch> ch > c Recessive

C Full color cch Chinchilla ch Himalayan c albino

Complex Inheritance and Human Heredity

Coat Color of Rabbits

Full Color Himalayan

Albino

Chinchilla

Let’s try a sample problem cc x Ccch

Genotype and phenotype ratios

What do you see?

What do you see?

Sex Linked Traits Traits located on the sex chromosomes

(X or Y) X linked: gene is located on the X

chromosomes Y linked: gene is located on the Y

chromosome

What are the chances of having a girl?

How would you go about solving it?

Sex-Linked Traits A man who is color blind marries a woman

that is heterozygous for color blindness. What is the chance of having a color blind boy?

Do Now A man that is color blind marries a woman

that is a carrier for the disorder. What is the chance of having a color blind girl?

Hemophilia Sex linked disorder characterized by

delayed blood clotting Located on the X Chromosome Seen in the Royal Family of England

Hemophilia

Complex Inheritance and Human Heredity

Polygenic Traits

Polygenic traits arise from the interaction of multiple pairs of genes.

Chapter 11

Skin Pigment

Polygenic Inheritance

Figure 9.22

P Generation

aabbcc(very light)

AABBCC(very dark)

F1 Generation

AaBbCc AaBbCc

F2 Generation

Eggs Sperm

What is the difference between polygenetic and multiple alleles?

Complex Inheritance and Human Heredity

Environmental Influences

Environmental factors

Diet and exercise

Sunlight and water

Temperature

Complex Inheritance and Human Heredity

Twin Studies

Helps scientists separate genetic contributions from environmental contributions

Traits that appear frequently in identical twins are at least partially controlled by heredity.

Traits expressed differently in identical twins are strongly influenced by environment.

Let’s try to explain the inheritance of the babies’ skin color.

Chromosomal Mutations