Download Genetics

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 shortterm (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 + White = Pink

Codominance
Neither trait is dominant instead, both
traits are shown (No Blending)
 Ex) Roan Cows
 Red + White = 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 alleles
Ex. 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
Chinchilla
Albino
Full Color
Himalayan
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
Chapter
11
Complex Inheritance and Human Heredity
Polygenic Traits
 Polygenic traits arise from the interaction
of multiple pairs of genes.
Polygenic Inheritance
P Generation
aabbcc
(very light)

Skin Pigment
AABBCC
(very dark)
F1 Generation
AaBbCc
AaBbCc
F2 Generation
Eggs
Sperm
Figure 9.22
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