albinism
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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
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