Transcript Chromosomal Inheritance

Chapter 14
Human
Heredity
Chromosomal
Inheritance
Human Genetic Disorders
Autosome - Any chromosome other than a sex
chromosome
Genetic disorders caused by genes on autosomes
are called autosomal disorders
Some genetic disorders are autosomal dominant
- An individual with AA has the disorder
- An individual with Aa has the disorder
- An individual with aa does NOT have disorder
Other genetic disorders are autosomal recessive
- An individual with AA does NOT have disorder
- An individual with Aa does NOT have disorder, but is a
carrier
- An individual with aa DOES have the disorder
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Chromosomal
Autosomal Recessive Pedigree
Chart
Inheritance
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Chromosomal
Autosomal Dominant Pedigree
Chart
Inheritance
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Chromosomal
Inheritance
Autosomal Recessive Disorders
Tay-Sachs Disease
Progressive deterioration of psychomotor
functions
Cystic Fibrosis
Mucus in bronchial tubes and pancreatic
ducts is particularly thick and viscous
Phenylketonuria (PKU)
Lack enzyme for normal metabolism of
phenylalanine
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Chromosomal
Cystic Fibrosis Therapy
Inheritance
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Chromosomal
Inheritance
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Autosomal Dominant Disorders
Neurofibromatosis
Tan or dark spots develop on skin and darken
Small, benign tumors may arise from fibrous
nerve coverings
Huntington Disease
Neurological disorder
Progressive degeneration of brain cells
- Severe muscle spasms
- Personality disorders
Chromosomal
Inheritance
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Autosomal Dominant Disorders
Neurofibromatosis
Tan or dark spots develop on skin and darken
Small, benign tumors may arise from fibrous
nerve coverings
Huntington Disease
Neurological disorder
Progressive degeneration of brain cells
- Severe muscle spasms
- Personality disorders
Chromosomal
A Victim of Huntington Disease
Inheritance
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Huntington Disease:
Chromosomal 10
Inheritance
Normal and Diseased Brain
Chromosomal
Inheritance
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Multiple Allelic Traits and Codominance
Some traits controlled by multiple alleles
The gene exists in several allelic forms (but each individual
only has two)
ABO blood types
The alleles:
 IA = A antigen on red cells, anti-B antibody in plasma
 IB = B antigen on red cells, anti-AB antibody in plasma
 I = Neither A nor B antigens, both antibodies
Phenotype
(Blood Type)
A (actually AA or AO)
B (actually BB or BO)
AB
O (actually OO)
Genotype
IAIA or IAi
IBIB or IBi
IAIB
ii
Chromosomal 12
Inheritance of Blood Type
Inheritance
Human X-Linked Disorders:
Red-Green Color Blindness
Chromosomal
Inheritance
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Color vision In humans:
Depends three different classes of cone cells
in the retina
Only one type of pigment is present in each
class of cone cell
- The gene for blue-sensitive is autosomal
- The red-sensitive and green-sensitive genes are
on the X chromosome
- Mutations in X-linked genes cause RG color
blindness:
males with mutation (XbY) are colorblind
 Only homozygous mutant females (XbXb) are
colorblind
 Heterozygous females (XBXb) are asymptomatic
carriers
 All
Chromosomal 14
X-Linked Recessive Pedigree
Inheritance
Chromosomal
Inheritance
•
What is a karyotype?
•
What patterns of inheritance do human traits follow?

Dominant and Recessive Alleles

Codominant and Multiple Alleles
•
How can pedigrees be used to analyze human inheritance?
•
How do small changes in DNA molecules affect human traits?
•
What are the effects of errors in meiosis?

nondisjunction
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Chromosomal
Inheritance
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http://www.dnalc.org/resources/3d/17-sicklecell.html
Chromosomal
Inheritance
What is Sickle Cell Anemia?
 A serious condition in which red
blood cells can become sickleshaped
 Normal red blood cells are smooth
and round. They move easily through
blood vessels to carry oxygen to all
parts of the body.
 Sickle-shaped cells don’t move easily
through blood. They’re stiff and
sticky and tend to form clumps and
get stuck in blood vessels.
 The clumps of sickle cell block blood
flow in the blood vessels that lead to
the limbs and organs. Blocked blood
vessel can cause pain, serious
infection, and organ damage.
Normal and Sickled Red Blood
in Blood Vessels
Chromosomal
Cells Inheritance
Figure B shows abnormal, sickled red blood cells
clumping and blocking the blood flow in a blood vessel.
The inset image shows a cross-section of a sickled red
blood cell with abnormal strands of hemoglobin.
Figure A shows normal red blood cells flowing
freely in a blood vessel. The inset image shows a
cross-section of a normal red blood cell with
normal hemoglobin.
Source from http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html
Chromosomal
Inheritance
http://www.youtube.com/watch?v=5n29ZCvtCI
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What is cystic fibrosis (CF)?
Chromosomal
Inheritance
Cystic Fibrosis
Inherited monogenic disorder presenting as a
multisystem disease.
Typically presents in childhood
7% of CF patients diagnosed as adults
Most common life limiting recessive trait
among whites
Chromosomal
Inheritance
Cystic Fibrosis
Prognosis improving
>38% of CF patients are older than 18
13% of CF patients are older than 30
Median survival
Males: 32 years
Females: 29 years
Nondisjunction
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Trisomy 21
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Chromosomal
Inheritance
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Chromosome Number:
Abnormal Sex Chromosome Number
Result of inheriting too many or too few X or Y
chromosomes
Caused by nondisjunction during oogenesis
or spermatogenesis
Turner Syndrome (XO)
Female with single X chromosome
Short, with broad chest and widely spaced
nipples
Can be of normal intelligence and function
with hormone therapy
Chromosomal
Inheritance
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Chromosome Number:
Abnormal Sex Chromosome Number
Klinefelter Syndrome (XXY)
Male with underdeveloped testes and
prostate; some breast overdevelopment
Long arms and legs; large hands
Near normal intelligence unless XXXY,
XXXXY, etc.
No matter how many X chromosomes,
presence of Y renders individual male
Turner and Klinefelter Syndromes
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Chromosomal
Inheritance
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Chromosome Number:
Abnormal Sex Chromosome Number
Ploy-X females
XXX simply taller & thinner than usual
Some learning difficulties
Many menstruate regularly and are fertile
More than 3 Xs renders severe mental
retardation
Jacob’s syndrome (XYY)
Tall, persistent acne, speech & reading
problems
Chromosomal
Inheritance
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Abnormal Chromosome Structure
Deletion
Missing segment of chromosome
Lost during breakage
Translocation
A segment from one chromosome moves to a
non-homologous chromosome
Follows breakage of two nonhomologous
chromosomes and improper re-assembly