UNIT 11 HUMAN GENETICS
Flashcard Warm-up
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Pedigree
A chart of an individual's
ancestors used in human
genetics to analyze
inheritance of certain
traits
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Nature vs. Nurture
Nature is our DNA (genes)
Nurture is our environment
The debate is over which
has a greater influence
We use identical twins to
study
Problems studying human genetics

1. Ethically unresponsible to conduct testcrosses on
humans.
 Testcross:
method to determine the genotype for a
dominant phenotype, always use homozygous recessive
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2. Humans have long life spans and it requires
decades to produce several generations to study.
3. Small number of offspring (and long gestational
periods)
Techniques used to study human genetics
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Population Sampling:
 determine
how often a trait appears in a small
randomly selected group, then apply to the
entire population
 ex.

How many people can roll their tongue?
Take this number and project for the entire population.
Techniques used to study human genetics
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Pedigrees: graphical
record of the
inheritance of a single
trait over several
generations.
 determined
based on
family/historical
documents, interviews,
photographs, and medical
records
Pedigrees
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Shapes represent individuals in pedigrees,
connecting lines represent relationships
Female
Without
trait
Female
WITH
trait
Male
without
trait
Male
WITH
trait
Ticket Out the Door
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1. When red cattle are bred with white cattle they
produce roan (red and white spotted). Cross a roan
cow with a red cow. Give phenotype percentages
of the offspring.
2. Colorblindness is sex-linked recessive. Cross a
colorblind male with a female carrier. What is their
chance of having a colorblind son?
3. Cross a mom with type AB blood with a dad
who is type O. List all possible phenotypes.
Helpful Hints for figuring out pedigrees
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If the pedigree is showing a SEX-LINKED trait:
 No
male carriers
 Trait cannot be passed from father to son
 More males will express the trait
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If the pedigree is showing an AUTOSOMAL
recessive trait
 Trait
can skip a generation
 Trait CAN be passed from father to son
Flashcard Warm-up
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Autosomal Trait
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Trait inherited on one
of the first 22 pairs
of chromosomes…….
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 NOT
sex-linked
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Aneuploidy
Having too many or too few
chromosomes
Caused by mistakes in
Meiosis--nondisjunctionhomologous pairs do not
separate during meiosis
Flashcard Warm-up
Gene Disorders vs. chromosomal disorders
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Gene disorders: Diseases inherited as a single gene
on a single chromosome
 Arise
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from mutations on within a single gene
Chromosomes disorder: caused by receiving a
missing or extra chromosome--- like Down Syndrome
 Often
caused by NONDISJUNCTION during Meiosis
 Called ANEUPLOIDY
 Can be detected on a KARYOTYPE: a picture of the
chromosomes
Pattern of Inheritance for Genetic
Disorders
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Autosome: the first 22 pairs
of chromosomes
 Autosomal
Dominant:
dominant trait found on any of
the first 22 chromosomes
 Example : Huntington’s disease,
found on chromosome 4, causes
brain to break down, symptoms
appear in your 40’s
Genetic Disorders
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Autosomal Codominant:
 Found
on chromosomes 1-22,
and both version of trait are
equally dominant
 Example: Sickle-cell Anemia,
leads to misshapen red
blood cells, leads to poor
circulation and pain,
 Heterozygous
individuals are
resistant to malaria
 Primarily in African-Americans
Genetic Disorders
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Autosomal Recessive: recessive traits found on any of
the first 22 chromosomes
Examples:
 Cystic fibrosis (increased mucus in lungs and digestive tract)
caucasians
 Tay-Sach’s disease- break down of central nervous system
leading to premature death (die before 2)
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Found in jewish and pennsylvania dutch populations
PKU (phenylketonuria)
Inability to break down the amino acid phenylalanine
 Can be controlled by diet
 Can build up in brain and lead to decreased mental function
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Cystic Fibrosis- autosomal recessive
Sex Chromosomes: Pair 23;
XX- female, XY- Male
 Sex-linked
disorder: Disorder
carried ON the X
 Examples:
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Hemophilia (sex-linked
recessive trait)-blood does not
clot normally
colorblindness
Chromosomal Disorders
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Inherited due to problems
with the ENTIRE chromosome
 Example:
Down’s Syndrome,
caused by a mistake in
MEIOSIS
 Nondisjunction= incorrect
distribution of chromosomes;
occurs during meiosis
Chromosomal Disorders
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Anueploidy: an incorrect
number of chromosomes
in a fertilized zygote
 Autosomal
Chromosome
Aneuploidy: having an extra
autosome
 Example:
Down’s Syndrome is
caused by an extra
chromosome #21
Sex Chromosome Aneuploidy
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Examples
 Klinefelter’s
Syndrome (XXY)
--male but develops female secondary sex
characteristics
-- usually sterile
--use testosterone therapy to treat
Sex Chromosome Aneuploidy
 Turner’s
Syndrome (XO)
 Female
infertile
with underdeveloped gonads,
Detection of Genetic Disorders
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Genetic Counseling: can
help parents determine the
chances of passing a harmful
genetic trait to their child
Sonograms: use of sound
waves to produce a picture
of a fetus
 Used
to evaluate baby’s
growth and development
Detection of Genetic Disorders
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Blood tests:
 Screen
for proteins
 Alpha-Feto
protein
test (AFP)
 Levels determine if
baby is at risk for
Down’s syndrome,
Turner’s , or spina
bifida
Detection of Genetic Disorders
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Amniocentesis:
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Removes amniotic fluid with
fetal cells which can be
cultured and produce a
karyotype
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Karyotype: a picture of the
chromosomes
Chorionic Villi Sampling:
removes tissue from the
placenta for karyotyping,
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Can be done earlier in
pregnancy and more risky
Karyotypes
Human Genome
Project

Human Genome
Project:
 develop
certain
genetic markers to
detect presence of
certain gene
variations on the
chromosomes
Knowledge of a genome unlocks the secrets of
what DNA is making which proteins. This will
ultimately help scientist to better understand the
inner workings of biology.
Prevention/Treatment
Genetic diseases cannot be cured but treated:
 Pain medication: manage pain
 Occupational Therapy: help people who have
conditions improve their ability to perform every
day tasks
 Blood Transfusions: Sickle-cell/ Hemophiliacs may
require
 Gene Therapy: use vectors (viruses) to replace
defective genes with normal ones
Environmental Factors
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Diet:
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can stop the progression of PKU, andlimit the risk for
genetic predispositions such as heart disease,
alcoholism, and certain cancers.
Environmental Toxins: environmental factors such as
UV radiation or tobacco can directly change our
genes