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Understand what are the following: human
cell, chromosomes, and genes.
Explain the errors that can occur in Meiosis
and Mitosis
Explain the differences between autosomal
recessive, autosomal dominant, and XLinked genetic disorders.
Understand inheritance patterns in singlegene disorders which are seen through
geno-imprinting, anticipation, and
mitochondrial inheritance
Understand that environmental issues can
also cause issues with development
 Disease
cause by an error in an
individuals DNA during fetal
development
› These errors include…
 Errors in Cell Division
 Errors in Chromosome Division
 Adding or deleting Chromosomes
 Mutations within Gene’s or a Single
Gene
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Two Key Parts: Nucleus and Cytoplasm
› Nucleus
 Chromosome & DNA organized into Gene’s
needed for life
› Cytoplasm
 Gene in the nucleus are dependent on the
cytoplasm
› The Nucleus and Cytoplasm need to be working
in unison so that there are NO defects in Gene
Development
› If an error occurs an any phase during
development it opens a wide range of genetic
disorders

Two Types of Cell Division
› Mitosis (Non-reductive Division)
 Two Daughter Cells (46 chromosomes each)
formed from one parent cell
› Meiosis (Reductive Division)
 Four Daughter Cells (23 chromosomes each)
are formed from one parent cell
 Only Seen in Germ Cells (Cells creating Sperm & Egg)
› Differences in Mitosis & Meiosis
 Different in the 1st phase of cell division –
Crossing over of Genes which can cause
disorders but very rare
 Prevents the chances of having “clones” as siblings
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Division Errors: Nondisjunction
› 1 sperm or Egg gets 22 or 24 chromosomes
not the required 23
› Error causes defects like…Down Syndrome or
Turners Syndrome
 Children will suffer from intellectual delays,
unusual facial features, congenital
malformations
 Occurrence: 6-9/1000 live births
 95% of individuals with Down Syndrome
develop this way
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Chromosomal Loss
› Turners Syndrome: 45 Chromosomes – Missing a X or
Y
› 99% miscarriage rate
› Features include.. Webbed neck, nonfunctional
ovaries, poor development of the cardiac muscle
 Unlike Down Syndrome – No real delay in intelligence
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Mosaicism
› Loss of extra chromosome
› Very rare and seen only in 5-10% of Chromosomal
abnormalities
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Translocation
› Transfer of 1 chromosome to a completely different 1
› Results in Down Syndrome because of extra
chromosome (Trisomy 21)
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Deletion
› Part if not all chromosome is lost
 1 in 50,000
 Causes: Unusual Facial features with round
face, wide spread eyes, lower set ears,
intellectual disabilities
› Williams Syndrome of Micro-deletion
 Causes: Intellectual Disabilities, distinctive
facial features, heart defects
› YCFS
 Causes: cleft palate, heart defects,
characteristic facial features, learning
disabilities
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Function of Gene
› Produce proteins and to regulate the function
and development of the body
› Composed of DNA (Double Helix)
 A-T and C-G meet up to make gene combinations
› Over 3.3 Gene combinations
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Genes can turn on and off
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Errors occurs when the body does not
properly turn gene’s on and off.
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Errors caused by…
› Transcription
› Translation
› Mutations
 Point Mutations
 Insertion and Deletions
 Triple Repeat Disorder
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Gene Disorders…
› Selective Advantage
› Single Nucleotide Polymorphisms (SNPs)
› Single Gene (Mendelian) Disorders
 Autosomal Recessive Disorders
 Autosomal Dominant Disorders
 X Linked Disorders

TRANSCRIPTION:
› Rarely see any errors during this process
› DNA unzipping allowing mRNA to make a
copy of information
› Errors are prevented because of “Proof
Reading” enzyme
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TRANSLATION:
› mRNA travels from nucleus to cytoplasm to
create protein
 Point
Mutations
 Most common type caused by single based pair
substitution
› Missense Mutation : change in triple pair
causing the wrong amino acid to attach
in a protein chain
› Nonsense Mutation: Termination of
Protein
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Insertion and Deletion:
› Most common Insertion: Polio
› Most common Deletion: Duchenne Muscular
Dystrophy
› Frame Shift: Tay-Sachs Disease
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Triplet Repeat Expansion:
› Over production of codons causing genes to
turn off
› Causes: Huntington Disease and Fragile X
Syndrome
Incidence in genetic diseases depends
on the amount of mutations that occur
and the amount that are removed
 National selection helps eliminate these
problem genes
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› Sickle Cell Anemia
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Autosomal Recessive
Disorders
› Incidents are very rare
› 1700 disorders- inherited
from mother and father
› EXAMPLE: Tay-Sachs
which is when the body is
unable to properly break
down nerve cells causing
a build up of toxins in the
brain
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Autosomal Dominate
Disorders
› 4500 autosomal
disordered identified
› 1 in 500 live births
› Single abnormal allele
› Example:
Achondroplasia and
Neurofibromatosis
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X-Linked Disorders
› Mutation in the sex
chromosome (X
chromosome)
› 900 X-Linked Disorders
› 25% of males and 10% of
females with
intellectual/learning
disabilities are affected by
X-Link Disorder
› Example:
 Duchenne Muscular
Disorder
 Mutation in the muscle cell
membrane
 Fragile X-Syndrome
 Most common X-Link Disorder
Genomic Imprinting
- Traits are inherited from the mother and
father but there is a gene deletion that
occurs from either the mother or the
father.
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- Prader-Willi Syndrome which is characterized
by short statue, obesity, and intellectual
disabilities.
- Angelman Syndrome which is characterized
by intellectual disabilities and epilepsy.
**Reasons for genomic imprinting is remains unclear

Anticipation
› Abnormal gene manifest increasing the
severity of the disease or disorder with each
generation.
› Example: Huntington Disease
 Caused by a triple repeat in gene formation.
 Autosomal dominant progressive neurological
disease which is associated with movement
and cognitive disorders and impairments
which increases with each generation
 Mitochondrial inheritance
› The genes with-in the DNA can mutate
causing the mitochondria to not perform
efficiently causing deficient energy
production and disease.
 EXAMPLE: MELAS which stands for
Mitochondrial encephalomymelopathy
lactic acid and stroke like episodes.
 It is carried on by the female gene only
 An unaffected mother is able to pass the
deficient gene on to her children both male
and female. Males can be effected but they
can not be carriers.
- The
environment can affect the
phenotype of an individuals gene’s.
- Environmental factors can effect the ways
at which gene’s are expressed.
- EXAMPLE: 2nd generation Asians growing up in
the U.S. are taller than their parents due to an
increase in protein intake during adolescence
- Disorders
like diabetes,
meningomyelocele, cleft palate, pyloric
stenosis are affected by both the
genotype and phenotype factures.
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Humans have 46 complementary genetic
chromosomes which determine our physical
appearance and biological makeup but
effect what we pass on to our offspring.
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When genes mutate, split incorrectly, delete or
add chromosomes it can have a lasting effect
on the outcome of a persons offspring
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Many problems can occur during pregnancy
however even with all the issues that can
occur, 95% of infants are born with out defects.

What is a human cell? Chromosome? Gene?
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What errors can occur in Meiosis and Mitosis?
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What are the differences between autosomal
recessive, autosomal dominant, and X-Linked
genetic disorders?

What are the inheritance patterns in single-gene
disorders (geno-imprinting, anticipation, and
mitochondrial inheritance)?

What environmental factors can also cause issues
with development ?
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Females have over 2 million Eggs
Trisomy is the common cause of miscarriages
Human genome contains 20,000-25,000 genes.
Fruit Fly contains 13,000 and a Round Worm
contains 19,000
Chimps share 99% of your human genome
People of all races and geography share 99.9%
of the same genetic identity There is only 1%
that we do not share. (SNP’s)
Many problems can occur during pregnancy
however even with all the issues that can
occur, 95% of infants are born with out defects.
Batshaw, M. L., Pellegrino, L., Roizen, N.J. (2007). Children with
Disabilities (6th ed., pp 3-20). Baltimore, MD: Paul H Brooks
U.S. National Library of Medicine. (2012, July 9). Genetics Home
Reference: Your Guide to Understanding Genetic
Conditions. Autosomal Recessive. Retrieved July 12, 2012
from http://www.beyondbatten.org/aboutprevention.html
Mayo Clinic Foundation for Medical Education and Research.
(2012, May 24). Autosomal Dominate Inheritance Pattern.
Retrieved July 11, 2012 from http://www.mayoclinic.
com/health/m edical/IM00991
Mayo Clinic Foundation for Medical Education and Research.
(2012, May 24). Muscular Dystrophy X-Linked Recessive Inheritance
Pattern with Carrier Mother. Retrieved July 11, 2012 from
http://www.mayoclinic.com/health/medical/IM02723