 We
need to look into cells for the answer
 Analyzing chromsomes enables biologists to
look at the human genome
 Karyotype is a picture of chromosomes
arranged in a specific way
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Photograph cells in mitosis
Fully condensed chromosomes are easy to see
Cut chromosomes out of the photograph
Group them in pairs
Cells for karyotypes are taken by procedures like
amniocentesis for unborn children
 46
chromosomes
in human cell
 Sex
chromosomes
 Autosomes: all
other
chromosomes
except sex
chromosomes
Animation
 These
are useful for determining sex of an
unborn child
 Determining diseases caused by chromosomal
mutations
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Most common error in mitosis is called
“nondisjunction”
This is the failure of homologous chromosomes to
separate during meiosis I
Causes abnormal numbers of chromosomes
 Other
mutations are deletions,
translocations, duplications, and inversions
 Two
copies of an
autosomal chromosome
fail to separate in the
gametes
 Individual born with
three copies of a
chromosome, “trisomy”
 Patau Syndrome –
trisomy of chromosome
13- results in Mental
retardation and minor
physical deformaties
 Two
copies of an autosomal chromosome fail
to separate
 Causing an individual to be born with three
copies of a chromosome, “trisomy”
 Down’s syndrome is three copies of
chromosome 21
 In the US, 1 in 800 children are born with this
disorder
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Produces mild to severe mental retardation,
increased susceptibility to other diseases, higher
frequency of birth defects
 Turner’s
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Syndrome
Only occurs in females
Characterized by missing an “X” chromosome
(karyotype 45, X)
Women with Turner’s are sterile, sex organs do
not develop
 Klinefelter’s
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Syndrome
Only occurs in males
Characterized by an extra “X” chromosome
(karyotype 47, XXY or XXXY)
Men with Kleinfelter’s are sterile
 Genes
are inherited according to Mendel’s
principles of heredity
 However, in order to apply to human traits,
biologists must identify what traits are
controlled by which genes
 Pedigrees are charts that show relationships
between families
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Pedigree charts can show the relationships
between traits of many generations of families
 Human
traits are almost impossible to
associate with one gene
 Genetic counselors use pedigrees to make
assumptions about inheritance of genes
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However, environment effects the expression of
many genes
Genes can be influences by nutrition and
exercise
Environmental effects on genes ARE NOT
inherited
 Human
genome consists of thousands of
genes
 Studying this is not easy, due to long
generation time, complex life cycle,
production of very few offspring
 Biologist were able to identify genes that
control human traits
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One of the first genes identified was human
blood
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Concept Map #4 Time!!!!!
 Phenotypes
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A, B, AB, O
Genotype (A) IAIA, IAi
Genotype (B) IBIB, IBi
Genotype (AB) IAIB
Genotype (O) ii
 Type
O is the universal donor
 Type AB is the universal recipient
 Identification
of genes shows many recessive
alleles and disorders caused by them
 If the genotype has one functioning gene, the
disease will not show
 Recessive disorders are caused by having two
copies of the defective gene
 PKU-lack
enzyme needed to break down
phenylalanine
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Causes severe mental retardation when this
enzyme builds up (chromosome 12)
 When
dominant allele is present the disorder
is shown in the individual
 Dwarfism and Huntington’s Disease are
caused by a Dominant allele
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Codominant alleles: disorders caused by a
heterozygous condition
Example: Sickle Cell Disease
 Some
are issues of misfolded proteins which
affects the structure and purpose of the
protein
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Cystic Fibrosis: caused by recessive allele on
chromosome 7
Caused by deletion of (3) bases in the middle of a
sequence of a protein, causing misfolding
Characterized by digestive problems, thick,
heavy mucus that clogs the lungs
 Sickle
Cell Disease: Caused by one base
change in the hemoglobin protein that
carries oxygen, result abnormal hemoglobin
 Sex
Linked Genes: genes located on X
chromosome or Y chromosome
 Causes Sex Linked genetic disorders
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X-Chromosome contains genes for survival
Y-Chromosome contains genes for maleness
Determining sex of unborn children can be done
using a Punnett Square for probabilities
Determine sex linked disorders using punnett
squares for probabilities
 Sex
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linked disorder carried on X-chromosome
Gene helps control blood clotting
Recessive allele present on gene can cause the
disorder
Protein necessary for normal blood clotting is
missing
 Muscular
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Dystrophy
Caused by defective gene that codes for muscle
protein
Progressive weakening and loss of skeletal muscle
 If
parents suspect they are carrying a
disorder, they can find out using many
different ways
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Genetic tests are available for many disorders
Karyotyping
DNA fingerprinting: analysis of genes that are
introns (sections that do not code for anything)
This area is the area that we all differ the most
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Get DNA from blood, semen, saliva, urine, skin, hair,
etc
Used for Identification of suspects, parents, dead
bodies, diseases
 Project
began in 1990
 Designed to analyze the human DNA
sequence
 In June 2000, scientists announced a working
copy of human genome was complete
 An
absent or faulty gene is replaced by a
normal, working gene
 This can correct the protein needed
eliminating the cause of the disorder
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Scientists do not yet know the benefits of this
type of treatment
Or if it will last through the lifetime of the
individual
 Viruses
are often used to get into the cell’s
DNA
 Virus’s DNA is modified so they do not cause
disease
A
DNA fragment containing the replacement
gene is spliced into the viral DNA
 The patient is infected with the virus which
should carry the replacement gene to the
cells to correct the genetic defects
 What
will happen to the human species if we
gain the opportunity to design our bodies???
 Interactive
Review Concept Map