Download Chapter 14- Human Genome

Chapter 14- Human
Genome
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I. Human Heredity
A. Human chromosomes
1. A picture of chromosomes
arranged in a picture is called a
karyotype.
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Untouched Picture
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Karyotype
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2. A normal human has 46 chromosomes, 23
pairs.
3. The number of chromosomes helps
identify what the organism is.
4. Egg and sperm are haploid, containing
half the amount of chromosomes-23. These
cells are called sex cells. A female
chromosomes is XX, a male is XY.
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5. All other cells have 46 chromosomes
in them, they are diploid. These cells
are called autosomes.
6. All human egg cells carry a single X
chromosome.
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7. Half of all sperm cells carry an X and
half carry a Y chromosome.
8. This ensures that just about half of
the zygotes will be diploid, XX and the
other half will be diploid, XY.
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B. Human Traits
1. Human genes are inherited
according to the same principles that
Mendel discovered.
2. A pedigree chart shows relationships
within a family.
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3. Genetic counselors analyze pedigree
charts to infer the genotypes of family
members.
4. Many traits are strongly influenced
by environmental, or non-genetic
factors, including nutrition and exercise.
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C. Human Genes
1. The human genome- our complete
set of genetic information includes tens
of thousands of genes.
2. Some of the very first genes to be
identified were those that control blood
type.
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D. Blood Group Genes
1. Human blood comes in a variety of
genetically determined blood groups.
2. The different blood types are A, B,
AB, O plus there is a Rh+ or Rh- factor.
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BLOOD GROUPS
Phenotype
A
B
Genotype
IAIA or IAIo
IBIB or IBIo
Antigen
A
Antibodies
B
B
A
AB
IAIB
A and B
-------
O
IoIo
--------
A and B
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E. Recessive Alleles
1. Many human genes have become
known through the study of genetic
disorders.
2. In most cases genetic disorders are
USUALLY recessive.
3. See page 345 to see details
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Albinism
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Cystic Fibrosis
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Dwarfism
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Sickle Cell Disease
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F. Dominant Alleles
1. Not all genetic disorders are caused
by a recessive allele.
2. Two examples of a genetic disorder
caused by autosomal dominant alleles
are dwarfism and Huntington’s disease.
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Huntington’s disease
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G. Codominant alleles
1. Sickle cell disease is caused by a
codominant allele.
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H. From Gene to molecule
1. In both cystic fibrosis and sickle cell
disease, a small change in the DNA of a
single gene affects the structure of a
protein, causing a serious genetic
disorder.
2. CF is most common among people
with Northern Europe ancestors.
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3. People with CF have serious
digestive problems in addition they
produce thick, heavy mucus that clogs
their lungs and breathing passageways.
4. Sickle cell is a disease found in
African Americans.
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5. It is a bent and twisted shape of the
RBC’s.
6. As a result, blood stops moving through
these vessels, damaging cells, tissues and
organs.
7. Sickle cell disease produces physical
weakness, and damage to the brain, heart,
and spleen.
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II. Human Chromosomes
A. Human Genes and Chromosomes
1. Chromosomes 21 and 22 are the
smallest human autosomal chromosome.
Chromosome 22 contains 43 million DNA base
pairs! Chromsomes 21 contains about 32
million!
2. MILLIONS of base pairs!
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B. Sex Linked Genes
1. Many sex-linked genes are found on
the X chromosomes. More than 100
sex-linked genetic disorders are found
on the X.
2. Males have just one X chromosome,
thus all X-linked alleles are expressed in
males even if they are recessive.
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3. Some sex-linked disorders are
colorblindness, hemophilia, and
Duchenne muscular dystrophy.
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C. Color Blindness
1. The most common disorder is redgreen colorblindness affecting 1 in 10
males in the US.
2. Among females colorblindness is
only 1 in 100.
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D. Hemophilia
1. Two important genes carried on the
X chromosome help blood to clot.
2. In hemophilia, a protein necessary
for normal blood clotting is missing.
3. About 1 in 10,000 males is born with
hemophilia.
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E. Duschenne Muscular
dystrophy
1. This is a disorder that results in the
progressive weakening and loss of
skeletal muscles.
2. In the US 1 out of 3000 males are
born with this.
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F. X-Chromosome Inactivation
1. Females have 2 X chromosomes, but
males have only 1.
2. In female cells, one X chromosome
is randomly switched off.
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G. Chromosomal disorders
1. The most common error in meiosis occurs
when homologous chromosomes fail to
separate. This is known as nondisjunction.
2. If nondisjunction occurs, abnormal
numbers of chromosomes may find their way
into gametes, and a disorder of chromosome
numbers may result.
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3. IF two copies of an autosomal
chromosome fail to separate during
meiosis, an individual may be born with
three copies of a chromosome.
4. This is known as trisomy
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5. The most common trisomy is down
syndrome- having an extra
chromosome on pair number 21.
6. 1 in 800 babies are born with Down
syndrome.
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7. Disorders also occur among the sex
chromosomes. Two of these are Turner
syndrome and Klinefelter’s.
8. In Turner syndrome there is only 1
X. The female is sterile and their sex
organs do not develop at puberty.
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9. In males,
Klinefelter’s has an
extra X, XXY, XXXY
or even XXXXY.
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10. There have been no reported cases
of babies being born without the X
chromosome, indicating that the X
chromosome contains genets that are
vital for the survival and development.
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III. Human Molecular Genetics
A. Human DNA analysis
1. DNA fingerprinting is used by
molecular biology to identify individuals.
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2. The human genome project is an
ongoing effort to analyze the human
DNA sequence.
3. In gene therapy, an absent or faulty
gene is replaced by a normal, working
gene.
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4. It would be great to cure genetic
disorders= BUT, if human cells can be
manipulated to cure disease, should
biologists try to engineer taller people
or change their eye color?
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The END
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