AP Biology 2006-2007 Genetic Disorders AP Biology Chromosomal abnormalities Incorrect number of...
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Transcript of AP Biology 2006-2007 Genetic Disorders AP Biology Chromosomal abnormalities Incorrect number of...
AP Biology 2006-2007
Genetic Disorders
AP Biology
Chromosomal abnormalities Incorrect number of chromosomes
nondisjunction chromosomes don’t separate properly
during meiosis breakage of chromosomes
deletion duplication inversion translocation
AP Biology
Nondisjunction Problems with meiotic spindle cause errors in
daughter cells homologous chromosomes do not separate
properly during Meiosis 1 sister chromatids fail to separate during Meiosis 2 too many or too few chromosomes
2n n
n
n-1
n+1
AP Biology
Alteration of chromosome number
AP Biologytrisomy
2n+1
Nondisjunction Baby has wrong chromosome number
trisomy cells have 3 copies of a chromosome
monosomy cells have only 1 copy of a chromosome
n+1 n
monosomy2n-1
n-1 n
AP Biology
Human chromosome disorders High frequency in humans
most embryos are spontaneously aborted alterations are too disastrous developmental problems result from
biochemical imbalance imbalance in regulatory molecules?
Certain conditions are tolerated upset the balance less = survivable characteristic set of symptoms = syndrome
AP Biology
Box #1 What are two causes of
nondisjunction? What is the outcome?
AP Biology
Down syndrome Trisomy 21
3 copies of chromosome 21 1 in 700 children born in U.S.
Chromosome 21 is the smallest human chromosome but still severe effects
Frequency of Down syndrome correlates with the age of the mother
AP Biology
Down syndrome & age of mother
Mother’s ageIncidence of
Down Syndrome
Under 30 <1 in 1000
30 1 in 900
35 1 in 400
36 1 in 300
37 1 in 230
38 1 in 180
39 1 in 135
40 1 in 105
42 1 in 60
44 1 in 35
46 1 in 20
48 1 in 16
49 1 in 12
Rate of miscarriage due to amniocentesis: 1970s data
0.5%, or 1 in 200 pregnancies
2006 data<0.1%, or 1 in 1600 pregnancies
AP Biology
Genetic testing Amniocentesis in 2nd trimester
sample of embryo cells stain & photograph chromosomes
Analysis of karyotype
AP Biology
Sex chromosomes abnormalities Human development more tolerant of
wrong numbers in sex chromosome But produces a variety of distinct
syndromes in humans XXY = Klinefelter’s syndrome male XXX = Trisomy X female XYY = Jacob’s syndrome male XO = Turner syndrome female
AP Biology
XXY male one in every 2000 live births have male sex organs, but
are sterile feminine characteristics
some breast development lack of facial hair
tall normal intelligence
Klinefelter’s syndrome
AP Biology
Klinefelter’s syndrome
AP Biology
Jacob’s syndrome male XYY Males
1 in 1000 live male births
extra Y chromosome slightly taller than
average more active normal intelligence, slight learning disabilities delayed emotional immaturity normal sexual development
AP Biology
Trisomy X XXX
1 in every 2000 live births produces healthy females
Why? Barr bodies
all but one X chromosome is inactivated
AP Biology
Turner syndrome Monosomy X or X0
1 in every 5000 births varied degree of effects webbed neck short stature sterile
AP Biology
Box #2 Describe two types of sex chromosome
abnormalities
AP Biology
Changes in chromosome structure deletion
loss of a chromosomal segment
duplication repeat a segment
inversion reverses a segment
translocation move segment from one chromosome
to another
err
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AP Biology
Certain human genetic disorders can be attributed to the inheritance of single gene traits or chromosomal changes.
AP Biology
Sickle cell anemia is a hereditary blood disorder caused by a single nucleotide substitution that results in abnormally shaped hemoglobin.
• Fatigue• Rapid heart rate• Strokes• Painful joints• Delayed growth
AP Biology
Sickle cell disease is more common in those of African descent, due to heterozygote advantage. (People who are heterozygous for sickle cell have less chance of acquiring malaria.)
HAHA Normal blood cells
HAHS Heterozygote; less
likely to get malaria
HSHS Sickle cell disease
AP Biology
Box #3 What are the advantages and
disadvantages of the sickle cell trait
AP Biology
Huntington’s disease is an autosomal dominant disorder that causes degeneration of the nervous system. Affected individuals usually begin showing symptoms at 35-40.
• Hallucinations• Psychosis• Dementia• Jerking movements• Confusion• Rigidity• Death
AP Biology
Color blindness is caused by a sex-linked recessive mutation. Because of this, males are twice as likely to inherit this trait as females.
• Trouble seeing colors and the brightness of colors.
• Trouble differentiating between shades of the same color or similar colors.
AP Biology
AP Biology
Tay-Sachs disease is an autosomal recessive disorder of the nervous system, more prevalent in the Ashkenazi Jewish population.
• Deafness• Blindness• Dementia• Eventual
paralysis• Seizures• Death, usually
before age 4 or 5.Cherry-red spot
AP Biology
Many ethical, social and medical issues surround human genetic disorders.
Genetic screening for Tay-Sachs
AP Biology
Ethical Considerations of Genetics Testing:
Possible discrimination by employers or health insurers
The need for ethical standards for work with human research subjects or tissues
Consideration of social, cultural and religious perspectives on genetics and health
Marketing of genetics tests Informed consent
AP Biology
Box #4 Describe your stance on genetic
testing.
AP Biology
The Human Genome Project sequenced the entire human genome.
An international collaboration between hundreds of labs in the United States, the UK, Japan, France, Germany and Spain.
Began in 1990; completed in 2000. Mostly funded by the US Department of
Energy, National Institute of Health and private interest groups.
AP Biology
The Human Genome Project can help us understand diseases by:
Genotyping of specific viruses to direct appropriate treatment Identification of oncogenes and mutations linked to
different forms of cancer The design of medication and more accurate prediction of
their effects Advancement in forensics Biofuels and other energy applications; agriculture, Comparative sequencing to establish evolutionary
relationships (such as BLAST) The commercial development of genomics research
related to DNA based products (a multibillion dollar industry).
AP Biology
Box #5 Describe the purpose of the human
genome project.
AP Biology
Historical Ethical, Legal, and Social Issues (ELSI) of Genetics
Eugenics advocates improving
human hereditary traits through
selective reproduction of more desired people and traits, and reduced
reproduction of less desired people and
traits.
AP Biology
Sterilization Laws were practiced by many states during the 1900s.
Compulsory sterilization of mental health patients
Men sterilized to treat aggression and criminal behavior
Coerced sterilization of many ethnic groups
The American eugenics movement was the model for Nazi eugenics policies.
AP Biology
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities. A small amount of amniotic fluid, which contains fetal tissues, is sampled and the fetal DNA is examined for genetic abnormalities. The test is usually performed between the 15th – 20th week of pregnancy.
AP Biology
Amniocentesis can lead to Selective Reduction of Multiple Embryos
Nadya Suleman , known as Octomom in the media, is an
American woman who came to international attention when she gave birth to octuplets in
January 2009. Suleman octuplets are only the second full set of octuplets to be born alive in the United States. The
circumstances of their high order multiple birth have led to
controversy in the field of assisted reproductive technology as well as an
investigation by the Medical Board of California of the fertility specialist involved.
AP Biology
Actress Angelia Jolie made the headlines when she underwent a prophylactic mastectomy after finding out that she was genetically predisposed to breast cancer.
AP Biology
The Genetic Information Nondiscrimination Act of 2008, also referred to as GINA, is a new federal law that protects Americans from being treated unfairly because of differences in their DNA that may affect their health. The new law prevents discrimination from health insurers and employers.
The Genetic Information Nondiscrimination Act (GINA)
AP Biology
Can a gene be patented? Not according to the US Supreme Court.
• In Association for Molecular Pathology vs. Myriad Genetics, Inc., the Supreme Court ruled that a natural gene cannot be patented. However, synthetic genes, such as cDNA are patentable. (June 2013)
AP Biology
Box # 6 Do you agree with the supreme courts
decision? Explain
AP Biology 2006-2007
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