Genetics

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Genetics

• Karyotypes, Disorders, and
• Genetic Engineering

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Essential Question

• What are Chromosomes?
• How do chromosomal abnormalities create
  disorders?

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Karyotype

• Karyotype? picture of chromosomes arranged
  together in pairs.
• To make a karyotype scientists take pictures of
  cells going through mitosis. They cut the
  photographs and group the chromosomes in pairs

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Karyotype

• 46 chromosomes in diploid human cell
• 23 chromosomes in a haploid sperm or egg
• Autosomes pairs 1-22
• Sex chromosomes pair 23
• Biologist will write 46XX female and 46XY male

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Disorders

• Cystic Fibrosis
• Usually fatal found on chromosome 7 (recessive
  allele)
• Serious digestive problems and heavy mucus that
  clogs their lungs and breathing passageways
• Cause? deletion of 3 bases in the middle of a
  sequence for a protein
• About half of the children survive into their 20s

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Disorders

• Sickle Cell Disease
• Cells bent and twisted shape
• Cells more rigid than normal
• Get caught in the capillaries as a result blood
  flow stops moving through these vessels, damaging
  cells and tissues
• Abnormal hemoglobin (protein carries oxygen)

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Disorders

• Because abnormal hemoglobin the cell carries less
  oxygen causing hemoglobin to stick together
  causing shape
• African Americans carry the sickle cell b/c
  ancestry to West Africa heterozygous resistant to
  Malaria

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Chromosomal Disorders

• Nondisjunction? error in meiosis when homologous
  chromosomes fail to separate
• If nondisjunction occurs abnormal numbers of
  chromosomes may find their way into gametes

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Chromosomal Disorders

• Down Syndrome
• Trisomy? an individual will have three copies of
  a chromosome
• Most common Trisomy 21? Down syndrome 1 in 800
  babies are born with Down Syndrome? produces mild
  to severe mental retardation

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Sex Chromosome Disorders

• Turners syndrome? nondisjunction in females
  inherit only one X chromosome
• Women usually sterile and sex organs do not
  develop at puberty
• Klinefelters syndrome? nondisjunction in males
  inherit an extra X chromosome
• Usually prevents individual from reproducing
• No cases of NO X meaning it is essential for
  normal development

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Testing

• Genetic tests use labeled DNA probes to detect
  specific sequences found in disease-causing
  alleles.
• Some tests look at changes in the lengths of
  normal and abnormal alleles

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Testing

• DNA Fingerprinting? analysis of sections of DNA
  that have little or no known function, but vary
  widely from one individual to another, in order
  to identify individuals
• This works because the human genome ensures that
  no individual is exactly like any other

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Testing

• Gene Therapy? process of changing the gene that
  causes a genetic disorder

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Genetic Testing

• amniocentesis, can be used beginning at the 14th
  to 16th week of pregnancy to assess the presence
  of a specific disease.
• Fetal cells extracted from amniotic fluid are
  cultured and karyotyped to identify some
  disorders.
• Other disorders can be identified from chemicals
  in the amniotic fluids.

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• chorionic villus sampling (CVS) can allow faster
  karyotyping and can be performed as early as the
  eighth to tenth week of pregnancy.
• This technique extracts a sample of fetal tissue
  from the chorionic villi of the placenta.
• This technique is not suitable for tests
  requiring amniotic fluid.

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Genetic Engineering

• Genetic Engineering? making changes in the DNA
  code of living organism
• Years ago scientists used chance to breed plants
  and animals
• Today scientists use their knowledge of the DNA
  and its chemical properties to study and change
  DNA molecules

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Genetic Engineering

• In order for scientist to change DNA they must be
  able to extract DNA
• The first step is to cut the DNA with a
  restriction enzyme
• Second step is Separating the DNA through a
  process called gel electrophoresis
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Genetic Engineering

• Once the DNA is in manageable form its sequence
  can be read
• Then scientist use recombinant DNA? enzymes make
  it possible to take a gene from one organism and
  attach it to the DNA of another organism Video
  Clip
• Then PCR or polymerase chain reaction is used to
  make copies of DNA

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Genetic Engineering

• The previous steps show how scientists get the
  genetic information and where changes can be
  made.

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Genetic Engineering

• Once scientist have the genetically modified DNA
  they use a process of transformation to get the
  DNA into the cell
• Scientists use a bacterium that produces tumors
  in plants to introduce the new DNA
• Scientist inactivate the tumor producing gene and
  insert the foreign DNA
• The DNA is transformed into the plant cell

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Genetic Engineering

• In animal cells scientists will inject the cell
  with the DNA. Once inside the nucleus, enzymes
  normally responsible for DNA repair and
  recombination may help insert the foreign DNA
• Or DNA might be knocked out of the way and the
  foreign DNA inserted in its place

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Genetic Engineering

• Transgenic Organisms
• Transgenic? an organism that contains genes from
  other organisms
• Genetic engineering has brought about the growth
  of biotechnology
• We now have Transgenic microorganisms, animals,
  plants

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Genetic Engineering

• Transgenic bacteria are used to produce insulin,
  growth hormone, and clotting factor
• Transgenic animals are used to study genes and
  improve food supply
• Livestock will be given extra copies of growth
  hormone which means faster growth, more meat and
  less fat

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Genetic Engineering

• Transgenic plants are important part of our food
  supply
• Many plants have a natural insecticide so crops
  do not need to be sprayed and some resist weed
  killing chemicals.

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Genetic Engineering

• Cloning
• Clone? is a member of a population of genetically
  identical cells produced from a single cell
• Ian Wilmut in 1997 cloned a sheep called Dolly
• The nucleus of an egg cell is removed, then a
  cell is fused with a cell taken from another
  adult. The egg begins to divide.