Genetic Changes

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Genetic Changes

• 8th Grade Science II

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Genetics

• The branch of biology that deals with heredity,
  especially the mechanisms of gene transmission
  and the variation of inherited characteristics.

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History

• Gregor Mendel
• an Austrian Monk
• known as the father of genetics
• first presented his findings in 1856 for
  transmission of certain traits from generation to
  generation.
• Using garden peas

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Chromosome

• Chromosomes are fundamental to all life. All the
  instructions (genes) the human body needs to
  function are organized into these structures
  called chromosomes. Genes are the blueprints
  which make us human and keep us alive. This
  complete set of instructions, organized as genes
  and carried on the chromosomes is called the
  "human genome."

http//www.ornl.gov/sci/techresources/Human _Genom
e/project/about.shtml
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Allele

• Each different form of a gene.

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Allele Traits

• Recessive
• The alleles are in hidden combination with other
  alleles.
• Lower case letter is used to represent a
  recessive allele

• Dominant
• Alleles that are never hidden.
• Example Color is dominant over yellow
• Capital letters are used to represent a dominant
  allele

http//k12science.ati.stevens-tech.edu/curriculum/
genproj/traits.html
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How do we recognize different traits?Physical
Written

• Phenotype
• Sum of visible traits
• Ex. Color

• Genotype
• Alleles that each individual carries.
• Ex. GG Gg gg

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Inherited traits

• A trait that is passed on from parent to offspring

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Blood Types
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• Heterozygous
• Having different alleles
• ex. Gg
• Homozygous
• Having the same alleles
• Ex. GG or gg

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Punnet SquareUsed to help predict the
possibility of offspring receiving a particular
combination of alleles from its parents. Each
square represents ¼ or 25 chance the parents
will produce this type of offspring
g
G
Mother
G
g
Father
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Punnet SquareTtalltshort
T
T
t
t
13
T
T
T t
t
t
14
T
T
T t
T t
t
t
15
T
T
T t
T t
t
t
T t
16
T
T
t
T t
T t
T t
T t
t
Probability tall 4/4 short 0/4
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Punnett Squares

• http//www.borg.com/lubehawk/psquare.htm
• http//biology.clc.uc.edu/courses/bio105/geneprob.
  htm

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Two Different Traits
Mother
Activity 4 Punnett Square
Father
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Genetic Diseases

• Negative changes that convert normal genes into
  harmful genes, due to an error in copying the DNA

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MutationsThe mistakes or changes in the genetic
information.

• Mutagens
• Radiation
• Hemophilia
• Sickle Cell Anemia
• Hemoglobin
• Carriers
• Huntington disease

• Cystic Fibrosis
• Trisomy
• Down Syndrome
• Amniocentesis
• Karyotype
• Tumors
• Adaptation

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Mutagens

• Agents that increase the probability of
• Mutations.
• Example chemicals found in tobacco

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Radiation

• Emission and propagation and emission of energy
  in the form of rays or waves.
• Example Ultraviolet radiation from the sun can
  increase mutations.

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Sickle Cell Anemia

• Caused by a mutation in the hemoglobin gene.
• Hemoglobin is the pigment that makes our red
  blood cells red and allows them to carry oxygen
  to all the organs. This impairs the ability of
  red blood cells to carry oxygen because the
  mutant hemoglobin cannot hold oxygen due to a
  crystallization inside the blood.
• Affects brain,lungs,kidney, and muscles

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Sickle Cell Cont.

• The sickle cell mutation is common among people
  with ancestors that came from Africa.
• People that carry one copy of this mutant allele
  are called carriers.
• Both normal and the mutant forms are carried but
  not necessarily appear.

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Tumors

• Mutations causing cells to behave abnormally and
  reproduce too quickly

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Hemophilia

• Genetic disease that prevents the blood from
  clotting properly.
• Example
• Bruise and bleed more easily than other people.
• Recessive allele of a gene that normally required
  for blood clotting.

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Huntington Disease

• Rare genetic disorder caused by a dominant allele
  on a specific chromosome. Most people will not
  show symptoms until later in life.
• Lose control of muscles and their nerves begins
  to break down. Results in death.
• 50-50 chance of passing the disorder to offspring.

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Cystic Fibrosis

• Caused by recessive allele on chromosome 7
• Makes a defective cell membrane protein which
  causes a problem with movement of water in and
  out of the cell
• The liquid around the cell in the lungs becomes
  thick and clogs the lungs and breathing passages

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Trisomy

• It is when a person has 3 copies of a chromosome
  instead of the normal 2
• Down syndrome trisomy of chromosome 21. Causes
  circulatory and immune problems and mental
  retardation

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Amniocentesis

• Procedure done on developing fetus to detect
  genetic disorders
• Cells are taken from fluid or tissue surrounding
  the fetus and the chromosomes are mapped
• From this map (karyotype), deletion of part or
  all of a chromosome or extra chromosomes can be
  seen and genetic disorders detected

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Reebop Traits

• Phenotype
• 1 antenna
• 2 antenna
• no antenna
• 1 green bump
• 2 green bumps
• 3 green bumps
• Red nose

• Genotype
• AA
• Aa
• aa
• MM
• Mm
• mm
• QQ

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Reebop Traits

• Phenotype
• Orange nose
• Yellow nose
• Curly Tail
• Straight Tail
• 2 Eyes
• 3 Eyes
• Blue legs

• Genotype
• Qq
• qq
• TT or Tt
• tt
• EE or Ee
• ee
• LL or Ll

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Reebop Traits

• Phenotype
• Red legs
• 3 body segments
• 2 Body segments

• Genotype
• ll
• DD or Dd
• dd

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ADAPTATION VS. EXTINCTION

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ADAPTATION

• When organisms are best suited to their
  environment may adapt to new food sources or
  camouflage
• ex. - insects have developed a resistance to
  insecticides
• ex. - bacteria are becoming resistant to
  antibiotics
• ex. P.224 discussion questions

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Natural selection

• Charles Darwin proposed a theory that organisms
  best adapted to their environment will pass down
  their traits to their offspring
• survival of the fittest

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Extinction

• Species become extinct because of changes in
  their environment

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Endangered Species

• Species of any kind -- plant or animal - that are
  disappearing.
• Animals on the list cannot be hunted
• species may be removed from the list if the
  species has recovered (reproduced)
• ex. Jan. 2001 discussion is underway to remove
  the bald eagle from the endangered species list

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All systems try to reach a point of balance or
equilibrium whether its in space, the human
body, or environmental systems. Organisms try to
adapt to find that balance but they must have
time.