Genetics

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Chapter 4 Genetics
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Heredity
is the passing of traits from the parents to the
offspring and is controlled by genes
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Georgia Performance Standard

• S7L3. Students will recognize how biological
  traits are passed on to successive generations.
• a. Explain the role of genes and chromosomes in
  the process of inheriting a specific trait.
• b. Compare and contrast sexual and asexual
  reproduction in organisms (bacteria, protists,
• fungi, plants animals).
• c. Recognize that selective breeding can produce
  plants or animals with desired traits.

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• http//learn.genetics.utah.edu/units/basics/print-
  and-go/traitsreference.pdf

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What are genes?

• Made of segments of DNA
• Control the traits of an organism
• Found on the chromosomes
• Have different forms called alleles

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What are alleles?
Alleles are the different forms that a gene can
have for a trait.
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So, what is genetics?
Genetics is the study of how traits are inherited
through the actions of alleles.
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Alleles
determine the traits of the organisms
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Alleles

• An organism with the same two alleles for a trait
  is homozygous.
• An organism with two different alleles for a
  trait is heterozygous.

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Therefore

• An organisms genetic makeup is its genotype.

• An organisms physical makeup is its phenotype.

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Gregor MendelFather of Genetics
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Gregor Mendel

• Born in 1822 in Austria and lived in Europe.
• Was a monk who studied mathematics and science.
• Determined the basic laws of Genetics.

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Mendels Garden

• As a boy, he worked in his fathers orchard and
  became interested in plants
• He experimented with peas.

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Gregor Mendel
Called the form of a trait that appears to
dominate or mask another form of the same trait
dominant.
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Gregor Mendel
Called the weak form of a trait that is
prevented from showing up by a dominant trait
recessive.
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Probability
The branch of mathematics that helps you predict
the chance something will happen is called
probability
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Punnett Square
The tool used to predict the probability of
certain traits in offspring that show the
different ways alleles can combine.
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Punnett Square
Dominant allele is Upper case letter
G
Recessive allele is Lower case letter
g
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G
G
Gg
g
Gg
g
Gg
Gg
Punnett Square
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• Traits governed by simple dominance
• (not an exhaustive list)
• Dominant Recessive
• Brown Eyes Blue Eyes
• Curled Up Nose Roman Nose
• Clockwise Hair Whorl Counter-clockwise
  hair Whorl
• Can Roll Tongue Can't Roll Tongue
• Widow's Peak No Widow's Peak
• Facial Dimples No Facial Dimples
• Able to taste PTC Unable to taste PTC
• Earlobe hangs Earlobe attaches at base
• Mid-digital hair No mid-digital hair
• No hitchhiker's Hitchhiker's thumb
• thumb
• Tip of pinkie bends Pinkie straight
• in

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Genetics Since MendelCh. 5 section 2

• Are all traits inherited only by dominant or
  recessive alleles?

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INCOMPLETE DOMINANCE

• Production of a phenotype,(physical trait), that
  is intermediate, (blended), between the two
  homozygous parents.

WHITE
RED
PINK
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Incomplete Dominance
Chestnut Horse
Cremello Horse
Palomino Horse
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Multiple Alleles

• A trait that is controlled by more than two
  alleles.
• Examples is blood type which is controlled by
  three alleles, A, B, O which gives us four
  phenotypes A, B, AB, or O.

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Polygenic Inheritance

• Poly means many.
• Polygenic inheritance is when many gene pairs act
  together to produce a trait.
• Examples for this inheritance would be eye color,
  height and skin color. This is why we might not
  have the same shade of color of eyes or skin as
  our parents have. Also this is why it is hard
  to predict height just based on our parents
  height. eyes

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• Even though your traits are determined by your
  genes, environmental influences can alter how
  your trait is expressed.
• Examples
• If you have a gene for skin cancer, you can
  limit your exposure to the sun and take care of
  your skin.
• If you have a gene for lung cancer, you can make
  sure you do not smoke and try to control your air
  quality.
• Himalayan rabbits have alleles for dark-colored
  fur. But this allele can only express itself at
  lower temperatures which are areas located away
  from the main body heat.

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Mutations

• Mutations are changes in genes.
• Some mutations are harmful some are helpful.
• Mutations in genes can occur when the DNA is
  copied and something goes wrong. Chemicals can
  also alter genes.
• Examples of things that can mutate genes are
  radioactive material and X-rays

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Chromosome Disorders

• Occur when mistakes in the process of meiosis
  results in an organism with too many or too few
  chromosomes.
• Examples
• Down Syndrome- baby has 47 chromosomes instead of
  46 chromsomes.

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Downs Syndrome
characteristic facial features, short stature
heart defects susceptibility to respiratory
disease, shorter lifespan prone to developing
early Alzheimer's and leukemia often sexually
underdeveloped and sterile, usually some degree
of mental retardation. Down Syndrome is
correlated with age of mother but can also be the
result of nondisjunction of the father's
chromosome 21.
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• Patau syndrome (trisomy 13) serious eye, brain,
  circulatory defects as well as cleft palate.
  15000 live births. Children rarely live more
  than a few months.

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• Edward's syndrome (trisomy 18) almost every
  organ system affected 110,000 live births.
  Children with full Trisomy 18 generally do not
  live more than a few months.

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Too few chromsomes

• Monosomy X (Turner's syndrome) 15000 live
  births the only viable monosomy in humans -
  women with Turner's have only 45 chromosomes!!!
  XO individuals are genetically female. Have short
  stature, normal intelligence and are sterile.
  (98 of these fetuses die before birth)

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Recessive Genetic Disorders

• When each parent has the recessive gene and their
  baby receives the recessive gene from both
  parents.
• Examples of this type of disorder
• Cystic Fibrosis- affects for Caucasian Americans
• Causes thick mucus in lungs and intestinal tract
• Sickle Cell Anemia-affects more African Americans
• Causes clogging of blood vessels, organ damage,
• kidney failure
• Tay-Sachs- Buildup of lipids causes death by
• age 2-3.

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Sex-Determination

• Female chromosomes are XX
• Male Chromosomes are XY

X
X
XX XX
XY XY
X
Y
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SEX LINKED DISORDERS

• An allele inherited on a sex chromosome, X or Y
  is called a sex linked disorder.
• Males are more likely to have sex linked
  disorders than females. The reason for this is
  that for a male to have a disorder he only has to
  have the allele on one chromosome, XcY. In order
  for the female to have the disorder she has to
  have the allele on both her sex chromosomes,
  XcXc. If she has the allele only on one of her
  sex chromosomes she is considered to be a
  carrier, XcX and can pass it on to her children.
  

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• Examples of sex linked disorders
• Color Blindness-is a recessive trait on the X
  chromosome

A
B
Y
Xc
Y
X
XcX XY
XcX XY
XcX XcY
XX XY
X
X c
X
X
In example A, a color blind Male has a child with
a normal Female. They will have a 50 Chance of
having a normal male Baby and a 50 chance of
having A female baby who is a carrier for Color
blindness.
In example B, a normal male has a child with a
carrier female. They will have a 25 chance of
having a female who is a carrier, 25 chance of
having a male who is colorblind, 25 chance of
having a normal female and 25 chance of having a
normal male.
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• Another example of a sex linked disorder is
  hemophilia. A person with this disorder do not
  make enough platelets in their blood that helps
  the blood to clot when they are cut.

Pedigree Chart
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• Why would you use a Pedigree Chart?
• A geneticist would study a pedigree chart of
  someone to predict the probability that a baby
  would be born with a specific trait.
• Breeders of animals or plants can study the
  pedigree of these organisms for desirable
  physical and ability traits.

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Genetic Engineering

• It is biological and chemical methods to change
  the arrangement of a genes DNA to improve crop
  production, produce large volumes of medicine,
  and change how cells perform their normal
  functions.
• Recombinant DNA-(helps with making insulin)
• Gene Therapy-(using a virus to deliver a normal
  allele to replace a defective allele cystic
  fibrosis and cancers)

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• Cloning- Dolly the sheep

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Genetically Engineered Tobacco Plants that are
resistant to the Tobacco Mosaic Virus
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Human Genome Project
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Thank You