Genetics

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Genetics

• AP Biology
• Chapter 12

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Genetics

• Is the science of heredity.
• Heredity is the transmission of genetic or
  physical traits from parent to offspring.

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Gregor Mendel

• Austrian Monk
• Considered the Father of Heredity
• He conducted plant breeding experiments in the
  Monastery garden.
• In 1865 he made his work public, units of
  inheritance, wasnt accepted at that time

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What makes us unique?

• Each of the 100 Trillion cells in our body except
  the red blood cells contains the entire human
  genome, in the nucleus of every cell is the
  genetic information blueprint to construct the
  individual.
• It is the Deoxyribonucleic acid (DNA)
• Function of DNA
• Genetic code for almost every organism.
• Provide template for protein synthesis.

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Composition of DNA

• The structure of DNA was discovered by Watson and
  Crick in 1953.(Remember Rosalind Franklin)
• It is a twisted double helix molecule, containing
  sugar, phosphates, and nitrogenous bases.
• The sugar is deoxyribose and the phosphoric acid
  molecules are always the same and provides for
  the structure (side of the ladder).
• The only difference between us is the order and
  arrangement of the four bases (rungs of the
  ladder).

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Bases of DNA

• Adenine A
• Thymine T
• Guanine G
• Cytosine C
• A always pairs with T
• C always pairs with G

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Bases of RNA

• Adenine A
• Uracil U
• Guanine G
• Cytosine C
• G always pairs with C
• T from the DNA A in the RNA
• A from the DNA U in the RNA

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DNA Model
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Chromosomes

• The DNA in every cell is located in rod like
  segments called chromosomes
• Chromosomes occurs in pairs in every cell of our
  body except in the sperm and ovum.
• Chromosomes numbers are the same for each specie.

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Chromosome Numbers

• Specie Diploid Haploid
• Cattle 60 30
• Swine 38 19
• Sheep 54 27
• Horse 64 32
• Human 46 23
• Chicken 78 39
• Goat 60 30
• Donkey 62 31

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Chromosomes

• There are 2 sex chromosomes included in the
  diploid number of the chromosomes.
• All of the other chromosomes are referred to as
  autosomes.
• In mammals if the sex chromosomes are alike, XX
  it results in a female.
• If the sex chromosomes are different, XY it
  results in a male.

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Sex Determination

• Female can contribute only a X chromosome towards
  the sex of their offspring.
• Male can contribute an X or a Y chromosome toward
  the sex of their offspring.
• Absence of an Y chromosome results in a the
  embryo developing into a female.
• Presence of an Y chromosome results in the embryo
  developing into a male.

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Sex Determination

• Gametogenesis Formation of gametes through
  meiosis.
• Male 4 viable spermatids
• Female 1 viable ovum, 3 polar bodies.

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Tell me what I am ?????
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Tell me what I am ?????
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Cell Division

• Mitosis
• Is the form of cell division which results in the
  formation of identical daughter cells, keeps the
  chromosome number constant.
• Tissue growth and repair.
• Occurs throughout the body except in the sex
  cells.
• Meiosis
• Is the form of cell division which results
  reducing the chromosome number from the diploid
  to the haploid .
• Occurs only in the sex cells, sperm and ovum.

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Genotype or Gamete

• Genotype contains two copies of the gene.
• AaBB
• Gamete (sex cells) contains only one copy of the
  gene.
• AB
• Determine the possible gametes of AaBB
• AB aB

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List all the possible gametes.

• From the genotype AaBb
• AB
• Ab
• aB
• ab

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Genes

• Chromosomes contains several units of inheritance
  genes.
• Genes usually occurs in pairs, one from each
  parent.
• Some traits are inherited directly from one set
  of genes.
• Some traits are inherited through several sets of
  genes.

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Genes

• It was presumed that we were composed of about
  100,000 genes.
• Today, The Human Genome Project has shown that
  number is about 30,000.

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Terms to know

• Homozygous- contains 2 identical genes for the
  same trait, AA, BB, cc
• Heterozygous- contains 2 different genes for the
  same trait, Aa, bB, Cc
• Phenotype- Outward appearance of a trait, coat
  color, polled, horned.
• Genotype- Genetic classification of a gene, AA,
  Aa, aa.
• Allele- Location of a gene on the chromosome.
• F-1 First cross mating.
• F-2 Second cross mating.

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What are dominant genes?

• The gene that express itself, the powerful and
  dominant gene.
• It has the power to overshadow the recessive gene
  when there is complete dominance.

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What are Recessive Genes?

• The gene that is overshadowed by a dominant gene
• Recessive genes can only express themselves in
  the absence of the dominant gene
• Black wool vs white (Ww) (ww)
• Dwarfism vs normal size (dd)

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Punnett Square

• Angus- Black coat color is dominant.
• BB Homozygous Dominant and Black
• Bb Heterozygous and is black
• bb Homozygous recessive and red
• A heterozygous bull is mated to 50 homozygous
  recessive cows.
• How many calves are black?
• How many calves are red?
• What is the genotypic and phenotypic ratios?

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Punnett Square
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Results

• 2 heterozygous Bb
• 2 Homozygous Recessive bb
• 25 Black, 25 Red
• Genotypic ratio 022
• Phenotypic ratio
• 2 Black 2 Red

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What are Sex Linked Genes?

• Some recessive genes are attached to the X and Y
  chromosomes
• Humans Colorblindness and Baldness are on the X
  chromosomes
• In Women, must have two recessives to show trait
• Considered to be on the sex chromosomes 23

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If Dad is bald, will you be bald?
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Baldness is carried by the mother
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What if Mom is bald?
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What is Incomplete Dominance?

• If both genes express themselves
• Shorthorn Cattle Red male mated to a White
  female Roan calf
• RR crossed rr Rr

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Punnett Square

• Shorthorn Cattle
• RR Red
• rr white
• Rr roan
• If a red bull (RR) is mated to a white cow (rr),
  what color will the calves be?

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Shorthorn Red X White
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Punnett Square

• If a red bull (RR) is mated to a roan (Rr) cow,
  what color will the calves be?

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Shorthorn Red X Roan
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What if Both Parents are Roan?
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What is a Mutation?

• Dramatically different from what is expected
  genetically
• Horned calf from polled parents
• Loss of some or extra body parts
• Lethal Mutation causes death at birth
• Sublethal Mutation limits animals ability to
  grow to maturity
• Beneficial Mutation loss of tail in lambs

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What is Heritability?

• Chance that traits will be inherited
• Low multiple births, fat covering
• Medium birth wt, wean wt, milk, wool grade,
  carcass wt, rate of gain
• High Loin eye area, fleece length quality