Genetics

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Genetics

• Chapter 3

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Gregor Mendel

• Mendelian genetics (Mendel is the father of
  genetics)
• Heredity is the passing of characteristics from
  parent to offspring.
• Get 50 of characteristics from each biological
  parent. (fertilization occurs when the egg
  sperm meet)
• Some traits appear and others are hidden.

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Traits

• Each different characteristic is called a trait.

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Punnett Square

• Crossing traits
• Purebred organisms have the same trait. (TT or
  tt)
• Hybrid organisms have two different alleles for a
  trait. (Tt)
• P generation is the parent generation.
• F1 is the first filial.
• F2 is the second filial.

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Alleles

• A gene is the factor that controls a trait.
• Alleles are different forms of a gene.
• Some alleles are dominant.
• Some alleles are recessive.
• In Mendels experiment, only one trait appeared
  in the F1 generation, but in the F2 generation,
  the lost form of the trait always reappeared in
  25 of the plants.

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Probability

• Probability and Heredity
• Probability is the chance that a particular
  outcome will occur.
• Punnett squares are used to predict that a
  particular trait will show.
• In a genetic cross, the allele each parent passes
  on to the next generation offspring is dependent
  on probability.

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What is an adaptation?

1. A change in DNA.
2. An over production of offspring.
3. A competition between two members of the same
   species.
4. A modification in a species for survival.

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Which of the following is true about the rate of
evolution?

1. Evolution can occur over a weekend.
2. Evolution occurs in several months.
3. Evolution occurs over hundreds of years.
4. Evolution occurs over millions of years.

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If tree grew taller over time, what physical
characteristics of a giraffe would allow them to
survive?

1. Thick neck.
2. Thin neck.
3. More teeth.
4. Long neck.
5. Short neck.

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Which of the following is a result of adaptations
over a long period of time?

1. Species are very diverse.
2. Species are very similar.
3. Species quickly become extinct.
4. I dont know.

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Codominance

• Codominance is when the allele is neither
  dominant nor recessive both alleles are
  expressed in the offspring.

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Problem 1

• Cross
• B is dominant brown eyes
• b is recessive blue eyes
• BB x bb
• Bb x Bb
• Bb x bb
• Show phenotype and genotype

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Phenotype vs. Genotype

• The phenotype is the physical appearance of the
  organism.
• The genotype is the genetic makeup of the
  organism or the allele combination.
• Homozygous is when the organism has two identical
  alleles for a trait.
• Heterozygous is when the organism has two
  different alleles for a trait.

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Problem 2

• Cross
• T is dominant tall pea plant
• t is recessive short pea plant
• TT x tt
• TT x Tt
• Tt x tt

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What type of allele prevent other alleles from
being shown?

1. Codominant
2. Dominant
3. Recessive
4. Help! I have no clue!

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16
What is the phenotype of the offspring if a blue
eyed parent (bb) is crossed with a brown eyed
parent (Bb)?

1. 25 blue eyed, 75 brown eyed
2. 50 blue eyed, 50 brown eyed
3. 75 blue eyed, 25 brown eyed
4. 100 brown eyed

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Chromosomes

• The Cell and Inheritance
• Sutton explored chromosomes through the study of
  the grasshopper.
• According through the chromosome theory of
  inheritance, genes are carried from parents to
  their offspring on chromosomes.

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Meiosis

• Meiosis is the process by which the number of
  chromosomes is reduced by half to form sex cells
  (sperm and eggs)
• During meiosis, the chromosome pairs separate and
  are distributed to two different cells. The
  resulting sex cells have only half as many
  chromosomes as the other cells in the organism.

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Human Genome

• A Punnett square shows the events that occur at
  meiosis.
• Chromosomes are made up of many genes joined
  together like beads on a string.
• Humans have 23 chromosome pairs

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Deoxyribonucleic Acid

• DNA
• Genes control the production of proteins.
• Proteins determine the traits of an organism.
• Chromosomes are composed of DNA.
• Chromosomes have four nitrogen bases.
• adenine
• thymine
• guanine
• cytosine

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Protein Synthesis

• The arrangement of the nitrogen bases along a
  gene determines the type of protein produced.
• Proteins are made of amino acids.
• Three-base code determines the amino acid used in
  the making of proteins.

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Amino Acids

• During protein synthesis, cells use the
  information from a gene on the chromosome to
  produce a specific protein.
• Protein synthesis takes place in the ribosome of
  a cell.

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Ribonucleic Acid

• RNA is a single helix.
• Contains uracil instead of thymine.
• mRNA copies the coded message from the DNA in the
  nucleus, and carries the message to the ribosome
  in the cytoplasm.
• tRNA carries the amino acid to the ribosome and
  adds the amino acid to the protein chain.

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Producing Proteins

• Steps in Protein Synthesis
• First step DNA molecule unzips and one strand
  directs the production of mRNA. Cytosine pairs
  with guanine and uracil pairs with adenine.
• Second step mRNA enters cytoplasm and attaches
  to the ribosome. mRNA provides the code to
  produce the protein.

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Transcription

• Third step tRNA attaches to the mRNA to attaché
  a specific amino acid to the protein. The order
  of the amino acid determines the type of protein.
• Protein chain grows longer. The tRNA releases
  into the cytoplasm to get another amino acid.

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Mutations

• Mutations cause a cell to produce an incorrect
  protein that may lead to a different phenotype.
• One type of mutation may occur when a nitrogen
  base is changed during DNA replication.

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Helpful or Harmful?

• Another mutation may occur when chromosomes do
  not separate correctly during meiosis.
• Mutations are helpful if they increase an
  organisms chance for survival and are harmful if
  they decrease an organisms chance for survival.