Genetics

1
Genetics
2
What is Genetics

• Genetics is the scientific study of heredity.
• Heredity is what makes each species unique.

3
History
4
Gregor Mendel

• Austrian Monk
• Famous for his work with pea plants
• He is known as the father of genetics

5
Mendel
6
Mendels Work

• Mendel used true-breeding plants which means if
  they were left to breed with themselves they
  would produce offspring identical to themselves.
• Mendel studied 7 different traits in pea plants.
• A trait is a specific characteristic that varies
  from one individual to another.

7
More on Mendels Work

• Hybrids are offspring from parents with different
  traits.
• Genes are the chemical factors that determine a
  trait.
• The different forms of a gene are called alleles.

8
The Principle of Dominance

• The principle of dominance states that some
  alleles are dominant and others are recessive.
• Dominant alleles are always expressed.
• Recessive alleles are only expressed if both
  alleles are recessive.

9
Segregation Independent Assortment

• The separation of alleles during meiosis to form
  gamates (sex cells).
• The Law of Independent Assortment states that
  genes for different traits can segregate
  independently during the formation of gamates.

10
Laws of Inheritance
11
Probability Genetics

• Probability is the likelihood that an event will
  happen.
• The principle of probability can be used to
  predict the outcomes of genetic crosses.

12
Probability
13
Punnett Squares

• Diagram used to predict genetic crosses.
• Individuals with identical alleles are called
  homozygous
• Individuals with different alleles are called
  heterozygous
• Phenotype physical characteristic
• Genotype genetic makeup

14
How to use Punnett Squares

• Choose a letter to represent the alleles in the
  cross.
• Write the genotypes of the parents.
• Determine the possible gametes (reproductive
  cells) that the parent can produce.
• Enter the possible gamete at the top and side of
  the Punnett square.

15
More Punnett Squares

• Complete the Punnett square by writing the
  alleles from the gametes in the appropriate
  boxes.
• Determine the phenotypes of the offspring.
• Using the results of step E and F write down the
  genotypic and phenotypic ratios.

16
Naked Punnett Square
17
Punnett Squares Monohybrid Dihybrid Crosses
18
Punnett Squares
19
Mendels Principles

• The inheritance of biological characteristics are
  determined by genes.
• For two or more forms of a gene, dominance and
  recessive forms may exist.
• Most sexually reproductive organisms have two
  sets of genes that separate during gamete
  formation.
• Alleles segregate independently.

20
Beyond Dominant and Recessive

• Incomplete Dominance One allele is not
  completely dominant over the other. White flower
  crosses with a red pink flower.
• Codominance Both alleles contribute to the
  phenotype. Red cow X White Cow Roan Cow.
• Multiple Alleles More than two alleles control
  the phenotype. Coat color of rabbits.
• Polygenic traits Several genes control the
  trait. Skin color in humans.

21
Examples