Genetics

1

• Genetics
• Gregor Mendel
• Known as the father of genetics.
• Worked with garden peas.
• Led to knowledge of inheritance.
• Heredity transmission of traits from parents to
  the offspring.
• Gene the basic unit of inheritance.
• Made of DNA.
• In sexual reproduction
• One gene from the male parent.
• One gene from the female parent.
• Why you have two copies of same chromosome.

2

• Alleles alternate forms of a gene.
• Ex seed color (yellow, green seed)
• Dominant and Recessive alleles
• Dominant alleles an allele that masks the
  presence of another allele.
• Always use capital letters.
• Recessive alleles an allele that is being
  masked by the dominant allele.
• Always use lower-case letters.
• Homozygous when both alleles are the same (homo
  same).
• Homozygous Dominant (AA) or homozygous recessive
  (aa)
• Heterozygous when both alleles are NOT the same
  (Hetero different)
• Heterozygous dominant (Aa)

3

• Genotype genetic makeup of an organism.
• Ex AA, Aa, aa
• Geno genes, genetics
• Phenotype physical appearance of an organism.
• Ex tall, yellow, wrinkled
• Pheno physical
• Mendels work
• Three Principles
• Principle of dominance an allele masks another
  allele.
• Principle of Segregation two alleles for a
  characteristics separate during gamete formation.

4

• Principle of Independent Assortment alleles for
  different characteristics (genes) are distributed
  to gametes independently.
• Punnett Squares used to describe the ratio of
  expected outcomes of a genetic cross.
• Monohybrid cross (mono meaning one) 1 trait is
  crossed.
• Have two alleles for each gene.
• Ex T tall, dom
• t short
• TT x tt (parents)

5

• More ex
• TT x Tt
• Tt x Tt
• Testcross an individual with unknown genotype
  is crossed with a homozygous recessive
  individual.
• Ex rabbit color B black, dom
• b brown
• BB x bb Bb x bb
• If any brown rabbits then the parents were
  heterozygous, if not then they were homozygous.

6

• Incomplete dominance when one allele does not
  completely mask another.
• The organism shows a blend of the two.
• Ex Japanese 4 oclocks R red
• W white
• RR x WW RW pink
• Codominance when both alleles contribute to the
  phenotype of the organism (no blending).
• Ex cattle color R red
• r white
• RR x Rr Rr roan
• Polygenic traits traits controlled by two or
  more genes. (poly many)

7

• Sex-linked traits trait occurs only on a sex
  chromosome.
• Ex colorblindness XX female
• B normal, dom XY male
• b colorblindness
• XBXB normal female
• XBXb normal female, carrier
• XbXb colorblind female
• XBY normal male
• XbY colorblind male
• XBXb x XBY

8

• Blood types
• A blood IAIA or IAi
• B blood IBIB or IBi
• AB blood IAIB
• O blood ii
• Dihybrid Crosses two genes are crossed at the
  same time.
• Ex seed color and texture
• P purple kernel, dom
• P yellow kernel, rec
• S smooth, dom
• S wrinkled
• PpSs x PpSs (remember Foil for all possible
  combinations of gametes)