Genetics

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Genetics

• Gregor Mendel - the father of modern genetics

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Mendel applied new science of Statistics to his
observations

• Heredity - transmission of traits, parents to
  progeny
• P1 - parental generation
• F1 - first filial generation
• F2 - second filial generation
• Filial son

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Mendel crossed two pure plants - green and
yellowF1 - all yellowF2 - all green
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Dominant trait that which appears in the 1st
generationRecessive trait that which
reappears in the 2nd generationnot known to
Mendel - genes and alleles
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Mendels conclusions - 3 principles

• 1) dominance recessiveness
• 2) Segregation - each reproductive cell receives
  only one factor for each characteristic. The 2
  factors for each trait segregate/separate during
  formation of eggs and sperm.
• 3) Independent assortment - factors for
  different characteristics not connected. They
  distribute independently to the reproductive
  cells.
• Mendels work sat on the shelf for 35 years! He
  did not know about mitosis and meiosis.
• His work was rediscovered in 1902.

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What do we now know?Genes - segments on a DNA
strand (chromosome) that controls a particular
hereditary trait (thru production of a particular
protein).Chromosomes - occur in pairs ? - genes
occur in pairs.Each contrasting form of a gene
is an alleleAlleles represented by
letters upper case dominant allele (A) lower
case recessive allele(a) Co-dominance Incomp
lete dominance
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http//highered.mcgraw-hill.com/sites/0072495855/s
tudent_view0/chapter28/animation__how_meiosis_work
s.htmlGametes (egg sperm) each receive one
allele? an individual receives one allele for
each trait from each parentGenotype - genetic
makeup of an organismPhenotype - external,
physical appearance of an individual.Examples ge
notypes phenotypes TT tall
Tt tall tt short
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Homozygous - both alleles for one trait are the
same. May be dominant or recessive.Heterozygous
- alleles are different.Some traits have
multiple alleles(more than two)i.e. - blood
types, ABO blood groups
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Probabilities of one kind of eventnumber
of all eventsrule of additionrule of
multiplication
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Monohybrid crossessingle trait inheritance -
cross between individuals involving a contrasting
trait.Punnett square helps predict
probabilities.
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Homozygous (dom.) x homozygous (rec.)TT x
ttHomozygous (dom.) x HeterozygousTT x Tt
Heterozygous x Heterozygous Tt x Tt