Genetics

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Genetics Heredity

• Psst, pass it on

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Predicting Inherited Characteristics

• Gregor Mendel
• Studied heredity using pea plants
• His work is the foundation of modern Genetics

http//www.dnaftb.org/dnaftb/
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Peas were used because

• 1. Many traits in peas exist in 2 forms
• Tall or Short
• Wrinkled or Non Wrinkled
• Green or Yellow
• 2. Many offspring are produced in one generation.
• 3. They Self-Pollinate this ensured pure
  breeding.

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http//www.dnaftb.org/dnaftb/
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Mendels Conclusions

• Individual Factors (later known as genes) control
  inherited characteristics.
• These factors are inherited from parents.
• 3. These Factors exist in pairs
• 4. One Factor can mask or hide another (known as
  dominance).

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Gene

• A segment of a DNA molecule
• Contains information about a specific trait

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Asexual reproduction

• One parent
• Parent divides to produce a copy of itself
• Offspring is genetically the same as parent

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Sexual reproduction

• Two parents
• Offspring has genes from both parents
• Offspring is genetically DIFFERENT from parents

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Alleles

• Different forms of a gene
• An organism gets one allele from each parent for
  a gene
• It takes two alleles to make a complete gene
  for a trait

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Dominant allele

• This is the allele for a trait that always shows
  up in the organism
• Shown with a capital letter when working genetics
  problems
• DD would be a pure form of this dominant trait
• Dd would be a hybrid form of this dominant trait

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Recessive allele

• Hidden when a dominant allele is present
• Only shows when offspring has two alleles for the
  recessive trait
• Shown with a lower case letter when working
  genetics problems
• dd would be how this pure recessive trait is
  shown

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Homozygous

• This means the trait is pure
• DD or dd
• The organism has two dominant or recessive
  alleles for this trait

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Heterozygous

• This means the trait is hybrid
• The organism has a dominant and a recessive
  allele for this trait
• Dd is how this is shown
• the dominant trait will always show in this
  case

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Genotype

• This is the GENETIC makeup of a trait
• You cant see the genotype

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Phenotype

• This is the PHYSICAL EXPRESSION of a trait
• You CAN see the phenotype
• The dominant allele will ALWAYS show in a
  phenotype

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Monohybrid Punnet Squares (Only one
characteristic)
Example Garden Pea Plant- height
T
t
T
TT
Tt
Tt
tt
t
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Monohybrid Punnet Squares (Only one
characteristic)
TT
Tt
Tt
tt
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The sex of an animal is determined by chromosomes

• Female XX
• Male XY
• What are the chances of an offspring being male?
  (hint do the cross on a Punnett square)

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Lets try some more

• Long fur (L) is dominant over short fur (l) in
  cats.
• Cross a heterozygous dominant male with a short
  furred female.
• Your cross should be between the male (Ll) with
  the female (ll)