Download Pea In Your Genes

Pea In Your Genes
Gregor Mendel
• Liked to play with pea plants.
• Father of Genetics
• Noted passing of traits from
parents to offspring –
heredity
• Study of heredity - Genetics
• A single trait can be expressed
(shown) in different ways.
• Allele is the different
representation of the same
trait. Ex. Seed color: Yellow
or Green
• Yellow is one Allele for Seed
Color
• Green is another Allele
Genotype & Phenotype
• Genotype – “code” for a trait. Letters we use. Ex. Yy
• Phenotype – what you actually see.
• Yellow peas – Use Y to represent Yellow
• Green peas – Use y to represent Green
Yellow and Green Peas
Genotype
• YY – Yellow – Homozygous Dominant
• Yy – Yellow - Heterozygous
• yy – Green –Homozygous Recessive
Phenotype
The ONLY way a recessive trait is EVER seen is if the GENOTYPE is
Homozygous Recessive – or yy.
Three different Genotypes but Two Colors.
Why?
• YY – Yellow
• Yy – Yellow
• yy - Green
• Dominant Allele – rep. by
a capital letter – Y
• Recessive Allele – rep. by a
lowercase letter - y
Dominant Alleles OVER POWER Recessive Alleles
• YY – Homozygous Yellow
• Yy – Heterozygous Yellow
• yy – Homozygous Green
Complete Dominance
• Dominant Allele completely masks recessive allele.
Incomplete Dominance
• Incomplete
dominance = one allele is
not completely dominant
over the other.
Codominance
• Codominance=
condition in which both
alleles for a gene are
expressed when present
What to know: Mitosis
• Cells begin and end 2N
• Be able to know, draw, and
recognize EACH step.
• Know what the “Big
Event” of each step is. Ex.
Metaphase – line up
middle
Cross-Over
• Increases Genetic Variety
What to know: Meiosis
• Prophase I – ONLY stage where
Cross-Over occurs
• Meiosis begins 2N and ends 1N
• Be able to know, draw, recognize
EACH stage of Meiosis.
• Know what the “Big Event” of
each step is.
How do alleles pass from parent to child?
• Punnett Squares
• What if you cross a
Homozygous Yellow Pea
(YY) with a Homozygous
Green Pea (yy)?
100% Heterozygous
Yellow Peas
25% Homozygous Yellow
50% Heterozygous Yellow
25% Homozygous Green
Genotype Ratio: 1:2:1
Incomplete and
Complete Dominance
Complete Dominance
• Dominant Allele completely masks recessive allele.
Incomplete Dominance
• Incomplete
dominance = one allele is
not completely dominant
over the other.
Codominance
• Codominance=
condition in which both
alleles for a gene are
expressed when present
Dihybrid Cross
1. Start with FOIL
2. Put results of FOIL for parent
one at top
3. Put results of FOIL for parent
two to the left
4. Distribute like monohybrid cross.
FOIL
• First
• Outside
• Inside
• Last
Always
results in a
9:3:3:1
Ratio!!!