Download GREGOR MENDEL

GENETICS
GREGOR MENDEL (1822- 1884)
Self Fertilization
Offspring= Purebred
Cross Fertilization
Offspring = Hybrid
CROSS POLLINATION
HYBRID
COCKER
SPANIEL
+
POODLE
COCKAPOO
HYBRID
PUG
+
BEAGLE
PUGGLE
HYBRID
DOG AND WOLF
Liger
male lion
and
a female
tiger
Peas!
GENETIC
TERMINOLOGY
• Dominant
• Recessive
• Homozygous
• Heterozygous
• Genotype
• Phenotype
• Trait
• Allele
Dominant and Recessive Alleles
• Dominant allele- trait is always expressed if
present
- Written as capital letter
- Ex. Tall= T
• Recessive allele- only expressed if no
dominant allele is present
– (Dominant allele masks this one)
- For a particular trait written as the same
letter but lower case
- Ex. Short= t
• Genotype- the genes you get from your parents
– Two letters represent the two alleles
– One from mom one from dad
– TT, Tt, tt
• Phenotype- the physical trait, what you look like
– Tall short, yellow or green
– TT, tt what is the phenotype??
• Homozygous - the same alleles for a gene
– TT, tt
• Heterozygous - having different alleles for a
gene
– Tt
Trait = Height
TALL
 alleles  SHORT
Gene- unit of inherited information in DNA
Allele- alternative form of a gene ( white
purple)
Flower Color Trait
Test Cross- mate an unknown genotype ( TT or Tt)
with homozygous recessive (tt)
Reginald Punnett
In Starfish being
red is dominant
over being pink.
What would
Patrick’s
phenotype be?
What would his
genotype be?
Because
Patrick is
pink… his
phenotype is
PINK
And since pink
is recessive –
his genotype
would be “rr”
Red is dominant
over pink
Suppose we
had a
HETEROZYGOUS
red starfish what
would the
genotype be?
Let’s do some…
MONOHYBRID
CROSSES!
Monohybrid means
we are only using
ONE TRAIT
STEP by STEP
1. Select a “good” letter to use
2. Write down your “givens”
3. Determine parents and record
4. Set up Punnett Square
5. Determine genotypes &
phenotypes of offspring
(use percentages or fractions)
In pea plants being
Tall is dominant over
being short
Cross a Heterozygous
Tall plant with a
Homozygous Tall plant
Aa x AA
A
A
A
Geno =
50% AA
50% Aa
Pheno =
100% Tall
Heterozygous
Blue = Bb
Recessive
Yellow = bb
so we cross…
Bb x bb
Time for some
LOONEY
Monohybrid
Crosses on
your own!
Red
is dominant
over Blue
T
E
S
T
C
R
O
S
S
MENDELS LAWS
1. Dominance &
Recessiveness
2.Segregation
3. Independent
Assortment
PEDIGREE
male
female