Download cross-fertilized

Mendel’s Genetics
Chapter 11
Who was Gregor Mendel?
– He was known as the “FATHER OF
GENETICS”
– He discovered how traits were
inherited
• GENETICS – study of heredity
• HEREDITY – the passing of traits
from parents to offspring
Mendel’s Peas
– Mendel did his study
on pea plants
– Pea plants have many
traits (tall/short,
purple flowers/white
flowers)
– Pea plants can be
self-fertilized or
cross-fertilized
True Breeding
• Meaning that if they
are allowed to selfpollinate, they will
produce offspring
identical to themselves
– Self-pollinate: some
plants have both male
and female flowers
– One plant is producing
both male and female
gametes that are
fertilized
Dominance
• Some traits are dominant over others.
• Tall x Short = all tall offspring (hybrids)
• *Tall is the dominant trait
• * Short is recessive
Genes and Alleles
• Mendel
discovered that
each trait is
controlled by two
factors (alleles)
• Genes – factors
that determine
your traits
Mendel’s Experiments
The Cross
• Monohybrid
Cross, that
is
Explaining the Cross
• When a parent makes sperm or eggs, their
genes separate
(PRINCIPLE/LAW OF SEGREGATION)
• The GAMETES (egg or sperm) contain either
a T allele (tall) or a t allele (short)
– This works for various traits like hair color
More on the Cross
Genes→Traits
• GENOTYPE - what genes ( letters) the
organism has (TT, Tt, tt)
• PHENOTYPE - what it looks like (tall or
short)
Understanding Check
1. A one-eyed purple people eater is crossed with a two eyed
purple people eater. All of their offspring have two
eyes. Which trait is dominant?
• 2. If you use the letter E for this
gene. What is the genotype of
the offspring?
•
Are these offspring the F1 or
F2 generation?
• 4. If you crossed the offspring
with each other? How many ofthe new offspring would you
expect to have two eyes?
Incomplete Dominance
• When both alleles are expressed, making
colors somewhere in the middle
– More like a mixing of the two alleles
Codominance
• When both alleles are
expressed equally
– Not mixing, but
blotched usually
Another Cross
• Dihybrid Cross
– When you do a cross
for two traits at the
same time
– For example: a cross
for eye AND hair
color
Example Cross
• What do you get when you cross a
tall purple flower plant with a short
white flower plant???