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Genetics is the study of
heredity
Heredity is the passing of
traits from parent to
offspring
Gregor Mendel is considered
the Father of Modern
Genetics
Why did Mendel use
pea plants?

Easy to grow

Make lots of
offspring

Can manipulate
pollination
1.
2.
Peas can selffertilize (pollinate
flowers on same
plant)
Peas can crossfertilize (pollinate
flowers on a
different plant)
3.
Peas have
several traits
with only 2
contrasting
forms
Step 1: Produce the P (parent)
generation
◦ Parents are true-breeding
plants created by selffertilization
Step 2: Produce the F1 generation
◦Cross 2 different parent plants
together
◦All F1 offspring looked alike
Step 3: Produce
the F2
generation
◦ Cross any 2
F1 plants
together
◦ Offspring
come out in a
3:1 ratio
1.
Parents transmit
information about
traits to their
offspring using
gametes, or sex cells
◦ Females make egg
cells (ovum)
◦ Males make sperm
cells
Each individual has 2 genes for
each trait
What is a gene?
segment of DNA that codes for a
trait
Where did your genes come from?
your parents
2.
 If
the 2 units you inherit are the
same you are homozygous
ex. purple & purple (P generation)
 If
the 2 units you inherit are
different you are heterozygous
ex. purple & white (F1 generation)
The different forms of a gene are
called alleles (these are the trait
choices)
◦ An individual’s alleles (genes) are
its genotype
3.
◦ The physical
appearance that
results from the
alleles is the
phenotype
Not all alleles get expressed:
◦ the dominant allele is ALWAYS
expressed when present
 symbol is a CAPITAL letter (P)
◦ the recessive allele is covered up
in the heterozygous condition
 symbol is a lower-case letter (p)
4.