Mendel Notes
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Transcript Mendel Notes
Classical Genetics
The Legacy of Gregor Mendel
Or
The Monk with the Missing “Peas”
The Big Question
Why
do children
look like their
parents?
That’s GENETICS!
The
scientific study
of heredity
Heredity:
the
passing down of
traits from parents
to offspring via
genes and
chromosomes
Gregor
Who started genetics?
Gregor Mendel of course!!!
Mendel
Austrian monk in
1860’s
Studied
different
traits of the
garden pea
Discovered
the
basic laws of
genetics
“Father of
Genetics”
More Mendel!!!
1st
person to
succeed in
predicting how
traits are passed
from one
generation to
next
Why is Mendel SO important?
Studied
one trait
at a time
Analyzed his data
mathematically
Looked at
multiple traits
Used multiple
trials
Why peas?
Quick
growing
Lots of different traits
So what did Mendel find out?
Genes
and Alleles
GENE:
section of DNA
that determines a trait
(Mendel called them
factors)
ALLELE:
particular form of
a trait (represented by
letters)
EX: plant size
“T”
is the tall allele
“t”
is the short allele
Combinations of Alleles
We
get one allele from each
parent
Three
TT:
possible combinations
homozygous dominant
Tt: heterozygous
tt: homozygous recessive
Dominant/Recessive
One
allele is dominant over the other
(capable of masking the recessive allele)
PP = purple
Pp = purple
pp = white
New Vocabulary
Genotype
- combination of alleles that an
individual has. (TT, tt, Tt)
Phenotype
- physical appearance of a
trait (Tall, Tall, Short)
So how do we write this?
Remember
T = Tall and t = short
So if a plant is..
Genotype
Homozygous Dominant:
TT
Heterozygous:
Tt
tt
Homozygous Recessive:
Phenotype
Tall
Tall
Short
Punnett Square
Father’s Genes
way to show
which genes can
combine when an
egg and sperm join
Letters are used in
place of genes
Large letter =
dominant gene (T)
Small letter =
recessive gene (t)
Mother’s Genes
A
Punnett Square
Large
letter goes
first in heterozygous
organisms (Ff)
Let’s do a cross
between a pure
dominant male
(sperm) for free
earlobes (FF) and a
female (egg) who is
heterozygous for
free earlobes (Ff)
F
f
F
FF
Ff
F
FF
Ff
F is dominant over f
What are the expected results?
F
F
F
f
FF
Free
Earlobes
Ff
Free
Earlobes
FF
Free
Earlobes
Ff
Free
Earlobes