Download Gregor Mendel

Gregor Mendel
-Breeded purple and white flowered pea
plants and observed the flower color.
-Noticed the 3:1 ratio of purple flowers
to white flowers
“Hmmm… why is this
happening?!” 
http://philosophyofscienceportal.blogspot.co
m/2010/06/gregor-mendel-and-peabreeding.html
Terms to Know!
(These will be Helpful!)
A. Alleles: The alternative versions of a gene. A
potential characteristic for an organism.
1. Example: In pea plants, the plant’s flower can
either be white or purple. White and purple are
the alleles.
B. Dominant Allele: The allele that determines the
organism’s appearance. (Always written in
capitalized italic letters. Ex: AA )
C. Recessive Allele: The allele that does not have
noticeable effect on an organism’s appearance.
(Always written in lowercase italic letters. Ex: aa )
More Terms that will help you A LOT…
D. Law of Segregation: An egg and sperm only carry one
allele each for inherited character because the two
members of an allele pair separate from each other
during the production of gametes.
E. Homozygous: An organism that has two identical
alleles for a gene. (Hint: Homo=Same)
F. Heterozygous: An organism that has two different
alleles for a gene. (Hint: Hetero=Different)
G. Phenotype: An organism’s physical traits. Ex: purple
flowers vs. white flowers
H. Genotype: An organism’s genetic makeup Ex: Pp, pp,
or PP (This will make more sense after the next
slide!!)
Punnett Square: A diagram used in the study
of inheritance to show the results of random fertilization
For example: In pea plants, purple flowers are
the dominant allele (G), and white flowers are
the recessive allele (g). This is the cross of one
heterozygous and one heterozygous parent.
In this case, each
parent’s genotype
is Gg. It’s
offspring’s
genotype will either
be GG, Gg, or gg.
The offspring has a
3:1 chance of being
purple, because
purple is the
donimant allele.
What color is
each parent
plant?
PURPLE!
Purple is each
parent’s
phenotype
http://www.hobart.k12.in.us/jkousen/Biology/psquprac.htm
Two Kinds of Crosses:
1. Monohybrid Cross: The crossing of organisms
which only differ by one characteristic. Ex:
Breeding pea plants with white and purple flower
color. The only different characteristic between the
two is their color.
2. Dihybrid Cross: The crossing of organisms that
only differ by two characteristics. Example: pea
seeds differ in both color and shape. They can be
either yellow or green, and round or wrinkled.
Punnett Squares:
DihybridCross:
Cross:
Monohybrid
Refer to picture in
book on page 150
.
http://slohs.slcusd.org/pages/teachers/rhamle
y/Biology/Genetics/monocross.html
Probability
-All genetic crosses obey the rules of
probability. These are the same rules
that would apply to a coin toss, rolling
dice, or drawing a card.
-All genetic crosses abide by the rule of
multiplication.
Rule of multiplication: The probability that a
dual even is the product of the separate
probabilities of the independent events.
For example: The probability of flipping two
coins and both landing on heads.
-Probability of Coin 1 being heads: ½
-Probability of Coin 2 being heads: ½
-Probability of both coins being heads: ¼
-We get this because… ½ x ½ = ¼
(See page 152 for reference)
Any Questions?
Now we get to fill in some punnett squares!!