Transcript 1 Patterns of Geneticsx

Mendelian Patterns of
Inheritance
Chapter 10
Inheritance
23 pairs of chromosomes
46 total
A Gene is one section of a
chromosome that determines
one trait.
11.1 Gregor Mendel
●Developed the fundamental
laws of heredity
●He studied science and
mathematics
●Theory of Inheritance
Funfact: Mendel originally
wanted to breed mice, but
wasn't allowed to because it
was considered scandalous
Mendel chose garden peas (Pisum sativum)as
his subjects as they are easily grown and their
pollination is easily controlled. He controlled
pollination by manually moving pollen between
plants
Developed True-breeding plants by selfpollination
Developed hybrid plants by crossbreeding two
plants of differing characteristics
Tall v Short
Mendel examined varieties of peas for heritable characters
and traits for his study. (stem length, pod shape, seed shape,
seed color..etc)
In 1865, Mendel published his
findings in a paper
called Experiments on Plant
Hybridization, which was
mostly ignored at the time due
to a number of reasons. First,
Mendel was not well known in
scientific community. Second,
his theory ran against the
popular model of blended
inheritance.
11.2 Mendel's Law of Segregation
(MONOHYBRID CROSS)
Because the purple flower trait completely masks
the white flower trait when true-breeding plants are
crossed, the purple flower trait is called dominant,
and the white flower trait is called recessive.
Creating the F2 generation
*Cross the F1 generation
together to create F2
*Ratio is always 3:1
Mendel proposed that
the units responsible for
inheritance were discrete
particles - particulate
theory of inheritance
Practice
1. Round (RR) vs wrinkled (rr)
2. Heterozygous Cross (Rr x Rr)
Review Terms
F1 vs F2
True Breeding vs Hybrid
Self Pollination vs Cross Pollination
Homozygous vs Heterozygous
Particulate Theory vs Blending Theory
Genotype & Phenotype
Practice picking letters.... the following traits are
found in the common Shirtus americanus.
1. Polka dots are dominant to stripes.
2. Long sleeves are dominant to short sleeves.
3. Collared shirts are recessive.
4. Buttons are dominant over snaps.
5. Pockets are recessive.
In dragons...
Wings are a dominant
trait, but some dragons
are born wingless.
What are the chances
that two heterozygous
dragons have a whelp
that is wingless?
If a wingless dragon is crossed with
one that is heterozygous, how many
of its offspring will also be
wingless?
What is a test cross?
Help, help! I don't know
what my genotype is!!
Am I Dd or DD?
I can help
you! Let's have
offspring!
Dihybrid Crosses
Why does the punnett square work?
*it represents all the ~possible gametes that each parent can
contribute
If a parent has this genotype RrYy, what combinations are
possible in the gametes?
What are the gametes possible for an
organism that is AaBbRr?
Dihybrid Cross: RrYy x RrYy
All of these type of crosses will follow the same ratio
AaBb x AaBb
9 - (two dominant traits)
3 - (one dominant, one recessive)
3 - (one recessive, one dominant)
1 - (two recessive traits)
It may be faster to solve problems mathematically.
This one is NOT 9:3:3:1
Consider the cross between a plant with round seeds, purple
flowers to one with wrinkled seeds and white flowers ...
RrPp x rrpp
What does INDEPENDENT ASSORTMENT mean?
In your own words, describe what it means with regard to
Mendelian genetics.
Mendel would have never developed this law if he'd chosen
traits located on the same chromosome. Why do you think
that would have altered his results?
A note about probability
* It doesn't matter how often you flipped a coin or how many
times it's already shown heads, the probability is ALWAYS
50% of heads/tails.
The gambler's fallacy is a logical fallacy where people
gambling believe that a losing streak will turn around.
Example: I've tossed a coin 4 times, all four times it came up
heads. What is the probability that my next toss will be heads?