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Genetics: all the rage in bio
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One of the fastest changing fields in
biology
People started studying it back to
ancient Greece but they were limited
to PHENOTYPE: what something
looks like
Due to our great new knowledge
(human genome project and much
more) we can now get meaningful
information form the GENOTYPE: the
genes/ versions that individuals
contain
Historically it was easy to see
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We all already know too…
You look like both of your parents.
 Each feature is a one or the other kind of thing… not a blend
 Ie. I have my dad’s eyes, my dads mouth shape and my mom’s hands.
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I am a blend but my features are not
It took Gregor Mendel to start truly understanding WHY
Mendel changed the world
with his peas
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Mendel had a hypothesis that
all of our features were
controlled by heritable factors
(genes)
He set out to prove it but
needed a model organism…
something that was easy to
work with and showed what
he needed it too
He chose the pea plant
Why garden peas?
1. Easy to control fertilization.
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Insure self fertilization and cross fertilization
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For cross he removed the stamen before the pollen
was mature
Why garden peas?
2. Had a variety of characters to explore
What Mendel did…
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First he let the peas selffertilize so they would be pure
He then crossed a purple
flowering plant with a white
flowering plant (crossfertilization or hybrid) This was
the _________________ P
(parental) generation
The progeny from that
generation are F1
When the F1 are crossed…
their progeny produce what is
referred to as F2
How he did it
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Started with plants that differ in only
one characteristic (monohybrid
cross)
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The F1 progeny were all _______
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Flower color (purple vs white)
Oh no! Did the white disappear?!?
Few… in the F2 generation the
white reappeared in a ratio of _____
_______ to _______________
So the white was not lost just
covered for a while
What he concluded
1.
2.
3.
4.
There are different forms of each unit that
determine heritable traits (alleles)
Principle of __________: During the formation of
egg and sperm the parental alleles segregate then
the diploid status of the offspring is restored at
fertilization
Principle of Independent assortment: Each trait is
inherited _________ from _____________. They
segregate on their own
Law of dominance and recessiveness: Within each
pair of alleles, there is an option for a ________
(fully expressed) and ______________ (largely
unexpressed) variations
How we can use it
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First, each trait is named for the
_________ version (P for purple
because it is dominant) The
recessive is just ______ ______
of the (p for white)
Each parent can be either
homozygous (both alleles the
same) or heterozygous (one
dominant and one recessive)
We track their succession using
a Punnett square
Genes v Look
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The genetic makeup of an individual trait is the _________
(heterozygous, homozygous dominant, homozygous recessive)
The look of the individual is it’s __________ (purple or white)
You can use the genotype to tell the phenotype and sometimes the
phenotype to tell the genotype
Monohybrid cross: pod color
(2 generations)
Test Cross
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If an individual is __________, it is
impossible to determine its genotype (could
be ___________ __________or
_____________)
Use a test cross… breed it with a known
____________ ____________
What would the F1 look like if the unknown
were homozygous dominant?…
heterozygous?
Dihybrid crosses
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Looks at _____ different characters… seed color and
seed shape.
If they were inherited together we would see a
dominant seed color/shape combo and a recessive
combo
As it is the most characters exhibit _____________
______________.
Dihybrid example
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If yellow is
dominant to
green and
round to
wrinkled
You cross a
yellow round
seed with a
green wrinkled.
What do you
get?
** need a
bigger Punnett
square!
Ratios… memorize instead of
huge Punnett squares!
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Heterozygous dihybrid cross always yields a
phenotype ratio of _:_:_:_ (dominant both:
dominant one: dominant one: recessive both)
Homozygous dominant- recessive cross gives
all the ______________ (phenotypically the
dominant character)
Incomplete dominance (blend)
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Not all traits are a one or the
other thing
With __________
_________both alleles work
together to determine the final
phenotype
Take a cross for two flowers…
One red (RR) and one white
(WW)
With incomplete dominance the
heterozygote is an
___________ between the two
homozygotes
Now both the genotypic and
phenotypic ratios are 1:2:1 in a
Codominance
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Each allele is
__________
_________in different
regions or cells
Calico cat, rone horse
Neither one is totally
dominant and the two
traits co-exist without
bothering each other,
each controlling their
own area
Blood types are codominant
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A or B or both or neither may be
expressed
If you have __antigens you
recognize things with ___ and fight
anything with ___
If you have AB you recognize
_________
If you have O you recognize no
one but they don’t detect you
A donates to __
B donates to __
AB can receive from anyone but
only donate to AB
O can donate to _______ but only
receive O
Linked traits
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Some traits do not independently assort
We know that chromosome have loci, all the loci on
the same ___________ HAVE to be inherited
together (unless crossover moves them)
Genes on the same chromosome are inherited
together!
Sex linked traits
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Sometimes the link is with a sex
chromosome.
The __ is notorious for being linked… color
blindness, hemophilia, and MANY other
things in other animals
Who would be more likely to be affected?
Why?
Sex-Linked continued
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_______ are usually
affected more often
because they get only one
X… so good gene or bad
gene automatically shows
up
A female has another
chance for a second X to
cover the bad (or just
recessive trait)
Females are often
________
Changes in DNA during
replication
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Deletion: a portion is _____________
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____________: a portion is doubled
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Where is the dog?  Where is the the dog?
__________: If a deleted piece reattaches in the
wrong orientation
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Where is the dog?  Where the dog?
Where is the dog?  Where is dog?  Where is dog
eht?
Translocation: removed from chromosome and
added ___________ to another
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Where is the dog? The dog is in the backyard.  Where
is dog? The dog is in the backyard the.
Human Genetic Analysis
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We can display human inheritance using a display called a
_______.
In a pedigree, _______ are represented by ________ and
females by circles .
An individual who exhibits the trait is represented by a _____
symbol.
A _____________ line between two symbols represents a
mating .
The ________ are connected to each other by ___________
line above the symbols and to the ________ by _________
lines.
Roman numerals (I, II, III, etc.) symbolize generations.
Autosomal
Recessive
Autosomal dominant