Genetics - Cloudfront.net
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Transcript Genetics - Cloudfront.net
Genetics: all the rage in bio
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
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.
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
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.
Insure self fertilization and cross fertilization
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…
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
Started with plants that differ in only
one characteristic (monohybrid
cross)
The F1 progeny were all _______
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
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
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
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
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
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!
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)
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
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
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
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
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
_______ 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
Deletion: a portion is _____________
____________: a portion is doubled
Where is the dog? Where is the the dog?
__________: If a deleted piece reattaches in the
wrong orientation
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
Where is the dog? The dog is in the backyard. Where
is dog? The dog is in the backyard the.
Human Genetic Analysis
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