Transcript GENETICS

GENETICS
Genetics- the
scientific study
of heredity.
Heredity- the
passing down of
traits/characte
ristics from one
generations to
the next.
GREGOR MENDEL
o The father of
Genetics.
o Austrian Monk.
o Worked with Pea
Plants.
o Not fully
appreciated until
after his death.
o Born 1843 died 1884
o 1st Scientist to put
Math and Science
together
1.
Why Pea Plants?
o Short Life
Cycle…90 days
o No Intermediate
traits
o They could self
breed or be cross
breed by hand.
General Terms..you will have to
add these to your notes!!
o Gametes- Sex Cell. Like an egg or
sperm
o Haploid Cell is a cell that only
contains ½ the number of
chromosomes…like gametes!!
o Diploid Cell- has a full number of
chromosomes. Like every cell in
your body EXCEPT your gametes.
Pea Plants
A Pea plant has
both the male and
female gametes
enclosed within
the flower.
Pea Plants
Pollen (aka
Stamen) grains
are the male
haploid cells.
Ovules (aka
pistil) are the
female haploid
cells.
Pea Plant
o The gametes can
fuse together to
make a viable
offspring called a
PureBreed in a
process called
SELFFERTILIZATION
o Or the gametes
can be bred by
hand….called
EXPERIMENTAL
CROSS
EXPERIMENTS
 Mendel began his experiment by
allowing a given variety to selffertilize for several generations.
This assured what he called a
purebreed.
 He crossed a :
tall X tall = all tall
EXPERIMENTS
Then he would take and cross
Tall X Short (also a purebreed) = All
Talls in the F1 generation.
Through this he discovered what are
called Dominant Traits…which is the
trait observed in a hybrid.
Recessive Trait-a trait that is NOT
observed in hybrid.
MENDEL’S PEA PLANTS
 After many experimental crosses
Mendel determined that many traits of
the pea plants were
dominant/recessive.
 He established a chart that is stilled
widely used today.
 Copy the chart in its entirety.
Genetic Video Clip
Traits
Dominant Traits
will be
represented by
Capital Letters.
Recessive Traits
will be
represented with
Lower Case
letters.
TRAITS
Traits
o You determine which letter to use by
taking the 1st letter of the dominant trait
o REMEMBER- one letter represents one
trait (Height is one trait so it includes tall
and short…still one letter)
o If you change letters than you change
traits.
CONCLUSION
Conclusion
o During Mendel’s work he concluded that
each trait was controlled by something he
called a “factor”…we know today he was
talking about GENES.
o He then continued by saying that each trait
is really controlled by TWO
“factors”,alleles, or genes…one from
each parent.
CONCLUSION
Conclusion
o Therefor the gametes of an individual
contain one factor for a trait.
REMEMBER: Gene, alleles, and
“factors” are all the same thing…just
different names.
GENOTYPE
GENOTYPEthe actual
genetic makeup of an
organism.
PHENOTYPE
PHENOTYPE
PHENOTYPEthe form of the
trait that is
observed or
seen.
HOMOZYGOUS
HOMOZYGOUS
TT
 An organism where
the two alleles for a
trait are the same.
 Can be dominant
or recessive.
tt
 Also called Pure
Breed
HETEROZYGOUS
HETEROZYGOUS
Tt
o An organism
where the two
alleles for a trait
are DIFFERENT.
o Also called a
hybrid.
Mendel's Law
Law
Mendel’s
The chromosomes of homologous
pair are made of matching
sequences called
genes…therefor they have two
copies of a gene for any given
trait.
Mendel's Law
Law
Mendel’s
 The Law of Segregation-That
each pair of alleles separates
during Meiosis
Mendel's Law
Law
Mendel’s
oThe Law of DominanceWhen two alleles for a given
trait are different (hybrid) one
allele will be dominant over the
other.
Mendel’s
Mendel's Law
Law
oLaw of Independent
Assortment - The alleles/gene pairs
separate into gametes randomly and
independently of each other. (Those
alleles located on different chromosomes).
Randomly- You have no control.
Independently- One trait has no control on
another.
PROBABILITY
Genetics uses probability to
predict the phenotypes and
genotypes.
PUNNETT
Punnett SQUARE
Square
A grid for
organizing
genetic
information
Rules for the Punnett
Square
 Determine the alleles of the parents
 Put one parent on top; one parent far left.
Do not Mix Parents
 Combine alleles inside grid
 Determine genotype and phenotype
Ratios
Practice Time!!
o DO THE FOLLOWING CROSS
Cross a heterozygous tall pea plant with
a short pea plant.
Tt X tt
Practice Time!!
RATIO
Phenotypic Ratio: 2:2 (reduce down)
Tall:short
Genotypic Ratio: Tt:tt
2:2 (reduce down)
PUNNETT SQUARE
o MONOHYBRID CROSS- Cross that
involves only 1 trait. Simple Punnett
square.
o DIHYBRID CROSS- Cross that involves 2
traits. A Punnett square that has 16
squares.