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GENETICSGENETICS
GeneticsGenetics- the scientific study of heredity.
HeredityHeredity- the passing down of traits/characteristics from one generations to the next.
GREGOR MENDELGREGOR MENDELo The father of
Genetics.o Austrian Monk.o Worked with Pea
Plants.o Not fully appreciated
until after his death.o Born 1843 died 1884o 1st Scientist to put
Math and Science together
1.
Why Pea Plants?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 General Terms..you will have to add these to your notes!!to add these to your notes!!
oGametes- Sex Cell. Like an egg or sperm
oHaploid Cell is a cell that only contains ½ the number of chromosomes…like gametes!!
oDiploid Cell- has a full number of chromosomes. Like every cell in your body EXCEPT your gametes.
Pea PlantsPea Plants
A Pea plant has both the male and female gametes enclosed within the flower.
Pea PlantsPea Plants
Pollen (aka Stamen) grains are the male haploid cells.
Ovules (aka pistil) are the female haploid cells.
Pea PlantPea Plant
o The gametes can fuse together to make a viable offspring called a PureBreed in a process called SELF-FERTILIZATION
o Or the gametes can be bred by hand….called EXPERIMENTAL CROSS
EXPERIMENTSEXPERIMENTS
Mendel began his experiment by allowing a given variety to self-fertilize for several generations. This assured what he called a purebreed.
He crossed a : tall X tall = all tall
Then he would take and crossTall 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.
EXPERIMENTSEXPERIMENTS
MENDEL’S PEA PLANTSMENDEL’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 ClipGenetic Video Clip
TraitsTraits
Dominant Traits will be represented by Capital Letters.
Recessive Traits will be represented with Lower Case letters.
TRAITSTRAITS
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.
TraitsTraits
CONCLUSIONCONCLUSION
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.
ConclusionConclusion
CONCLUSIONCONCLUSION
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.
ConclusionConclusion
GENOTYPEGENOTYPE
GENOTYPE-GENOTYPE- the actual genetic make-up of an organism.
PHENOTYPEPHENOTYPE
PHENOTYPE- the form of the trait that is observed or seen.
PHENOTYPEPHENOTYPE
HOMOZYGOUSHOMOZYGOUS
TT
tt
An organism where the two alleles for a trait are the same.
Can be dominant or recessive.
Also called Pure Breed
HOMOZYGOUSHOMOZYGOUS
HETEROZYGOUSHETEROZYGOUS
Tto An organism
where the two alleles for a trait are DIFFERENT.
o Also called a hybrid.
HETEROZYGOUSHETEROZYGOUS
Mendel’s LawMendel’s Law
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 LawMendel's Law
Mendel’s LawMendel’s Law
The Law of Segregation-That each pair of alleles separates during Meiosis
Mendel's LawMendel's Law
Mendel’s LawMendel’s Law
oThe Law of Dominance-When two alleles for a given trait are different (hybrid) one allele will be dominant over the other.
Mendel's LawMendel's Law
Mendel’s LawMendel’s 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.
Mendel's LawMendel's Law
PROBABILITYPROBABILITY
Genetics uses probability to predict the phenotypes and genotypes.
PUNNETT SQUAREPUNNETT SQUARE
A grid for organizing genetic information
Punnett SquarePunnett 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
Rules for the Punnett Rules for the Punnett SquareSquare
Practice Time!!Practice Time!!
o DO THE FOLLOWING CROSS
Cross a heterozygous tall pea plant with a short pea plant.
Tt X ttTt X tt
Practice Time!!Practice Time!!
RATIORATIO
Phenotypic Ratio: 2:2 (reduce down)
Tall:short
Genotypic Ratio: Tt:tt
2:2 (reduce down)
PUNNETT SQUAREPUNNETT 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.
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