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.