GeneticsGenetics

What is Genetics?What is Genetics?GeneticsGenetics is the field of is the field of Biology devoted to Biology devoted to understanding how understanding how characteristics are characteristics are transmitted from parents to transmitted from parents to offspring.offspring.

Genes:Genes: Hereditary Hereditary information passed down information passed down from parent to offspring that from parent to offspring that codes for a trait.codes for a trait.

ExamplesExamplesGenes for eye color, hair color, Genes for eye color, hair color, dimples, flower color, seed dimples, flower color, seed color, seed shape, etc…color, seed shape, etc…

The “father of genetics”The “father of genetics”Genetics was founded with Genetics was founded with the work of Gregor Mendel the work of Gregor Mendel an Austrian monk who an Austrian monk who worked with garden peas, worked with garden peas, Pisum sativum. Pisum sativum.

What would happen if…?What would happen if…?

The unexpected resultsThe unexpected results

All of the offspring had round peas.All of the offspring had round peas.

This is called the FThis is called the F11 generation. generation.

It gets even stranger for MendelIt gets even stranger for Mendel

He crosses now the plants from FHe crosses now the plants from F11 generationgeneration

Now what do you expect?Now what do you expect?

A magic ratio aroseA magic ratio arose

•3 : 1 Ratio of Round : Wrinkled

•The F2 generation

Other traits that had the same Other traits that had the same patternpattern

Why did this happen?Why did this happen?

He realized that there must be two alleles He realized that there must be two alleles that control each trait.that control each trait.

AlleleAllele - one alternative form of a gene.- one alternative form of a gene. In our example there are two alleles for seed In our example there are two alleles for seed

shape: one allele for round (R) and one allele shape: one allele for round (R) and one allele for wrinkled (r).for wrinkled (r).

He also realized that each individual gets He also realized that each individual gets one allele from each parent.one allele from each parent.

So how does this explain the resultSo how does this explain the result

Starting with the Starting with the original plantsoriginal plantsGenotypeGenotype - the - the specific allelic specific allelic combination for a combination for a certain gene or set of certain gene or set of genesgenesRR x rrRR x rrWhat are the possible What are the possible genotypes for the genotypes for the offspring?offspring?

All the offspring in FAll the offspring in F1 1 are are HeterozygousHeterozygous

HeterozygoteHeterozygote - an individual which - an individual which contains one of each member of the gene contains one of each member of the gene pairpair In our example this means RrIn our example this means Rr

HomozygoteHomozygote - an individual which - an individual which contains only one allele at the allelic paircontains only one allele at the allelic pair In our example the parents are homozygousIn our example the parents are homozygous

One had an RR genotype and the other had an rr One had an RR genotype and the other had an rr genotypegenotype

Why are all the peas round?Why are all the peas round?

Round is DominantRound is DominantPhenotypePhenotype - literally means "the form that is - literally means "the form that is shown"; it is the outward, physical appearance shown"; it is the outward, physical appearance of a particular trait and is determined by a of a particular trait and is determined by a persons genotype.persons genotype. What is the phenotype for the Rr genotype?What is the phenotype for the Rr genotype?

Rr =Rr =

This means that the Round allele is dominant over the This means that the Round allele is dominant over the Wrinkled allele.Wrinkled allele.

Dominant vs RecessiveDominant vs Recessive

DominanceDominance - the ability of one allele to - the ability of one allele to express its phenotype at the expense of express its phenotype at the expense of an alternate allelean alternate allele In our example round is dominant over In our example round is dominant over

wrinkledwrinkled

RecessiveRecessive - an allele whose expression is - an allele whose expression is suppressed in the presence of a dominant suppressed in the presence of a dominant alleleallele

Why do we a 3 : 1 ratio of Why do we a 3 : 1 ratio of Round : Wrinkled Round : Wrinkled

in the Fin the F2 2 generation?generation?