GeneticsGenetics

It all started with Mendel!It all started with Mendel!

GeneticsGenetics

It all started with Mendel!It all started with Mendel!

Review: Types of ReproductionReview: Types of Reproduction

Sexual reproduction: Sexual reproduction: twotwo organisms organisms produce a new produce a new uniqueunique organism = organism = VARIABLITYVARIABLITY!!!!!!

Asexual reproduction: Asexual reproduction: oneone organism organism produces a new nearly produces a new nearly identicalidentical organism organism = = no variabilityno variability!!

• The branch of biology that is concerned The branch of biology that is concerned with the ways in which with the ways in which hereditaryhereditary information is transmitted information is transmitted from parents from parents to offspring.to offspring.

GeneticsGenetics

How does it work?How does it work?Women carry XX sex chromosomesWomen carry XX sex chromosomes

Men carry XY sex chromosomes (technically, Men carry XY sex chromosomes (technically, men determine the sex of a baby)men determine the sex of a baby)

Many diseases/conditions are carried on the Many diseases/conditions are carried on the X chromosome (X chromosome (nothing is carried on the Ynothing is carried on the Y))

** ColorBlindness** ColorBlindness

** Hemophilia** Hemophilia

Women can be healthy ‘carriers’Women can be healthy ‘carriers’

Men either have or don’t have the disease.Men either have or don’t have the disease.

Gregor MendelGregor Mendel

An Austrian monk that An Austrian monk that studied math and studied math and science and taught science and taught science in a monasteryscience in a monastery

““Father of Genetics” Father of Genetics”

Performed the first Performed the first scientific study of scientific study of inheritanceinheritance on on pea pea plantsplants

Pea PlantsPea PlantsUse parts of the flowers to reproduceUse parts of the flowers to reproduce Pollen = male sex cellsPollen = male sex cells Eggs in flower = female sex cellsEggs in flower = female sex cells

Pea plants normally reproduce by Pea plants normally reproduce by self-self-pollinationpollination Pollen fertilizes flower of the same plantPollen fertilizes flower of the same plant True-breedingTrue-breeding pea plants (“pure bred”) pea plants (“pure bred”)

} form a seed

Pea PlantsPea PlantsPea plants can Pea plants can cross-pollinatecross-pollinate Pollen fertilizes flower of a Pollen fertilizes flower of a differentdifferent plant plant New plants have New plants have twotwo parent plants parent plants

Infer if the new plants would be identical or Infer if the new plants would be identical or different from the parents. Why?different from the parents. Why?

Mendel cross-pollinated pea plants!Mendel cross-pollinated pea plants!

Mendel’s 1Mendel’s 1stst experiments experimentsTraitTrait = specific characteristic that varies = specific characteristic that varies from one individual to anotherfrom one individual to another Height (tall or short)Height (tall or short) Seed color (green or yellow)Seed color (green or yellow) Seed texture (smooth or wrinkled) Seed texture (smooth or wrinkled)

Mendel crossed plants with contrasting traitsMendel crossed plants with contrasting traits PP (Parental) = original pair of plants (Parental) = original pair of plants FF11 (First Filial) = first set of offspring (First Filial) = first set of offspring

(filius means “(filius means “sonson” in Latin)” in Latin) HybridsHybrids = offspring of parents crossed = offspring of parents crossed

with different traits (aka HETEROzygous)with different traits (aka HETEROzygous)

Mendel’s 1Mendel’s 1stst conclusions conclusions

Biological inheritance is determined by Biological inheritance is determined by factors passed from one generation to the factors passed from one generation to the next = next = genesgenes

Each gene occurred in two contrasting Each gene occurred in two contrasting forms that produced different forms that produced different characteristics = characteristics = allelesalleles

The Principle of DominanceThe Principle of Dominance

Some alleles are Some alleles are dominantdominant

and and

others are others are recessiverecessive

Dominant vs. RecessiveDominant vs. Recessive

An organism with a dominant allele for a An organism with a dominant allele for a particular trait will particular trait will always always have that formhave that form When will a dominant allele show up?When will a dominant allele show up? The characteristic almost The characteristic almost alwaysalways shows up shows up

An organism with a An organism with a recessiverecessive allele for a allele for a particular trait particular trait will have that form only when will have that form only when the dominant allele for the trait is not presentthe dominant allele for the trait is not present When will a recessive allele show up?When will a recessive allele show up? The characteristic only shows up when the The characteristic only shows up when the

dominant allele is not presentdominant allele is not present

Mendel’s 2Mendel’s 2ndnd experiments experiments

Mendel crossed the FMendel crossed the F11 hybrid plants hybrid plants FF11 (First Filial) = first set of offspring (hybrids)(First Filial) = first set of offspring (hybrids)

FF22 (Second Filial) = offspring of self-pollinated F(Second Filial) = offspring of self-pollinated F11

Dominant vs. Recessive allelesDominant vs. Recessive alleles Upper case letter Upper case letter = dominant allele= dominant allele Lower case letter Lower case letter = recessive allele= recessive allele

Mendel’s 2Mendel’s 2ndnd conclusions conclusions The dominant allele masked the The dominant allele masked the

corresponding recessive allele in the Fcorresponding recessive allele in the F11

generationgeneration The reappearance in the FThe reappearance in the F22 generation generation

indicated that the alleles indicated that the alleles separatedseparated during during gamete (sex cell) formationgamete (sex cell) formation Each gamete contains a single copy of each Each gamete contains a single copy of each

genegene The recessive alleles can be The recessive alleles can be pairedpaired up again in up again in

the Fthe F22 generation generation

The Principle of SegregationThe Principle of Segregation

Alleles are Alleles are separatedseparated (segregated) (segregated)

during during

gametegamete (sex cell) formation. (sex cell) formation.

concluded that

which is called the

which is called the

GregorMendel

Law ofDominance

Law ofSegregation

Peaplants

“Factors”determinetraits

Some alleles are dominant, and some alleles are recessive

Alleles are separated during gamete formation

Section 11-3

Concept Map

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