1. Mendel’s Laws ofMendel’s Laws of
HeredityHeredity
Why we look the wayWhy we look the way
we look...we look...

2. What isWhat is heredityheredity??
TheThe passingpassing on ofon of
characteristicscharacteristics (traits)(traits)
from parents to offspringfrom parents to offspring
GeneticsGenetics is the study ofis the study of
heredityheredity

3. Mendel used peas...Mendel used peas...
They reproduceThey reproduce sexuallysexually
They have two distinct,They have two distinct,
malemale andand femalefemale, sex cells, sex cells
calledcalled gametesgametes
TheirTheir traitstraits are easy toare easy to
isolateisolate

4. MendelMendel crossedcrossed themthem
FertilizationFertilization - the uniting- the uniting
of male and femaleof male and female
gametesgametes
CrossCross - combining gametes- combining gametes
from parents withfrom parents with
different traitsdifferent traits

5. QuestionsQuestions
What did Mendel cross?What did Mendel cross?
What areWhat are traitstraits??
What areWhat are gametesgametes??
What isWhat is fertilizationfertilization??
What isWhat is heredityheredity??
What isWhat is geneticsgenetics??

6. What Did Mendel Find?What Did Mendel Find?
He discovered differentHe discovered different
lawslaws andand rulesrules that explainthat explain
factors affectingfactors affecting heredityheredity..

7. Rule of Unit FactorsRule of Unit Factors
Each organism has twoEach organism has two
allelesalleles for eachfor each traittrait
–AllelesAlleles - different forms of- different forms of
the samethe same genegene
–GenesGenes - located on- located on
chromosomes, they controlchromosomes, they control
how an organism developshow an organism develops

8. Rule of DominanceRule of Dominance
The trait thatThe trait that is observedis observed
in the offspring is thein the offspring is the
dominant traitdominant trait (uppercase)(uppercase)
The trait thatThe trait that disappearsdisappears
in the offspring is thein the offspring is the
recessive traitrecessive trait (lowercase)(lowercase)

9. Law of SegregationLaw of Segregation
The two alleles for a traitThe two alleles for a trait
must separatemust separate whenwhen
gametes are formedgametes are formed
A parent randomly passesA parent randomly passes
only oneonly one allele for eachallele for each
trait to each offspringtrait to each offspring

10. Law of IndependentLaw of Independent
AssortmentAssortment
The genes for differentThe genes for different
traits aretraits are inheritedinherited
independentlyindependently of eachof each
other.other.

11. Questions...Questions...
How manyHow many allelesalleles are thereare there
for each trait?for each trait?
What is anWhat is an alleleallele??
How manyHow many allelesalleles does adoes a
parent pass on toparent pass on to eacheach
offspring foroffspring for eacheach traittrait

12. Questions...Questions...
What do we call the traitWhat do we call the trait
that isthat is observedobserved??
WhatWhat casecase (upper or lower)(upper or lower)
is it written in?is it written in?
What about the one thatWhat about the one that
disappearsdisappears??
WhatWhat casecase is it written in?is it written in?

13. Phenotype & GenotypePhenotype & Genotype
PhenotypePhenotype - the way an- the way an
organismorganism lookslooks
– red hair or brown hairred hair or brown hair
genotypegenotype - the- the genegene
combinationcombination of an organismof an organism
– AAAA oror AaAa oror aaaa

14. Heterozygous & HomozygousHeterozygous & Homozygous
HeterozygousHeterozygous - if the two- if the two
alleles for a trait arealleles for a trait are
differentdifferent ((AaAa))
HomozygousHomozygous - if the two- if the two
alleles for a trait are thealleles for a trait are the
samesame ((AAAA oror aaaa))

15. Dihybrid vs MonohybridDihybrid vs Monohybrid
Dihybrid CrossDihybrid Cross - crossing- crossing
parents who differ inparents who differ in twotwo
traitstraits ((AAEEAAEE withwith aaeeaaee))
Monohybrid CrossMonohybrid Cross --
crossing parents whocrossing parents who
differ in onlydiffer in only one traitone trait
((AAAA withwith aaaa))

16. Questions...Questions...
What is theWhat is the phenotypephenotype??
What is theWhat is the genotypegenotype??
What isWhat is homozygoushomozygous??
What isWhat is heterozygousheterozygous??
What isWhat is monohybridmonohybrid
crossingcrossing??