GeneticsGeneticsThe Study of Inherited The Study of Inherited

CharacteristicsCharacteristics

ChromosomeChromosomeDNACodefortraits

GeneGeneSegments of Segments of

DNA DNA Code for a Code for a

traittrait

HairColor

EyeColor

Gene Segment For Hair color

TraitTraitCharacteristicCharacteristicFeatureFeatureVariations in Variations in

a populationa population

Dominant TraitDominant Trait ““Dominates”Dominates” Shows in the Shows in the

outward outward appearanceappearance

Even when Even when recessive trait is recessive trait is presentpresent

BBbb

BBor

Bb

Recessive TraitRecessive Trait““hidden”hidden”May be May be

masked by a masked by a dominant dominant traittrait

BBbb

Albinism

bb

AllelesAlleles Letters of the Letters of the

alphabetalphabet Code for a traitCode for a trait One from One from

fatherfather One from One from

mothermother

Dominant Dominant Allele:Allele:

Upper case Upper case letter of the letter of the alphabetalphabet

Codes for Codes for dominant dominant traitstraits

Recessive Recessive Allele:Allele:

Lower case Lower case letter of the letter of the alphabetalphabet

Codes for Codes for recessive recessive traitstraits

Chromosomes in NucleusChromosomes in Nucleus

GeneSegmentsFor a Trait=“A” or “a”

Monohybrid CrossMonohybrid CrossCross for Cross for oneone trait trait

Example:Example:Hair colorHair color

BB bbBB BBBB BbBb

BB BBBB BbBb

Punnet Square

F1 GenerationF1 GenerationGenetic Genetic

Cross=Cross=

Mating Mating F1=F1=

ChildrenChildren11stst “filial” “filial”

generationgeneration

ParentsParents

BB bbBB BBBB BbBb

BB BBBB BbBb

22ndnd Filial Generation- Filial Generation- F2F2 ChildrenChildren of of

the cross the cross between the between the children of an children of an F1F1

““Incest” Incest” among F1among F1

Only after Only after pure x purepure x pure

F1=F1=

F2=F2=

BB BB

bb BbBb BbBb

bb BbBb BbBb

BB bb

BB BBBB BbBb

bb BbBb bbbb

PhenotypePhenotypeOutward Outward

appearanceappearanceTrait that is Trait that is

shownshownBb Bb lookslooks brown brown

(has “b” =white (has “b” =white allele)allele)

GenotypeGenotypeAllele setAllele setTrue genetic True genetic

makeupmakeup of of the the chromosomechromosome

BbBb

Homozygous:Homozygous:Pure Pure

conditioncondition2 same case 2 same case

allelesallelesBBBB= =

dominantdominantbbbb= recessive= recessive

Heterozygous:Heterozygous:Hybrid Hybrid

conditioncondition2 different case 2 different case

allelesallelesBbBb appears appears

dominantdominant

Dihybrid CrossDihybrid Cross Cross withCross with twotwo traits traits Example:Example:1.1. Hair ColorHair Color2.2. Eye ColorEye Color2 types of 2 types of allelesalleles

parentsparents

ChildrenChildren ChildrenChildren ChildrenChildren ChildrenChildren

ChildrenChildren ChildrenChildren ChildrenChildren ChildrenChildren

ChildrenChildren ChildrenChildren ChildrenChildren ChildrenChildren

ChildrenChildren ChildrenChildren ChildrenChildren ChildrenChildren

CodominanceCodominance ““Incomplete” Incomplete”

dominancedominance HybridHybrid is a is a blend blend of of

traitstraits Example:Example:

RR=redRR=redRrRr=pink=pinkrr=whiterr=white

Pink Carnation

Multiple AllelesMultiple AllelesMore than More than

one type of one type of allele for a allele for a traittrait

Example:Example:

Blood TypeBlood Type

TYPES:TYPES:

A A IIAAIIAA, I, IAAii

B B IIBBIIB B , I, IBBii

AB AB IIAAIIBB

O O iiii

X-Linked TraitsX-Linked Traits Sex-linkedSex-linked Trait in on the sex Trait in on the sex

chromosomechromosome XXXX== Female Female XYXY MaleMale Ex:Red & white Ex:Red & white

eyeseyes

Female=Female=XXXXAdd eye trait=Add eye trait=XXRRXXR R or X or XRRXXr r

XXrrXXrr

Male=Male=XYXYAdd eye trait=Add eye trait=XXRRY or XY or XrrYY““Y” is emptyY” is empty

KaryotypeKaryotype

Chromosome NumberChromosome Number

Different # for different Different # for different speciesspecies

Full setFull set = 2N= = 2N=DiploidDiploid N=N= # pairs# pairs 1 pair from mother1 pair from mother 1 pair from father1 pair from father Humans= Humans= 23 pairs23 pairs or or 46 total46 total

Homologous Chromosomes are the sets of each pair

Autosomes & Sex ChromosomesAutosomes & Sex Chromosomes

Autosomes = # 1-22 for all traits except sex

Sex chromosomes= Pair # 23 XX(female) orXY(male)

Down Syndrome= 3 of #21Down Syndrome= 3 of #21

Klinefelter’s = XXYKlinefelter’s = XXY

Pedigree ChartsPedigree Charts

Male =Male =

Female=Female=

Sexual Union=Sexual Union=

Offspring=Offspring=

Pedigree Chart -Cystic FibrosisPedigree Chart -Cystic Fibrosis