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GGENETICSENETICS

Mendel’s Laws of Mendel’s Laws of HeredityHeredity

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Mendel’s LawsMendel’s LawsLaw of segregationLaw of segregation

The two alleles for The two alleles for ______________________________________________________________________

A parent will pass down A parent will pass down ______________, only one allele for ______________, only one allele for each traiteach trait

Law of independent assortmentLaw of independent assortmentGenes for Genes for ____________________________________________________________________________________________________________________________________________

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Some Needed Some Needed VocabularyVocabulary

HeredityHeredityPassing on of characteristics Passing on of characteristics ______________________________________________________

TraitsTraitsCharacteristics that _________________Characteristics that _________________

GeneticsGeneticsThe study of HeredityThe study of Heredity

GametesGametesSex cells Sex cells

Sperm = male gameteSperm = male gameteEgg = female gameteEgg = female gamete

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Gregor MendelGregor MendelA monk who studied heredity A monk who studied heredity using garden pea plantsusing garden pea plants

Why garden peas?Why garden peas?________________________________________________________________________________________________________________________

What did he do?What did he do?He transferred pollen from one plant He transferred pollen from one plant ____________________________________________________________________________

This is called “_________________________”This is called “_________________________”

Mendel first “crossed” tall plants with Mendel first “crossed” tall plants with short plantsshort plants

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Mendel’s Monohybrid Mendel’s Monohybrid crossescrosses

Monohybrid crossMonohybrid crossFocuses on one (___________) traitFocuses on one (___________) trait

11stst generation generationCrossed a ___________pea plant with a Crossed a ___________pea plant with a ________pea plant________pea plantAll of the offspring were ____________All of the offspring were ____________

22ndnd generation generation Crossing the offspring of the 1Crossing the offspring of the 1stst generationgeneration_____of the offspring were tall; ______of _____of the offspring were tall; ______of the offspring were shortthe offspring were short_______ ratio (tall to short)_______ ratio (tall to short)

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Mendel’s FindingsMendel’s FindingsMendel found that each chromosome has Mendel found that each chromosome has two factors for each traits… called two factors for each traits… called ________________

Alleles = forms of genesAlleles = forms of genesTypes of alleles Types of alleles (mask means hidden)(mask means hidden)

DominantDominantThe trait that has the ability to The trait that has the ability to _________the other_________the otherRepresented with a ____________ letter (A)Represented with a ____________ letter (A)

Recessive Recessive The trait that will be masked by the The trait that will be masked by the dominant trait… it will be there, but will dominant trait… it will be there, but will not be show (expressed)not be show (expressed)Represented with a _______________ letter (a)Represented with a _______________ letter (a)

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Phenotype vs. Phenotype vs. GenotypeGenotypePhenotypePhenotype

The way that The way that a___________________; how the a___________________; how the trait appearstrait appears

Tall, shortTall, short

GenotypeGenotypeThe offspring’s The offspring’s ________________________________________

TT, Tt, ttTT, Tt, tt

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Homozygous vs. Homozygous vs. HeterozygousHeterozygous_______________ _______________ (“homo” means “same”)(“homo” means “same”)

Having two identical alleles for a Having two identical alleles for a traittrait

TT, ttTT, tt

________________ ________________ (“hetero” means (“hetero” means “different”)“different”)

Having two different alleles for a Having two different alleles for a traittrait

TtTt

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____________ square____________ squareShort way to find the Short way to find the expected proportions of expected proportions of possible genotypes in the possible genotypes in the offspring of a ________________.offspring of a ________________.

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Mendel’s Punnett Mendel’s Punnett SquareSquare

11stst generationgenerationT = TallT = Tall

t = shortt = shortTT x ttTT x tt

TT TT

tt

ttTTtt TTtt

TTtt TTtt

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Interpreting the Punnett Interpreting the Punnett SquareSquare

All ____________ are All ____________ are heterozygous tall heterozygous tall (Tt)(Tt)Ratio Ratio

________ (Tall : Short)________ (Tall : Short)PercentagePercentage

________ Tall________ Tall

Each offspring box Each offspring box represents _______ of represents _______ of the population of the population of offspring producedoffspring produced

TT TT

tt

ttTTtt TTtt

TTtt TTtt

Tall = TShort = t

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Mendel’s Punnett Mendel’s Punnett SquareSquare

22ndnd generationgenerationTall = ____

Short = ___

Parents: _______ x _______Parents: _______ x _______

oHomozygous Tall: Homozygous Tall: oGenotype: _______ Genotype: _______ oHow many? ______How many? ______

oHeterozygous Tall: Heterozygous Tall: oGenotype: _______ Genotype: _______ oHow many? ______How many? ______

oShort: Short: oGenotype: _______Genotype: _______oHow many? ______How many? ______

oTOTAL # OF TALL: _____TOTAL # OF TALL: _____oTOTAL # OF SHORT: _____TOTAL # OF SHORT: _____

oRatio of Tall : Short Ratio of Tall : Short __________ __________oPercentages: Percentages:

oPercent Tall: ___________Percent Tall: ___________oPercent Short: __________Percent Short: __________

TT

tt

TtTt TtTt

TT ttTT t t

TTTT TtTt

TtTt tttt

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TtTt

11

11

3:13:1

75%75%

1313

GGENETICSENETICS

Patterns of HeredityPatterns of Heredity

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Simple Mendelian Simple Mendelian InheritanceInheritanceThe type of inheritance we The type of inheritance we have discussed thus far have discussed thus far (Mendel’s peas)(Mendel’s peas)

Not all patterns in heredity Not all patterns in heredity are as simple…are as simple…

There is more than just There is more than just dominant and recessivedominant and recessive

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Incomplete Incomplete DominanceDominanceThe phenotype of the The phenotype of the ____________is intermediate ____________is intermediate (____________) between those of (____________) between those of the two __________________.the two __________________.

For Example:For Example:A cross between a particular A cross between a particular RED flower and a WHITE flower RED flower and a WHITE flower will produce a _____________ will produce a _____________ flowerflower

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Punnett Square for Punnett Square for Incomplete Incomplete

DominanceDominance

RR = RedRR = RedR’R’ = R’R’ = WhiteWhite

RR’ = PinkRR’ = Pink

Cross:Cross:

(RR) Red flower X (R’R’) White flower(RR) Red flower X (R’R’) White flower

RR RR

RR’’RR’’

RRR’R’ RRR’R’

RRR’R’ RRR’R’

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______________________________________The phenotypes of both The phenotypes of both homozygotes is produced homozygotes is produced (__________or strips) in the (__________or strips) in the ________________ individual________________ individual

For Example:For Example:A black rooster and a white hen A black rooster and a white hen might produce a chick with might produce a chick with some black feathers and some some black feathers and some white featherswhite feathers

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Multiple Alleles Multiple Alleles Traits controlled by more than Traits controlled by more than ___alleles …___alleles …

For Example:For Example:______________alleles are ______________alleles are commonly seen in the coat commonly seen in the coat color of rabbits (as well as in color of rabbits (as well as in dogs, cats, horses, humans, dogs, cats, horses, humans, hamsters etc.) hamsters etc.)

Also… Blood Typing…Also… Blood Typing…

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Multiple Alleles – Blood Multiple Alleles – Blood Types Types

Human blood types are Human blood types are determined by the ____________ or determined by the ____________ or __________of certain molecules on __________of certain molecules on the surfaces of red blood cellsthe surfaces of red blood cells

There are three alleles for blood There are three alleles for blood type…type…

IIAA …………………… written as “A” …………………… written as “A”

IIBB …………………… written as “B” …………………… written as “B”

i …………………… written as “O”i …………………… written as “O”

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Sex-linked traitsSex-linked traitsTraits that are controlled by genes Traits that are controlled by genes located on sex chromosomeslocated on sex chromosomes

These traits help explain why some These traits help explain why some characteristics and disorders are characteristics and disorders are more common in one sex than in more common in one sex than in the otherthe other

Commonly referred to as “X-Commonly referred to as “X-linked” because the trait is usually linked” because the trait is usually linked to the X-chromosomelinked to the X-chromosome

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Background Background InformationInformation

Humans have _______chromosomes; Humans have _______chromosomes; or ________ pairs of chromosomesor ________ pairs of chromosomes

Of these, 22 pairs are autosomes Of these, 22 pairs are autosomes auto auto

means “self”means “self” (“self” chromosomes (“self” chromosomes for the body)for the body)

The last (23The last (23rdrd) pair is different in ) pair is different in males & females… these are the ______ males & females… these are the ______ chromosomeschromosomes

Females have two “X” chromosomes Females have two “X” chromosomes (______)(______)

Males have one “X” and one “Y” Males have one “X” and one “Y” chromosome (_____)chromosome (_____)

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““Sex-linked” traitsSex-linked” traits

B = Blue eyesB = Blue eyesb = Green b = Green

eyeseyes

Green-eyed male (XGreen-eyed male (XbbY)Y)

XX

Heterozygous Blue-eyed female (XHeterozygous Blue-eyed female (XBBXXbb) )

XX____ YY

XX____

XX____

XXBBXXbb

XXbbXXbb XXbbYY

XXBBYY

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““Sex-linked” traitsSex-linked” traits

B = Blue eyesB = Blue eyesb = Green b = Green

eyeseyes

Green-eyed male Green-eyed male (X(XbbY)Y)

XX

Heterozygous Heterozygous Blue-eyed female Blue-eyed female

(X(XBBXXbb) )

XXbb YY

XXBB

XXbb

XXBBXXbb

XXbbXXbb XXbbYY

XXBBYY

OFFSPRINGOFFSPRING• MALES (XY)MALES (XY)

•Blue EyesBlue Eyes•Genotype _______Genotype _______•How many? _____How many? _____

•Green EyesGreen Eyes•Genotype _______Genotype _______•How many? _____How many? _____

•FEMALES (XX)FEMALES (XX)•Blue EyesBlue Eyes

•Genotype _______Genotype _______•How many? _____How many? _____

•Green EyesGreen Eyes•Genotype _______Genotype _______•How many? _____How many? _____

XBY

XbY

1

1

XBXb

1

XbXb

1

24MalesMalesFemalesFemales

Sex-linked Sex-linked percentagespercentages

B = Blue eyesB = Blue eyesb = Green b = Green

eyeseyes

Green-eyed male Green-eyed male (X(XbbY)Y)

XX

Heterozygous Heterozygous Blue-eyed female Blue-eyed female

(X(XBBXXbb) )

XXbb YY

XXBB

XXbb

XXBBXXbb

XXbbYY

oPercentagesPercentages

oWhen figuring percents for When figuring percents for sex-linked punnett squares, sex-linked punnett squares, you must be careful to only you must be careful to only count what is asked for…count what is asked for…

% of females with blue eyes% of females with blue eyes

% of males with blue eyes% of males with blue eyes

% of females with green eyes% of females with green eyes

% of males with green eyes% of males with green eyes

50%50%

50%50%

50%50%

50%50%

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Polygenic Inheritance Polygenic Inheritance When a trait is controlled by When a trait is controlled by more than one genemore than one gene

For Example:For Example:Skin color is actually the Skin color is actually the accumulation of dominant accumulation of dominant genes for pigment in the skingenes for pigment in the skin