1 Mendelelian Mendelelian Genetics Genetics GPS: Using Mendel’s laws, explain the role of Meiosis in reproductive variability
Jan 17, 2016
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Mendelelian Mendelelian GeneticsGenetics
GPS: Using Mendel’s laws, explain the role of Meiosis in reproductive variability
Gregor Gregor MendelMendel
(1822-1884)(1822-1884)Studied the Studied the inheritanceinheritance of of traits in traits in pea pea plantsplantsDeveloped the Developed the laws of laws of geneticsgeneticsaka aka “Father of “Father of Genetics”Genetics”
Mendel stated Mendel stated that physical traits that physical traits are inherited as are inherited as “particles”“particles”
Mendel did not Mendel did not know that the know that the “particles” were “particles” were actually actually GENESGENES
Particulate InheritanceParticulate Inheritance
Genetic TerminologyGenetic Terminology
TraitTrait - any characteristic - any characteristic that can be passed from that can be passed from parent to offspring parent to offspring HeredityHeredity - passing of traits - passing of traits from parent to offspring from parent to offspring GeneticsGenetics - study of - study of heredity heredity
Types of Genetic Types of Genetic CrossesCrossesPunnett Square Punnett Square - - cross cross
involving a single traitinvolving a single traite.g. flower color e.g. flower color AKA AKA Monohybrid crossMonohybrid crossDihybrid crossDihybrid cross - - cross cross involving two traits involving two traits e.g. flower color & plant heighte.g. flower color & plant height
Punnett SquarePunnett SquareA diagram used A diagram used to show the to show the probabilityprobability of a of a trait being trait being present in present in offspring.offspring.
““Genes”Genes”
AllelesAlleles - - two forms of a two forms of a gene gene (dominant & recessive)(dominant & recessive) DominantDominant - - stronger of two stronger of two genes. Expressed in a cross; genes. Expressed in a cross; represented byrepresented by aa capital letter (R)capital letter (R) RecessiveRecessive - - gene that shows up gene that shows up less often in a cross; is dominated less often in a cross; is dominated or or overpoweredoverpowered by the dominant by the dominant gene; represented by agene; represented by a lowercase lowercase letter (r)letter (r)
More TerminologyMore Terminology
GenotypeGenotype – – genetic makeup genetic makeup oror gene combination for a gene combination for a traittrait (e.g. RR, Rr, rr) (e.g. RR, Rr, rr) PhenotypePhenotype - - the physical the physical feature resulting from a feature resulting from a genotypegenotype (e.g. red, white) (e.g. red, white)
GenotypesGenotypesHomozygousHomozygous genotype - genotype -
gene combination where gene combination where both alleles are the same both alleles are the same (e.g. RR or rr);(e.g. RR or rr); also called also called pure bred pure bred HeterozygousHeterozygous genotype - genotype - gene combination where gene combination where the alleles are different the alleles are different ((e.g. Rr);e.g. Rr); also called also called hybridhybrid
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Mendel’s LawsMendel’s Laws
Law of DominanceLaw of Dominance •Some alleles are Some alleles are dominant dominant and some are and some are recessiverecessive..
•When combined in a When combined in a hybrid, the dominant hybrid, the dominant overpowers the overpowers the recessive.Like recessive.Like RrRr
•The dominant form of The dominant form of the trait ALWAYS shows the trait ALWAYS shows in the phenotype.in the phenotype.
Law of DominanceLaw of DominanceT = tallT = tall ( (dominantdominant))
t = shortt = short ( (recessiverecessive))
TT – tallTT – tall
Tt – tallTt – tall
tt - shorttt - short
R = roundR = round ( (dominantdominant))
r = wrinkledr = wrinkled ((recessiverecessive))
RR – roundRR – round
Rr – roundRr – round
rr - wrinkledrr - wrinkledY = yellowY = yellow ((dominantdominant))
y = greeny = green ( (recessiverecessive))
YY – YY –
YYyy – –
yyyy - -
P = purpleP = purple ((dominant)dominant)
p = whitep = white ( (recessiverecessive))
PP – PP –
PPpp – –
pppp - -
Law of SegregationLaw of Segregation
During meiosis, the During meiosis, the two allelestwo alleles responsible for a trait responsible for a trait separateseparate from each other. from each other. (when the homologous (when the homologous chromosomes separate)chromosomes separate)
Alleles for a trait are Alleles for a trait are "recombined" at fertilization"recombined" at fertilization
Study diagram!!!
Law of Law of SegregationSegregation
Let’s Practice Using SpongeBob!!!Assignments For Today!!
Begin Spongebob Practice Sheet
Watch Video to Better Understand How to use Punnett Squares.
Practice Doing Punnett Squares – Spongebob Worksheet.
Complete Lecture Quiz
Paper Pet Genetics
Power Notes
MaleGametes
Male Parent M E I O S I s
Meiosis
Female Parent
Female Gametes
Law of Independent Law of Independent AssortmentAssortment
Alleles for Alleles for differentdifferent traits are traits are distributed to the gametes distributed to the gametes independently of one independently of one another.another.
This law can be illustrated This law can be illustrated using using dihybrid crossesdihybrid crosses..
GENOTYPE vs. PHENOTYPEB – brown eyes (B – brown eyes (dominantdominant))b – blue eyes (b – blue eyes (recessiverecessive))What are the possible genotypes for brown What are the possible genotypes for brown
eyes?eyes?What are the possible genotypes for blue What are the possible genotypes for blue
eyes?eyes?
W – widow’s peak ( W – widow’s peak ( ?? ) ) w – no widow’s peak ( w – no widow’s peak ( ?? ) )Possible genotypes for having a widow’s Possible genotypes for having a widow’s
peak:peak:
Possible genotypes for not having a widow’s Possible genotypes for not having a widow’s peak:peak:
HETEROZYGOUS vs. HOMOZYGOUSF – free earlobe (F – free earlobe (dominantdominant))f – attached earlobe (f – attached earlobe (recessiverecessive) ) FF – homozygousFF – homozygousFf – Ff – ff -ff -
H – hitchhiker’s thumb ( H – hitchhiker’s thumb ( ?? ) )h – no hitchhiker’s thumb ( h – no hitchhiker’s thumb ( ?? ) )HH – HH – hh – hh – Hh - Hh -
PUNNETT PUNNETT SQUARESSQUARES
Trait: Seed ShapeTrait: Seed Shape
Alleles: Alleles: RR – Round – Round rr – Wrinkled – Wrinkled
Cross: Cross:
homozygous homozygous RoundRound seedsseeds xx Wrinkled Wrinkled seedsseeds
xx
Genotype:Genotype:
PhenotypePhenotype:
GenotypicGenotypic
Ratio:Ratio:
PhenotypicPhenotypic
Ratio:Ratio:
Trait: Seed ShapeTrait: Seed Shape
Alleles: Alleles: RR – Round – Roundrr – Wrinkled – Wrinkled
Cross: Cross:
Heterozygous RoundHeterozygous Round seeds seeds xx HeterozygousHeterozygous Round Round seedsseeds
xx
Genotype:Genotype:
PhenotypePhenotype:
G.Ratio:G.Ratio:
P.Ratio:P.Ratio:
Trait: Seed ShapeTrait: Seed ShapeAlleles: Alleles: RR – Round – Roundrr – Wrinkled – WrinkledCross:Cross: Homozygous Homozygous RoundRound seeds xseeds x Heterozygous Heterozygous
Round Round seedsseeds
Genotype:Genotype:
PhenotypePhenotype: GenotypicGenotypicRatio:Ratio:
PhenotypicPhenotypicRatio:Ratio:
MaleGametes
Male Parent M E I O S I s
Meiosis
Female Parent
Female Gametes
MaleGametes
Male Parent M E I O S I s
Meiosis
Female Parent
Female Gametes
Dihybrid Cross
▪Examines the cross of 2 different Examines the cross of 2 different traitstraits
Y = Yellow (Y = Yellow (dominantdominant))
y = green (y = green (recessiverecessive))
R = Round (R = Round (dominantdominant))
r = wrinkled (r = wrinkled (recessiverecessive))
Cross 2 heterozygous yellow, Cross 2 heterozygous yellow, heterozygous round plants: what are heterozygous round plants: what are the genotypes?the genotypes?
Seed color
Seed shape
Y = Yellow Y = Yellow y = green y = green R = Round R = Round r = wrinkled r = wrinkled
YyRrYyRr
YyRrYyRr
Summary of Mendel’s Summary of Mendel’s lawslaws
LAWLAW PARENT PARENT CROSSCROSS OFFSPRINGOFFSPRING
DOMINANCEDOMINANCE TT x ttTT x tt tall x shorttall x short
Tt Tt 100% tall 100% tall
SEGREGATIONSEGREGATION Tt x TtTt x Tt tall x talltall x tall
75% tall 75% tall 25% short25% short
INDEPENDENT INDEPENDENT ASSORTMENTASSORTMENT
RrGg x RrGgRrGg x RrGg round & round & green x green x round & round & greengreen
9/16 round seeds & green 9/16 round seeds & green pods pods
3/16 round seeds & yellow 3/16 round seeds & yellow pods pods
3/16 wrinkled seeds & 3/16 wrinkled seeds & green pods green pods
1/16 wrinkled seeds & 1/16 wrinkled seeds & yellow podsyellow pods
Non-Mendelian Non-Mendelian Inheritance Inheritance
Incomplete DominanceIncomplete DominanceOne trait is not dominant over the One trait is not dominant over the
other. other.
The offspring’s trait is a mixture of The offspring’s trait is a mixture of the 2 parents.the 2 parents.
+
CodominanceCodominanceOne trait is not dominant over the One trait is not dominant over the
other.other.Both alleles are expressed in the Both alleles are expressed in the
offspring.offspring.
++ ==WW BB WB
++
==
Homozygous Homozygous RedRed
RoanRoan
Homozygous WhiteHomozygous White
Human Blood typeHuman Blood type
POLYGENETIC TRAITPOLYGENETIC TRAIT
▪Trait produced by 2 or more genes that interact
▪Human skin color
▪Human eye color
Order of dominance: brown > green > blue.
SEX LINKED TRAITSSEX LINKED TRAITS
▪Genes located on sex chromosomes are Genes located on sex chromosomes are called sex-linked genes. called sex-linked genes.
▪Y chromosome genes in mammals are Y chromosome genes in mammals are responsible for male characteristics.responsible for male characteristics.
▪X chromosome genes in mammals affect X chromosome genes in mammals affect many traits.many traits.
SEX LINKED TRAITSSEX LINKED TRAITSMost sex linked (X-linked) disorders are Most sex linked (X-linked) disorders are
recessive and show up only in males.recessive and show up only in males.
Females are carriers of sex linked Females are carriers of sex linked disordersdisorders
PEDIGREESPEDIGREES
▪A pedigree is a chart for tracing A pedigree is a chart for tracing genes in a familygenes in a family
▪Trace phenotypes to infer the Trace phenotypes to infer the genotypesgenotypes
-Male carrier
Autosomal genes: widow’s peak-Male without trait
-Male with trait
-Female without trait
-Female with trait
-Female carrier
-Male carrier
Sex Linked genes: colorblindness M – normal color visionM – normal color vision
m - colorblindm - colorblind
-Male without trait
-Male with trait
-Female without trait
-Female with trait
-Female carrier
-Male carrier