basic genetics gregor mendel the father of genetics
TRANSCRIPT
Basic GeneticsBasic Genetics
Gregor Mendel
The Father
of Genetics
Objectives:Objectives: To distinguish between To distinguish between
heredity and inheritanceheredity and inheritance
To define pollinationTo define pollination
To identify the major parts To identify the major parts of a flowering plantof a flowering plant
To describe Mendel’s To describe Mendel’s experiments in heredityexperiments in heredity
HeredityHeredity – – transmission of transmission of traits traits from parents tofrom parents to their their
offspringoffspring
Inheritance passing of traits byheredity
Mendel’s experimentsMendel’s experiments used pea plantsused pea plants
PollinationPollination – transfer of pollen from – transfer of pollen from anthers to stigma in flowersanthers to stigma in flowers
1)1) self pollination self pollination occurs within the occurs within the same flowersame flower or or same plantsame plant
2) 2) cross pollinationcross pollination occurs between occurs between different plantsdifferent plants
Receptical
Mendel’s Crosses with Pea PlantsMendel’s Crosses with Pea Plants
Pure tallplants
X Pure shortplantsP1
parentalgeneration
Cross Pollination
All Tall plantsF1
first filialgeneration
Self Pollination
787 tall plants, 277 short plants F2
second filialgeneration
3 to 1 ratio
Objective:Objective:
To describe Mendel’s 3 To describe Mendel’s 3 principles of inheritanceprinciples of inheritance
1) 1) Principle of Dominance and Principle of Dominance and RecessivenessRecessiveness
Each trait is Each trait is controlled by 2 controlled by 2 factorsfactors, , one one factor factor ((dominant dominant ) ) may may mask the othermask the other factor factor ((recessiverecessive ) ) preventing it from having an effect.preventing it from having an effect.
P1 F1 F2
2) 2) Principle of SegregationPrinciple of Segregation
The two The two factors for a factors for a characteristicharacteristic c separate separate during the during the formation of formation of eggs and eggs and sperm.sperm.
3) 3) Principle of Independent Principle of Independent AssortmentAssortment
Factors for Factors for different different characteristics characteristics are are distributed distributed to reproductive to reproductive cells cells independently.independently.
Objectives:Objectives:
To define geneTo define gene
To define alleleTo define allele
GeneGene – segment of DNA on a – segment of DNA on a chromosome that chromosome that codes for a codes for a
particular proteinparticular protein
genes genes occur in occur in pairspairs
AlleleAllele – alternative form of a gene – alternative form of a gene
g = yellow pods
G = green pods
t = short
T = tall
Dominant capital letter
Recessive Lowercase letter
Objectives:Objectives:
To define genotype and To define genotype and phenotypephenotype
To distinguish between To distinguish between homozygous and homozygous and heterozygousheterozygous
To define multiple allelesTo define multiple alleles
GenotypeGenotype – – genetic makeup genetic makeup of an organism ( of an organism (genesgenes))
(internal information)
(external appearance)
Phenotype –physical characteristics of an organism
What does Phenotypes come form
Example of Genotype and Example of Genotype and PhenotypePhenotype
TT
genotype
Tall
phenotype
HomozygousHomozygous – – when when both both allelesalleles of a pair are the of a pair are the samesame
homozygous dominant
homozygous recessive
TT
tt
HeterozygousHeterozygous – – when when bothboth allelesalleles of a pair are of a pair are notnot the samethe same
heterozygous (tall)
Tt
Multiple allelesMultiple alleles – – 3 or more3 or more alleles alleles that control a trait that control a trait
ExampleExample – blood type (I – blood type (IAA,I,IBB,i,ioo))
GENOTYPESGENOTYPES IIAAIIAA IIAAiioo
RESULTING PHENOTYPESRESULTING PHENOTYPES Type AType A Type AType A
IIBBIIBB IIBBiioo
Type BType B Type BType B
IIAAIIBB Type ABType AB
iiooiioo Type OType O
Objectives:Objectives:
To define probabilityTo define probability
To predict the results To predict the results of monohybrid of monohybrid crosses by using a crosses by using a Punnett squarePunnett square
Probability =number of times a particular event occursnumber of opportunities for the event to occur
ProbabilityProbability – likelihood that a – likelihood that a particular event will occurparticular event will occur
Example 1: Example 1: Flipping a CoinFlipping a Coin
Chances of coming up heads = ½
Example 2: Example 2: Rolling DiceRolling Dice
16 x
16
=136
probabilityof rolling a
six on 1 dice
probabilityof rolling a
six on 1 dice
probabilityof rolling a
six on 2 dice
monohybrid crossmonohybrid cross – –
Objectives:Objectives:
To define test crossTo define test cross
To define incomplete To define incomplete dominancedominance
To define codominanceTo define codominance
Test crossTest cross – an individual – an individual with with unknown genotypeunknown genotype is is crossed crossed withwith a a homozygous homozygous
recessiverecessive individual individual used to used to
determine the determine the genotype genotype of any of any individual whose individual whose phenotype is phenotype is dominantdominant
In rabbits, In rabbits, blackblack fur color is fur color is dominant over browndominant over brown fur color fur color
B = black furb = brown fur
bb
BB or Bb
Incomplete DominanceIncomplete Dominance
when 2 when 2 or more allelesor more alleles influence the phenotypeinfluence the phenotype
resultsresults in a trait in a trait intermediate intermediate between between the the dominantdominant and and recessive traitsrecessive traits
Incomplete Incomplete DominanceDominance
CodominanceCodominance – condition in – condition in which which both allelesboth alleles of a gene are of a gene are
expressedexpressed
exampleexample – roan coat in horses – roan coat in horses
white hair (Hwhite hair (HWW)) is codominant with is codominant with redred hair (hair (HHRR))
horses with genotype (horses with genotype (HHRRHHWW) ) have have coats with a mixture of coats with a mixture of redred andand whitewhite hairshairs (roan) (roan)
Roan CoatRoan Coat
Objectives:Objectives:
To predict the results of To predict the results of dihybrid crosses by using dihybrid crosses by using a Punnett squarea Punnett square
dihybrid crossdihybrid cross – cross – cross between individuals that involves between individuals that involves two pair of contrasting traitstwo pair of contrasting traits