mendel’s theory
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Mendel’s Theory. Mendel: The man, the myth , the legend. Mendel’s Hypotheses. Mendel found that there are two separate “heritable factors” for each trait Alleles. Mendel’s Findings in Modern Terms. Dominant alleles Recessive alleles Homozygous Heterozygous Genotype Phenotype. - PowerPoint PPT PresentationTRANSCRIPT
Mendel’s TheoryMendel’s Theory
Mendel: The man, the Mendel: The man, the myth , the legendmyth , the legend
Mendel’s HypothesesMendel’s Hypotheses Mendel found that there are two Mendel found that there are two
separate “heritable factors” for each separate “heritable factors” for each traittrait AllelesAlleles
Mendel’s Findings in Modern Mendel’s Findings in Modern TermsTerms
Dominant allelesDominant alleles
Recessive alleles Recessive alleles
HomozygousHomozygous
HeterozygousHeterozygous
GenotypeGenotype
PhenotypePhenotype
Laws of HeredityLaws of Heredity
Law of SegregationLaw of Segregation The two alleles for a trait segregate The two alleles for a trait segregate
when gametes are formedwhen gametes are formed Law of Independent AssortmentLaw of Independent Assortment
Found that inheritance of one trait does Found that inheritance of one trait does not influence inheritance of any other not influence inheritance of any other traittrait
Punnett SquaresPunnett Squares
A diagram that A diagram that predicts the predicts the expected outcome expected outcome of a genetic crossof a genetic cross
The cross of a long-stem (LL or Ll) The cross of a long-stem (LL or Ll) and short-stem (ll) plants involves a and short-stem (ll) plants involves a single pair of alternate single pair of alternate characteristics. Give the genotype characteristics. Give the genotype and phenotype ratios of the F1 and phenotype ratios of the F1 generation when a homozygous long-generation when a homozygous long-stem plant is crossed with a short stem plant is crossed with a short stem plant.stem plant.
Cross plants from the F1 generation Cross plants from the F1 generation in the above problem and determine in the above problem and determine the genotype and phenotype ratios the genotype and phenotype ratios of the F2 generation.of the F2 generation.
ProblemProblem In pea plants, inflated pods are dominant to In pea plants, inflated pods are dominant to
constricted pods. Show the cross between a constricted pods. Show the cross between a true-breeding inflated pod plant with a true-true-breeding inflated pod plant with a true-breeding constricted pod plant. What are breeding constricted pod plant. What are the expected phenotypes and in what the expected phenotypes and in what proportion?proportion?
ProblemProblem In goats, a recessive gene causes the goats In goats, a recessive gene causes the goats
to "faint" when they are startled. A farmer to "faint" when they are startled. A farmer breeds two goats (that have never fainted) breeds two goats (that have never fainted) and their first offspring faints two days after and their first offspring faints two days after its birth. What must the parent's genotypes its birth. What must the parent's genotypes have been? Show the cross to prove it.have been? Show the cross to prove it.
Determining Unknown Determining Unknown GenotypesGenotypes
Perform a test crossPerform a test cross An organism with an unknown genotype An organism with an unknown genotype
is crossed with a homozygous recessive is crossed with a homozygous recessive individualindividual
ExampleExample
A pea plant with A pea plant with yellow seeds has yellow seeds has an unknown an unknown genotype. It is genotype. It is crossed with a crossed with a plant with green plant with green seeds.seeds.
YyYy YyYy
YyYy YyYy
YyYy yyyy
YyYy yyyy
Y Y
y
y
Y y
y
y
Dihybrid ProblemDihybrid Problem
In peas, the allele for tall (T) plants is In peas, the allele for tall (T) plants is dominant to the allele for dwarf (t) plants and dominant to the allele for dwarf (t) plants and the allele for round (R) peas is dominant to the allele for round (R) peas is dominant to that for wrinkled (r) peas.that for wrinkled (r) peas.
Find both phenotypic for the results of the Find both phenotypic for the results of the following cross:following cross:
TtRrTtRr xx TtRrTtRr
Dominant or Recessive?Dominant or Recessive?
Family GeneticsFamily Genetics