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THE DIHYBRID CROSS Studying the inheritance of two characters simultaneously © 2007 Paul Billiet ODWSODWS
Mendel’s peas CharacterTraitAllele Seed shapeRound Wrinkled Cotyledon colourYellow Green © 2007 Paul Billiet ODWSODWS
Combinations GenotypePhenotype Round Yellow Round Green Wrinkled Yellow Wrinkled Green © 2007 Paul Billiet ODWSODWS
Is the inheritance of one character affected by the inheritance of another? P Phenotypesx(Pure Bred) F 1 PhenotypesAll(Selfed) F 2 Phenotypes Seedcolour YellowGreenTOTALRATIO SeedRound315108423 shapeWrinkled10132133 TOTAL416140556 RATIO © 2007 Paul Billiet ODWSODWS
A dihybrid cross can be treated as two separate monohybrid crosses The expected probability of each type of seed can be calculated: Probability of an F 2 seed being round = Probability of an F 2 seed being wrinkled = Probability of an F 2 seed being yellow = Probability of an F 2 seed being green = © 2007 Paul Billiet ODWSODWS
Therefore Probability of an F 2 seed being round and yellow = ¾ x ¾ = 9/16 =56.25% Probability of an F 2 seed being round and green = Probability of an F 2 seed being wrinkled and yellow = Probability of an F 2 seed being wrinkled and green = © 2007 Paul Billiet ODWSODWS
Predicting how many seeds we could expect to get in a sample We could expect What Mendel observed 556 x 9/16 round yellow313315 556 x 3/16 round green108 556 x 3/16 wrinkled yellow101 556 x 1/16 wrinkled green32 © 2007 Paul Billiet ODWSODWS
THE LAW OF INDEPENDENT ASSORTMENT It appears that the inheritance of seed shape has no influence over the inheritance of seed colour The two characters are inherited ___________________ The pairs of alleles that control these two characters assort themselves independently © 2007 Paul Billiet ODWSODWS
Mendel & Meiosis The pairs of chromosomes could orientate in different ways at Anaphase 1 © 2007 Paul Billiet ODWSODWS
PPhenotypesRound Yellow seed XWrinkled Green seed (Pure bred) GenotypesRRYYrryy meiosis GametesRYry fertilisation F1F1 PhenotypesRrYy(Selfed) GenotypesRound Yellow Proportions100% Dihybrid cross genetic diagram © 2007 Paul Billiet ODWSODWS
F1F1 PhenotypesRrYy(Selfed) GenotypesRound Yellow Proportions100% meiosis GametesYy R r Dihybrid cross genetic diagram © 2007 Paul Billiet ODWSODWS
GametesYy RRYRy rrYry fertilisation F2F2 GenotypesRYRyrYry RY Ry rY ry Dihybrid cross genetic diagram © 2007 Paul Billiet ODWSODWS
Dihybrid cross proportions PhenotypesProportions Round Yellow9/16 or56.25% Round Green Wrinkled Yellow Wrinkled Green © 2007 Paul Billiet ODWSODWS
Dihybrid test cross In monohybrid crosses, to know if a dominant trait is homozygous (RR) or heterozygous (Rr) it is necessary to carry out a _____________ This is done with a ___________________ (rr) individual The same is true for a dihybrid cross where the test cross is made with an individual which is homozygous recessive for ______ characters (rryy) © 2007 Paul Billiet ODWSODWS
Dihybrid test cross PhenotypesX Genotypes Gametes GenotypesRYRyrYry PhenotypesRound Yellow Round Green Wrinkled Yellow Wrinkled Green Proportions © 2007 Paul Billiet ODWSODWS
THE DIHYBRID CROSS Studying the inheritance of two characters simultaneously © 2007 Paul Billiet ODWSODWS.
Definition Crosses looking at two traits simultaneously Mendels law of segregation states that Mendels law of independent assortment states that.
GENERAL GENETICS (PRACTICAL SESSION) BIO221 LECTURER ALSHEHRI, DOKHNAH SAEED Alshehri, Dikhnah Saeed.
THE DIHYBRID CROSS Studying the inheritance of two characters simultaneously BY- DR (Mrs.) T.S.KHAN (PGT BIOLOGY)
THE DIHYBRID CROSS Studying the inheritance of two traits simultaneously © 2007 Paul Billiet ODWSODWS.
Jumpstart 11/27 Create a Venn Diagram comparing monohybrid and dihybrid crosses. Your venn should have at least 5 differences and 3 similarities.
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Dihybrid Crosses Inheritance of two characteristics at the same time Objective: E3 - Predict possible outcomes of various genetic combinations such as…dihybrid.
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Test Cross Tall (dominant phenotype) plants of the F1 generation will have one of the following genotypes: DD or Dd.
Mendel and Genetic Crosses. Mendel Gregor Mendel – botanist Studied inheritance through pea plants 1850’s Pea plants – sexual reproduction Usually self-fertilize.
Genetics Take 2 Dihybrid Crosses. Monohybrid vs. Dihybrid Monohybrid crosses are crosses that examine the inheritance of only one specific trait. Dihybrid.
Genetic Crosses Section 9.2. Genotype The genetic makeup of an organism Consists of the alleles that the organism inherits from its parents Example:
Mendel also investigated the inheritance of two pairs of contrasting characters in the pea plant. This is referred to as the dihybrid cross.
Basic Genetics *. View video at: https://www.youtube.com/watch?v=YxKFdQo10rE.
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Chapter 11: Introduction to Genetics Section 11-2: Applying Mendel’s Principles 1.
Chapter ,9.5, Homologous chromosomes bear the alleles for each character P P a a B b PP aa Bb Dominant allele Recessive allele Gene.
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BIOLOGY 12 Two-Trait Inheritance Dihybrid Cross. Remember Mendel’s Peas… CharacterTraitAllele Seed shapeRoundR Wrinkledr Seed colourYellowY Greeny.
Review Monohybrid & Dihybrid Crosses. DOMINANT/RECESSIVE _____________ allele is represented by a ____________ letter. (usually the first letter of the.
1 Review What is probability Use Models How are Punnett squares used to predict the outcomes of genetic crosses 2 Review What is independent assortment.
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GENETICS Why do you look like that?!?. A little background… Gregor Mendel- “Father of Genetics” –Austrian monk and biologist in the mid-1800s –Used pea.
Genetics often comes down to probability Mendel stated that traits in an organism are controlled by different factors ◦ We know that each allele is.
Dihybrid Inheritance Dihybrid inheritance refers to the simultaneous inheritance of two characters.
Monohybrid Cross. F1 Cross 2 factor test cross Parents= RRYY x rryy Test for Color & Shape RY ry F1 generation Homozygous dominant Homozygoys recessive.
Chapter 11-3: Exploring Mendelian Genetics. To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles,
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Gregor Mendel carried out the first important studies of HEREDITY used pea plants which reproduce sexually by way of sex cells called gametes.
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Genetics: an Introduction. Genetics: the study of Heredity Heredity: transmission of traits from one generation to the next Gregor Mendel: father of modern.
Is the likelihood that something will happen. Expressed as a decimal, percentage, or a fraction. Genes combine according to the rules of probability.
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