11 13 09 Notes
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11/13/09 – Notes Monohybrid cross P generation – true breeding parents F1 generation – hybrids 3:1 ratio = monohybrid cross Phenotype – 3 red, 1 white Genotype – RR – red Rr – red [dominant] rr – white [recessive] Dominance – functional protein generates pigment. Recessive – wrong shaped mutative protein, wrong amino acid sequence, does not work properly, and therefore is not displayed Law of Segregation -In diploid organisms, the “paired factors” (alleles on homologous chromosomes) are separated during the production of gametes. -The purple allele was said to be dominant over the white allele which is said to be recessive. -When a dominant allele is present that allele will show its trait.
Transcript of 11 13 09 Notes
11/13/09 – Notes
Monohybrid crossP generation – true breeding parentsF1 generation – hybrids
3:1 ratio = monohybrid crossPhenotype – 3 red, 1 whiteGenotype – RR – red Rr – red [dominant] rr – white [recessive]
Dominance – functional protein generates pigment.Recessive – wrong shaped mutative protein, wrong amino acid sequence, does not work properly, and therefore is not displayed
Law of Segregation-In diploid organisms, the “paired factors” (alleles on homologous
chromosomes) are separated during the production of gametes.-The purple allele was said to be dominant over the white allele which is
said to be recessive.-When a dominant allele is present that allele will show its trait.-Recessive alleles only show their trait when there is no dominant allele
present.
Genotype vs. Phenotype
Genotype PhenotypeHomozygous – PP Purple flowersHeterozygous – Pp Purple flowersHomozygous – pp White flowers
Phenotypic ration: 3:1 [3 purple, one white]Genotypic ratio: 1:2:1 [1/4 PP, 2/4 Pp, 1/4 pp
Mendel used “true breeding” [homozygous] parents.-Homozygous – purple plants PP, and homozygous white plants pp-But, how did Mendel know his purple plants were “homozygous” PP and not “heterozygous” Pp which also have purple flowers?
Test cross – cross unknown genotype with known genotype. [Know white for sure pp]. 2 possibilities – parent is PP, or Pp. Outcome can be seen and will be different.]
Organisms contain many alleles, how does the segregation of the alleles of one trait effect the segregation of the alleles of another trait?Mendel did experiments where he followed two traits, called a dihybrid cross
The Dihybrid Cross-By the law of independent assortment, each pair of alleles ssegregates
into gametes independently.-Mendelian inheritance reflects the rules of probability
-Rule of multiplication, Rule of addition.
Dihybrid cross-cross yellow, round seeds YYRR with green, wrinkled seeds yyrr
“Letters” separated during meiosis
FOIL YyRr-YR-Yr-yR-yr
Dihybrid cross: 9:3:3:1 ratio.
