3.1 mendel´s work
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3.1 mendel´s work

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  • http://www.brainpop.com/science/cellularlifeandgenetics/heredity/
  • Gene: It is a segment of DNA on a chromosome that codes for a specific trait

3.1 mendel´s work 3.1 mendel´s work Presentation Transcript

  • Chapter 3Genetics: The science of heredity Miss Luzma Fabre
  • Section 1: Mendel´s workGregor Mendel madeexperiments on plants thatrevolutionized the study ofheredityHeredity is the passing ofphysical characteristics fromparents to offspring
  • Each different form of a characteristic iscalled a traitEx: eye colorMendel observed plant traits such asheight and seed colorGenetics is the study of heredity
  • Mendel´s experiments Mendel used pea plants He developed a method by which he cross- pollinated, or “crossed” pea plants: he took pollen from one and brushed it into the second plant Fertilization is the process in which an egg cell and a sperm cell join to form a new organism
  • Crossing pea plantsMendel crossed plants with contrastingtraits (ex: tall and short)He started with purebred plantsA purebred organism is the offspring ofmany generations that have the sametrait
  • The F1 offspringMendel crossed purebred tall plantswith purebred short plants (P= parentalgeneration)The offspring from this cross are calledF1 generationAll the F1 plants were tall
  • The F2 offspringThe F1 generation self-pollinated,resulting in the F2 generationSome plants were tall and some shortin the F2 generationTall= ¾ plantsShort= ¼ plants
  • In all of Mendel´s crosses, only oneform of the trait appeared in the F1generation. However, in the F2generation, the “lost” form of thetrait always reappeared in about onefourth of the plants
  • Dominant and recessive allelesA gene is the set of information that controls atrait.Alleles are the different forms of a geneAn orgnaism´s traits are controlled by the allelesit inherits from its parents. Some alleles aredominant, while other alleles are recessive.
  • A dominant allele is one whose traitalways shows up in the organism whenthe allele is present. Ex: YA recessive allele is hidden wheneverthe dominant allele is present. Ex: y
  • A hybrid is an organism that has 2different alleles for a traitEx: Yy
  • A dominant allele is represented by acapital letter (Ex. T= tall)A recessive allele is represented by alowercase letter (Ex. t= short)Examples:Purebred= TT, ttHybrid= Tt
  • Mendel´s contributionMendel´s discoveries demonstrated thattraits are determined by individual,separate alleles inherited from eachparent rather than being a blend fromthe parents´traits