Genetics
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GENETICS Nature’s Solar Panel ASEXUAL REPRODUCTION Reproduction without sex Genetically identical Cloning Propagating SEXUAL REPRODUCTION Fertilization between male and female plants Gametes Sexual cells Sperm Egg Gametes form a single offspring cell Zygote First cell of a new individual SEXUAL REPRODUCTION Gamete cells have 1 set of chromosomes Haploid cells Sperm (1n) Egg (1n) Sperm and egg combine to create a zygote cell with 2 sets of chromosomes (2n) Diploid cell One set from each parent Meiosis is the cell division that creates gametes Similar to mitosis SEXUAL REPRODUCTION Sperm and egg merge to form zygote Complete set of chromosomes SEXUAL REPRODUCTION Genetic recombination can spontaneously occur during meiosis Crossing over of DNA Variability SEXUAL REPRODUCTION Zygote is a diploid cell 2 sets of chromosomes (2n) Three sets can occur (3n) Triploid Sterile organism STRUCTURE OF DNA Chromosomes composed of 2 types of large molecules DNA Protein STRUCTURE OF DNA DNA is a long double helix chain Resides in nucleus Composed of nucleotides Adenine (A) Guanine (G) Cytosine (C) Thymine (T) STRUCTURE OF DNA Nucleotides form only two “rungs” on the double helix ladder A—T C—G The sequence of pairs is the code or instructions on growth, color, function, etc. Base pairs Morse code or Braille A typical plant cell contains billions of pairs GENETIC INFORMATION A segment of the DNA strand Gene Determine plant height, flower color, drought tolerance… Direct the production of enzymes (protein) Proteins function as enzymes Facilitate chemical reactions GENETIC INFORMATION The total sum of DNA in an organism’s chromosomes Single cell bacterium Genome Several thousand genomes Complex organisms 50,000 genomes DUPLICATION OF DNA Duplication of DNA needed to divide cells The base pairs are disconnected Rungs broken apart The double helix strands unzipped New pairs can be reestablished on each strand A—T C—G Two double helices are completed DUPLICATION OF DNA Mismatch error occurs about once every million pairs Mutation Corn contains 4 billion base pairs 4000 mutations possible MUTATION Causes of mismatching errors are mutagens Genetic recombination UV light Radiation Carcinogens Mismatching errors change sequence of base pairs Repair enzymes fix mutations Do not catch all of them MUTATION Most mutations are silent No visible consequence Mutations that occur in cell and passed on through mitosis Somatic mutation Not through seeds Branch that looks different than rest of plant Sport Can be propagated Naval oranges Red delicious apples MUTATION Mutations that occur in gametes Germ-line Genetic changes passed on to offspring Flower color Fragrance Taste MUTATION Mutation essential for evolution Organisms adapt to changing environment MENDELIAN GENETICS Cross breeding different characteristics Removed stamens on one parent plant Manually fertilized with pollen from other parent plant Tall pea plant x short pea plant = intermediate plant? MENDELIAN GENETICS Parent plants (P) P tall x P dwarf Offspring between parent plants (F1) P tall plant x P dwarf plant = ALL TALL PLANTS (F1) MENDELIAN GENETICS Offspring between F1 plants gives rise to F2 F1 tall plant x F1 tall plant = 3 TALL PLANTS (F2) and 1 DWARF (F2) For every 3 tall plants, there will be one dwarf MENDELIAN GENETICS Every cell has one set of chromosomes One from each parent Alternative forms of gene expression Alleles Height Seed color Flower color MENDELIAN GENETICS One allele is considered dominant G = green-pod dominant g = yellow-pod recessive Green-pod allele dominant over yellow-pod allele If both parent plants had G allele F1 offspring will have GG Green-pod If one parent plant has G allele, the other parent plant had g allele F1 offspring will have Gg Green-pod MENDELIAN GENETICS If both parent plants have g allele F1 offspring will have gg Yellow-pod MENDELIAN GENETICS Genetic make up of an organism Genotype MENDELIAN GENETICS Physical appearance of an organism Phenotype MENDELIAN GENETICS Both alleles are identical Homozygous GG = green-pod gg = yellow-pod Alleles are different Heterozygous Gg = green-pod MENDELIAN GENETICS Single trait is studied Monohybrid cross MENDELIAN GENETICS Multiple traits are linked Dihybrid cross MENDELIAN GENETICS Neither allele is completely dominant Incomplete dominance Snapdragon flower color RR = red rr = white Rr = pink MENDELIAN GENETICS Recessive allele the result of a mutation Not fully functional allele Smooth peas (SS) versus wrinkled peas (ss) s allele due to malfunction in converting glucose into starch Water loss higher during drying period S will produce adequate starch
