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  Base pairs  A—T  C—G  The sequence of pairs is the code or instructions on growth, color, function, etc.  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  Genome  Single cell bacterium  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