GENETICSNature’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