less genetic variability to select improved varieites
repro resulting from the fertilization of ovules and subsequent formation of viable seed
sexual reproduction
the union of pollen nucleus with the egg nuclei
fertilization
transfer of pollen from the stamen to the pistil
pollination
plants where the pistil is pollinated by the stamen of the same plant
self-pollinated plants
plants whose pistil is pollinated with pollen from different plants by insects or wind
cross-pollinated plants
unique characteristics controlled by one or more genes
traits
unit of inheritance passed from parents to offspring located on chromosomes
genes
forms of a gene
allele
allele expressed only in homozygous condition
recessive allele
allele that expresses itself whenever present
dominant allele
when reproductive cells are formed, the gene pairs seperate and are distributed as units to each gamete
law of segregation
the distribution of one pair of factors is independent of the distribution of other pairs
law of independent assortment
alleles must be on different chromosomes
law of independent assortment
hybridization involving a single allele
monohybrid cross
hybridization involving two alleles
dihybrid cross
what is the purpose of plant breeding?
to produce new crop cultivars and varieties with improved agronomic traits
what is considered during plant breeding?
yield
pest resistance
maturity
quality
response to speceific situations
the extent to which a plant's phenotype is the result of the genotype rather than the environment
hertiability
equation of heritability
phenotype= genotype+environment
how to figure out heritability
H=Vg/Vg+Ve*100
the greater the heritability,
the greater the chance to develop plants with that trait
factors affecting crop production that is the result of growing conditions
environmental variations
examples of differences in environmental variations
soil type
fertility
pest infestation
how do you test for environmntal influence?
grow plants with similar heredity in different environments
variation that results from genetic differences
heredity variation
genetic variability originates from
gene recombinations after hybridization
mutations
polyploidy
sudden changes in heredity material of a cell
mutations
what do mutations result from?
change in gene from one allele to another
rearrangement of chromosome material
loss or duplication of chromosome segments
typically, mutations are
lethal
are mutations dominant or recessive?
typically recessive
a condition in which individuals have more than 2 chromosome sets or genomes in their somatic cells
polyploidy
what is the significance of polyploidy
adds genetic diversity
recessive traits are more likely to appear
what is the purpose of selection?
to select a plant with superior features
the selection of a quantity of plants with similar characteristics while still maintaining some diversity in the gene pool
mass selection
the improvement of a trait of a hybrid over its parents
hybridization
a form of recurrent hybridization by which a superior characteristic may be added to an otherwise desirable variety
backcrossing
how is backcrossing done?
two parents are crossed where one is a productive variety which lacks some superior quality and another with a superior quality but is otherwise not desierable
a species is a group of organisms that
mate
produce viable offspring
offspring also mate and produce viable offspring
subspecies
members of hte same species that have become geographically isolated
an organism with one or more genes from another species
GMO
naturalists began to identify hybrids of plants (began plant breeding)
1700s
Gregor mendel- father of modern genetics
1856
Louis Pasteur defines role of micro-organisms and establishes the science of microbiology
1861
first in vitro culture of a whole plant
1950
Watson & Crick discovered the double helix of DNA
1953
green revolution-introduction of hybrid crops into food-short third world
1970s
researches able to isolate genes
1973
discovery of plasmids and restriction enzymes in bacteria
1970s
recombinant DNA technology discovered
1980s
the ability to transfer pieces of genetic info from one organism to another
gene splicing or genetic engineering
first commercial application of gene splicing; human insulin for diabetes
1982
first genetically engineered plant
1983
tobacco
plants ressitant to insects, viruses and bacteria; first field tests
1985
field trial for Bt cotton
1990
Monsanto created; approved for sale
1995-1996
round up ready cotton first commercialzied
1997
YieldGard corn sold in US
1998
GMO crops used
soybeans
cotton
corn
canola
organisms taht have one or more genes fro ma different species using recombinant DNA technology
transgenic plants (GMO)
what is the goal of transgenic plants?
design organisms with specific characteristics by the artificial insertion of genes from other species
discrete segments of DNA that encodes the info necessary for assembly of a specific protein-trait
gene
production of multiple copies of a gene
gene cloning
recombination or joining DNA segments from two different species
Recombinant DNA
enzyme that cuts stands of DNA at specific places
restriction enzyme
enzyme that can join sticky ends of two strands of DNA
DNA ligase
delivery vehicle used to introduce rDNA into a host cell
vector
molecules of DNA that are found in bacteria seperate from the bacterial chromosome
plasmids
changes in the DNA sequence of a gene
mutation
steps of genetic engineering
isolate desired gene
remove DNA from donor with restriction enzyme
transfer novel gene to the host through a vctor
a soil bacterium that causes crown galls in many plants
Agrobacterium tumefaciens
how does agrobacterium tumefaciens work?
in vivo infection requires wounding of the plant tissue
the bacteria attaches to the cell wall and is activated by compounds from the wounded cell
how does the gene cannon work?
minute metal beads of gold coated with DNA are shot directly into plant cells and as the plant heals, some of the DNA is incorporated into the plant
what plants are resistant to broad spectrum herbicides (round up ready)
corn
cotton
soybeans
canola
what bacteria is the gene donor in round up ready GMOs?
salmonella
how do round up ready GMOs work?
degrades herbidice inside the plant
what plants are Bt crops?
cotton
potatoes
corn
what is the gene donor in Bt crops?
bacillus thuringiensis
how do Bt crops work?
insecticidal toxin for control of catepillars
what are the pro's of transgenic crops?
cost effective
fewer pesticides needed
what are the con's of transgenic crops?
more pesticides needed
cost
more evolutionary pressure; greater chance of resistance
possibility of transferring genetic materials to other organisms
environmental consequences
effects on non-target organisms (allergins, toxins)