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11/18/12
Ch 13: Genetics &
Ch 14 Plant Breeding (some)
His garden
His experimental
subject: garden pea
J. Gregor Mendel:
father of genetics
Mendel’s Discoveries
Do parents contribute equally to offspring?
Is there an equal chance of getting either version of a
characteristic that a parent has?
Are characteristics/traits found only in 1 form?
Do the versions from each parent blend together?
How do the versions interact?
Are characteristics inherited independently of 1
another or together?
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Do parents contribute equally to offspring? yes
Is there an equal chance of getting either version of a
characteristic that a parent has?
yes
Are characteristics/traits found only in 1 form? no
Mendel’s Discoveries
Do parents contribute equally to offspring?
Is there an equal chance of getting either version of a
characteristic that a parent has?
Are characteristics/traits found only in 1 form?
Do the versions from each parent blend together?
usually not
How do the versions interact?
Dominant -> visible result
Recessive -> something missing
Mendel’s Discoveries
Do parents contribute equally to offspring?
Is there an equal chance of getting either version of a
characteristic that a parent has?
Are characteristics/traits found only in 1 form?
Do the versions from each parent blend together?
How do the versions interact?
Are characteristics inherited independently of 1
another or together?
if on different chromosomes, no
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Remember:
Independent Assortment
in Meiosis I
Example:
Chromosomal
arangements in cells
with 2n = 6
(these will give
gametes with n = 3)
Pea
chromosomes
Are characteristics
inherited
independently of 1
another or together?
if on the same
chromosome, possibly
yes, but sometimes
possibly no (why?)
Genetic
Vocabulary
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YY
Genotype:
Y
Yy
Y
Phenotype: yellow seeds
Y
yy
y
y
y
yellow seeds green seeds
Punnett Square: used to predict the trait(s) of offspring from a
mating
Monohybrid Cross: Inheritance of 1 trait
Other parents can be AA or aa or Aa (like these)
Monohybrid
cross: follow
1 trait
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Dihybrid cross:
follow 2 traits
simultaneously
Pleiotropic gene: 1 gene, many effects
Polygenic trait:
trait governed
by more than 1
gene
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Incomplete
dominance: the
recessive
modifies the effect
of the dominant
Multiple alleles:
Coleus leaf color & pattern
Pea chromosomes
Linkage: how often
do 2 traits travel
together
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Hardy-Weinberg Law: used to examine if evolution is
occurring in a population
Then examine next generation
Is the ratio of green to yellow
genes present in that generation,
the same as the first?
Starting population
If it is – no evolution is happening
If it isn’t – evolution is occurring
Maternal inheritance
DNA is the genetic material
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DNA
nucleotide
RNA
U
nucleotide
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Amino acid
hydrolysis
Building a polypeptide/
protein
dehydration
synthesis
Peptide bond
Protein structure:
alpha helix
3 or 4 levels
DNA Replication
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Base-pairing rules
In
eukaryotes
Non-template
strand
Non-template
strand
DNA!
Template
strand
3
5 5 3
DNA!
RNA!
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3 kinds of RNA:
messenger
transfer
ribosomal
Genetic Code
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Initiation
Elongation
Termination
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Origins of agriculture
6 major food plants feed most people (80% of all calories consumed):
wheat, rice, maize (corn), potato, sweet potato, cassava/
manioc (from 30,000 known edible plants)
How did we get these?
Careful initial choice
Breeding of favorable varieties
mutations
Choice of unusual individuals
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Case study:
modern bread wheat
polyploidy = extra sets of
chromosomes -> leads to ?
2x
(Cultivated 10,000
yr BP); durum
wheat similar
2x
(~ 8,000 yr BP)
Newer
technology:
Genetic
engineering
- adding new
genes
Polymerase chain reaction = PCR
makes more DNA (small pieces) rapidly
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Cloning by plant tissue
culture
Cloning by cuttings, etc.
Transgenic plants:
Color change
Transgenic potatoes: pest -resistant
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Transgenic tomatoes:
salt tolerance
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