Midterm 2 Flashcards
(186 cards)
1
Q
DNA is packaged in ________, which come together to make _______; people say this is analogous to _________
A
histones; nucleosomes; beads on a string
2
Q
Centromere
A
where sister chromatids connect. primary constriction site. hold chromatids together
3
Q
Kinetochore
A
Attaches spindle fiber for mitosis and meiosis, located on centromere.
4
Q
Why are we diploid?
A
One chromosome from mother and one chromosome from father
5
Q
Mitosis promotes _________
A
Stability. Means that progeny are genetically identical to their parent
6
Q
Meiosis promotes __________
A
Change. Means that progeny are not genetically identical to their parents
7
Q
Autosomes are __________. Gametes are ________.
A
diploid; haploid
8
Q
Two ways meiosis creates genetic diversity
A
Crossing over and independent assortment
9
Q
Independent Assortment
A
Genes are inherited independent of one another. the allele a gamete receives for one gene does not influence the allele received for another gene.
The placement of chromosomes in the cell during cell division determines which progeny it is inherited by
10
Q
Phases of Interphase and what happens there
A
G1- copy organelles, cell grows
S- cell synthesizes a complete copy of its DNA in the nucleus
G2- cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for meiosis
G0 is the bonus jonas where cells go to chill and not divide
11
Q
Phases of Mitosis
A
Prophase- chromatin condenses, nucleolus disappears, spindle forms, nuclear envelope breaks down
Metaphase- line up in the middle
Anaphase- sister chromatids split up
Telophase- split into two daughter cells. chromatin decondenses we get our nuclear envelope back and the spindle disappears
12
Q
How many chromosomes does a skin cell have immediately after S phase (in G2)?
A
Twice as many
13
Q
The chromosome number problem
A
organisms that reproduce sexually must find a way to reduce the chromosome number in their gametes by half, to prevent an exponential increase in chromosome number.
14
Q
Chiasma
A
site of crossing over
15
Q
Meiosis I
A
Prophase 1- Chromosomes replication
Metaphase 1- homologous chromosomes pair up and crossing over happens
Chiasma- site of crossing over
Anaphase & Telophase- create haploid cells that will enter Meiosis 2. Homologues separate sister chromatids stay together
16
Q
Meiosis II
A
Basically mitosis where sister chromatids now split to form the haploid gametes
17
Q
Key differences between Meiosis and Mitosis
A
Meiosis homologous chromosomes do pair together, mitosis they do not
Meiosis creates haploid gametes, mitosis creates diploid progeny
18
Q
External Fertilization
A
Associated with larger egg cells. When males fertilize eggs outside of the female body.
19
Q
Eggs
A
Yolk = egg cell with a nucleus in it
Liquid around it = albumin
White strands = chalaza = what holds the yolk at the center of the egg
Egg is fertilized before the shell forms
20
Q
How does the USDA grade eggs?
A
By quality of the albumin. Fresher eggs have tighter, thicker albumin
21
Q
Why are plants often cloned?
A
To preserve their genotype
22
Q
Mendel pea plant study process
A
Remove stamens to prevent self pollination
Transfer pollen to carpel by hand
Observe seed traits in F1
Observe plant traits in F1
23
Q
Dominance
A
some genes have a stronger effect on phenotype than others
24
Q
Gene Stability
A
The gene controlling the recessive trait in heterozygote will be inherited unchanged
25
Law of Segregation
Genes controlling the same trait segregate from one another during gamete formation (ie. every gamete only has one allele, so pp breaks down to p and p) during meiosis
26
Origin of butter and cream corn
Understanding the concept of dominance and selecting for traits accordingly
27
Explain the mutation behind sweet corn
Sweet corn has a mutation that blocks the break down of sugar into starch
28
Mendel's first prediction and how to test it
Prediction 1: Those with dominant phenotype (purple) should be ⅓ homozygous and ⅔ heterozygous → do a progeny test
Breed them with different known genotypes and see what comes out
29
Mendel's second prediction and how to test it
Prediction 2: If the model is correct, then F1 plants should segregate ½ dominant and ½ recessive progeny in a cross to a homozygous recessive parent → do a test cross (breed with recessive)
30
Penn Greenhouse Peas
Environment has an effect on the expression of traits
31
If genes aren't linked what is their ratio?
9:3:3:1 ratio
32
What did Mendel discover?
Phenotype is controlled by stable particulate factors (genes)
These factors come in two forms (dominant and recessive)
Factors are present in 2 copies in embryos after fertilization, but in only 1 copy in gametes (= law of segregation)
Gametes unite randomly during fertilization
The factors that control different phenotypes (traits) segregate independently of one another during gamete formation (= law of independent assortment)
33
Why was Mendel only partly right?
He didn’t account for crossing over
34
What types of mutations can cause cancer?
Regulatory features of the cell cycle mutated
Shutting off tumor suppressor genes
Oncogenes
DNA Repair Genes
35
Average Germline Mutation Rate in Humans
0.5 x 10-9 per bp, per year
The human genome is 3 x 109 bp (haploid). Assuming that your first child is born when you are 25 (U.S. average), this means that your child will inherit approximately 37 mutations that you did not have when you were born.
36
Recessive mutations are __________
loss of function mutations
37
Alleles of Tyrosinase C gene in mice
Wild type is dark, weakened allele is the middle, and albino (complete loss of function) is white
Temperature sensitive too.
38
Conditional Mutation
mutation that has wild-type (or less severe) phenotype under certain "permissive" environmental conditions and a mutant phenotype under certain "restrictive" conditions.
Ex. temperature sensitive fur color and sickle cell
39
Sickle Cell
Sickle cell changes the structure of the beta subunit of hemoglobin (amino acid switch from glutamate to valine)
This causes atypical and unwanted behaviors of hemoglobin
Now all of a sudden the molecules can associate with one another
This causes them to crystallize and in turn the hemoglobin cannot carry oxygen as well
40
How is sickle cell a conditional mutation?
The sickle cell phenotype depends on the oxygen concentration in the blood. In cases where the oxygen level drops below a certain level, the cells sickle. This is particularly problematic in small capillaries, because the cells clog the veins. The severity of this problem depends on whether the person is homozygous or heterozygous for the mutation—children who are homozygous often die quite young.
Sickle cell is typically used as a model for balancing selection—that is, the mutation is maintained in a population because the heterozygous condition confers resistance to malaria. Of course, this is not a problem in the US, so it will eventually be eliminated from the African-American population in the US.
41
Co dominant alleles
red + white = pink
42
Polyploidy
increase in the number of haploid chromosome sets
increases genetic variation but decreases stability
happens commonly in plants but often makes them sterile
43
Aneuploidy
variation in the number of individual chromosomes
Comes from defects in meiosis if sister chromatids don’t separate in meiosis 2 or homologous chromosomes don’t separate in meiosis 1 (non-disjunction)
44
Instance of aneuploidy in humans
5-25%
45
Duplication, Inversion, Deletion, Reciprocal Translocation
Duplication = extra copy of segment of DNA
Deletion = loss of a segment of DNA
Inversion = inverted segment of DNA
Reciprocal Translocation = exchange between non-homologous chromosomes
46
Homeobox genes
Molecular evidence for evolution
Found in fruit flies and shown that other animals have them
similar genes that direct the formation of many body structures during early embryonic development.
47
Darwin's theory of natural selection
Pre-existing heritable variation -> differential reproduction due to competition -> population changes -> variable environments select for different traits in different populations, leading to speciation.
48
What was missing from Darwin's theory?
A mechanism for heredity
49
Modern Synthesis
Darwin & Mendel Mashup
50
Natural Selection operates on __________
phenotypes
51
Evolution
change in allele freq in a pop over time
52
Population
a localized group of individuals capable of inter-mating and producing fertile offspring
53
Three Modes of Selection
Positive selection: leads to an increase in the frequency of an allele
Negative, or purifying, selection: leads to a reduction in the frequency of an allele
Balancing selection favors heterozygotes.
54
Heterozygote advantage in sickle cell anemia
Purifying selection doesn't happen in areas with malaria for the sickle cell recessive allele because heterozygosity gives malaria resistance
in the us this doesn't apply though because we do not have malaria
homozygous for sickle cell die young
55
Descent with modification
traits are passed on from parent to offspring
56
Directional selection
positive or negative selection but basically the population shifts toward a certain phenotype
57
Disruptive selection
one phenotype is particularly bad for survival so you see literally all of the other phenotypes grow (like extremes)
58
Non-adaptive (neutral) variation
```
new mutations (when they don't introduce any new function)
linkage of neutral and selected alleles
gene flow
non-random mating
genetic drift
bottleneck
```
59
Linkage of neutral alleles to selected alleles
something selected for becomes a package deal with something neutral, thus increasing the frequency of the neutral
60
Non-random mating
people tend to mate with people who look like them
61
Genetic Drift
variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.
works best in small population
62
Bottleneck
Event drastically reduces the size of a population and only the surviving population lives to mate. This decreases genetic diversity
Genetic drift can be catalyzed by this
As infrequently occurring alleles are more likely to be lost
63
When did homo sapien begin?
150,000 bp
64
Lactose Intolerance
Starting condition is that lactase disappears after birth because infants do not subsist on milk as they get older
Persistent lactase expression is caused by mutations. These were advantageous to people who depend on cows for food. People in West Africa, the Middle East, and Europe developed distinct regional mutations to digest lactose
Lactase expression is controlled by several mutations. These are advantageous in people who depend on cows for food
65
Where is there the most genetic diversity in humans?
The amount of genetic diversity in Africans is greater than anyone else in the world
This is because they have been around the long. 1.2 to 1
The farther away you move from Africa the less genetic diversity there is
Fewer alleles the further you get from Africa
Why is that?
The way humans have migrated
Around 70,000 years ago humans left and migrated eastward into south asia and china northward, then australia than the americas
Bottleneck effect
Entire human population outside of africa came from about 2,000 individuals
Selective bottlenecking effect caused us to lose diversity over time
66
Founder Effect
Huntington’s Disease
If you come from a small population with small gene pool then you could have a higher frequency of sick
Amish another example, a small founder population so they have less genetic diversity which is a detriment to health
67
Most of our calories come from ______ and _______
cereals and legumes
68
Most farmed cereals
Maize > rice > wheat top most produced crops
69
Most farmed legumes
Soybeans > ground nuts > beans
70
How do we know that most of the food we eat comes from somewhere else in the world?
Compare the % of calories consumed to the % use of foreign crops
71
Agricultural Revolution
Originated about 10,000 years ago in several places
Western civilization originated in the fertile crescent between the tigris and the euphrates 5,000 bp
But a lot popped up at the same time, central and south american civilizations as well as ancient chinese
72
Niche construction by humans
Essentially we design ecosystems that benefit us
Example
Settlement mounds and canals in the Amazon
Domesticating landscape
Compare the fertile crescent 10,000 years ago (ie. fluorishing with life) to today deforestation and overgrazing
73
Where did domestication occur? Evidence: Location of ancestral species
Vavilov centers of origin
essentially there are parts of the world where agriculture and plants first started
74
Where did domestication occur? Evidence: archaeological
Bone size
flotation
sediment cores
75
Domestication Syndrome
specific traits that you see in domesticated plants only.
76
Phylogenetic analysis of DNA Sequence
compare dna sequences to see how closely related species are
Example: DNA sequences of cows
Can determine that not only do cows from different places look different, but their mitochondrial DNA is actually quite different
Cows from Africa have cysteines in certain positions whereas cows in Europe do not
Cows in India have a very dark composition because they have a hump on their back
77
PCR
Get large amounts of small DNA fragments
Steps:
1) Heat and denature DNA
2) Cool and allow primers (oligonucleotides) to hybridize
3) Wait for TAQ polymerase to extend primers
4) Repeat the cycle
78
Sources of genetic variation
* Natural
* Induced
* Transgenes (GMO)
79
Transcribed region
part of gene where protein is synthesized from
80
Regulatory region
part of gene that controls its expression (promoter, parts where transcription factors can bind to amplify prod)
Contains controls for timing, location, and rate of transcription
Transcription factors bind to enhancer sequences and RNA polymerase binds to the promoter
81
How to make a transgenic organism
take a transcribed and regulatory region of interest and place it into an organism
82
Transgenic organisms
has extra genes (transgenes) added to organism by techniques used in molecular biology
83
Transgenes
extra genes added. typically beneficial when expressed. will be determined by regulatory promoter. Can use promoter that has a particular pattern of expression.
84
Cloning
Make a synthetic gene and propagate it in bacteria.
1) Take plasmid out.
2) Take DNA from any source and insert into plasmid
4) Then put plasmid back in org
85
Plasmids for cloning have to have ___________
a selectable marker. select for gene typically that has antibiotic resistance
86
Restriction enzyme
cuts plasmid at particular dna sites
87
Cloning in detail
1) Isolate bacterial plasmid and foreign DNA .
2) Cut plasmid and foreign DNA with same restriction enzyme. Generates sticky ends that are complementary to gene you want to insert
3) Mix DNA and treat with DNA ligase to seal the pieces together
4) Transform bacteria with plasmid.
5) Plate bacteria on selective medium(containing an antibiotic) to identify those that contain the plasmid because they have a selective marker you can tell.
6) Cells that grow contain plasmid
88
Essential features of plasmids
* Need gene of interest that has a particular expression factor
* Need selectable marker makes it possible to ID the transgene, know what has taken it up
* contains sequences on plasmid that allow it to integrate itself into the host and incorporate into DNA
89
Herbicide tolerance (RR)
o Round up resistance- bacterial gene confers resistance.
♣ EPSP synthase- enzyme that will make amino acids.
♣ Round up has glyphosate which binds to EPSP and prevents it from making amino acids, will starve the plant.
Resistant plants will not bind
90
Insect resistance
• Insect resistance (Bt)
o Gene from bacillus thuringiensis (Bt)
o Will punch holes in gut of larva, they die
Important for cotton
91
Virus resistance
o A mutant form of viral coat protein confers resistance to virus
o All papayas in Hawaii will be resistant to ringspot virus
92
______ corn, soybeans, cotton are GM crops
95%
93
CRISPR
♣ CRISPR binds DNA guide molecule, finds target DNA strand
94
Cas9
♣ Cas9 cuts cutting enzyme cuts off target DNA strand
95
CRISPR/Cas9
Basically if you have a gene you want to knock out you synthesize complementary RNA to that gene. Then it will associate with Cas9, the DNA cutting enzyme, to cut at that location. Then you can introduce new complementary DNA in that location that can knock out gene expression or modify it.
If you don’t do anything it can eventually repair itself
♣ If you introduce a DNA that is complementary with some changes, you can introduce engineered gene
96
Plant genetic engineering depends on _______
Agrobacterium tumefaciens, the bacterium that causes Crown Gall disease
97
Agrobacterium tumefaciens
o Bacterial cell with DNA, can bind to plant cell wall, pilus injects its DNA into plant cell
the injected DNA is T-DNA (transfer dna)
a tumor is created. bacteria essentially tricks plant into synthesizing more food (amino acids and hormones) to support its own growth.
Engineers fixed the tumor situation by removing genes that code for plant hormones and essentially got rid of everything except for the gene that gives it the ability to get into the cell
98
T-DNA must haves
o Left and right borders have sequences necessary to get into chromosome (1)
o Have gene of interest driven by promoter (2)
o Have selectable marker (3)
99
How to do gene editing in arabidopsis
o Take plant while its flowering, dip into bacterial suspension, let it sit, spray with insecticide, transgenic plants will not die (herbicide resistance), treat with plant horomones
must cross transgene multiple times
100
Selectable marker in plant genetic engineering is often ________________
herbicide resistance
101
Transformed cells are turned back into plants by _____________
treating them with plant hormones
102
Stacked traits
having more than one kind of resistance
103
Who is making GE crops
Big institutions like Monsanto!
But recently developing countries are starting to outgrow industrial countries in GE crops
104
Corn, soybeans, and cotton are all pretty much __________ in the us
genetically engineered
105
Two ways to make a transgenic animal
Inject DNA into nucleus of fertilized egg
| Produce transgenic tissue culture cells. Transfer nuclei into enucleated eggs.
106
Examples of transgenic crops
magic rice
| engineered casava
107
Enviropig
Transformed with an phytase gene from E. coli, these pigs are able to digest the phytate in their plant-based feed, reducing the amount of phosphorus in their manure by 65%
108
Domestication
Change in genotype brought about by humans, that adapts an organism for life in an environment managed by humans.
109
Characteristics of Domestication Syndrome in plants
Loss of seed shattering
· Loss of seed dormancy
· Large seeds, fruits, inflorescence
· Photoperiodic responsiveness
· Uniform flowering
· Loss of toxic chemicals
110
Loss of seed shattering
seed stays on stock, doesn't fall off
111
Loss of seed dormancy
seeds fertilize super easily
112
How did domestication syndrome arise?
Unconscious selection- harvesting and replanting seeds from that same harvest
Conscious selection- Choosing seeds from plants we like the look of
113
Allopolyploid
polyploid derived from different species
114
Pre-adaptations in plants
Ability to grow in disturbed environments
| Relatively simple genetic changes lead to desirable traits
115
Pre-adaptations in animals
```
Omnivorous diet (eat lots of things), easy to raise
Fast growth rate
High fecundity
Dominance hierarchies
Docile, do not panic easily
```
116
Hybrid seed corn
A seed corn grower does not plant a variety but rather 2 inbreds (homozygous, If you’ve been self pollinated many times, the plant will be homozygous, genetically the same at all areas) that cross to produce the seed of a variety. Hybrid seed corn production involves the crossing of two (2) inbred lines, hybridization
farmers can't recreate b/c don't have inbreds
117
Corn evolved from Teosinte
Ancient mesoamericans selected for large ears and softer kernels
Corn and teosinte crossed do produce fertile hybrids
Nucleotide diversity is low in the promoter of the tb gene
(regulates inflorescence) in corn, but not in teosinte
-this indicates that it has been selected for
118
Post transcriptional modifications
Add 5’ cap and poly a tail and splice out the introns
119
Selection creates _________ that reduce genetic variation
bottlenecks
120
Polyploid makes plants ________
sterile
AA + BB --> AA BB --> AA BB + DD --> AA BB DD
121
Agouti genes, melanocytes
loss of function alleles of agouti associated with msh controlling melanin production leading to black coat color
if we overexpress asp we see yellow color
122
Most popular cows
Holsteins
9 gallons a day
123
Kenya agroforestry
milk as purity's main source of income
1.8 gallons a day from her cows
124
Milk production trends
post world war II our cows started making a lot more milk
determined by genetics and environment
125
Qualities of milk production
o Must be pregnant in order to produce milk
o Dairy farmers use calves produced by their cows to maintain stock (daughters replace mothers when the mothers milk declines)
o Farmers manipulate the productivity of their herd by controlling fertilization
o There is a strong demand for bulls that produce high yielding daughters
126
Most popular breed for beef production
Angus
```
♣ Good mothers
♣ High fertility
♣ Small calves so birth easy
♣ Mature early
*marketing
```
127
How to tell meat is higher quality?
The more marbling the better
128
Hybrids versus pure breds (cows)
Hybrids have a 77 dollar edge on pure breds
pure breds are higher quality meat
but hybrids have a better feed conversion rate and lower mortality
129
How many lactations for holsteins in a lifetime?
3.2
130
Milk production cycle
```
• Artifical insemination
• Pregnant (abort if male)
• Dry period (no milk for 60 days before you calve)
• Calving
o While you’re calving you produce milk
```
131
Semen Extenders
♣ Keeps semen alive so that it can be shipped around the world to be used to fertilize female cows (this is when you got that good semen)
♣ Data is kept in a central database to determine the quality of the sire
132
Total value of starbuck’s semen
25 million
133
Super ovulation and embryo transfer
o Induce cows with hormones (30 at a time) to produce multiple eggs
o Then inseminate her and take the embryos and put them in surrogate cows
o That means a valuable cow can produce more offspring then they ever could have because they have to be pregnant 9 months and can only have one calf at a time
134
In-vitro fertilization
o Put immature eggs in a surrogate cow. Usually a last resort for older cows not responding to superovulation
135
High qual characteristics of cows
good rump width, teat length, udder depth, and rear leg view
136
What does a breeder of cows look for?
o Few metabolic disorders
o Shows heat and conceives when breeding
o Produces a live calf without assistance
o High milk yield with correct composition, inexpensive ration and low maintenance cost
o Walks and stands comfortably rarely needs trimming
o Resists mastitis
o Avoids injury
137
Bovine Array Chip
o New technology to see a cow’s genotype
| Marker Assisted Selection: using genomics to speed cow breeding
138
BST/rBST
o 17% of cows are treated with this
| o recombinant BST
139
How do you determine quality of meat before you kill the cow?
ultrasound between second and third rib
140
Broilers
chickens bred for their meat. They are selected to be so fat that they are infertile
141
How are chicks sexed?
Chicks are sexed using a sex-linked mutation that affects the length of wing feathers: uneven feathers = females
142
Why is it important that broilers have white feathers?
Mechanized processing so we have more errors with the plucking process and you can't see white feathers as much when mistakes come up
143
Factors that contribute to increased chicken productivity
1) Confinement
2) Disease control
3) Nutrition
4) Genetics
144
Feeding chickens
65% of cost of raising chickens is feed
do like corn soybeans vitamins
Chickens are harvested at a standard weight so there is a high priority to achieve this weight fast and as cheaply as possible
we have also selected for chickens that get fatter with less food
145
Broilers go up to ____ lbs
6.6 up from 2.2
146
Layers lay up to ______ eggs per year
300, up from 15-25
147
Bottlenecks
decrease genetic diversity
we did that to chickens
148
Layers
white leghorns and rhode island red
149
Broilers
British Cornish indian game cock and white Plymouth rock hen
150
Negative consequences of selection for increased growth rate in chickens
1. Ascites (increased fluid in body cavity)
2. Excess abdominal fat
3. Sudden death syndrome
4. Reduced immune competence (more antibiotics)
5. Tibial dychondroplasia
6. Reduced reproductive performance
7. A variety of other metabolic disturbances.
151
Free-range chicken
term for broilers not layers. Minimum requirement is that they are reared in large houses with a small door to the outside
152
Cage-free chicken
euphemism for high density floor confinement
153
Pastured poultry
chickens raised in yards and pastures
154
Big difference between domestic and wild chickens
ability to lay eggs continuously
155
When you confine chickens _________
all energy produced is turned to fat
156
Sugary2 mutation as basis for sweet corn
The mutation blocks sugar from turning into starch
157
Polyploidy in plants why is it important
increases opportunity for genetic diversity because more opps for crossing over also makes plants sterile
158
Quantitative Trait
exists on gradient
159
Mendelian Trait
one trait, this or that
160
Most fruits and vegetables we like are created from _______
some single trait changes and some quantitative traits
example tomatos
we select ones that degrade chlorophyll
161
Plant mutation patterns
• shoot apical meristem creates layers
Cells that arise in a layer tend to stay there. So if a mutation occurs in a layer, the progeny will stay in that layer
o Think a leaf with lighter color on the edges
162
Chimeras
• genetic mosaics; any plant that has tissues of two or more genotypes
163
Vegetative reproduction
is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment of the parent plant or a specialized reproductive structure.
Many fruit trees are propagated from cuttings (i.e. cloned) to maintain their genotype.
164
Induced mutations
used to created varieties that wouldn't occur naturally
example peanuts used for the mr.goodbar has two mutations to lower lineolic acid content
165
Mass selection
save the best looking individuals and propagate their offspring
166
Directed selection
identify gene of interest and select specifically for this gene in crosses, ex. Using genetic markers
167
Introgression
the transfer of genetic information from one species to another as a result of hybridization between them and repeated backcrossing.
168
Backcrossing
crossing of a hybrid with one of its parents or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent
169
Hybrids
• Interbeed corn
• Basically take pollen from one breed of corn to pollinate another
• A/A B/B x a/a b/b -> A/a B/b x (basically need to buy hybrids because you can’t save the seeds) you can’t produce the hybrids because you don’t have the inbreds
Alleles from wild plants are transferred to cultivated plants by multiple rounds of backcrossing
170
Spend ____ more on curing people than feeding them
10x
171
The Green Revolution
increase in food production post ww2
172
The amount of US disposable income that is spent on food is _________
declining; we spend less of our disposable income on food than any other country. food is getting cheaper
173
Increase in food production post WWII at a consequence of
```
o Mechanization
♣ Tractors replace horses which allows you to tow fields faster
o New varieties of crops
♣ Hybrid corn
o Synthetic fertilizers
♣ Produced from petroleum & legumes
o Herbicides
♣ Kill plants weeds
o Pesticides
♣ Kill insects
o Better irrigation
```
174
Farm boom in America in the 70s led to farm bust in the 80s where many farmers lost their livelihood
o All of the things that allowed us to increase food production allowed bigger farms to slash their prices and put smaller farmers out of business
175
Herbert Heine: advent of mechanization
o Horses required rest and needed to devote some of the land to making feed for the horses
trade in for tractor go faster, use less resources (land to grow feed)
176
Tractors took plowing a 40 acre field from ____ to ____
55 hours to 66 minutes
177
Fertilizer use has _________ over time
increased
178
Why do you want plants to be shorter/what is the value of dwarfism?
they won't blow over and ruin the crop and when you fertilize a dwarf instead of growing it will produce more seeds.
179
Shuttle breeding
moving crops at different parts of the year when the climate changes seasonally
180
Trait that lead to an increase yield in wheat and rice
dwarfism!
181
Origin of ir8 miracle rice
```
♣ 1) dwarf cross peta (tall)
• 130 plants all were tall
• means its recessive
♣ 2) took f1 plants and self fertilized
• 10,000 plants, ¾ tall ¼ dwarf
• so single gene
♣ 3) Save just dwarf plants and self pollinate them
• 298 families (plants) and saved seeds
♣ 4) family 288, chose 3rd plant from row and saved seeds from it and that became miracle rice
```
182
Gibberellin
is a plant hormone that promotes stem elongation
183
Ethylene gas
ripens fruit
184
How do dwarfing mutations in wheat work?
Wheat mutations block ga perception of receptors
185
How do dwarfing mutations in corn work?
Rice mutation blocks ga synth
186
what does the different mechanisms of dwarfing in corn and wheat say about mutation?
• the same phenotype can be caused by mutations in different genes
