Midterm #2 Flashcards
1
Q
1869
A
Johann Meischer: discovers nuclein from human white blood cell which later gets called nucleic acid
2
Q
For a molecule to serve as genetic material, it must be able to… (3)
A
- Replicate accurately
- Store large amount of information
- Allow for phenotypic variation
3
Q
1928
A
Fredrick Griffith: cells can be transformed, uses rough (virulent) and smooth virus in mice, called transforming principle
4
Q
1944
A
Avery, Macleod and McCarthy: DNA is genetic material, DNA-ase destroyed transforming substance in virus
5
Q
1952
A
Alfred Hersey and Martha Chase: label protein and DNA, DNA found in progeny and therefor transmitted to progeny
6
Q
1952
A
Heinz Fraenkel-Conrat and Beatrice Singer: some viruses use RNA as genetic material, used Tobacco Mosaic Virus and protein coat from different virus
7
Q
Nucleotide composition
A
Sugar + Base + Phosphate
8
Q
Chargaff’s Rule
A
Base composition species specific
Purine (AG)/Pyrimidines (CT) ~1.0
9
Q
1910
A
Aaron Levene: DNA is made of repeating units called nucleotides
10
Q
Late 1800s
A
Albrecht Kossel: nucleic acid contains four nitrogenous bases: Adenine, Cytosine, Guanine and Thymine
11
Q
1948
A
Edwin Chargaff: analyzed the nucleotide composition of DNA, A=T, C=G
12
Q
Nucleoside composition
A
Sugar + Base
13
Q
1953
A
Watson & Crick: 3D structure of DNA from X-Ray diffraction data from Rosalind Franklin, DNA helix constant diameter, used modelling techniques from Linus Pauling
14
Q
What causes constant diameter of DNA?
A
Purines bonding with pyrimidines
15
Q
4 main concepts of 3D DNA
A
- phosphates on outside, bases on inside
- double helix
- strands run antiparallel
- specific base pairing
16
Q
Double helix characteristics
A
Bases are flat and perpendicular to acts, stacked 0.34nm apart with 10 bases per turn, major and minor grooves, structure is more conserved than sequence
17
Q
A form DNA
A
Right-hand turns, 11 residues/turn, usually found in cells
18
Q
B form DNA
A
Right-hand turns, 10 residues/turn, usually found in cells
19
Q
Z form DNA
A
Left hand turns, 12 residues/turn, no major grooves, biological significance unknown
20
Q
Secondary structures of DNA
A
Hairpin, Stem and Cruciform
21
Q
Hairpin
A
Inverted complementary sequence forms bond, with loop at top
RNA
22
Q
Stem
A
Inverted complementary sequence
RNA
23
Q
Cruciform
A
Inverted repeats in dsDNA
24
Q
DNA melting
A
Separation of 2 DNA strands, can be renatured
Caused by increase in temperature, reduced salt concentration, increased pH, solvents
25
Measuring DNA melting
Using absorbance, absorbance increases as DNA is denatured
26
Tm
Measure of stability, affected by G=C content, ionic strength of buffer, length of DNA molecule
27
Formamide
Disrupts H bonds, form H bonds with bases
28
DMSO
Disrupts H bonds, form H bonds with bases
29
Strand of nucleic acid
Polymer of nucleotides, 3'-5' phosphodiester bonds link nucleotides together to form polynucleotide chains with negatively charged sugar phosphate backbone, each chain has polarity at 5' (phosphate) end and 3' (hydroxyl) end
30
RNA structures
Driven by hydrophobic bases, some unconventional base pairing, form A-helices, complexity of structures analogous of what is seen in proteins, important for biological function
31
Meselson and Stahl Experiment
Grew E. coli in 15N medium, then switched to 14N medium, used equilibrium density gradient centrifugation to determine isotope composition of DNA, determined semiconservative DNA replication
32
Requirements for DNA Synthesis
Template of ssDNA, deoxyribonucleoside 5' triphosphate (dNTPs), DNA polymerase (other enzymes), free 3' OH
33
Replication fork
Division of DNA at replication site, both strands are synthesized simultaneously
34
Replicon
DNA strand that is synthesized from single origin of replication
35
Synthesize takes place inside (replication fork)
Replication bubble, replication fork at both sides
36
Leading strand
Synthesized continuously
37
Lagging strand
Synthesized in fragments, opposite direction of replication fork
38
Direction of synthesis
Always 5' to 3'
39
Circular genome replication
1. Theta replication (bacteria)
| 2. Rolling cycle replication (viruses)
40
Linear genome replication
Linear replication (eukaryotes)
41
Theta replication
Bacteria, single replicon, bidirectional replication at both replication forks, replication terminates on other side of circular DNA
42
Rolling circle replication
Viruses, uncoupling of two strands of DNA
43
Linear replication
Eukaryotes, multiple replicons, origins of replications, and replication bubbles, if one origin of replication, cells would take a month in S phase
44
Single strand binding proteins
Keep DNA separated during replication
45
Oric
Origin of replication
46
DNA Helicase
Breaks H bonds to separate two strands of DNA
47
DNA Gyrase
Alleviates supercoiling by breaking DNA and resealing strands
48
RNA primer
Gives 3'OH for DNA polymerase to begin replication, later replaced with DNA molecules
49
E. coli DNA polymerases
I-V, all 5' to 3'
50
Polymerase III
Principle polymerase of E. coli, stalls when incorrect pairing and uses 3' to 5' exonuclease activity to correct
51
Polymerase I
Replaces RNA primers with DNA, uses 3' to 5' exonuclease activity
52
DNA Ligase
Seals sugar phosphate backbone at primer
53
Licensing factors
Eukaryotic DNA replication
| Monochrome maintenance proteins at origin
54
Origin recognition complexes
Initiation of DNA replication, binds to origins
55
Germinin
Deactivates origins
56
Telomere
At 3' end
G-rich short repeating sequence
Stabilizes chromosomes
Each round of replication leaves ~200bp unreplicated
57
Telomerase
Reverse transcriptase, adds to end of DNA using own RNA template
58
Homologous recombination
Exchange of genetic material between two homologous chromosome, commonly occurs during meiosis, can happen during mitosis, Prophase I homologous chromosomes pair to form tetrad where crossing over occurs
59
Holliday model
1. Single strand break (on one of each homologous pairs)
2. Strand invasion
3. Holliday junction
4. Branch migration
5. Cleavage at horizontal or vertical plane
60
Holliday model cleavage at horizontal plane
Non crossing over recombinants
61
Holliday model cleavage at vertical plane
Crossover recombinants
62
Double stand break model
1. Double strand break of both strands of one homologous pair
2. Strands degrade to give 3' overhands
3. Strand invasion and 3' elongation
4. Two Holliday junctions
5. Cleavage
63
Double Strand Break model: HH and VV cleavage
Non crossing over (Holliday junction H cleavage)
64
Double Strand Break model: HV and VH cleavage
Crossover recombinants (Holliday junction V cleavage)
65
RecBCD
Enzyme complex in DSB, both nuclease and helices activity, recombination repair, generation of 3' single strand terminus
66
Chi
Crossover hotspot instigator, digests 5' terminated strand to make 3' overhand then dissociates
67
RecA
Loaded by RecBCD complex to 3' overhand, family of recombinases, promotes strand invasion and pairing with homologous DNA
68
RuvAB complex
Promotes branch migration and heteroduplex formation
69
RuvA
Recognizes Holliday junction
70
RuvB
Binds to DNA and RuvA complex, drives DNA unwinding and rewinding that is necessary for branch migration
71
RuvC resolvase
Endonuclease that resolves Holliday junctions, nicks strands for either horizontal or vertical plane resolution, functions with RuvAB to locate and cut sites
72
Gene conversion
Postulated when abnormal segregation ratios were observed, associated with homologous recombination events during meiosis, occurs from heteroduplex formation during recombination events, heteroduplexes with mis-matched bases are repaired using one strand or other for template for correction: causes one copy of gene to take other allele
73
Tetrads
Haploid organism in which products of a single meioses remain together as a group of four cells called a tetrad in a saclike structure
74
First division segregation pattern
4:4, alleles segregate after first division, simple segregation, no crossing over
75
Second division segregation pattern
2:2:2:2, 2:4:2, alleles segregate in second division, crossing over
76
Gene conversion (aberrant segregation types)
6:2, heteroduplexes with mismatched nucleotides, with mismatch repair
77
Post-meiotic segregation
Failure to repair mismatch, repair of only one mismatched heteroduplex, 5:3 ratio
78
Transcription
Selective synthesis of RNA, not all DNA in a cell is transcribed, synthesis is complementary and in 5' to 3' direction, numbers RNA molecules are simultaneously transcribed from each DNA strand, no requirement of 3' OH, template is always read 3' to 5'
79
Transcription unit
Region of DNA that codes for a RNA molecule and sequences necessary for transcription:
1. Promoter
2. RNA coding region
3. Termination site
80
Promoter
Upstream of start site, bound/recognized by transcription apparatus, indicates direction of transcription, binding of RNA polymerase orient enzyme to start site
81
RNA coding region
Downstream to start site, only part that is transcribed, includes termination site
82
Termination site
Downstream to start site
83
RNA polymerase
Control centre for transcription, multi protein complex, produces RNA 5' to 3', catalyzes the formation of phosphodiester bonds, unwinds DNA duplex, prokaryotes have 1, eukaryotes have 3 or more
84
Consensus sequences
Prokaryotes only, nucleotide sequence that summarizes or approximates pattern observation in a group of aligned nucleotide sequences, -10 (Pribnow box) and -35, variation affects strength of promoter (frequency)
85
Up mutation
Strengths promoters, makes it more accurate to consensus sequence
86
Down mutation
Weakens promoter, makes it less accurate to consensus sequence
87
Sigma factor
Works with RNA polymerase in prokaryotes to recognize promoter, without sigma factor, RNA polymerase would bind randomly
88
Holoenzyme
Complete complex with RNA polymerase and sigma factor
89
Prokaryotic transcription initiation
RNA polymerase binds to promoter with help of sigma factor
90
Prokaryotic transcription termination
1. Rho dependent
| 2. Rho independent
91
Rho dependent termination
Rho binds to RNA upstream of terminator, RNA polymerase pauses at terminator and Rho catches up, Rho unwinds DNA-RNA hybrid using helicase activity
92
Rho independent termination
Inverted repeats causes hairpin in RNA, followed by string of uracils
93
RNA polymerase II promoter
Made of core promoter and regulatory promoter
94
Core promoter
```
Eukaryotic transcription, extends upstream and downstream of start site, minimal sequence required for accurate transcription initiation, includes number of consensus sequences for transcription factor binding:
TFIIB
TATA box
Initiator
Downstream core promoter element
```
95
Regulatory promoter
Upstream of core promoter, transcription activator protein binds to consensus sequences and affect rate of transcription, regulatory proteins bind and affect rate of transcription
96
Basal transcription apparatus
Consists of RNA polymerase II, general transcription factors, and mediator protein, bind to core promoter close to transcription start site, necessary for transcription at minimal or basal levels
Tata binding protein, general transcription factors, Pol II
97
Enhancer sequences
Effect rate of transcription, regulatory binding proteins can bind to affect the rate of transcription
98
Eukaryotic transcription termination
Cleavage of mRNA at a specific site, RAT1 exonuclease degrades remaining RNA to terminate transcription
99
RAT1
Degrade remaining mRNA after cleavage using 5' to 3' exonuclease activity
100
Exons
Sections of DNA that code for genes, separated by noncoding introns, introns are spliced out
101
Operon
Protein coding genes in continuous array, single transcription site for multiple genes, little to no introns, eukaryotic genes are each transcribed from own start sites
102
Eukaryotic premRNA processing
```
Modification after transcription
1. Capping at 5' end
2. Poly(A)tion
3. Splicing
Coupling of transcription and processing by Pol II
```
103
Capping
5' end, methylated guanine nucleotide with 5' to 5' linkage with 3 phosphate groups, protect mRNA
1. Phosphate group removed from 5' end
2. GMP added
3. Methyl groups added to guanine of GMP and 2' position of first 2 RNA nucleotides
104
Polyadenylation
3' end, 50-250 adenine (A) nucleotides added to preRNA, protect mRNA, premRNA is cleaved 11-30 nucleotides from 3' consensus sequence in 3' UTR
105
Spicing
Removal of introns, requires 3 consensus sequences for spliceosome to recognize and remove introns
1. 5' splice site
2. 3' spice site
3. branch point
Introns removed in form of lariat, takes place on spliceosome
106
Spliceosome
300 proteins and 5 small nuclear RNAs (snRNAs)
| U1 and U2 bind to consensus sequence and branch point, U4, U5 and U6 join spliceosome and U1 and U4 are released
107
snRNP
snRNA + protein
108
Small nuclear RNA
snRNA, U1-6
109
C-terminal repeat domain
Couples mRNA transcription and processing, recruits 5' capping proteins at beginning of transcription and receipts pol(A) factors at end of transcription
110
Oncogenic
Potential to transform cell into malignant cell
111
Beta-thalassemia
Genetic disease, mutation in beta-globing gene that disrupts normal splicing of RNA, misses part of intron
112
Alternative processing
Produce different mRNA from same preRNA, different forms of proteins give different cell types
113
Alternative splicing
Each mRNA produced has different combinations of exon, each mRNA when translated produces different protein (isoforms)
1. Exon skipped
2. Intron retention
3. Alternative 5' or 3' splice site
4. Mutually exclusive exons
114
Alternative Poly(A) 3' cleavage site
multiple 3' cleavage sites in premRNA, each mRNA when translated produces similar proteins of different sizes
115
Tra (Drosophilia)
Absence makes Drosophila male
116
RNA editing
Sequence of nucleotides does not exactly match RNA product
117
Substitution editing
Base conversation by specific enzymes
118
Insertion editing
Addition of U nucleotides by cleavage of mRNA or ligation of ends, reactions catalyzed by complex enzymes under guide-RNA: gRNA, base pair with mRNA to act as template for nucleotide addition
119
RNA interference
RNAi: short regulatory RNAs repress or silence expression of homologous genes using siRNA or miRNA by mRNA segregation, inhibition of transcription and inhibition of translation
120
Transgenes
Incorporation into genome can increase gene activity or inhibit
121
RNA silencing
a gene incorporated into the genome (a transgene) could not only induce or stimulate gene activity but could also inhibit the expression of homologous sequences
122
Discovery of RNA interference
Addition of dsRNA causes mutation which silences genes
123
siRNA
Produced by cleavage of dsRNA by Dicer to give 21-25 bp sequences
124
miRNA
Produced by cleavage of dsRNA of specific genes by Dicer to give 21-25 bp sequences
125
RISC complex (siRNA)
RNA-induced silencing complex: siRNA combines proteins to form RISC complex, base pairs with target mRNA and causes cleavage and degradation
126
RITS complex
RNA transcriptional silencing: siRNA binds with proteins to form RITS complex, bind to target RNA and recruit methylating enzymes that add methyl groups to histones (histone modification), methylated histones bind tightly to DNA and restrict access to enzymes needed for transcription
127
RISC complex (miRNA)
Partial pairing between miRNA and its target mRNA, blocks initiation of translation or causes premature termination
128
Triplet code
3 consecutive ribonucleotides specify 1 amino acid, 4^3 = 64 possible codons
129
Nuremberg and Leder
Deciphered genetic code using known genetic code, mRNA and tRNA
130
61 sense codons
For amino acids, included Met (AUG), does not include 3 stop or nonsense codons
131
Degeneracy
Amino acid specified by more than one codon
132
Partial degeneracy
Changing third codon from one pyrimidine to another pyrimidine or from a purine to a purine
133
Complete degeneracy
Changing third codon to any of 4 bases
134
Synonymous codons
Codons that specify the same amino acid
135
Isoaccepting tRNA
tRNAs that bind the same amino acid, even though they have different anticodons, 30 tRNAs but only 20 amino acids
136
Wobble effect
Allows tRNA to bind with more than one codon though wobbling, wobbling occurs between 3' codon of tRNA anticodon and 5' (1st) codon - non Watson-Crick pairing, hydrogen bonding for last codon pair is looser than first two codons allowing for wobbling
137
Reading frames
Protein coding regions of mRNA, single protein start and end sites, all begin with Met (AUG), no gaps, codons do not overlap
138
Open reading frame
Portion of DNA with no stop codons
139
Point mutations
Alter single nucleotide
140
Frameshift mutations
Insertions and deletions of nucleotides
141
5' end of protein
Amino group
142
3' end of protein
Carboxyl group
143
RNA-protein complex
Ribonucleoprotein, prokaryote complex has 3 proteins and 2 subunits
144
5'CCA3'
tRNA attachement site for amino acid
145
A site
Accepting incoming aa-tRNA
146
P site
Holds the tRNA holding growing polypeptide
147
E site
Discharged tRNAs leave ribosome from this site
148
Antibiotics
Many alter translation apparatus, i.e. block exit site
149
Prokaryotic translation
20 amino acids/second, only 1 codon at a time read by tRNA, catalytic section of large RNA subunit forms peptide bonds, energy provided by GTP hydrolysis
1. tRNA charging
2. Initiation
3. Elongation
4. Termination
150
tRNA charging
Amino acid attachment to tRNA at A end (5'CCA3'), energy for binging from ATP
151
Aminoacyl-tRNA
tRNA + amino acid
152
Aminoacyl synthetase
Attached amino acid to tRNA, 20 different
153
Initiation of prokaryotic translation
Assembly of ribosomal subunits at translation state site AUG, 16S unit of small RNA subunit bind with Shine-Dalgarno sequence, IF-3 keeps two ribosome subunits separated, IF-1 and IF-2 facilitate charged aatRNA(Met) to bind at correct site), IF dissociate and allow large subunit to bind
154
IF-3
Keeps large and small subunit apart
155
IF-1 and IF-2
Mediate aatRNA(Met) binding to start site
156
Elongation of prokaryotic translation
Synthesis of polypeptide chain, A, P and E sites, EG guide incoming aatRNA to A site, peptide transferase catalyses peptide bond formation (large ribosomal subunit), peptide bond formation releases amino acid from tRNA at P site: growing polypeptide now attached at A-site and P site becomes E site
157
Termination of prokaryotic translation
Occurs when ribosome translocates to stop codon, no aatRNA enters A site with stop codon, release factor binds to A site and triggers release of polypeptide at P site
158
Peptide transferase
Catalyses peptide bond formation between amino acids, part of large ribosomal subunit
159
Release factor
Binds to A site and triggers release of polypeptide at P site
160
Eukaryotic translation
Same as prokaryote transcription with differences:
1. 5' cap and poly(A)tail
2. Initiation complex scans along mRNA until first AUG is found
3. 40S + 60S = 80S ribosome
161
Chromosomal variations
Permanent chromosomal changes that can be passed to offspring if they occur in cells that can become gametes
162
Chromosome rearrangements
Changes in structure of individual chromosomes
163
Variation in chromosome number
One or more individual chromosomes added or deleted
164
Human karyotype
n=23 (22 autosome, 1 sex), diploid: 2n=46
165
Cri du Chat
Deletion of 1 chromosome in 5 pair
166
Downsyndrome
Addition of 21 chromosome (3x21)
167
Duplication
Retention of a segment of a chromosome arm, no loss of genetic information and gametes are usually viable but bad affects from abnormal gene dosage can occur, caused by unequal crossing over of misaligned chromosomes in meiosis, detected by loop when chromosomes are aligned in prophase I
168
Tandem duplication
Simplest form of duplication, two segments are adjacent
169
Dosage effects
Excess copies of genes or chromosome segment can affect phenotype, can be caused by excess copies of gene mutations
170
Redundancy (duplication)
Both copies remain the same on chromosome with duplication
171
Pseudogene (duplication)
One copy of gene becomes inactive
172
Neofunctionalization (duplication)
One develops new function, sources of new genes (ie. Globin gene family)
173
Deletion
Loss of segment, either internal or terminal from chromosome, caused by terminal-end breaks or internal breaks with rejoining of incorrect ends, effect depends on size of deletion, detected by formation of deletion loop in prophase I, causes other mutations of genes to be expressed (no longer hidden by other gene copy)
174
Homozygous deletions
Deletions on both homozygous chromosomes, usually lethal
175
Heterozygous deletions
Deletion on one copy of homozygous chromosome, usually viable but may have low fitness
176
Inversion
Reversal of a sequence of genes on a segment of a chromosome, gametes are usually viable because genetic material is not lost or gained, viability changes if crossing over occurs, position effect
177
Position effect
New location of gene on chromosome may silence or hinder gene
178
Pericentric inversions
Include genes on both sides of centromere
179
Paracentric inversions
Include genes on one side of centromere
180
Crossing over of inverted chromosomes
Inviable if in inverted region
| Viable outside of inverted region
181
Crossing over of paracentric inversion
Creates dicentric chromatid link between homologous chromosomes that is broken when they are pulled apart in anaphase I, acentric chromatid is lost, resulting recombinant gametes are nonviable as they are missing some genes
182
Crossing over of pericentric inversion
Recombinant gametes are nonviable because they have multiple copies of genes and are missing some genes
183
Reciprocal translocation
Exchange between non-homologous chromosomes, creates a gene fusion or hybrid gene
184
Philadelphia chromosome
Fused BRC-ABL gene ( 5' BCR fused with most of ABL) causes inappropriate gene function and cancer
185
Alternate segregation (reciprocal translocation)
In meiosis, no loss or gain of genetic information
186
Adjacent segregation (reciprocal translocation)
(1 or 2 - more rare) In meiosis, causes loss and gain of genetic information
187
Robertsonian translocation
Fusion of 2 chromosomes, centromeric fusion, fragments lost causes loss of genetic information, can segregate 3 ways
188
Adjacent 1 segregation (robertsonian translocation)
Common, unbalanced
| [(14;21)+21]x 2 + (-21)x2
189
Adjacent 2 segregation (robertsonian translocation)
Uncommon, unbalanced
| [(14;21)+14]x 2 + (-14)x2
190
Alternate segregation (robertsonian translocation)
Common, balanced
| (14;21)x2 + (normal)x2
191
Aneuploidy
Increase or decrease in number of individual chromosomes, caused by nondisjunction in meiosis or mitosis (failure of homologous chromosome or sister chromatids to separate) or deletion of a centromere
Most common cause of spontaneous abortion, 2% of fetuses with chromosomal defect survive to birth - usually trisomies of smaller chromosomes
192
Nullisomy
Loss of both members of a pair of homologous chromosomes (2n-2)
193
Monosomy
Loss of a single chromosome (2n-1)
| Not usually viable except in sex chromosomes
194
Trisomy
Gain of a single chromosome (2n+1)
| May be viable
195
Tetrasomy
Gain of two homologous chromosomes (2n+2)
196
Double monosomy
Less common, loss of two non-homologous chromosomes (2n-1-1)
197
Double trisomy
Less common, gain of two non-homologous chromosomes (2n+1+1)
198
Nondisjunction in meiosis I
(2n+1)x2 + (2n-1)x2
199
Nondisjunction in meiosis II
(2n+1), (2n-1) + (normal)x2
200
Primary Down Syndrome
```
Trisomy 21 (2n+1 = 47)
Mostly from random disjunction during meiotic division, mother contributes extra chromosome 75% of the time (increases with maternal age)
Could be because of suspended oocytes
```
201
Suspended oocytes
Oocytes form prebirth and are arrested in prophase I (diplotene stage) until just before ovulation, meiosis I completes and oocyte is suspended as primary oocyte until sperm penetrates: second meiotic division occurs immediately before nuclei of sperm and egg unite to form zygote
202
Familial Down Syndrome
Extra copy of chromosome 21 is attached to another chromosome, usually 14 or 15, 3-4% of cases, arise in offspring of a parent with Robertsonian translocation (carrier has 45 chromosomes, one of which is 14:21), 1/3 of gametes have normal phenotype but result in 2/3 of live births, 1/3 live births with Down Syndrome
Monosomy 21, monosomy 14, and trisomy 14 are aborted
203
Polyploidy
Increase in number of sets of chromosomes, presence of more than 2 sets of chromosomes
ie. triploid (3n), tetraploid (4n), pentaploid (5n)
Common in plants, less common in animals
204
Autopolyploidy
Multiple of the same genome, nondisjunction of all chromosomes during meiosis I produces diploid gametes
ie. Diploid + normal = 3n
diploid + diploid = 4n
Usually sterile, most gametes produced from career are genetically imbalanced, one or two copies of each chromosome in many possible combinations
205
Allopolyploid
Multiple of closely related genomes
ie. allotetraploid: 4n, 2n from Species 1, 2n from Species 2
Needed to convert sterile hybrid to fertile new species, chromosome doubling prevents unbalanced games from occurring in meiosis, if entire genre is doubled my mitotic non-disjunction, fertility problem is solved
206
Cabbish/Raphanobrassica
Geneticist Karpechenko in 1928, tries to cross radish and cabbage
207
Amphidiploid
Allotetraploid
208
Significance of polyploids in agriculture
Cell volume is correlated with nucleus volume, correlated to genome size
ie. larger fruits: commercial bananas (3n), commercial strawberries (8n)
209
Domestic bananas
Derived from 2 species, Musa acuminate (A) and Musa balbisiana (B)
Gros michel and Cavendish are AAA
Most plantains are ABB, or AAB
210
Gros michel
Banana, wiped out in 1960s from Panema Disease (Fusarium), replaced by Cavendish (resistant)
211
Tropical Race 4
New Fusarium, Cavendish not resistant
