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Biology 2030 > Midterm #2 > Flashcards

Midterm #2 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

1869

A

Johann Meischer: discovers nuclein from human white blood cell which later gets called nucleic acid

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2
Q

For a molecule to serve as genetic material, it must be able to… (3)

A
  1. Replicate accurately
  2. Store large amount of information
  3. Allow for phenotypic variation
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3
Q

1928

A

Fredrick Griffith: cells can be transformed, uses rough (virulent) and smooth virus in mice, called transforming principle

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4
Q

1944

A

Avery, Macleod and McCarthy: DNA is genetic material, DNA-ase destroyed transforming substance in virus

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5
Q

1952

A

Alfred Hersey and Martha Chase: label protein and DNA, DNA found in progeny and therefor transmitted to progeny

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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

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7
Q

Nucleotide composition

A

Sugar + Base + Phosphate

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8
Q

Chargaff’s Rule

A

Base composition species specific

Purine (AG)/Pyrimidines (CT) ~1.0

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9
Q

1910

A

Aaron Levene: DNA is made of repeating units called nucleotides

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10
Q

Late 1800s

A

Albrecht Kossel: nucleic acid contains four nitrogenous bases: Adenine, Cytosine, Guanine and Thymine

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11
Q

1948

A

Edwin Chargaff: analyzed the nucleotide composition of DNA, A=T, C=G

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12
Q

Nucleoside composition

A

Sugar + Base

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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

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14
Q

What causes constant diameter of DNA?

A

Purines bonding with pyrimidines

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15
Q

4 main concepts of 3D DNA

A
  1. phosphates on outside, bases on inside
  2. double helix
  3. strands run antiparallel
  4. specific base pairing
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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

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17
Q

A form DNA

A

Right-hand turns, 11 residues/turn, usually found in cells

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18
Q

B form DNA

A

Right-hand turns, 10 residues/turn, usually found in cells

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19
Q

Z form DNA

A

Left hand turns, 12 residues/turn, no major grooves, biological significance unknown

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20
Q

Secondary structures of DNA

A

Hairpin, Stem and Cruciform

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21
Q

Hairpin

A

Inverted complementary sequence forms bond, with loop at top

RNA

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22
Q

Stem

A

Inverted complementary sequence

RNA

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23
Q

Cruciform

A

Inverted repeats in dsDNA

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24
Q

DNA melting

A

Separation of 2 DNA strands, can be renatured

Caused by increase in temperature, reduced salt concentration, increased pH, solvents

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25
Q

Measuring DNA melting

A

Using absorbance, absorbance increases as DNA is denatured

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26
Q

Tm

A

Measure of stability, affected by G=C content, ionic strength of buffer, length of DNA molecule

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27
Q

Formamide

A

Disrupts H bonds, form H bonds with bases

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28
Q

DMSO

A

Disrupts H bonds, form H bonds with bases

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29
Q

Strand of nucleic acid

A

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

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30
Q

RNA structures

A

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

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31
Q

Meselson and Stahl Experiment

A

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

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32
Q

Requirements for DNA Synthesis

A

Template of ssDNA, deoxyribonucleoside 5’ triphosphate (dNTPs), DNA polymerase (other enzymes), free 3’ OH

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33
Q

Replication fork

A

Division of DNA at replication site, both strands are synthesized simultaneously

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34
Q

Replicon

A

DNA strand that is synthesized from single origin of replication

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35
Q

Synthesize takes place inside (replication fork)

A

Replication bubble, replication fork at both sides

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36
Q

Leading strand

A

Synthesized continuously

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37
Q

Lagging strand

A

Synthesized in fragments, opposite direction of replication fork

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38
Q

Direction of synthesis

A

Always 5’ to 3’

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39
Q

Circular genome replication

A
  1. Theta replication (bacteria)

2. Rolling cycle replication (viruses)

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40
Q

Linear genome replication

A

Linear replication (eukaryotes)

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41
Q

Theta replication

A

Bacteria, single replicon, bidirectional replication at both replication forks, replication terminates on other side of circular DNA

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42
Q

Rolling circle replication

A

Viruses, uncoupling of two strands of DNA

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43
Q

Linear replication

A

Eukaryotes, multiple replicons, origins of replications, and replication bubbles, if one origin of replication, cells would take a month in S phase

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44
Q

Single strand binding proteins

A

Keep DNA separated during replication

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45
Q

Oric

A

Origin of replication

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46
Q

DNA Helicase

A

Breaks H bonds to separate two strands of DNA

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47
Q

DNA Gyrase

A

Alleviates supercoiling by breaking DNA and resealing strands

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48
Q

RNA primer

A

Gives 3’OH for DNA polymerase to begin replication, later replaced with DNA molecules

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49
Q

E. coli DNA polymerases

A

I-V, all 5’ to 3’

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50
Q

Polymerase III

A

Principle polymerase of E. coli, stalls when incorrect pairing and uses 3’ to 5’ exonuclease activity to correct

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51
Q

Polymerase I

A

Replaces RNA primers with DNA, uses 3’ to 5’ exonuclease activity

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52
Q

DNA Ligase

A

Seals sugar phosphate backbone at primer

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53
Q

Licensing factors

A

Eukaryotic DNA replication

Monochrome maintenance proteins at origin

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54
Q

Origin recognition complexes

A

Initiation of DNA replication, binds to origins

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55
Q

Germinin

A

Deactivates origins

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56
Q

Telomere

A

At 3’ end
G-rich short repeating sequence
Stabilizes chromosomes
Each round of replication leaves ~200bp unreplicated

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57
Q

Telomerase

A

Reverse transcriptase, adds to end of DNA using own RNA template

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58
Q

Homologous recombination

A

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

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59
Q

Holliday model

A
  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
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60
Q

Holliday model cleavage at horizontal plane

A

Non crossing over recombinants

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61
Q

Holliday model cleavage at vertical plane

A

Crossover recombinants

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62
Q

Double stand break model

A
  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
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63
Q

Double Strand Break model: HH and VV cleavage

A

Non crossing over (Holliday junction H cleavage)

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64
Q

Double Strand Break model: HV and VH cleavage

A

Crossover recombinants (Holliday junction V cleavage)

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65
Q

RecBCD

A

Enzyme complex in DSB, both nuclease and helices activity, recombination repair, generation of 3’ single strand terminus

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66
Q

Chi

A

Crossover hotspot instigator, digests 5’ terminated strand to make 3’ overhand then dissociates

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67
Q

RecA

A

Loaded by RecBCD complex to 3’ overhand, family of recombinases, promotes strand invasion and pairing with homologous DNA

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68
Q

RuvAB complex

A

Promotes branch migration and heteroduplex formation

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69
Q

RuvA

A

Recognizes Holliday junction

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70
Q

RuvB

A

Binds to DNA and RuvA complex, drives DNA unwinding and rewinding that is necessary for branch migration

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71
Q

RuvC resolvase

A

Endonuclease that resolves Holliday junctions, nicks strands for either horizontal or vertical plane resolution, functions with RuvAB to locate and cut sites

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72
Q

Gene conversion

A

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

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73
Q

Tetrads

A

Haploid organism in which products of a single meioses remain together as a group of four cells called a tetrad in a saclike structure

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74
Q

First division segregation pattern

A

4:4, alleles segregate after first division, simple segregation, no crossing over

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75
Q

Second division segregation pattern

A

2:2:2:2, 2:4:2, alleles segregate in second division, crossing over

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76
Q

Gene conversion (aberrant segregation types)

A

6:2, heteroduplexes with mismatched nucleotides, with mismatch repair

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77
Q

Post-meiotic segregation

A

Failure to repair mismatch, repair of only one mismatched heteroduplex, 5:3 ratio

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78
Q

Transcription

A

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’

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79
Q

Transcription unit

A

Region of DNA that codes for a RNA molecule and sequences necessary for transcription:

  1. Promoter
  2. RNA coding region
  3. Termination site
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80
Q

Promoter

A

Upstream of start site, bound/recognized by transcription apparatus, indicates direction of transcription, binding of RNA polymerase orient enzyme to start site

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81
Q

RNA coding region

A

Downstream to start site, only part that is transcribed, includes termination site

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82
Q

Termination site

A

Downstream to start site

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83
Q

RNA polymerase

A

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

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84
Q

Consensus sequences

A

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)

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85
Q

Up mutation

A

Strengths promoters, makes it more accurate to consensus sequence

86
Q

Down mutation

A

Weakens promoter, makes it less accurate to consensus sequence

87
Q

Sigma factor

A

Works with RNA polymerase in prokaryotes to recognize promoter, without sigma factor, RNA polymerase would bind randomly

88
Q

Holoenzyme

A

Complete complex with RNA polymerase and sigma factor

89
Q

Prokaryotic transcription initiation

A

RNA polymerase binds to promoter with help of sigma factor

90
Q

Prokaryotic transcription termination

A
  1. Rho dependent

2. Rho independent

91
Q

Rho dependent termination

A

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
Q

Rho independent termination

A

Inverted repeats causes hairpin in RNA, followed by string of uracils

93
Q

RNA polymerase II promoter

A

Made of core promoter and regulatory promoter

94
Q

Core promoter

A 
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
Q

Regulatory promoter

A

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
Q

Basal transcription apparatus

A

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
Q

Enhancer sequences

A

Effect rate of transcription, regulatory binding proteins can bind to affect the rate of transcription

98
Q

Eukaryotic transcription termination

A

Cleavage of mRNA at a specific site, RAT1 exonuclease degrades remaining RNA to terminate transcription

99
Q

RAT1

A

Degrade remaining mRNA after cleavage using 5’ to 3’ exonuclease activity

100
Q

Exons

A

Sections of DNA that code for genes, separated by noncoding introns, introns are spliced out

101
Q

Operon

A

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
Q

Eukaryotic premRNA processing

A 
Modification after transcription
1. Capping at 5' end
2. Poly(A)tion
3. Splicing
Coupling of transcription and processing by Pol II
103
Q

Capping

A

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
Q

Polyadenylation

A

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
Q

Spicing

A

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
Q

Spliceosome

A

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
Q

snRNP

A

snRNA + protein

108
Q

Small nuclear RNA

A

snRNA, U1-6

109
Q

C-terminal repeat domain

A

Couples mRNA transcription and processing, recruits 5’ capping proteins at beginning of transcription and receipts pol(A) factors at end of transcription

110
Q

Oncogenic

A

Potential to transform cell into malignant cell

111
Q

Beta-thalassemia

A

Genetic disease, mutation in beta-globing gene that disrupts normal splicing of RNA, misses part of intron

112
Q

Alternative processing

A

Produce different mRNA from same preRNA, different forms of proteins give different cell types

113
Q

Alternative splicing

A

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
Q

Alternative Poly(A) 3’ cleavage site

A

multiple 3’ cleavage sites in premRNA, each mRNA when translated produces similar proteins of different sizes

115
Q

Tra (Drosophilia)

A

Absence makes Drosophila male

116
Q

RNA editing

A

Sequence of nucleotides does not exactly match RNA product

117
Q

Substitution editing

A

Base conversation by specific enzymes

118
Q

Insertion editing

A

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
Q

RNA interference

A

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
Q

Transgenes

A

Incorporation into genome can increase gene activity or inhibit

121
Q

RNA silencing

A

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
Q

Discovery of RNA interference

A

Addition of dsRNA causes mutation which silences genes

123
Q

siRNA

A

Produced by cleavage of dsRNA by Dicer to give 21-25 bp sequences

124
Q

miRNA

A

Produced by cleavage of dsRNA of specific genes by Dicer to give 21-25 bp sequences

125
Q

RISC complex (siRNA)

A

RNA-induced silencing complex: siRNA combines proteins to form RISC complex, base pairs with target mRNA and causes cleavage and degradation

126
Q

RITS complex

A

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
Q

RISC complex (miRNA)

A

Partial pairing between miRNA and its target mRNA, blocks initiation of translation or causes premature termination

128
Q

Triplet code

A

3 consecutive ribonucleotides specify 1 amino acid, 4^3 = 64 possible codons

129
Q

Nuremberg and Leder

A

Deciphered genetic code using known genetic code, mRNA and tRNA

130
Q

61 sense codons

A

For amino acids, included Met (AUG), does not include 3 stop or nonsense codons

131
Q

Degeneracy

A

Amino acid specified by more than one codon

132
Q

Partial degeneracy

A

Changing third codon from one pyrimidine to another pyrimidine or from a purine to a purine

133
Q

Complete degeneracy

A

Changing third codon to any of 4 bases

134
Q

Synonymous codons

A

Codons that specify the same amino acid

135
Q

Isoaccepting tRNA

A

tRNAs that bind the same amino acid, even though they have different anticodons, 30 tRNAs but only 20 amino acids

136
Q

Wobble effect

A

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
Q

Reading frames

A

Protein coding regions of mRNA, single protein start and end sites, all begin with Met (AUG), no gaps, codons do not overlap

138
Q

Open reading frame

A

Portion of DNA with no stop codons

139
Q

Point mutations

A

Alter single nucleotide

140
Q

Frameshift mutations

A

Insertions and deletions of nucleotides

141
Q

5’ end of protein

A

Amino group

142
Q

3’ end of protein

A

Carboxyl group

143
Q

RNA-protein complex

A

Ribonucleoprotein, prokaryote complex has 3 proteins and 2 subunits

144
Q

5’CCA3’

A

tRNA attachement site for amino acid

145
Q

A site

A

Accepting incoming aa-tRNA

146
Q

P site

A

Holds the tRNA holding growing polypeptide

147
Q

E site

A

Discharged tRNAs leave ribosome from this site

148
Q

Antibiotics

A

Many alter translation apparatus, i.e. block exit site

149
Q

Prokaryotic translation

A

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
Q

tRNA charging

A

Amino acid attachment to tRNA at A end (5’CCA3’), energy for binging from ATP

151
Q

Aminoacyl-tRNA

A

tRNA + amino acid

152
Q

Aminoacyl synthetase

A

Attached amino acid to tRNA, 20 different

153
Q

Initiation of prokaryotic translation

A

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
Q

IF-3

A

Keeps large and small subunit apart

155
Q

IF-1 and IF-2

A

Mediate aatRNA(Met) binding to start site

156
Q

Elongation of prokaryotic translation

A

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
Q

Termination of prokaryotic translation

A

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
Q

Peptide transferase

A

Catalyses peptide bond formation between amino acids, part of large ribosomal subunit

159
Q

Release factor

A

Binds to A site and triggers release of polypeptide at P site

160
Q

Eukaryotic translation

A

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
Q

Chromosomal variations

A

Permanent chromosomal changes that can be passed to offspring if they occur in cells that can become gametes

162
Q

Chromosome rearrangements

A

Changes in structure of individual chromosomes

163
Q

Variation in chromosome number

A

One or more individual chromosomes added or deleted

164
Q

Human karyotype

A

n=23 (22 autosome, 1 sex), diploid: 2n=46

165
Q

Cri du Chat

A

Deletion of 1 chromosome in 5 pair

166
Q

Downsyndrome

A

Addition of 21 chromosome (3x21)

167
Q

Duplication

A

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
Q

Tandem duplication

A

Simplest form of duplication, two segments are adjacent

169
Q

Dosage effects

A

Excess copies of genes or chromosome segment can affect phenotype, can be caused by excess copies of gene mutations

170
Q

Redundancy (duplication)

A

Both copies remain the same on chromosome with duplication

171
Q

Pseudogene (duplication)

A

One copy of gene becomes inactive

172
Q

Neofunctionalization (duplication)

A

One develops new function, sources of new genes (ie. Globin gene family)

173
Q

Deletion

A

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
Q

Homozygous deletions

A

Deletions on both homozygous chromosomes, usually lethal

175
Q

Heterozygous deletions

A

Deletion on one copy of homozygous chromosome, usually viable but may have low fitness

176
Q

Inversion

A

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
Q

Position effect

A

New location of gene on chromosome may silence or hinder gene

178
Q

Pericentric inversions

A

Include genes on both sides of centromere

179
Q

Paracentric inversions

A

Include genes on one side of centromere

180
Q

Crossing over of inverted chromosomes

A

Inviable if in inverted region

Viable outside of inverted region

181
Q

Crossing over of paracentric inversion

A

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
Q

Crossing over of pericentric inversion

A

Recombinant gametes are nonviable because they have multiple copies of genes and are missing some genes

183
Q

Reciprocal translocation

A

Exchange between non-homologous chromosomes, creates a gene fusion or hybrid gene

184
Q

Philadelphia chromosome

A

Fused BRC-ABL gene ( 5’ BCR fused with most of ABL) causes inappropriate gene function and cancer

185
Q

Alternate segregation (reciprocal translocation)

A

In meiosis, no loss or gain of genetic information

186
Q

Adjacent segregation (reciprocal translocation)

A

(1 or 2 - more rare) In meiosis, causes loss and gain of genetic information

187
Q

Robertsonian translocation

A

Fusion of 2 chromosomes, centromeric fusion, fragments lost causes loss of genetic information, can segregate 3 ways

188
Q

Adjacent 1 segregation (robertsonian translocation)

A

Common, unbalanced

[(14;21)+21]x 2 + (-21)x2

189
Q

Adjacent 2 segregation (robertsonian translocation)

A

Uncommon, unbalanced

[(14;21)+14]x 2 + (-14)x2

190
Q

Alternate segregation (robertsonian translocation)

A

Common, balanced

(14;21)x2 + (normal)x2

191
Q

Aneuploidy

A

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
Q

Nullisomy

A

Loss of both members of a pair of homologous chromosomes (2n-2)

193
Q

Monosomy

A

Loss of a single chromosome (2n-1)

Not usually viable except in sex chromosomes

194
Q

Trisomy

A

Gain of a single chromosome (2n+1)

May be viable

195
Q

Tetrasomy

A

Gain of two homologous chromosomes (2n+2)

196
Q

Double monosomy

A

Less common, loss of two non-homologous chromosomes (2n-1-1)

197
Q

Double trisomy

A

Less common, gain of two non-homologous chromosomes (2n+1+1)

198
Q

Nondisjunction in meiosis I

A

(2n+1)x2 + (2n-1)x2

199
Q

Nondisjunction in meiosis II

A

(2n+1), (2n-1) + (normal)x2

200
Q

Primary Down Syndrome

A 
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
Q

Suspended oocytes

A

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
Q

Familial Down Syndrome

A

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
Q

Polyploidy

A

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
Q

Autopolyploidy

A

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
Q

Allopolyploid

A

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
Q

Cabbish/Raphanobrassica

A

Geneticist Karpechenko in 1928, tries to cross radish and cabbage

207
Q

Amphidiploid

A

Allotetraploid

208
Q

Significance of polyploids in agriculture

A

Cell volume is correlated with nucleus volume, correlated to genome size
ie. larger fruits: commercial bananas (3n), commercial strawberries (8n)

209
Q

Domestic bananas

A

Derived from 2 species, Musa acuminate (A) and Musa balbisiana (B)
Gros michel and Cavendish are AAA
Most plantains are ABB, or AAB

210
Q

Gros michel

A

Banana, wiped out in 1960s from Panema Disease (Fusarium), replaced by Cavendish (resistant)

211
Q

Tropical Race 4

A

New Fusarium, Cavendish not resistant

Biology 2030 (13 decks)

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