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Microbiology > Chapter 7 - Genetics > Flashcards

Chapter 7 - Genetics Flashcards

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0
Q

Genome

A
  • entire genetic makeup of an organism

- genes and nucleotides

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1
Q

Genetics

A
  • the study of inheritance and inheritable traits as expressed in an organisms genetic material
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2
Q

Nucleic Acid Structure

A
  • polymers of nucleotides
  • nitrogenous bases bind to each other in DNA through Hydrogen bonds
  • 3prime end has an OH
  • 5prime end has a phosphate
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3
Q

DNA

A
  • genetic material
  • double stranded antiparallel
  • backbone is a deoxyribose ring with 1’ through 5’ carbons
  • 5’ Carbon attaches to the next base’s 3’ Carbon
  • A, T, C, G are nitrogenous bases attached to 1’ Carbon
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4
Q

RNA

A
  • no THYMINE, only Uracil
  • 2’ Carbon contains an OH
  • less stable
  • single stranded
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5
Q

Prokaryotic Chromosomes

A
  • haploid (single copy)
  • one long circular DNA in nucleoid
  • held in place by protein and RNA
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6
Q

Plasmid

A
  • prokaryotic
  • small circular molecules of DNA that are not connected to chromosomes
  • replicate independently of the chromosome
  • don’t contain genes necessary for normal function
  • each cell may have many copies of one plasmid
  • fertility, resistance, bacteriocin, virulence
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7
Q

Nuclear Chromosomes

A
  • Eukaryotic
  • within nucleus
  • more than one chromosome per cell
  • linear
  • diploid (two copies)
  • composed of nucleosomes-chromatin-euchromatin-heterochromatin
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8
Q

Nucleosomes

A
  • when negatively charged DNA wraps around positively charged histones to form beads
  • first step of making a Eukaryotic chromosome
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9
Q

Chromatin

A
  • nucleosomes clumped together with other proteins
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10
Q

Euchromatin

A
  • loosely packed active chromatin
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11
Q

Heterochromatin

A
  • densely packed inactive chromatin
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12
Q

DNA Replication

A
  • DNA becomes new DNA
  • semiconservative, new DNA is composed of 1 original and 1 daughter strand
  • anabolic polymerization process
  • DNA nucleotides carry the energy needed for DNA synthesis (dGTP, dTTP, dATP)
  • bidirectional
  • older strands are METHYLATED (need for DNA repair)
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13
Q

DNA Replication Differences for BOTH

A
  • semiconservative
  • 5’ to 3’
  • primase
  • DNA helicase
  • DNA polymerase
  • Ligase
  • RNAse
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14
Q

DNA Replication Differences for PROK.

A
  • only 1 origin
  • Okasaki fragments are 1000 long
  • occurs in nucleoid
  • all systems continue to work
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15
Q

DNA Replication Differences for EUK.

A
  • many origins
  • Okasaki fragments are about 400 long
  • occurs in Nucleus
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16
Q

Process of DNA Replication

A
  • DNA helicase unwinds DNA so it can be copied
  • replication starts at the origin and spreads both ways (PROK) or has many origins (EUK)
  • a primer is synthesized by primase and binds
  • DNA polymerase binds
  • always goes 5’ to 3’ for new strand (BUT you start at OLD 3’)
  • leading strand is synthesized continuously
  • lagging strand is made in okasaki fragments and glued together by ligase
  • RNAse eats the primer when it is not needed anymore
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17
Q

Genotype

A
  • set of genes in a genome

- series of nucleotides that carry instructions

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18
Q

Phenotype

A
  • physical features and functional traits that can be SEEN
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19
Q

Central Dogma of Genetics

A
  • DNA to RNA = transcription

- RNA to Proteins = translation

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20
Q

Transcription

A
  • DNA to RNA
  • makes RNA primers, mRNA, rRNA, tRNA, Regulatory RNA
  • 3 steps: Initiation, Elongation, Termination
  • need promoter, helicase, RNA polymerase
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21
Q

Transcription Differences in BOTH

A
  • promoter
  • helicase
  • RNA polymerase
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22
Q

Transcription Differences in PROK.

A
  • simple

- occurs in nucleoid

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23
Q

Transcription Differences in EUK.

A
  • occurs in nucleus
  • CAP
  • polyadenylation (AAAAAAAA at the end)
  • splicing
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24
Polyadenylation in Transcription
- Eukaryotes only | - adding 100 to 250 As at the end
25
Splicing in Transcription
- clipping out the pieces that don't code for anything (introns)
26
Intron
- Eukaryotic Transcription | - intervening segments, not used
27
Extron
- Eukaryotic Transcription | - expressed segments, used
28
Transcription Process
- INITIATION - RNA polymerase attaches to DNA and travels down until it recognizes a promoter - RNA polymerase then unzips DNA - ELONGATION - Triphosphate ribonucleotides align opposite their compliments - RNA polymerase links the two together and elongates the strand - TERMINATION - transcription stops
29
Translation
- RNA to proteins - use mRNA, tRNA, rRNA, and ribosomes - inititation and elongation require energy (GTP)
30
Translation Differences in PROK.
- polycistrone (multiple proteins from the same RNA) - translation can start before transcription has finished because it stays in the same place - Ribosomes bind at Ribosome Binding Site - there can be MANY ribosomes at once
31
Translation Differences in EUK.
- 1 mRNA codes 1 protein - RNA must be sent through nuclear pores and caught by cytoplasmic ribosomes - Ribosomes bind at 5' end CAP to start (only one ribosome) - Ribosomes can synthesize polypetides in RER through free ribosomes
32
Translation Process
- INITIATION - Ribosome binds to the RNA at the RBS (PROK) or at the 5' end (EUK) - the ribosome scans until AUG (start codon) - AUG locks into P site of ribosome - tRNA recognizes AUG via it's anticodon - the large subunit of the ribosome binds - ELONGATION - the tRNA that matches the next codon is put into the A site and read - rRNA in the ribosome joins the AUG methionine to the 2nd amino acid - the ribosome then moves on to the next codon - tRNA holding on to the AUG codon moves to the E site and releases - TERMINATION - this continues until a STOP codon is reached - the entire polypeptide chain is released
33
Transfer RNA
- used in Translation - 3 leaf clover shaped - anticodon on the end that is complimentary to mRNA codon
34
mRNA
- made by Transcription - used in Translation - what the ribosome reads to create the protein
35
Translation Ribosomes
- Prokaryotic = 70s - Eukaryotic = 80s - E site = exiting tRNA - P site = growing polypeptide, tRNA - A site = amino acids
36
STOP CODON
- UAA - UAG - UGA
37
START CODON
- AUG | - methionine
38
Operon
- prokaryotic - consists of a promoter and a group of structural genes - controlled by the operator - regulatory gene is at a different place completely to turn on/off operon - Inducible = catabolic and normally OFF - Repressible = anabolic and normally ON
39
Inducible Operon
- catabolic - normally OFF, get turned on - ex. lactose operon
40
Repressible Operon
- anabolic - normally ON, gets deactivated - ex. Tryptophan Operon
41
Lac Operon
- inducible operon - normally blocked by an inhibitor - lactose binds the inhibitor and inactivates it - lac operon is turned on - cAMP indicates low glucose and stimulates more lac transcription - inhibitor is transcribed and attaches to the operator again
42
Tryptophan Operon
- repressible operon - on until Trp binds to an inactive repressor in the environment - repressor becomes active and binds to operator to block it
43
Mutation
- change in the nucleotide base sequence of a genome - almost always bad - RNA has more than DNA - point => frameshift
44
Point Mutation
- most common - one base pair is effected - substitutions and frameshifts
45
Substitution Mutation
- point mutations - silent = no change in amino acid - missense = slightly different amino acid - nonsense = creates a STOP codon
46
Frameshift Mutations
- point mutations - BAD - insertion - deletion
47
Mutagens
- physical or chemical agents that cause an increase in mutation rate - radiation - chemical
48
Radiation Mutagens
- ionizing = xrays or gamma rays | - non ionizing = UV light which causes pyrimidine dimers
49
Chemical Mutagens
- nucleoside analogs - nucleotide altering chemicals - frameshift mutagens (cause an unreadable bulge)
50
Mutants
- when a mutagen is not removed, it carries on to the daughter cell - wild type is the "normal" found in the wild without a mutation - to distinguish mutants from wild type, use positive or negative selection
51
Ames Test
- a test to identify mutagen - positive selection - a strain of Salmonella lacking the ability to synthesize His- is subjected to the mutagen and plated - the rate of wild type His- is measured - if a higher rate of mutation is seen, this is considered a mutagen
52
Carcinogens
- mutations known to cause cancer
53
Vertical Gene Transfer
- organisms replicate their genomes and provide copies to descendants - normal in humans
54
Recombinants
- cells with DNA molecules that contain new pieces of nucleotide sequences - basically swapping bits and pieces back and forth
55
Horizontal Gene Transfer
- donor cell contributes part of it's genome to a recipient in the same generation - transformation, transduction, bacterial conjugation
56
Transformation
- horizontal gene transfer - bacteria picks up DNA from the environment and uses it as a plasmid or recombination into it's own DNA - plasmids are easier, "ready to use" - not many bacteria are competent (can pick up DNA) - ex. Griffith and the strepto rats
57
Competent Bacteria
- bacteria that are able to pick up DNA from the environment
58
Transduction
- When a virus infects a cell - transducing phage carries random DNA segment from donor to recipient - two types: general and specialized
59
Lytic Cycle
- phase in transduction - the bateriophage latches onto host cell and injects DNA - phage DNA changes cell to make more phage DNA - the host cell dies and lyses
60
General Transduction
- bacteriophage attaches to a cell - lytic cycle begins - some of the host DNA is accidentally packaged into a new bacteriophage - this new bacteriophage lands on a new cell, but doesnt enter lytic cycle because the DNA is not bacteria
61
Specialized Transduction
- when a phage is in the lysogenic cycle - the insertion point of the bacteria on the cell rips out the host DNA only in that specific spot - pulls out only a much more specific sequence - ex. Cholera toxin
62
Lysogenic Cycle
- during transduction - before lytic cycle - the phage injects it's DNA into the cell - phage recombines the host DNA - there is a period of waiting until the lytic stage
63
Bacterial Conjugation
- F+ bacteria carry a fertility plasmid that allows them to form a sex pilus - The F+ cell attaches to an F- cell to transfer one strand of the F+ plasmid to the F- cell - this makes both cells now F+
64
Hfr Conjugation
- type of bacterial conjugation - high frequency recombination - Hfr cell (F+ plasmid incorporates into DNA) joins an F- cell - the F+ plasmid portion is transferred to the recipeint, but because it has become incorporated into the DNA, all the DNA strand gets transferred - the sex pilus breaks the cells apart before the transfer is finished and the F- cell ends up with a portion of the Hfr cell - the new DNA is recombined with the F- cell and the cell stays F-
65
Transposition
- bits of DNA hopping from one place to another within a genome - copying itself, not removing - can jump into a plasmid and be sent out of the cell - results in a frameshift
66
Transposon
- the segment of DNA that moves from one location to another during Transposition - palindromic sequence at either end of segment to help with insertion
67
Simple Transposons
- insertion sequences | - have no more than 2 inverted repeats
68
Complex Transposons
- contain one or more genes not connected with transposition | - most successful

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