Chapter 11 and 12 Flashcards
(52 cards)
1
Q
deoxyribonucleotide
A
- sugar called deoxyribose, a phosphate group, and a nitrogenous base
2
Q
pyrimidines
A
- cytosine
- thymine
3
Q
purines
A
- adenine
- guanine
4
Q
genome
A
- each organism has a unique DNA sequence for that species
- genetic material that defines the organism
5
Q
central dogma
A
DNA encodes mRNA which in turn, encodes protein
6
Q
gene
A
unit of information encoded by DNA that can be expressed to form an RNA product
7
Q
gene expression
A
- RNA products of most genes are messenger RNA 9mRNA)
- mRNA directs the synthesis of a specific protein
- use of gene information to make mRNA and protein is called gene expression
8
Q
the specific sequence of nucleotides in the DNA can be copied to…
A
- make another DNA
- to make RNA that is directed toward protein synthesis
9
Q
phenotype
A
- determined by the specific genes within a geneotype that are expressed under specific conditions
- multiple cells may have the same genotype, they may exhibit a wide range of phenotypes resulting from differences in patterns of gene expression in response to different environmental conditions
10
Q
initiation
A
involves the unwinding of the helix, priming, and loading of the DNA Polymerase enzyme complex
- DNA Pol 3 adds nucleotides to growing chain
- unwinding only partially occurs
11
Q
Elongation
A
- the sequential extension of DNA by adding DNA nucleotide triphosphates with release of pyrophosphate, followed by proofreading
12
Q
termination
A
- in which the DNA helix is completely duplicated, and replication stops
13
Q
RNA primase
A
adds primer with 3’ OH group–> DNA Pol III can extend RNA primer
14
Q
RNA Polymerase
A
- adds nucleotides one by one to the 3’-OH group of the growing nucleotide chain
15
Q
difference between DNA polymerase and RNA polymerase
A
- DNA polymerase requires a 3’ OH group, thus necessitating a primer, whereas RNA polymerase does not
16
Q
sigma subunit
A
- enables RNA polymerase to bind to a specific promoter, thus allowing for the transcription of various genes
- various sigma factors allow for transcription of varous genes
17
Q
initiation of transcription of RNA
A
- begins at a promoter (DNA sequence onto which the transciption machinery binds and initiates transcription)
- initiation site= nucleotide pair in DNA double helix that corresponds to the site from which the first5’ RNA nucleotide is transcribed
18
Q
promoters
A
- located just upstream of the genes they regulate
- -10 and -35 positions in the DNA prior to the initiation site (+1)
- -10= TATA box, -35= bound by a sigma subunit
19
Q
elongation in transcription of RNA
A
- begins with the sigma subunit dissociates from the polymerase, allowing the core enzyme to synthesize RNA complementary to the DNA template in a 5’ to 3’ direction at a rate of 40 nucleotides per second
- DNA is continuously unwound ahead of core enzyme and rewound behind it
20
Q
termination of RNA
A
- bacterial polymerase must dissociate from the DNA template and liberate the newly made RNA= termination of transcription
- DNA template has repeated nucleotide sequences that act as termination signals, causing RNA polymerase to stall and release from the DNA template, freeing the RNA transcript
21
Q
protein synthesis machinery
A
- ribosomes (rRNA and proteins)
- transfer RNAs
22
Q
tRNAs
A
- exist in cytoplasm
- 60 to 90 types
- bind to specific codon on the mRNA template and add the specific amino acid to the polypeptide chain
23
Q
initiation, elongation, termination of translation
A
- initiation: transitional complex forms, and tRNA brings first amino acid in polypeptide chain to bind to start codon on mRNA
- elongation: tRNAs bring amino acids one by one to add to polypeptide chain
- termination: release factor recognizes stop codon, translational complex dissociates, and completed polypeptide is released
24
Q
post-translational modifications
A
- removal of translated signal sequences– short tails of amino acids that aid in directing a protein to a specific compartment
- proper “folding” of the polypeptide and association of multiple polypeptide subunits, often facilitated by chaperone proteins, into a distinct 3D structure
- proteolytic processing of an inactive polypeptide to release an active protein component and various chemical modifications (phosphorylation, glycosylation) or individual amino acids
25
point mutation
- base substitution
- when a single nucleotide is changed in a DNA sequence
- silent mutation
- missense mutation
- nonsense mutation
26
insertion/deletion
- involved the addition or subtraction of one or more nucleotides
- frameshift mutation
27
inversion
occurs when a fragment of DNA is flipped in orientation in relation to the DNA on the other side
28
what cuases mutations
- a "mistake" by DNA polymerase that fails to be repaired
- physical agents: cosmic rays, X-rays, UV radiation (cause pyrimidine dimers)
- chemical agents: reactive oxygen molecules, superoxide radicals, acridine orange, certain biological processes
29
base excision repair
- recognizes a specific damaged base and removes it from the DNA backbone
30
methyl mismatch repair
requires recognition of the methylation pattern in DNA bases
31
SOS repair
coordinated cellular reponse to damage that can introduce mutations in order to save the cell
32
DNA recombination
the process of "crossing over" and exchange of two DNA helices
33
changing the DNA sequence
some microbes change the DNA sequence to activate or disable a particular gene
34
control of transcription
transcription can be regulated by proetin repressors, activators, and alternative sigma factors
35
translational control
control of transcription initiation sequences that recognize specific repressor proteins
36
post-translational control
control of proteins that are already made
- ex: activate, deactivate, or degrade the protein
37
operon
- a set of genes controlled by same promoter
- Polycistronic mRNAs are RNA and are typically transcribed from operons.
- Genes on the a Polycistronic mRNA are typically regulated by the same promoter.
38
repression
- repressor binds to operator, preventing transcription of lac operon
39
sensing the intracellular environment
- different regulatory proteins bind to specific compounds to determine the compound's concentration
40
global regulators
- proteins that affect the expression of many differential genes are called global regulators
41
sensing the extracellular environment
- a common mechanism by bacteria to sense outside of the cell and transmit that information inside relies on a series of two-component protein phosphorylation relay systems
42
vertical gene transfer
occurs during reproduction between generationd of cells
- between mother and daughter cells
- exchange of genes between two DNA molecules
- crossing over occurs when two chromosomes break and rejoin
43
horizontal gene transfer
- the transfer of genes between cells of the same generation
- between one bacteria and another
44
plasmids
- mostly circular, double-stranded, extrachromosomal DNA
- self replicating by the same mechanisms as any other DNA
- most of plasmids have been identified due to having some function they allow the bacterium to survive
45
plasmid functions
| F, resistance, virulence, tumor induce, catabolic enzme, bacteriocinogen
1. F plasmids direct synthesis of protein towards the pili
2. Resistance plasmids carry genes that provide resistance to antimicrobials
3. Virulence plasmids cause disease signs and symptoms
4. tumor inducing plasmids-- cause tumor formation in plants
5. genes for catabolic enzymes-- not essential for cell growth
6. Bacteriocinogen plasmid-- direct synthesis of bacteriocins
46
transposable elements
- genes that can move from one chromosome to another
- cannot replicate outside a larger DNA molecule
- all transposable elements include transposase gene whose enzyme product moves the element from one DNA molecule into another
- simplest= short DNA sequences (insertion sequences)
- insertion sequence has transposase gene flanked by short inverted repeat sequences
- transposase binds to these inverted repeats and cuts the DNA
- transposase creates staggred cuts in the target DNA wo which the excised insertion sequence is ligated
47
transformation
- importing free DNA from the environment into bacterial cells
- naturally inherent to many bacterial species
48
electroporation
a brief electrical pulse "shoots" DNA across the membrane
49
transduction
- gene transfer is mediated by a bacteriophage vector
50
Why is transduction significant
1. transfer genetic material from one bacterial cell to another and alters the genetic characteristics of the recipient cell
2. Incorporation of phage DNA into a bacterial chromosome demonstrates a close evolutionary relationship between the prophage and the host bacterial cell
3. viruses bring along genes from their previous host--> type of DNA incorporated into us might belong to another animal (we're transgenic)
4. can study gene linkage
51
conjugation
- gene transfer requires contact between donor and recipient cells
- larger quantities of DNA are transferred compared to transduction/transformation
52
why is conjugation significant?
1. contributes to genetic variation
2. increases genetic diversity because larger ampunts of DNA are transferred
3. may represent and evolutionary stage between asexual processes and the actual fusion of whole cells
