Block 2.1 Microbial Genetics Flashcards
(63 cards)
1
Q
Genome
A
- All of the genes on all chromosomes
- The Hereditary info
2
Q
Chromosome
A
- 1 double strand of DNA containing multiple genes
- AKA Nuclear Material
- AKA Nucleic Acid
- Always DNA except in RNA viruses
3
Q
Gene
A
-Piece of DNA that contains the genetic code for a functional product (e.g. codes for a specific protein)
4
Q
The genetic codes is translated into proteins for (blank x3) within the cell with the aid of messenger RNA and ribosomes
A
- Structural Functions
- Catalytic Functions
- Regulatory Functions
5
Q
How is the genetic code for each protein carried?
A
As a sequence of nucleotide molecules in the nucleic acid (DNA) macromolecule
6
Q
Genotype
A
Total genetic makeup of organism
7
Q
Phenotypes
A
Actual, expressed properties of an organism (e.g.) proteins
8
Q
Composition of Nucleic Acid
A
- Nucleotide- basic building block of Nucleic Acid
- Nitrogenous Base- on the 1’ carbon nucleotide
- Phosphate Group- on the 5’ carbon of nucleotide
9
Q
What is a nucleotide made of?
A
5-carbon sugar
Either Ribose or Deoxyribose
10
Q
2 Types of Nitrogenous Bases
A
- Purine - Adenin & Guanine
2. Pyrimidine- Thymine, Cytosine, Uracil
11
Q
Binding of Nucleotides
A
A –> T (or U in RNA)
G –> C
12
Q
DNA Strand
A
Long strand of nucleotides
13
Q
Strand Direction
A
3’ End- where NO phosphate is bound to 3’
5’ End- where phosphate IS bound only to the 5’
14
Q
What does antiparallel mean?
A
- Strand run in opposite directions
- Nucleotide of 3’ end of one strand pairs with nucleotide of 5’ end
- Strands are COMPLEMENTARY, not identical
15
Q
How are replication forks formed?
A
- Helicase, DNA Gyrase, & Topoiosomeras enzymes break the hydrogen bonds between bases or hold part of the strand stable
- Short lengths of double-stranded DNA UNWIND
- Unwinding exposes the separated strands
16
Q
What does DNA polymerase do?
A
Generates a new strand by binding to DNA & insertingCOMPLEMENTARY nucleotides
17
Q
What end are nucleotides added to?
A
- The exposed 3’ end of the growing strand
- Grows from 5’ –> 3’
18
Q
DNA (blank) for errors
A
Edits
19
Q
What is the “Leading Strand”
A
- The newly growing strand that has the 3’ end of the exposed nucleotide leading TOWARDS the replication fork
- Strand grows towards replication fork
- Continuously Replicated (easy)
20
Q
What is the “Lagging Strand”
A
- Strand that has 5’ end facing the replication fork
- New strand grows AWAY from replication fork
- Replicates fragments, then joins them together
21
Q
Lagging Strand Growth Process (Discontinuous)
A
- RNA polymerase initiates strand growth in absence of nucleotide with 3’ binding site… RNA polymerase PROVIDES the 3’ binding site
- DNA polymerase- goes over what RNA did and puts doesn’t DNA nucleotide
- DNA ligase joins strand fragments together by inserting nucleotide
22
Q
What does “Semiconservative” Replication mean?
A
When the entire chromosome is copied, each double helix is made of 1 parent strand & 1 new strand
23
Q
3 Types of Ribonucleic Acid
A
- Messenger RNA
- Transfer RNA
- Ribosomal RNA
24
Q
What is RNA
A
Large, single-strand molecule of nucleotides attached to the ribose sugar
25
Purpose of RNA
1. Transfer of genetic code from DNA
| 2. Insertion of amino acids in protein synthesis
26
mRNA function
Carry genetic code from DNA to ribosomes
27
What is a Codon?
- 3 nucleotides (triplet code) on mRNA that specify amino acid composition & sequence in a polypeptide
- 3 Nucleotides = 1 Codon = 1 Amino Acid
28
tRNA Function
Transport & Transfer amino acid to developing polypeptide chain
29
What is an Anticodon?
- Site on tRNA that bonds with the Codon on mRNA
- 3 bases that compliment the codon
- Specifies which amino acid will be carried by tRNA
30
rRNA Function
- Assists Protein Synthesis
- "Facilitator" for mRNA & tRNA functions
- Site where codons & anticodon come together
- Site where amino acids become polypeptides
31
Steps of protein synthesis
1. Transcription
| 2. Translation
32
Transcription
Transfer of genetic code on DNA into mRNA via DNA-dependent RNA polymerase
33
5 Steps of Transcription
1. DNA unwinds a portion & strands separate (exposes nucleotide bases)
2. RNA polymerase binds to DNA @ PROMOTOR SITE (aka beginning of the gene)
3. Complementary RNA nucleotides are joined by RNA polymerase
4. Transcription ends when RNA polymerase reaches TERMINATION region of the gene
5. New SINGLE-stranded mRNA is released & DNA rewinds
34
Translation
Synthesis of polypeptide @ the ribosome by linking amino acids in a sequence specified by mRNA
35
4 Steps of Translation
1. mRNA attaches to ribosome w/ "Start" codon
2. tRNA w/ anticodon matches to codon on mRNA... placing the 1st Amino Acid
3. Amino acids are linked together, and tRNA releases (like a stamp)
4. Polypeptide chain is released at "stop" codon
36
3 Types of Genes (Concerning Regulation of Gene Expression)
1. Constitutive Genes- constantly expressed (majority)
2. Inducible Genes- can be turned ON
3. Repressible Genes- can be turned OFF
37
Operon
- Related genes that are regulated as a group/series
| - E.x. genes that code for enzyme of a single metabolic pathway
38
Repressor Gene
- Located in another part of the chromosome
| - Codes for a "repressor" protein that can bind to the "operator" region
39
Operator Site
- Region of chromosome which permits/blocks access of the RNA Polymerase to the structural genes of the operon
- Site where the Repressor Protein binds
40
Genes of the Operon
Adjacent genes of the operon which direct synthesis of proteins with Related Functions & that are regulated as a unit
41
Inducible Operon
- Genes that are expressed only when certain conditions are present
- Ex substrates cause operator site to be unblocked
42
Repressible Operon
- Genes are always expressed EXCEPT in certain conditions
| - Ex Presence of metabolic products causes Operator site to be blocked
43
Mutation
Changes (substitutions or deletions in DNA sequence that change the genetic code
44
Mutations can cause Protein Changes that result in what?
Changes to metabolic, antigenic, or structural features
45
2 Types of Mutations
1. Base Substitution
| 2. Frameshift Mutation
46
Base Substitution
- A single base is replaces with another, which changes the codon
- Can results in wrong amino acid in the protein
47
3 Types of Base Substitutions
1. Silent- No changes in the protein
2. Missense- Different amino acid in the protein (not a big deal)
3. Nonsense- RNA polymerase is STOPPED from reading the code... results in incomplete (nonfunctional) protein
48
Frameshift Mutation
Insertion or Deletion of bases can SHIFT the codon reading frame of the mRNA in the ribosome
49
What do frameshift mutations result in
1. Missense Mutation
| 2. Significantly different, nonfunctional, or incomplete protein
50
What Causes Mutations?
1. Spontaneous Mutation
2. Chemical Mutagens
3. Radiation- X-ray, Gamma Rays, UV Light
51
Recombination
Gain, Loss, or Substitution of ENTIRE gene segments (or inversions/transpositions) to FORM NEW COMBINATIONS of genes
52
What does recombination result in?
Major Change or Nonfunctional Cell
53
Sources of Gene Recombination
1. DNA from the same microbe
2. DNA from another microbe
3. RNA from viruses
54
Plasmid
- Small Circular, Self-Replicating piece of DNA in bacteria
- Separate from Chromosomal DNA
- Not essential for growth of bacterium
- Used in genetic engineering (Hepta-Vax)
55
Lysogeny
Integration of DNA from bacteriophage (virus) into bacterial chromosome where it replicates along with bacterial chromosome
56
What can viral genes in lysogeny code for?
1. Antibiotic Resistance
| 2. Disease-Causing factors
57
What does lysogen produce?
New Bacteriophage upon separation from bacterial DNA
58
Conjugation
- Transfer of genetic info between donor & recipient cells
- Direct Cell-to-Cell contact
59
2 Steps of Conjugation
1. Sex Pilus is used to transfer DNA
| 2. Copy of DNA strand (or plasmid) is transferred to the recipient cell
60
Transformation
- Direct uptake of DNA segment from one bacterium to another as "naked" DNA in solution
- Happens after bacterial cell dies & breaks down
61
Result of Transformation
New characteristics for the recipient cell
62
Transduction
- Transfer of DNA from donor to recipient bacterium via a Bacterial Virus as the vehicle
- Host DNA is accidentally enclosed in virus
63
Result of Transduction
New characteristics for the recipient Cell
