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Miocrobiology > Micro Exam 2 - Ch 9 > Flashcards

Micro Exam 2 - Ch 9 Flashcards

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1
Q

Genome definition

A

The total sum of genetic material in an organism

Mostly organized into chromosomes (tightly coiled DNA)

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2
Q

What do bacteria have in addition to chromosomes?

A

Plasmids - small, circular pieces of DNA with non-essential information

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3
Q

Gene definition

A

Fundamental unit of heredity. They contain all necessary information to make a molecule of protein or RNA.

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4
Q

Nucleotide definition

A

Basic unit of nucleic acid structure

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5
Q

What is the general make up DNA?

A

Deoxyribose + phosphate = backbone
Nitrogenous bases held together by hydrogen bonds

(The nucleotides attach at the D sugar)

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6
Q

How are nitrogenous bases bonded?

A

They bond covalently to the 1’ carbon of each base onto the sugar
They pair complementary to the other strand

A bonds to T with 2 hydrogen bonds
G bonds to C with 3 hydrogen bonds

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7
Q

Why is base pairing important?

A

Because it guarantees the code will be retained. It serves as a template for the other half to be replicaged.

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8
Q

DNA replication overview

A

This is the copying of DNA inside the cell
It occurs in the cytoplasm and begins at the origin of replication (ORI) and proceeds outwards from there in what is called replication forks. Then binary fission.

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9
Q

Why is replication called Semi-Conservative?

A

Because each replicate has one parent strand and one new one

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10
Q

What are the 4 steps in DNA replication?

A
  1. Helicase unwinds the DNA helix
  2. Primase makes a RNA primer is made at the ORI (origin of replication)
  3. DNA polymerase III then adds nucleotides in a 5’ to 3’ direction
  4. DNA polymerase I removes the RNA primers and replaces them with DNA
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11
Q

What is the difference between the leading strand and the lagging strand?

A

At the ORI, the leading strand and lagging strands are working in opposite directions but still in the 5-3 pattern.

The leading strand is going 5-3, no complications.
The lagging strand goes 5-3 in segments, so it looks like its going 3-5.

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12
Q

What is the central dogma of biology? (3)

A

DNA can replicate itself (DNA replication)
DNA is transcribed into RNA (transcription)
RNA is translated into protein (Translation) (or in special cases into DNA)

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13
Q

What is transcription?

A

The process where genetic information in DNA molecules is conveyed to RNA

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14
Q

What is translation?

A

When the information contained in a RNA molecule is then used to produce proteins

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15
Q

What are the three differences in the structure of RNA compared to DNA?

A

RNA is single stranded and lead to specialized forms
RNA contains Uracil instead of Thymine
RNA used ribose sugar instead of deoxyribose sugar

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16
Q

What is the function of mRNA?

A

Contains the code for sequences of amino acids in protein
It carriers the DNA master code to the ribosomes

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17
Q

What is the function of tRNA?

A

It contains the code for specifying a given amino acid
It carries amino acids to ribosomes during translation

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18
Q

What is the function of rRNA?

A

It contains the code for several large structural RNA molecules
It forms the major part of the ribosomes and participates in protein synthesis

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19
Q

What is the function of primer?

A

It contains the code for an RNA that can begin DNA replication
It primes DNA

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20
Q

What are the three stages of transcription?

A

Initiation
Elongation
Termination

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21
Q

What happens during initiation?

A

RNA polymerase binds to promoter region upstream of the gene

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22
Q

What happens during elongation?

A

RNA polymerase adds nucleotides to the DNA template strand in the 5-3 direction.
(U compliments A in this part)

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23
Q

What happens during termination?

A

RNA polymerase recognizes a STOP sign in the DNA and releases the transcript
The transcript can now be 100-1,200 bases long

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24
Q

What direction does the template strand run?

A

3 to 5
Because we can only build 5 to 3, the template strand will be the opposite

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25
What happens during translation?
1. mRNA binds to a ribosome in the cytoplasm 2. One of the two types of RNA gets to work. (rRNA for ribosome or tRNA for transfer) 3. tRNA decodes the mRNA and brings the correct amino acids in pieces of 3 called codons 4. The 20 amino acids are decoded from the codons
26
Where does translation always start and end?
It always starts with AUG which codes for methionine It ends when the tRNA reads UGA, UAG, or UAA
27
What regulates genes?
In prokaryotes, gene regulation is coordinated by operons. The are regulated to be active only when their products are required.
28
What are the two types of operons?
Inducible and repressibleW
29
What are inducible operons?
An operon that is turned ON by a substrate They are catabolic Enzymes are produced when a substance is needed to be made Off, need to be turned on
30
What are repressible operons?
An operon that is turned OFF but the product synthesized They are anabolic Enzymes used to make things are turned off when they are not needed On, need to be turned off
31
What is the Lactose operon made of?
It is an inducible operon It has 3 segments: regulator, control locus, and structural locus Regulator codes for repressor Control locus is made of the promoter and operator The structural locus is made of 3 genes each coding for an enzyme needed to catabolize lactose
32
What are the 3 enzymes needed to catabolize lactose? What do they specifically do?
Beta-Galactosidase - hydrolyzes lactose Permease - brings lactose across the cell membrane Beta-galactosidase transacetylase - we don't know
33
How does the Lac operon work?
1. The operon is off = no lactose. A repressor protein binds to the operon. This blocks the transcription of proteins that would be needed to make the enzymes that could break down lactose. 2. But when lactose enters the cell, it attaches to the repressor protein and knocks it off. The turns the operon "on" and now it can transcribe and build the proteins that make those lactose-catabolizing enzymes.
34
What is a mutation?
A permanent change in the DNA code
35
What causes a mutation?
It can be spontaneous or induced And it doesn't necessarily me it's going to be negative It can be caused by mutagens, usually chemical or radiation
36
What are the types of chemical mutagens?
Chemicals that make DNA base pairing not work properly. This could be nucleoside analog or intercalating agent. The nucleoside analog mimics a nucleotide, takes it place and messes up the base pairing. Intercalating agent slip in-between nucleotides and cause skipping.
37
What is a type of UV mutagen?
Thymine dimer- it is a bond between adjacent thymine nucleotides. It can be repaired, but even then you can still get errors in code.
38
What is a type of radiation mutagen?
X radiation makes free radicals that damage DNA
39
What do mutations lead to?
Selection for certain traits that over time can change the characteristics of a population Ex/ antibiotic resistance
40
What are point mutations?
Mutations that result in a small change on a single gene
41
What is a silent mutation?
A mutation that occurs because the genetic cocarde is redundant It does not change the actual sequence of coded amnio acids Ex/ GGC=CCG codes for PRO changes to GGT=CCA and still codes for PRO. Both code for Pro, nothing changes overall.
42
What is a missense mutation?
Like a silent mutation, but it DOES change the coding for amino acids. The effect depends on the location within the protein. If it's for something like an active site on an enzyme, the effect can be large. Ex/ TCT=AGA codes for ARG. TCA=AGU codes for Ser. Changing the last letter of codon coded for an entirely different amino acid.
43
What is a nonsense mutation?
When the mutation changes a codon to a stop codon. It shortens the length of the protein. Ex/ TCT=AGA codes for ARG. Mutates to ACT=UGA codes for STOP. Nothing beyond that point will get coded for.
44
What is an inversion mutation?
When adjacent letters switch places. This can result in significant changes in amino acid and protein functions. Ex/ TCT=AGA codes for ARG. Mutates to CCT=GGA now codes for GLY. The C before TCT switches with the T to become CCT. The G before the A switches to become GGA.
45
What is a frameshift mutation?
Adding or deleting a base during transcription, messing up the sequences of 3. This will result in an entirely different protein and sequence. Ex/ TAC GGC TCT = AUG CCG AGA. Mutates to TAC GGC TTC T = AUG CCG AAG A. Added a T in front of TCT, now the third pair is TTC when it should be TCT. Codes for a different amino acid.
46
What are the four ways a cell can repair a mutation?
- DNA polymerase - proofreads during replication - Mismatch repair - locates and repairs any mismatched bases that were missed by DNA polymerase - Light repair - for UV light damage - Excision repair - locates and repairs incorrect sequences by removing a segment of the DNA and then adding in the correct part
47
What is horizontal gene transfer?
When bacteria exchange DNA between cells
48
What is vertical gene transfer?
When bacteria pass DNA from one generation to the next following DNA replication
49
What are the three types of horizontal gene transfer?
Conjugation, transformation, and transduction
50
What is special about plasmids?
It can replicate in the cell without the chromosome replicating at the same time It's also only in prokaryotes
51
What is conjucation?
Passing DNA directly through the pilus A plasmid will duplicate itself, unwind, transfer through the pilus, and then become circular again
52
What are E. Coli's special fertility cells?
F+ cells make the pilus. They only conjugate with F- cells. The F+ cell makes a copy of F+ and sends it to the F- cells, turning it into an F+ cell. Newly F+ cells are called Hfr (High frequency recombination)
53
What experiment dealt with transformation?
Griffith's experiment
54
What is transduction?
A horizonal method of sharing genes where bacterial DNA is transferred by a virus called a bacteriophage ( a virus that only affects bacteria.)
55
What are the steps in transduction?
1. A virus infects a bacteria cell. 2. It tricks the cell into producing viral proteins and chops up the cell's DNA in the process. 3. When the viral proteins are packaged, sometimes the DNA will get mixed up and packaged with it. 4. The virus leaves and infects a new cell, accidentally transferring the first bacteria's DNA with it, making it recombinant.
56
A special enzyme called a topoisomerase packages a chromosome into a tight bundle in what kind of cells?
prokaryote
57
A segment of DNA that codes for protein or RNA is a(n)
gene
58
Which bases are purines? Which are pyrimidine?
Purines = A & G Pyrimidines = T/U & C
59
Which direction/arrangement are DNA strands?
anti-parallel
60
Which enzyme completes the final sealing of fragments in a newly synthesized DNA strand?
Ligase
61
The final sealing of Okazaki fragments in a newly synthesized DNA strand is catalyzed by the enzyme
ligase
62
What is another name for codon?
Triplet
63
What molecule contains codons?
mRNA
64
Which of the following types of RNA is the transcribed version of a structural gene in DNA, that is later read for translation into protein?
mRNA
65
What are 2 functions of RNA polymerase?
Unwinds the DNA so that transcription can take place Synthesizes an RNA molecule from DNA template
66
What is the function of tRNA?
Brings amino acids to the ribosome
67
The RNA form that contains the transcribed code for a protein from the original DNA strand is
mRNA
68
Transcription elongation involves ______.
adding of nucleotides to the growing mRNA chain
69
At termination, most mRNAs are a few ______ nucleotides in length.
thousand
70
The main enzyme responsible for transcription is:
RNA polymerase.
71
The type of RNA that brings the amino acids to the ribosome during translation is
transfer
72
how many stop codons are there?
3
73
What is the start codon?
AUG
74
Translation termination occurs when
one of three stop codons is reached by the ribosome
75
What are the three stop codons?
UAA, UAG, and UGA
76
Which are components of an operon in a sequence of DNA?
Structural genes Regulatory region
77
The control locus of the lac operon has a(n) ________ section that acts as an on/off switch for transcription.
operator
78
Which are parts of the lactose operon?
Regulator Structural locus Control locus
79
Lactose acts as an _______in the lactose operon.
inducer
80
Which kind of lac operon gene encodes an enzyme that is needed to catabolize lactose?
structural
81
The protein which is capable of stopping the output of product encoded by the lac operon is called a(n
repressor
82
What are three chemicals that can cause mutations?
Ethidium bromide, nitrous acid, and acridine dyes
83
When one bacterium donates DNA to other bacterium, it is known as
recombination
84
A cell with an integrated F factor transmits its chromosomal genes at lower frequency than does a cell with a free plasmid in the cytoplasm. T/F
False
85
The process by which there is uptake of free DNA by competent bacterial cells is
transformation
86
How do an Hfr cell and an F+ cell differ?
The plasmid is integrated into the chromosome of an Hfr cell but not in an F+ cell.
87
During the process of ______ a competent bacterial cell may accept soluble DNA from the surrounding environment.
transformation
88
Which type of plasmids confer the ability of an organism to survive treatment by antibiotics?
R factors
89
The transfer of DNA via bacteriophages is
transduction
90
A bacterial cell described as _______ can accept soluble DNA from the surrounding environment.
competent
91
R-factors or "resistance factors" can be shared between bacteria through conjugation to help them survive the effects of antibiotics. T/F
true

Miocrobiology (17 decks)

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