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Micro Lecture > Chapter 8 Microbial Genetics > Flashcards

Chapter 8 Microbial Genetics Flashcards

1
Q

Define genetics.

A

The study of what genes are, how they carry information, how information is expressed, and how genes are replicated

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2
Q

What is a gene?

A

A gene is a segment of DNA that encodes a functional product, usually a protein

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3
Q

What is a chromosome?

A

Structure containing DNA that physically carries hereditary information; the chromosomes contain the genes

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4
Q

What is a genome?

A

All the genetic information in a cell

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5
Q

What is genomics?

A

The molecular study of genomes

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6
Q

What is a genotype?

A

The genes of an organism

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7
Q

What is a phenotype?

A

Expression of the genes

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8
Q

What does it mean when a gene is express or turned on?

A

Means the gene product (protein is made)

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9
Q

What is recombination when referring to the flow of genetic information?

A

Recombination is genetic information can can be transferred between cells of the same generation.

Horizontally

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10
Q

What is the passing of genetic information vertically called?

A

Replication

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11
Q

DNA is made of polymers of nucleotides, what are they and how do they pair?

A

Adenine to Thymine

Cytosine to Guanine

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12
Q

What is the backbone of DNA made of?

How are they formed in space

A

Alternating Sugar-phosphate groups that are held together by hydrogen bonds between AT and CG

The strands are antiparallel

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13
Q

What is semi conservative DNA replication?

A

Means one strand is old and one strand is new

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14
Q

What is DNA polymerase? What does it do and in what direction does it do it?

A

It’s an enzyme that adds new nucleotides to the 3’ end and ligament act as a glue.

This happens in the 5’ to 3’ direction

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15
Q

What is the template strand?

How is this done?

A

The base sequence that determines the base sequence in the other strand

This is done by complementary base paring

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16
Q

What makes replications very accurate and why?

A

It’s accurate due to proof reading by polymerase

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17
Q

How is the leading strand copied and by what enzyme?

A

The leading strand is synthesized continuously by DNA polymerase

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18
Q

How is the lagging strand synthesized, and what enzyme is responsible for its synthesis? What is the product?

A

The laggin strand is synthesized discontinuously.

RNA polymerase synthesizes a short RNA primer, which is then extended by DNA polymerase.

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19
Q

What does DNA polymerase do in the lagging strand?

A

It digest RNA primers replacing them with DNA leaving fragmented pieces.

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20
Q

What are the fragments that DNA polymerase leaves behind. How is this fixed?

A

Okazaki fragments

DNA ligase joins the discontinuous fragments of the lagging strand

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21
Q

What do genes make and what are they responsible for?

A

Genes make proteins

Genes are responsible for traits

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22
Q

What is a segment of DNA that specifies a sequence of amino acids in a protein

A

Genes

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23
Q

What are the two mechanisms that carry out protein synthesis?

A

Transcription and Translation

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24
Q

What is the generic sequence of events that occur with transcription and translation?

A

Transcription: mRNA is transcribe (copied) from DNA

Translation: mRNA makes protein

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25
Q

DNA is transcribed to make what?

When does this begin and what starts this process?

A

DNA is transcribed into mRNA

Transcription begins with RNA polymerase bind to the promoter sequence on DNA

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26
Q

Which direction does transcription proceed in?

When does it stop

A

5’ to 3’

Transcription stops when it reaches a terminator sequence

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27
Q

What is genetic code and what is it called

A

Genetic code is Triplet Code

Each is a 3-nucleotide of mRNA and is called a Codon

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28
Q

How many sense codons are there and how many non sense codons are there?

A

61 sense codons

3 nonsense (stop) codons

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29
Q

What is the start codon and what AA is it?

What are the 3 nonsense codons (stop codons)

A

AUG start codon and its Methionine

Stop codons UAA, UAG, UGA

30
Q

What are snRNP’s?

What else does what snRNP’s do?

A

SnRNP’s are small nuclear ribonucleoproteins that excise out the introns and splice together the exon-derived RNA in to mRNA which then leave the nucleus as mRNA

Ribozyme

31
Q

What are exons?

A

Real genes

32
Q

What specifies the order of the amino acids in a protein?

A

Sequence of codon in mRNA

33
Q

What is tRNA and what is its function?

A

Has the anticodon i.e. The 3 complementary bases to the mRNA. This carries the amino acids that will be joined to the growing polypeptide chain

34
Q

What is are the three sites with a ribosome? Which site is the start site, the site that the incoming tRNA waits in, and the site were the tRNA leaves?

A

The P site is where it begins.

The A site is where the peptide bond forms and the incoming tRNA waits.

The E site is where the empty tRNA leaves the ribosome.

35
Q

This process of a growing polypeptide is called what and what is its function?

A

Translation and its forming a protein

36
Q

What is the start codon and what is its AA?

What are the three stop nonsense codons?

A

AUG = methionine

UAA UAG UGA

37
Q

What are the three steps to Translation?

A

Initiation

Elongation

Termination

38
Q

How do we regulated bacterial gene expression?

A

By controlling enzymes, if we don’t need them, we shouldn’t make them.

39
Q

What are the two genetic control mechanisms that regulate Pre-transcriptional control?

A

Repression

Induction

40
Q

What are Constitutive genes?

A

These are genes that are expressed at a fixed rate

Ex. Enzymes in Glycolysis

41
Q

Who discovered the Operon Structure?

A

Jacob and Monod 1961

42
Q

What is an Operon?

A

The combination of several genes which are located side-by-side on DNA and work together.

A set of operator and promoter sites and structural genes that defines and operon

43
Q

What are Structure Genes?

A

They determine the structure of the protein

44
Q

What is the promoter (P)?

A

Site for RNA polymerase attachment

45
Q

What is the operator (O)?

A

Site for Repressor molecule to attach

46
Q

What are Regulatory Genes?

A

Makes Repressor molecule.

The I gene that encodes for a repressor that switches inducible and repressible operons on and off.

47
Q

What are the two types of operons?

Give example and if on or off

A

Inducible operons: are not usually transcribed (OFF) meaning must be turned on
Example: Lac Operon

Repressive operons: operate in reverse fashion- they transcribe continually until turned (off) by repressors. They are always turned on.
Example: Tryptophan Operon

48
Q

What is an inducer and what is its function?

A

Inducers control Induction

Enzymes are called Inducible Enzymes bind to the repress or protein and inactive it allowing RNA Polymerase to bind and transcription of the gene to occur, which forms mRNA.

49
Q

What is repression. How does it work in the presence of Tryptophan?

A

Inhibits gene expression, which is controlled by a Repressor molecule.

Tryptophan attaches to an inactive repressor protein which activates it. It then blocks the binding site for RNA polymerase. This is similar to a feed-back mechanism

50
Q

Regulation of the Lac Operon also depends on concentration of what compound?

A

Glucose

51
Q

Explain the glucose effect. What happens when glucose is not present?

What type of regulation is this?

A

When glucose is not available, cells will produce cAMP in high amounts. -cAMP then binds to a protein called a Catabolite Activator Protein (CAP)

this complex binds to the Lac Promoter which is required for RNA Polymerase to bind and of transcription to proceed.

This is positive regulation

52
Q

What is cAMP?

A

Is an example of alarmone, which a chemical like hormone.

53
Q

What happens when lactose is present and glucose is present?

A

-cAMP is not generated and the CAP remains inactivated, therefore RNA Polymerase can not bind and transcription does not occur.

54
Q

What happens in the presence of Glucose?

A

If glucose is present, it is used up first, which produces a lag time then the lactose is used up turning on Transcription because cAMP is then produced

55
Q

What is a mutation? What does it cause

A

A permeant change in the base sequence of DNA, which creates a change in AA sequence of a protein

56
Q

What does a mutation cause?

A

Mutations may be neutral (silent), beneficial, or harmful

57
Q

What is a Mutagen?

A

Agent that causes mutations

58
Q

What is Spontaneous mutations?

A

These occur in the absence of mutagen

59
Q

What are the types of mutations?

A

Base substitution

Missense mutation

Nonsense mutation

Frameshift mutation

60
Q

What is a base substitution?

What does this lead to?

A

It is a change in one base sequence called a (point mutation)

This can cause the wrong base to be inserted and therefore code for the wrong protein. This causes missense mutations

61
Q

What does a Missense mutation cause?

Give an example

A

If a base substitution causes a change in AA then Missense mutation occurs.

An example is Sickle-cell disease

62
Q

What is Nonsense mutation?

A

A base substitution can cause a nonsense mutation which results in a stop codon (UAA, UAG, UGA) to be made and therefor an incomplete portion is made

63
Q

What is a Frameshift mutation?

Give an example?

A

This is the insertion or deletion of one or more nucleotide pairs. This shifts the translational reading frame of a triplet codon (three nucleotides)

The result is an inactive protein that is made.

Huntingtons Disease which is caused by the insertion of extra base-pairs

64
Q

What are chemical mutagens?

A

Agents in the environment such as chemicals or radiation that directly or indirectly bring about mutations.

65
Q

What is a chemical mutagen (example)?

A

Nucleoside analog (base analog)

66
Q

What is Nucleoside (base) analog?

Give and example and it effect

A

Analogs are structurally similar to normal bases.

Adenine nucleoside becomes 2-Aminopurine nucleoside

This is incorporated into DNA in place of the adenine but can pair with cytosine, so AT becomes CG

67
Q

What does Radiation as a mutagen cause? What gives off this radiation?

A

Ionizing radiation (X-rays and gamma rays) are potent mutagens

U.V. Light (260 nm) damages DNA

Basically way too much sun light can cause cancer.

68
Q

What does radiation do to DNA? What does it form?

A

UV radiation cause Thymine dimers

69
Q

How are thymine diners repaired?

A

By photolyases that separate thymine dimers, this is done in plants.

In humans is nucleotide excision repair.

70
Q

Define Nucleotide excision repair?

A

An endonuclease cuts the DNA removing the dimer, then DNA polymerase fills the gap by using the intact strand as a template

Micro Lecture (11 decks)

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