Microbiology > Genetics > Flashcards

Genetics Flashcards

(45 cards)

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1
Q

Structure and function of DNA

A

Structure: long, double stranded helix

  • “rungs” of DNA consist of nitrogen bases (A,T,G,C)
  • “side rails” of DNA consist of alternating patterns of sugar and phosphate held together by phosphodiester bonds
  • antiparallel arrangement (5’ to 3’- 3’ to 5’)
  • made of deoxyribonucleotides(sugar deoxyribose)

Function:

-directs and regulates the construction of proteins necessary for a cell to perform its functions

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2
Q

Structure and function of RNA

A

Structure:

  • single stranded
  • like DNA, RNA has 5’ to 3’ directionality
  • Uracil replaces Thymine
  • made of ribonucleotides (sugar ribose)

Function:

  • can fold on itself to form helical and loop structures
  • coding, decoding, regulation and expression of genes
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3
Q

What are nucleotides composed of? (* Be able to diagram a nucleotide)

A
  • Phosphate group
  • 5 carbon sugar
  • Nitrogenous base
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4
Q

Central Dogma of Gene Expression

A

-the general flow of genetic information from DNA to RNA to protein

* remember to include reverse transcription, transcription and translation (where those occur)

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5
Q

How is DNA replicated in prokaryotes?

A
  • DNA replication starts when factors called the primosome are recruited to the origin of replication in the chromosome
  • The primosome includes helicase to unwind the DNA and primase to lay down RNA primers to jump-start replication
  • Helicase unwinds the DNA and a bubble of single stranded DNA forms.
  • DNA polymerase III binds DNA with this bubble region and replication starts
  • At the replication fork (point where unwinding occurs) Helicase unwinds the DNA helix
  • Single-strand DNA-binding proteins bind to DNA to keep them seperated until they are copied
  • specialized enzymes gyrase and topoisomerases relieve coiling tension
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6
Q

What is protein synthesis?

A
  • genetic information within a cell is read and used to create gene products (proteins)
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7
Q

Where and how does proteins synthesis occur in a prokaryotes and eukaryotes?

A

Where?: the cytoplasm

How?: Transcription and Translation

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8
Q

What is transcription?

A

-The first stage of protein synthesis where genes in DNA are copied into a new format, RNA

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9
Q

Process of Transcription

A
  • RNA polymerase performs transcription
  • RNA polymerase binds to the promoter- beginning region of a gene in DNA
  • it unwinds the DNA to reveal single-stranded template DNA
  • lays down complementary ribonucleotides (U pairs wih A, G pairs with C)
  • continues until it reaches the termination sequence
  • RNA polymerase falls off the DNA
  • Newly made RNA transcript released
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10
Q

What is Translation?

A
  • reading mRNA to build proteins
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11
Q

Process of Translation

A

Initiation

- Ribosome attaches to mRNA and scans it until it reaches a start codon

  • Initiator tRNA carrying amin acid methionine enters the ribosomes P site
  • Multiple ribosomes latch onto a single mRNA molecule forming polysomes

Elongation

  • Incoming tRNA enters “A” site
  • Peptide bond forms between amin acids transferring growing protein to tRNA “A” site
  • Ribosome shifts down mRNA; tRNA in “P” site shifts to “E” site to exit ribosome; tRNA in the “A” site shifts to the “P” site
  • cycle repeats until stop codon is encountered

Termination

  • Ribosome encounters stop codon
  • Termination factor enters the ribosome
  • Ribosome releases the protein and detaches from mRNA
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12
Q

What is Reverse Transcription?

A
  • RNA is used as a template to build copy DNA
  • requires reverse transcriptase
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13
Q

What is mRNA?

A

-carries genetic message in triplet codons and is translated to build a protein

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14
Q

What is tRNA?

A

-adaptor molecule that ushers amino acids into the ribosome during translation

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15
Q

What is rRNA?

A

-takes on complex stem and loop structures and combines with proteins to build ribosomes

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16
Q

What is a codon? Where is it located?

A

-a triplet of nucleotides found in mRNA

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17
Q

What is an anticodon? Where is it found?

A

-sequence of three nucleotides forming a unit of genetic code in tRNA

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18
Q

What are Introns?

A
  • interveining sequences of mRNA that are not decoded to build the protein (these are cut and removed)
  • part of RNA splicing
  • allows one gene to actually code for more than one protein in a eukaryote
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19
Q

What are Exons?

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A
  • segments of mRNA decoded to build a protein (these are kept)
  • part of RNA splicing
20
Q

What are Inducible Operons?

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A
  • OFF by default
  • certain conditions activate transcription
    ex. ) (lac) operon
21
Q

What are Repressible Operons?

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A
  • ON by default
  • Actively transcribed until they are switched off (repressed)

Ex.) (arg) operon

22
Q

*Be able to diagram an operon and explain how it works!!!!!!

23
Q

What is post-transcriptional regulation?

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A
  • impacts how ofen mRNA is translated into a protein
24
Q

What is pre-transcriptional regulation?

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A
  • helps cells control when and how often transcription occurs (regulates RNA production)
  • important mechanism for controlling protein synthesis
25
What is **DNA Methylation?**
- adding methyl groups (CH3) to DNA - silences a gene by preventing transcription
26
What is **quorum sensing?**
- the collective sensing and responding to changes within a bacterial community - allows bacteria to alter their protein synthesis is response to changes in the density of a population
27
28
What is a **mutation?**
- change in the genetic material of a cell or virus
29
What is a **mutagen?**
- chemical, physical, or biological agents that increase the rate of a mutation
30
What is a **carcinogen?**
- mutagens that promote the development of cancers
31
How do mutagens contribute to bacterial evolution?
- can increase a cells likelihood of survival - can help a cell better manage a certain environmental stress
32
What is a **substitution mutation?**
-occur when an incorrect nucleotide is added
33
What is an **insertion mutation?**
-occur when a cell adds one or more nucleotides to its genome sequence
34
What is a **deletion mutation?**
- occur when one or more nucleotides are removed from a genome sequence
35
What are **silent, missense,** and **nonsense mutations**?
**silent:** mutations that do not change the amino acid sequence of a protein **missense:** the meaning of a codon is changed in a way that the wrong amino acid is added to the growing protein **nonsense:** a mutation that causes a codon to go from encoding an amino acid to encoding a stop signal
36
What is a **frameshift mutation?**
-inserting or deleting bases from the coding region of a genetic sequence
37
What are **spontaneous mutations?**
- naturally occurring due to errors in DNA replication
38
What are **reversion mutations?**
-occurs when a base substitution mutation is corrected by another base subsitiution
39
What is an **Ames Test?**
-identifies if a chemical is a mutagen of bacterial DNA
40
Process of **horizontal gene transfer-transfer of DNA from a donor cell to a recipient cell** (\*conjugation)
in picture - high frequency strains arise when the fertility plasmid merges with the bacterial cells chromosome
41
Process of horizontal gene transfer (\*transformation)- ability to pick up, incorporate and express DNA from the environment
in picture
42
Process of horizontal gene transfer (\*transduction)- the passing of new genetic material into a bacterial cell from a virus
in picture
43
Positive screening techniques to identify mutants
in picture
44
Negative screening techniques to identify mutants
in picture
45
What are **transposons?**
"jumping genes" **Retrotransposons:** - reverse transcriptases make cDNA from viral RNA genome - cDNA is inserted into a host cell **DNA transposons:** **-"**copy and paste" strategy (copy made and then posted in a new location - "cut and paste" strategy DNA transposon is not copied before it is excised and moved
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