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BI 234 > Exam 2: Ch 8 Part 1: Microbial Genetics > Flashcards

Exam 2: Ch 8 Part 1: Microbial Genetics Flashcards

1
Q

Chromosome

A

discrete cellular structure made of a neatly packaged DNA molecule

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2
Q

Eukaryotic chromsomes

A

DNA wound around histones
located in the nucleus
diploid (pairs; 2n; all of our cells except our sex cells) or haploid (single; 1n)
linear appearance

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3
Q

Prokaryotic chromosomes

A

DNA condensed into a packet by means of histone-like proteins
single circular chromosome (1n)

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4
Q

Genome

A

sum total of genetic material of an organism
Most of the genome exists in the form of chromosomes
Some appear as plasmids or in certain organelles of eukaryotes
Genome of cells: composed entirely of DNA
Genome of viruses: can contain either DNA or RNA

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5
Q

Gene

A

a segment of DNA that contains the necessary code to make a protein or RNA molecule
3 categories:
-Structural: code for proteins
-Regulatory: control gene expression
-Genes that code for RNA machinery in protein production

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6
Q

Genotype

A

an organism’s genetic makeup

its entire complement of DNA

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7
Q

Phenotype

A

the expression of the genes
the proteins of the cell and the properties they confer on the organisms
size, shape, color, environment

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8
Q

Nucleotide

A 
basic unit of DNA structure
covalently bond to each other in a sugar-phosphate linkage
3 parts:
-Phosphate 
-Deoxyribose sugar
-Nitrogenous base
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9
Q

Nitrogenous bases and base pairing

A

pairing dictated by the formation of hydrogen bonds btwn bases

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10
Q

Complimentary base pairing

A

if sequence of one strand is known, sequence of other strand is inferred

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11
Q

Antiparallel arrangement (of the double helix)

A

one side of the helix runs in the opposite direction of the other (one from 5’ to 3’, and other from 3’ to 5’)
significant factor in DNA synthesis and protein production

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12
Q

DNA replication

A

involves unwinding a DNA double helix and using each strand as a template for a new complimentary strand
semi conservative – since each new chromosome will have one “old” and one “new” strand

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13
Q

4 things needed to replicate DNA

A
  1. Original DNA template
  2. Nucleotides – a pool of nucleotides is free floating in the cytoplasm
  3. Enzymes – DNA polymerase, ligase
  4. Energy – ATP
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14
Q

DNA polymerase

A

required to successfully replicate a single strand of DNA

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15
Q

DNA replication in prokaryotes

A

Certain enzymes unwind the DNA → then DNA polymerase can read the parent strand and attach a complementary nucleotide to the new strand of DNA
Nucleotides are free in the cytoplasm of prokaryotes (free in the nucleoid region of eukaryotes)

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16
Q

DNA vs RNA

A

RNA:
contains ribose instead of deoxyribose
Is single stranded
There is no T in RNA (instead it is a U → A:U in RNA)
can assume secondary and tertiary levels of complexity, leading to specialized forms of RNA (tRNA and rRNA)

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17
Q

Transcription

A

DNA → RNA

copying, not changing the DNA or the language

18
Q

What are the 4 things needed for RNA synthesis?

A
  1. Original DNA template – chromosome w/a promoter site (DNA sequence indicating start site) and a terminator site
  2. Nucleotides – G, C, A, U – Uracil is substituted for thymine
  3. Enzymes – RNA polymerase
  4. Energy – ATP
19
Q

RNA polymerase

A

large, complex enzyme that directs the conversion of DNA into RNA

20
Q

Template strand

A

only one strand of DNA that contains meaningful instructions for synthesis of a functioning polypeptide

21
Q

Types of RNA (mRNA, tRNA, rRNA, regulatory)

A
  1. Messenger RNA (mRNA) – RNA molecule that serves as a message of the protein to be produced
  2. Transfer RNA (tRNA) – transfers amino acids to ribosome
  3. Ribosomal RNA (rRNA) – forms the ribosome
  4. Regulatory RNA – micro RNAs, anti-sense RNAs, riboswitches, small interfering RNAs
22
Q

Initiation

A

Initiate – need RNA polymerase (the running down of RNA polymerase, recognizing the promoter and starting this process)

RNA polymerase: recognizes promoter region → begins its transcription at a special sequence (the initiator) → As the DNA helix unwinds → it moves down the DNA synthesizing RNA molecule

when RNA polyermase hits the terminator sequence = whole thing will stop and close up

23
Q

Elongation

A

During elongation the mRNA is built → assembled by adding nucleotides that are complimentary to the DNA template → proceeds in the 5’ to 3’ direction → as elongation continues → the part of the DNA already transcribed is rewound into its original helical form

24
Q

Termination

A

The polymerase recognize another code that signals the separation and release of the mRNA strand/transcript

25
Q

Translation

A

mRNA → Protein
changing the language from nucleotide to amino acid
occurs at the ribosome
the green mRNa strand is threaded thru the ribosome
the ribosome “Reads” the mRNA strand codons with the help of the genetic code and tRNA

26
Q

Codons

A

groups of 3 mRNA molecules

27
Q

tRNA

A

decoder molecule which serves as a link to translate the RNA language into a protein language
One site of the tRNA has an ANTICODON which complements the codon of mRNA
The other site of the tRNA has an amino acid attachment site corresponding to a specific amino acid as noted in the genetic code

28
Q

Translation and the GENETIC CODE

A

Triplet code that specifies a given amino acid
We use the “genetic code” to translate mRNA nucleotide sequence (codons) into amino acid sequence which make up proteins
The “genetic code” is degenerate which allows for a certain amount of mutation (more than one genetic code can code for one amino acid)
There is one start codon (AUG) that codes for the amino acid methionine
There are 3 stop codons (UAA, UAG, UGA) that signal the ribosome to stop translation and let go of the polypeptide chain (protein)

29
Q

Translation at ribosome level

A

− Initiation – ribosomes bind mRNA near the start codon; tRNA anticodon with attached amino acid binds to the start codon
− Elongation – ribosomes move along to the next codon, allowing a new tRNA to bind and add another amino acid; two amino acids form peptide bonds
− Termination – stop codon terminates translation

30
Q

Polyribosomal complex

A

a single mRNA is long enough to be fed thru more than one ribosome
Permits the synthesis of hundreds of protein molecules from the same mRNA transcript
Would not see this in eukaryotes

31
Q

Transcription/translation for eukaryotes is similar to prokaryotes, except:

A

AUG encodes for a different form of methionine
Transcription and translation are not simultaneous in eukaryotes
Eukaryotes must splice out introns to achieve a mature mRNA strand to go to the ribosome
Introns can have regulatory RNA that regulate the mRNA of the exons; they also often developed from insertion of transposons

32
Q

Operons (& gene regulation)

A

Only found in bacteria
Coordinated set of genes to make proteins that are needed at the same time
All regulated as a single unit
Either inducible or repressible

33
Q

lac operon

A

When lactose is absent: the repressor block RNA polymerase from binding to the operator and transcribing downstream genes
When lactose is present: it binds to the receptor and it falls off the operator allowing RNA polymerase to bind
The downstream genes are responsible for digesting lactose and are only on when lactose is present

34
Q

Phase variation

A

bacteria turn on or off a complement of genes that leads to obvious phenotypic changes
New environment = new phenotype!
Most often traits affecting the bacterial cell surface

35
Q

Mutations

A

a change in the sequence of DNA
Possible effects of mutations:
-No effect → no change in amino acid sequence
-Good → new amino acid sequence; increases variability in the gene pool = evolution
-Bad → new amino acid sequence (cancer can be the product of a combo of bad mutations) – making the protein unable to work
(cancer can be the product of a combination of bad mutations)

36
Q

Mutagen

A

chemical or radiation that brings about mutations

mutagen mutations rate is 10-1000x the normal mutation rate

37
Q

Point mutation

A

a base is substituted in the DNA - may or may not change the amino acid
Put the cat out → puc the cat out
Put the cat out → put

38
Q

Frameshift

A

the addition, deletion or insertion of one or more nucleotides
drastically changes the amino acid sequence
reading frame of mRNA shifts
Put the cat out → put hec at out

39
Q

Thymine dimers caused by radiation

A

radiation, such as X-rays and UV rays can cause dimers to form in DNA; thymine dimers can interfere with DNA replication, transcription and translation

40
Q

Ames test

A

uses bacteria to identify possible mutagens by looking for mutations to occur; once a mutagen is identified, it is tested on animals to test if it is a carcinogen

BI 234 (16 decks)

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