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90 Cards in this Set
- Front
- Back
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What are nucleotides?
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monomers that make up nucleic acids
(DNA and RNA) |
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What are the 3 components of nucleotids?
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1. Nitrogen base
(purine and pyrimidine) 2. 5 carbon sugar (deoxy ribose or ribose) 3. Po4 - Phosphate group (serves as backbone) |
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What is the difference between deoxy ribose and regular ribose?
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Deoxy is short one oxygen
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What are the two types of nucleic acids?
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DNA and RNA
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What is DNA's function?
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storage molecule for genetic information
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SS or DS?
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Double stranded
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How many different ways can the 4 bases be arranged?
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4^4 , so 256 different ways
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If theres 100 nucleotides, how many different arrangements can be made?
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4^100 different combinations
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How many different combinations does E. coli have?
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4 x 10^6 bases
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What is RNA's job?
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primarily involved in protein synthesis
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what are the three types of RNA?
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1) mRNA - messenger RNA
(scaffold, place holder) 2) tRNA - transfer RNA (brings amino acids in) 3) rRNA - ribosomal RNA (makes ribosomes) |
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What is a gene?
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specific sequence of nucleotides in DNA that code for a functional product (a protein)
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What did Avery discover?
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a non-protein was responsible for heritable lethal traits in bacteria
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What did Macleod and McCarty discover?
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Helped Aver purify the "transforming" factor
- DNA was isolated, a compound ubiquitous to living organisms |
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Who is credited with discovering DNA's structure?
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Watson and Crick
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Who is credited for developing the first image of DNA?
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Rosalind Franklin
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What polymers of nucleotides make up DNA?
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A, T, C, G
A = T (double hydrogen bond) C---G (triple hydrogen bond) more stable than A=T |
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What is the term for how bases are paired in DNA?
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bases are COMPLIMENTARY
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How are DNA strands antiparallel?
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5' → 3', and 3' → 5'
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What is DNA replication?
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DNA → DNA
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Why is DNA replication considered semiconservative?
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resulting new double strand DNA after replication is made of one old strand and one new strand
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Describe the steps of DNA replication
(Fig 8.5) |
1. origin of replication
2. replication fork 3. leading strand - replication is continuous 4. lagging strand - discontinuous (always made 5' → 3') 5. RNA polymerase - adds RNA primer 6. RNA primer 7. DNA polymerase 8. DNA Ligase (patches the fragments together) |
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Describe prokaryotic replication
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Fig 8.7
-Typically once circular chromosome - One origin of replication (Euks have many) |
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What is transcription?
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DNA → RNA
CGAT → CGAU |
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What are the three important parts of transcription?
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a) promoter
b) RNA polymerase c) terminator |
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Promoter
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tells RNA polymerase where to bind
(where the gene begins) |
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RNA Polymerase
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unwinds DNA and adds RNA nucleotides to the DNA template
(complimentary nucleotides) |
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Terminator
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where the gene ends
(forms a loop where RNA polymerase gets stuck and stops) |
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What is Translation?
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mRNA → protein
nucelotides (RNA) → amino acids (protein) |
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What are the important parts of translation?
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a) codon
b) ribosome c) tRNA d) anticodon |
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What is a codon?
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3 nucleotide bases in a row that code for an amino acid
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How many different codon combinations are there?
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- 4 nucleotides (G C A U)
- 3 nucleotides to make a codon so 4^3 codons possible = 64 |
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Why are there only 20 amino acids then?
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Because some amino acids can be produced by multiple codon combinations
called DEGENERCY |
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What are sense codons?
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(61 of them)
Code for amino acids |
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What are nonsense codons?
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(3 of them)
not translated into amino acids they're stop codons |
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What is a ribosome?
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where protein synthesis occurs
made up of rRNA and protein 70S in proks, 80S in euks |
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What does tRNA do in translation?
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it brings the amino acid to the mRNA on the ribosome
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What is an anticodon?
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region of the tRNA that is complementary to the codon (AGCU)
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Do translation and transcription occur simultaneously?
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- NOT in euks because transcription occurs in the nucleus and translation in the cytoplasm
- is simultaneous in proks |
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Translation
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Fig 8.9
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Gene Expression
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DNA → RNA → Protein = Gene Expression
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What ate the two types of genes?
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Constitutive and Inducible
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What is a constitutive gene?
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Genes that are always expressed
Ex: the breakdown of glucose (glycolysis) |
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What is an inducible gene?
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Genes regulated on/off to conserve energy
Ex: breakdown of lactose (only expressed under certain conditions) |
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What is repression?
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the ability to turn genes off
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What are the components of repression?
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a) RNA polymerase
adds RNA nucleotides, mRNA b) Structural gene(s) encodes enzymes c) Promoter where RNA polymerase binds d) Operator where the repressor binds e) I gene codes for repressor gene |
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If the repressor is present, what cannot happen?
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Transcription cannot occur
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What is induction?
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the ability to turn genes on
Ex: the lactose (lac) operon |
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What is an operon?
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A group of coordinately regulated genes with related functions
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What is a regulatory gene?
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Encodes the repressor, is always transcribed and translated
"I gene" |
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What is the structure of the lac operon like?
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Promoter
Operator Structural Genes I Gene |
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In the absence of lactose, the lac operon is...?
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Off
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If lactose is present and glucose is not, the lac operon is...?
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On
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If lactose and glucose are present, the lac operon is...?
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Off
- 1st breaks down the glucose, then lactose - more energy expenditure to breakdown lactose - E. coli grows better on glucose Figure 8.13 |
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All E. coli have the genes to metabolize lactose (genotype)...
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but they don't always express them (phenotype)
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What happens if DNA is not copied exactly?
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A mutation occurs - a change in the sequence of DNA nucleotides
Can be neutral, harmful, or beneficial |
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What are the two types of mutations?
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1) Point Mutation
2) Frame Shift Mutation |
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What is a point mutation?
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base substitution
a single base is replaced with another |
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What are the three types of point mutations?
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1) Missense
2) Nonsense 3) Silent |
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What is a missense mutation?
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Results in a different amino acid
Can be 0, +, - |
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What is a nonsense mutation?
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results in a stop codon, produces a shortened protein
Almost always - |
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What is a silent mutation?
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no change in the amino acid produced
still codes for the same amino acid and protein neutral |
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What is a frame shift mutation?
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causes greater damage than a point shift mutation
almost always negative |
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What are the two types of frame shift mutations?
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1) Insertion - extra nucleotide is added
2) Deletion - subtracting a nucleotide |
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What are spontaneous mutations?
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It happens in the absence of a mutagen
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What is an induced mutation?
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Produced by agents (mutagens)
Can be physical or chemical Ex: Ethidium Bromide or UV Light |
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What are the three different way of exchanging genetic information?
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1) transformation
2) conjugation 3) transduction |
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What is transformation?
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- DNA released by one bacterium (naked DNA) is taken up by another
- Bacillus does this - Works best when donor and recipient are closely related - Can be DNA fragments or plasmids |
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What was Griffith's experiment?
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- Took smooth colonies of streptococcus, injected it into mice, mice died
- 2nd time, injected heat treated cells, didnt kill it - 3rd, took rough colonies, injected, mouse survived - took smooth heat treated, and rough, injected it into mouse, it died (b/c heat shock released DNA that rough took up) |
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What is conjugation?
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Exchange mediated by a plasmid
Requires direct cell-to-cell contact via a pillus (pills = modified fimbriae) Cell must be opposite types (F+ with an F-) |
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What is a plasmid?
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circuluar, self-replicating extrachromosomal DNA that carries nonessential genes for cell survival or growth under normal conditions
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What is transduction?
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Bacterial DNA is transferred from donor to recipient inside a virus
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Figures from textbook
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fig 8.28
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Are viruses technically considered living?
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No, they aren't cells
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What are the features that ALL viruses have?
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1. Nucleic acid
(DNA or RNA, but not both) 2. Protein coat (surrounds and protects nucleic acid) |
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What are some additional features viruses might have?
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1. May have an envelope
(made of carb, lipid, and/or protein) 2. Obligate intracellular parasites (multiply inside living cells using machinery of host) 3. Cause the synthesis of specialized structure that can transfer viral nucleic acids to other cells |
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What is the host range determined by?
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Determined by attachment
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Where do animal viruses attach?
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Plasma membrane of host cell
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Where do bacterial viruses attach?
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receptor is on cell wall, flagella, or fimbriae
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Where do plant viruses attach?
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Cell wall
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What are the typical sizes of viruses?
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they are usually very small, but there is a lot of variation
(30 nm = .03 micrometers) |
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What does a viruses structure look like?
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1. Virion
2. Nucleic acid 3. Capsids and Envelopes |
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What is a virion?
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complete, fully developed viral particle (infectious)
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What are the features of a viral nucleic acids?
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Can be DNA or RNA
Can be single stranded or double stranded. Doesn't have to be ds DNA or ss RNA, some pass on ds RNA |
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What is a capsid?
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a protein coat
* all have |
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What is a capsomere?
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protein subunit that makes up capsid
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What is a viral envelope?
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make of lipids, carbs, and proteins
* some have it naked vs. envelope |
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What are spikes?
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carbo-protein structures
- help recognize different structures - ex. influenza virus |
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What are the different viral morphologies?
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1) Helical - long rod
Ex: ebola and rabies Capsid and nucleic acids are both helical 2) Polyhedral - many sided Ex. most viruses 3) Complex Ex: bacteriophages |
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What are the two different cycles viruses go through when they multiply?
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Lytic Cycle
Lysogenic Cycle |
