Unit 3 Exam guide Flashcards
What is genetics?
What is the smallest unit of heredity?
The science that studies the inheritance of
biological characteristics by living things; heredity
Smallest unit: Gene
Define: DNA, gene, chromosome, genome.
DNA (Deoxyribonucleic acid): The genetic molecule
GENES: A specific segment of DNA with instruction for a single trait, or more specifically, a single protein or RNA.
CHROMOSOME: A discrete structure that is made up of a
single molecule of DNA (and all the genes for which that
DNA codes)
GENOME: The sum total of genetics material in a given cell. Chromosomes + plasmids = microbial genome
Draw each genome: eukaryotic (human vs. fruit fly), bacteria, viral
Eukaryotic: Nucleus and chromosome pairs
Bacterial: Circular DNA and plasmid
Viral: Sliver of DNA
The general structure of DNA consists of what three parts?
What type of bonds bind the 2 strands together?
What does complimentary base pair mean?
Three Parts:
Phosphate Group
Deoxyribose Sugar
Nitrogenous Base
Type of Bond:
Hydrogen Bond
Complimentary Base:
Pyrimidine - - - - Purine
A & T pairs
G & C pairs
The two strands make up a single molecule of DNA. The shape of DNA is what?
Double Helix
Protein synthesis is a 2 step process.
What are these 2 steps called?
Transcription and translation
Describe Transcription
DNA template –> mRNA
>Carried out by enzyme RNA Polymerase
Eukaryotes: Nucleus
Prokaryotes: Cytoplasm
Gene –> mRNA
(DNA sequence)
Describe Translation
MRNA –> amino acid sequence of polypeptide chain
Euk & Prok – Ribosome
MRNA –> amino acid sequence
Start codon AUG (polypeptide chain)
Ribosome unit binds to mRNA which binds to tRNA initiator that binds to start codon
Then the subsequent codons come, enter the ribosome carrying their amino acid which covalently bind with the previous amino acid. This will create the polypeptide chain, which will become the protein when folded properly.
(tRNA molecules can only bind to a single specific amino acid, respective to their structure and can only bind to their complementary codon pair in sequence)
During step 1, the genetic code is passed from ___ to ___
DNA to RNA
- RNA Polymerase synthesizes RNA strand based from DNA template
During the second step of protein synthesis , the genetic code (in the form of a nucleotide sequence) is translated in the language of proteins, the ______ ______ building blocks.
Amino Acid
Which enzyme carries out transcription
RNA Polymerase
What 3 steps are involved in transcription
Initiation: promotor region recognized, RNA Polymerase binds to promotor region
Elongation: RNA Polymerase moves down DNA strand, synthesizing corresponding mRNA
Termination: RNA Polymerase reaches terminator codon, mRNA is released, DNA refixes itself
Where does transcription occur in bacteria? In eukaryotes?
Bacteria: Cytosol
Eukaryotes: Inside the nucleus
What is a codon?
Codon: Triplet code from mRNA that codes for a specific amino acid
How does RNA differ from DNA? (think number of strands, nucleotides)
DNA is double stranded, RNA is generally single stranded
DNA’s bases: Adenine, Thymine, Cytosine, Guanine
RNA’s bases: Adenine, Uracil, Cytosine, Guanine
At what cellular structure does translation, the second step of protein synthesis occur?
Translation occurs at the ribosome (Both prok and euk)
The genetic code gets translated into the protein sequence consisting of _______ and a ________ chain is produced
Consisting of Amino Acids
A polypeptide chain is produced
What three steps are involved in translation?
Initiation: Ribosome binds to mRNA at start codon, first amino acid (methionine) binds to start codon,
Elongation: Ribosome moves along mRNA 5’ –> 3’, tRNA molecules bring amino acid to ribosome, peptide bonds form building polypeptide chain, the tRNAs release
Enzymes in ribosome make peptide bonds while . . .
Termination: When ribosome reaches stop codon translation ends, polypeptide chain is released
What is the role of the ribosome?
Protein synthesis
What is the role of tRNA?
Deliver the correct amino acids to the ribosome in the correct order
What about the tRNA ensures that the right amino acid is getting added to the growing polypeptide chain?
The tRNA’s anticodon holds a set of three nucleotides which is complementary to a specific codon on the mRNA.
What is a codon and what do they code for?
What is the start codon?
How would you determine the sequence of the anti-codon?
A codon is a sequence of three nucleotide bases in mRNA that code for specific amino acids.
Start codon: AUG
Determine sequence of anti-codon:
1. Identify the codon in the mRNA.
2. Find the complementary bases for the codon (remembering that RNA uses uracil (U) instead of thymine (T)).
3. Reverse the direction because the anti-codon is complementary and anti-parallel to the codon
In what direction would you “read” DNA or RNA? What is meant by the term “anti-parallel”?
From the 5’ end to the 3’ end
Anti-paralle: One strand runs in the 5’ - 3’ direction, while the complementary strand runs in the opposite 3’ to 5’ direction. This allows bases to pair correctly
Distinguish between mRNA. tRNA, and rRna.
On what type of RNA can the anti-codon be found?
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What is the purpose of a start codon? A stop codon? Identify both.
Start:
- Begins the process of Translation
- AUG = Methionine
Stop:
- Signals end of translation
- UAA, UAG, UGA = No amino acid
Can more than one codon code for a single amino acid?
Can more than one codon code for a single amino acid?
What is a polyribosomal complex? In what type of organisms do we find these (prokaryotic, eukaryotic, or both)?
The structure formed when multiple ribosomes simultaneously translate the same mRNA molecule
They are found in both proks + euks
Compare and contrast eukaryotic transcription and bacterial transcription. What extra steps occur during transcription in eukaryotic organisms? What is RNA processing (what three things happen?) in eukaryotic cells and what is its significance? What is the enzyme complex responsible for carrying out splicing?
Extra steps:
mRNA processing by spliceosome
Transport of mRNA from nucleus to ribosome
Define: exon, intron, spliceosome.
Exon: Regions of pre-mRNA that will be expressed
Introns: Regions of pre-mRNA that will be cut out; NOT be expressed
Spliceosomes: Cut the introns out of the mRNA and glue the exons together
What is alternative splicing and what is its significance? How does the concept of alternative splicing change the central dogma that 1 gene codes for 1 protein?
In eukaryotes, one gene can code for multiple proteins.
Cut out what’s not needed or add whatever for creation of the protein.
Think: recipe book, but you can always modify the recipe as needed
Why do cells regulate protein synthesis (think about it in terms of energy expenditure)?
Cells want to save energy
Regulate enzymes that won’t be used again right away
Regulation of protein synthesis in bacterial cells occurs via ________________________. What is an operator?
Via Operons (for prokaryotes)
Operon – Contains an operator gene that can switch genes on (induce) or off (repress)
Compare and contrast inducible and repressible operons (use the table from the slides as a guide).
Inducible operons: Many catabolic operons. The genes are turned on when the substrate is present.
>e.g. lactose present, B-galactosidase turned on
Repressible operons: Many genes for enzymes are responsible for anabolic reactions. The genes are turned off when the product begins to build up in the cell.
>“Don’t need any more of this product, it’s being wasted”
>e.g. genes responsible for amino acid production
Is the lac operon inducible or repressible?
Is it usually in the on or off position?
It is activated by an inducer molecule?
Is the inducer the substrate or the product?
Repressible, it is usually in the on position
The inducer is the substrate
In operons, the DNA sequences that code for the regulated proteins (such as enzymes) are called what?
Structural Genes
Which, inducible or repressible operons are important in the regulation in anabolic reactions? Catabolic reactions?
Anabolic reactions – Repressible operons
Catabolic reactions – Inducible operons
In regulation of protein synthesis, repressor proteins sit on/attach to the _______ , thus blocking the enzyme _________ from carrying out transcription.
Repressor proteins sit on the operator
Blocking the enzyme RNA Polymerase
Define:
operon
regulator
repressor protein
control locus
promoter
operator
structural locus
structural genes
Operator – On/off switch
Does the regulator region necessarily have to be right next to the operator region of a DNA strand?
Why or why not?
No it does not
Regulator proteins are considered “allosteric”. What does this mean and why is this important for their role in regulating protein synthesis?
They have more than one binding site
This is important as it allows excess of a product to bind to the allosteric site
When will protein synthesis for the enzymes involved in breaking down (or extracting energy from) lactose be “turned on”?
They will be induced whenever there is an excess of lactose in the system; i.e. whenever the substrate is present
Also If the substrate is present and glucose isn’t present
In eukaryotic organisms, although they don’t have operons, they are able to regulate protein synthesis using _____________ factors.
Transcription factors
Recent findings have identified small interfering RNA (siRNA) and micro-RNA.
The importance of these RNA’s is great.
What regulatory roles do these RNA’s play in protein synthesis?
They aid in regulation of protein synthesis
- Activate the destruction of RNA in viruses
- Degrade mRNA of regular genes (affecting what?)
- Regulate the coiling of chromatin (tight vs. loose)
- Bind to mRNA (“antisense” made from nontemplate DNA)
What is a mutation?
Mutation – Alteration in a natural (“wild-type”) DNA sequence
For mutations to have an effect on a population (and natural selection), would it need to occur in somatic (cells of the body) or sex (gametes) cells?
It must occur in the gametes
What are the three types of mutations?
Insertion
Deletion
Rearrangement
Define: Missense
Single nucleotide change in DNA leads to substitution of one amino acid for another
Define: Nonsense
Nonsense – Mutation in DNA sequence that results in an unfinished protein product (polypeptide chain) d/t mutation that results in premature addition of a stop codon;
>Ex: UGG which = TRP gets changed to UGA which = stop codon
>The polypeptide chain may be somewhat normal if it’s only stopped one or two amino acids early, but it’ll be really messed up if it happens early on in the sequence
Define: Frameshift
Ex:
> DNA – CCA TTG CGC ATA
mRNA – GGU AAC GCG
>First “C” gets deleted, so it becomes
DNA - (C) CAT TGC GCA
mRNA - GUA ACG CGU
> The two mRNA lines code for completely different amino acids, messes up entire polypeptide sequence
Define: Silent Mutation
Mutation where protein product is unaffected/unchanged; (codons are changed but they code for same amino acid)
> ex:
RNA sequence of CCU, so DNA sequence GGA
RNA sequence becomes CCA, so DNA sequence = GGT
Promine is still being created either way, has zero effect on the amino acid being added
What are the two causes of mutations?
Spontaneous – Change in DNA during replication
Induced – Occurs in the presence of mutagens
> Mutagens can be chemical or physical
What type of mutation causes little to no harm? Why? What types are deadly?
Silent mutations cause little to no harm, because the DNA will still code for the same amino acid as it did previously
Why is a frameshift so harmful?
A frameshift is so harmful as it will cause a change in nearly every codon in a sequence, resulting in virtually completely different amino acids being produced for the respective polypeptide chain
What is genetic recombination? Is it good, bad or ugly? Why is it important? What is its role in natural selection?
Recombination: When DNA originating from one bacterium is donated or transferred to another
When is the only time that genetic recombination occurs in eukaryotic organisms?
Meiosis (Prophase I)
Recombination in prokaryotic organisms such as bacteria occurs when either _____ or _____ get transferred from cell to another, thus becoming a new part of the genome for the cell that received the genetic material from the donor cell.
Plasmids
Fragments
Unlike eukaryotes, prokaryotes such as bacteria have multiple means through which they can genetically recombine their DNA. What are the four modes of transmission that we discussed in class? Define each.
Conjugation – Tube that allows bacteria to directly exchange DNA between each other
Transformation – Bacteria get DNA indirectly from their environment; ex: bacteria dies, and DNA leaks out
Transduction – Exchange of DNA by a virus
Transposable elements - “Jumping genes”, move around genome
Describe the experiment which indicated that material is passed from cell to cell (and not just form parent to offspring as in eukaryotes). In this experiment, genetic material was able to be passed from dead cells to living cells. What was the outcome?
Smooth and rough bacteria, smooth have capsule that help them invade mice. Smooth dies, rough takes up capsule and this allows them to invade the mice
Three controls
-See what the effect of S-Strain was solo
-See what R-strain did on its own
-Had to ensure it wasn’t a characteristic of a toxin itself
How can genetic recombination be used in biotechnology?
In general, how is human insulin for diabetics mass produced?
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What are viruses made of?
A bit of genetic information (DNA or RNA) wrapped in a bit of protein
Be able to discuss at least one theory by which viruses came to be .
Escape theory - Some of our genes DNA are able to “copy and paste” itself to other areas/sections, so the earliest virus may have been a gene that was able to “escape” and create itself a protein envelope
Why are viruses considered “infectious particles”? When are they considered “active”? When considered “inactive”? Why considered parasitic?
They are considered “infectious particles” because they cannot move on their own, they’re just moved around naturally until they come in contact with a host which is when they become “Active”
What is the role of viruses in population control?
They can function as a predator, wiping out parts of a population
A nucleocapsid consists of ____ and ______? What two shapes capsids come in are __________ and ___________.
Nucleocapsid = Capsid + nucleic acid
Two shapes
-Helical capsid
-Icosahedron capsid
What is a viral envelope? Do all viruses have these? Where do viruses obtain these envelopes?
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What are the steps in viral multiplication? Identify one difference between naked or enveloped virus invasion and multiplication
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Where do RNA viruses multiply? DNA viruses?
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What are spikes? What are their 2 main functions? Specifically, what does hemagglutinin do?
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What is a bacteriophage?
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Are viruses part of the three domains of life?
No, they are not
“Viridae” refers to viral __________, whereas “virus” refers to _________.
Viridae = Family
Virus = Genera
The main categories that we saw in terms of viral classification where separated based on what?
Based on evolutionary relationships
> Structure
Chemical composition
Genetic Makeup
Why do biologists cultivate viruses?
How do they cultivate them?
Why?
Isolate and identify them
For vaccine production
Study their structure and effects on a host
How?
Cell (Tissue) Cultures
Bird embryos
Live animals
Describe the process (step by step) of animal virus invasion and reproduction. Make sure you understand the terms highlighted in your slides and whether the term relates to naked or enveloped viruses.
APSAR
Adsorption
Penetration
Synthesis
Assembly
Release
What is a virion?
A virulent virus that has been released from a host cell
Describe the process (step by step) of bacteriophage invasion and reproduction. In what way(s) is it different from animal virus invasion and reproduction?
Attachment
Penetration
Biosynthesis
Maturation
Release
What is the medical importance of viruses? Are they always lethal?
Acute infections = temporary sickness
Death
Long-term effects
Antiviral drugs and vaccines
What is a prion? What is one example of a disease caused by a prion? What makes prions so unique?
Prion: BLANK
Ex: Mad cow disease
