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79 Cards in this Set
- Front
- Back
Genetics
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the study of the inheritance (heredity) of living things
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The Levels of Structure and Function of the Genome
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Genome
Chromosome Gene |
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Genome
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All genetic material in the cell
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Chromosome
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A discrete cellular structure composed of a neatly packed DNA molecule
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Eukaryotic chromosomes
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DNA molecule tightly wound around histone proteins
Appear linear |
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Bacterial chromosomes
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Condensed and secured by means of histone like proteins
Single, circular chromosome |
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Gene
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A segment of DNA that does something
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Structural genes
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code for proteins
code for RNA |
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Regulatory genes
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control gene exression
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Genotype
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what the genes look like; reading sequence
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Phenotype
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how the genes are physically expressed
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What is the basic unit of DNA?
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nucleotide
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What makes up a nucleotide?
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Phosphate
Deoxyribose sugar Nitrogenous base |
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How many nitrogenous bases?
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2: purines and pyrimidines
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What does adenine always pair with?
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thymine
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What does guanine always pair with?
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cytosine
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What does helicase do?
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unzips DNA
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What is the goal of DNA replication?
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synthesis of DNA
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Overall replication process of DNA
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Separate the strands
Copy its template Produce two daughter molecules |
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Overall sequence of events for DNA replication:
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DNA Replication: DNA to DNA
Transcription: DNA to mRNA Translation: mRNA to protein |
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T/F: Transcription and translation are occur at the same time in prokaryotes
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True
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Semiconservative
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Each new DNA strand is made of 1 parent and 1 daughter strand
(1/2 of strand was conserved, 1/2 was used) |
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Primase
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synthesizing an RNA primer
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DNA polymerase III
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Adding bases tot he new DNA chain; proofreading the chain for mistakes
Can only add a new base to an existing 3’ OH |
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DNA polymerase I
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Removing primer, closing gaps, repairing mismatches
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Ligase
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Final binding of nicks in DNA during synthesis and repair
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Gyrase
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Supercoiling
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What is the origin of replication?
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Enzymes
Denotes the of DNA synthesis Rich in A and T |
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Helicases bind to what at the origin?
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DNA
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Exonuclease activity:
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(DNA Polymerase III)
Error check Can “back up” and correct mistakes made during replication Greatly reduces mutation rate |
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RNA Primase
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Lays down primer. They don't need a 3' group. Allows DNA polymerase III to start replicating.
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DNA polymerase I removes ___ ______ and replaces them with ____.
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RNA primers
DNA |
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What does DNA ligase do to the strand?
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It seals the strand and moves along any lagging parts.
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Central dogma of DNA code:
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DNA to RNA to Protein
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The major participants in Transcription and Translation:
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mRNA
RNA Polymerase regulatory RNAs |
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mRNA
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made in DNA, sent to ribosomes
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RNA Polymerase
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codes DNA into RNA
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What is different about the assembly line in RNA vs DNA?
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Single stranded molecule
The sugar is ribose |
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What does a promoter do?
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starts transcription with the process of making RNA
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The triplet code and the relationship to proteins:
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DNA (triplets) to
RNA (codons) to Proteins (amino acids) |
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Redundancy
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a particular amino acid can be coded for by more than a single codon
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Wobble
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in many cases, only the first two nucleotides are required to encode the correct amino acid
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Anticodons are complement to what?
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codons
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Where are anticodons found?
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tRNA
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Translation:
The Second Stage of Gene Expression |
All of the elements needed to synthesize a protein are brought together on the RIBOSOMES
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Transfer RNA: The Key to Translation
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Also a copy of a specific region of DNA
Cloverleaf shape |
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The prokaryotic (70S) ribosome composed of:
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tightly packed rRNA and protein
ribosomal RNA aligns mRNA w/ tRNA |
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Initiation of Translation
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*mRNA molecule leaves DNA transcription site
*Is transported to ribosomes in the cytoplasm |
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What is the fundamental difference between prokaryotic ribosomes and eukaryotic ribosomes?
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size
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What is bringing amino acids to the ribosomes?
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tRNA
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Modifications to Proteins: Post translational modifications may be necessary
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Starting animo acid clipped off
Cofactors added Join with other proteins to form quaternary levels of structure |
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What are operons?
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*Prokaryotes organize collections of genes called operons.
*They are either inducible or repressible |
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3 important features of lactose (lac) operon:
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Regulator
Promoter Operator fig 9.18 |
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Regulator
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a gene that codes for a protein capable of repressing the operon [a Repressor]
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Promoter
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recognized by RNA polymerase
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Operator
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a sequence that acts as an on/off switch for transcription
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2 pathways for lactose operon:
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Operon off
Operon on |
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Operon off
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absence of lactose, repressor protein attaches to the operator of the operon. This locks operator and prevents any transcription. No more lactose.
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Operon on
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When entering the cell, lactose becomes an inducer by attaching to the repressor, which detaches. RNA polymerase can now bind to promoter and initiate transcription. Lactose made.
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Mutation
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when phenotypic changes are due to changes in the genotype
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Wild type
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an organism that exhibits a natural, non-mutated characteristic
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Mutant strain
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when a microorganism bears a mutation
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Causes of mutation:
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spontaneous mutation
induced mutation |
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Spontaneous mutation
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random change in the DNA arising from errors in replication
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Induced mutation
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results from exposure to known mutagens.
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Chemical mutagenic agents
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Nitrous acid, bisulfite
Ethidium bromide Acridine dyes Nitrogenous base analogs |
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Radiation mutagenic agents
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Ionizing
Ultraviolet |
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Point mutations
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involve addition, deletion, or substitution of single bases
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Missense mutation
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any change in the code that leads to placement of a different amino acid
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Nonsense mutation
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changes a normal codon into a stop codon
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Silent mutation
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alters a base but does not change the amino acid and thus has no effect
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Back-mutation
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when a gene that has undergone mutation reverses to its original base composition
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Frameshift mutations
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mutations that occur when one or more bases are inserted into or deleted from a newly synthesized DNA strand
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T/F:Most ordinary DNA damage is resolved by enzymatic systems specialized for finding and fixing such defects
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True
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Excision repair
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*Excise mutations by a series of enzymes
*Remove incorrect bases and add correct one |
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What are the three means of genetic recombination in bacteria?
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Conjugation
Transformation Transduction |
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Conjugation
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Direct
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Transformation
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Indirect
Living cell taking up "naked" DNA from the environment |
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Transduction
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indirect
virally mediated transfers |