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83 Cards in this Set
- Front
- Back
Genetics
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Genetics: The study of what genes are, how they carry information, how information is expressed, and how genes are replicated
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Gene
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Gene: A segment of DNA that encodes a functional product, usually a protein
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Chromosome
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Chromosome: Structure containing DNA that physically carries hereditary information; the chromosomes contain the genes
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Genome
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Genome: All the genetic information in a cell
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Genomics
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Genomics: The molecular study of genomes
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Genotype
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Genotype: The genes of an organism
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Phenotype
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Phenotype: Expression of the genes
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DNA-Polymer
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Polymer of nucleotides: Adenine, thymine, cytosine, and guanine
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What is Double helix of DNA associated with?
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Double helix associated with proteins
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What is the back bone of DNA?
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Backbone" is deoxyribose-phosphate
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What are the strands of DNA held together with?
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Strands are held together by hydrogen bonds between AT and CG
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DNA is copied by?
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DNA is copied by DNA polymerase
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Step 1 of DNA replication
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Topoisomerase relaxes supercoiled DNA.
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Step 2 of DNA replication
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Helicase unwinds the double helix by breaking hydrogen bonds between the base pairs.
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Step 3 of DNA replication
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Destabilizing Enzymes (SSB) bind to the single strands to keep the strands separated.
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Step 4 of DNA replication
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Primase adds RNA primers to initiate DNA synthesis.
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Step 5 of DNA replication
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DNA polymerase binds at the RNA primers, DNA polymerase I removes primers and DNA polymerase III synthesizes new DNA in the 5’ to 3’ direction on both the leading and lagging strands.
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Step 6 of DNA replication
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Fragments of DNA (Okazaki fragments on the lagging strand) are joined by the enzyme DNA ligase
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Define Transcription
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Transcription: RNA is made from the DNA code. The RNA has complementary bases to the DNA.
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Define Translation
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Translation: RNA is used as a template to make protein. Amino acids, protein building blocks are coded by the base pairs on the RNA.
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When does transcription stop?
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Transcription stops when it reaches theterminator sequence
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What is the direction of transcription?
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Transcription proceeds in the 5' to 3' direction
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When does transcription begin?
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Transcription begins when RNA polymerase binds to the promoter sequence
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What does transcribed DNA make?
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DNA is transcribed to make RNA (mRNA, tRNA, and rRNA)
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Define degenerate code
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Degenerate code: most amino acids specified by more than one codon.
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Define condon
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Codon: Group of three nucleotides on mRNA that codes for an amino acid.
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Structure of mRNA Nucleotides
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The mRNA nucleotides are arranged in 3 nucleotide units called codons. Codons do not overlap.
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Protein synthesis is based on?
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Protein is synthesized based on code in mRNA
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Genetic code structure
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64 sense codons on mRNA encode the 20 amino acids
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Translation of mRNA begins at what start codon?
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Translation of mRNA begins at the start codon: AUG
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Where does Translation end?
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Translation ends at nonsense codons: UAA, UAG, UGA
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What does tRNA carry?
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tRNA carries the complementary anticodon
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Name the three types of RNA.
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messenger RNA
transfer RNA ribosomal RNA |
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What is messenger RNA?
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messenger RNA (mRNA) – carries DNA message through complementary copy; message is in triplets called codons
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What is transfer RNA?
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transfer RNA (tRNA) – secondary structure creates loops; bottom loop exposes a triplet of nucleotides called anticodon which designates specificity and complements mRNA; carries specific amino acids to ribosomes
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What is ribosomal RNA?
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ribosomal RNA (rRNA) – component of ribosomes where protein synthesis occurs
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Step 1 of Translation
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Translation of mRNA begins at the start codon: AUG
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Step 2 of Translation
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Translation ends at a STOP codon:
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Step 3 of Translation
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The large and small ribosomal subunits and tRNA with UAC anticodon and corresponding methonine amino acid assemble at the AUG start codon.
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Step 4 of Translation
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The first tRNA moves to P site of the ribosome and the second tRNA with the next amino acid enters A site of the ribosome.
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Step 5 of Translation
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The ribosome joins the two amino acids with a peptide bond.
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Step 6 of Translation
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The first tRNA molecule leaves the ribosome and the second tRNA moves into P site while the third tRNA and its amino acid enters A site.
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Step 7 of Translation
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This process proceeds down the mRNA and amino acid chain is formed.
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Step 8 of Translation
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Translation ends when one of three nonsense (stop codons) UAA, UAG, UGA is reached and the ribosome subunits separate from the mRNA and release the polypeptide chain, tRNA.
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What genes are expressed at a fixed rate?
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Constitutive genes are expressed at a fixed rate
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What other genes are expressed only when needed?
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Repressible genes
Inducible genes Catabolite repression |
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What are normally turned off, but can be tured on?
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Inducible Operons
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When lactose is present what else is present?
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when lactose is present, allolactose is present which turns on b-galactosidase to process the lactose
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What does Allolactose induce?
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Allolactose induces the transcription of b-galactosidase.
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What happens to media when lactose is present?
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When lactose is present in the media it is converted by the cell to allolactose.
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What happens when no lactose is present in the media?
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When no lactose is present in the media, E. coli do not make b-galactosidase.
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What breaks down lactose into glucose?
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b-galactosidase breaks down lactose into glucose and galactose.
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What is required for lactose metabolism in E. coli?
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inducible genes
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Lac operon
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Genes required for tryptophan synthesis are normally transcribed.
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When excess tryptophan is present, it can act as a corepressor.
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Lac Operon Tryptophan Operon
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Normally on, can be turned off.
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Lac Operon Tryptophan Operon
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Define Spontaneous mutations.
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Spontaneous mutations: Occur in the absence of a mutagen
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Define Mutagen.
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Mutagen: Agent that causes mutations
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Describe Mutaion.
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A change in the genetic material
Mutations may be neutral, beneficial, or harmful |
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Base substitution
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Change in one base
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Missense substitution
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Result in change in amino acid
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Result in change in amino acid
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Insertion or deletion of one or more nucleotide pairs
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Frequency of Mutagens
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Mutagens increase to 10–5 or 10–3 per replicated gene
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Frequency of spontaneous mutation
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Spontaneous mutation rate = 1 in 109 replicated base pairs or 1 in 106 replicated genes
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Define Ionizing radiation
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Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone
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What does radiation cause?
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UV radiation causes thymine dimers
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Radiation repair
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Photolyases separate thymine dimers
Nucleotide excision repair |
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Horizontal Gene Transfer
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Horizontal gene transfer: The transfer of genes between cells of the same generation.
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Vericle Gene Transfer
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Vertical gene transfer: Occurs during reproduction between generations of cells.
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The Genetic recombination in bacteria are?
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Conjugation
Transformation Transduction |
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when does crossing over occur?
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Crossing over occurs when two chromosomes break and rejoin
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Define transformation.
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Transformation – chromosome fragments from a lysed cell are accepted by a recipient cell
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Explain Griffith’s Transformation Experiment.
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injected mice with bateria, encapsuled, non encapsuled, heat fixed encapsuled, and non heat encapsuled to see if they would live or die.
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Define Conjugation.
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Conjugation – transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via a direct connection
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Define high-frequency recombination.
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High-frequency recombination – donor’s fertility plasmid has been integrated into the bacterial chromosome
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Gram-negative cell donor has whas what type of fertility?
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Gram-negative cell donor has a fertility plasmid (F plasmid, F′ factor) that allows the synthesis of a conjugation (sex) pilus
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Define transduction.
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Transduction – bacteriophage serves as a carrier of DNA from a donor cell to a recipient cell
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what are the types of Transduction by a Bacteriophage?
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Generalized
Specialized |
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function of Complex transposons
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Carry other genes
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Transpons contain?
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Contain insertion sequences for cutting and resealing DNA (transposase)
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Transpons mobility
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Segments of DNA that can move from one region of DNA to another
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Genes and evolution
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Fittest organisms for an environment are selected by natural selection
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What do mutation and recombination provide?
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Mutations and recombination provide diversity
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