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83 Cards in this Set

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