TEST on DNA, Transcription, Translation

Griffith Experiment

Gave evidence that there was a biochem factor that allowed for virulence (deadly) trait from dying to living bacteria

Avery et. al. Experiment

Destroying DNA prevented transfer of dangerous strain to new strain of virus

Hershey & Chase

Transfer of genetic information from virus (bacteriophage) to bacteria correlated with transfer of DNA (protein can be wiped off, not imbedded)

Nucleotide structure

Phosphate group, sugar (deoxyribose), nitrogenous base

Antiparallel strands

one side has phosphate group facing up, other has phosphate group facing down (optimal positioning)

Sugar, phosphate, backbone

Sugar, deoxyribose, 3’; phosphate, 5’; nitrogenous base (A-T, G-C)

Base Pairing

Adenine w/ Thymine (two hydrogen bonds), Guanine w/ Cytosine (three hydrogen bonds)

Meselson-Stahl experiment

Demonstrated that DNA replicated semi-conservatively because the first generation was in the middle (ruled out conservative because it would be half up half down), second generation was top and middle (ruled out dispersive because it would be slowly approaching 14 top and would not stay in middle)

Helicase

unwinds the two strands of DNA

Single Stranded Bonding Proteins

stop the unwinded strands from bonding back together

Primase

puts down RNA primers for synthesis

DNA polymerase

goes from primer down the strand placing (5’ to 3’ always, on original strand going 3’ to 5’)

Ligase

Joins okazaki fragments made by lagging strand

Leading strand

synthesized continuously from 5’ to 3’

Lagging strand

Synthesized discontinuously from 5’ to 3’. New primers placed to it can continue, opposite direction of fork

Okazaki fragments

lagging strand makes little primer+DNA pieces, joined together by ligase

RNA polymerase

Transcription: synthesizes mRNA through DNA

Initiation

Polymerase lands on promoter site

Elongation

Happens when RNA polymerase is unwinding the DNA and adds nucleotides to the 3’ end of mRNA

Termination

End of gene is reached, mRNA and RNA polymerase are released

RNA processing in eukaryotes

Splicing removed non coding sequences (introns) leaving coding sequences (extrons). 5’ capping and 3’ poly A tail (a bunch of As) to stabilize mRNA after stop code

Role of ribosomes in tRNA

structure where protein synthesis takes place

Insertion mutation

Addition of base pair(s)

Deletion

deletion of base pair(s)

Point

change of a base pair(s)

Silent mutation

does not change amino acid sequence

Missense mutation

changes the amino acid sequence

Nonsense mutation

causes a premature stop codon

frameshift mutation

insertion/deletion that changes reading frame