DNA: Discovery and Replication Flashcards
How to purify something
1) separate components of a complex mixture
2) Assay each component to determine which has the desired property (assay,
Ragged end
5’ end goes further - cuz u always add to 3’ hydroxyls
How the cell replicates its DNA
Enzyme helicase unwinds the DNA strand
Enzyme primase makes short RNA primers (for lagging strand)
RNA & DNA –> DNA w primers
DNA polymerase III (main)
DNA polymerase I (fills gaps)
DNA ligase (fills last gaps - last phosphate bond in between adjacent okazoki fragments)
Epistasis
often results from genes involved in diff steps of the same process or pathway
Ex: interaction between albino (Aa) locus & agouti (Bb) locus. 1 gene/enzyme for pigment & another for distribution
Central dogma
DNA –>(transcription) RNA –>(translation) polypeptides
20 amino acids
must be codded by a 3 nucleotide code (4^3 = 64) - those that don’t code are stop codons
tRNA
can fold & form complementary strands with themselves - encodes info to form bonds with itself (like an enzyme)
1 (or more) tRNA for each amino acid
contains an anticodon (reverse complement of codon of amino acid) & has a unique sequence/>shape
Lining up tRNAs who’s codons match (H-bond) lines up amino acid sequence for ribosome
how to make sure that the right amino acid ends up on 3’ hydroxyl of tRNA
w series of protein enzymes (_nylalanine? aminoacyl tRNA synthase) w binding sites that recognizes 3D structure of tRNA and recognizes amino acid that should be placed on tRNA
coding strands
3’ sense/coding strand (same sequence as mRNA)
5’ antisense/template strand (to convert info into mRNA)
Transcription complex
or promoters
Recognizes which strand and where to start transcribing
–> RNAs correspond to individual genes
3 frame problem
ribosome (staring at 5’ end) looks for first thiamine (AUG) codon, defining reading frame –> every protein starts with thyamine
wobble coding
tRNA anticodon does not strictly obey base-pairing rules
See rules slide
Diff alleles = diff genes
Sickle cell anemia - autosomal recessive trait in humans (1 in 12 african-americans are heterozygous for sickle cell allele)
GAG (glutamate) to GTG (Val) –> Hemoglobin protein is diff shape
classifying mutations
point mutations - small changes in DNA usually affecting one gene (Missense, nonsense (to stop codon), deletion (frame shift lol fuck you, deletion (no frame shift, deletes 3), silent (plays with wobble))
Chromosomal mutation - large changes in chromosome affecting many genes (deletion, duplication & deletion (unequal recombination), inversion, reciprocal translocation (recombination w diff chromosomes))
