Genetics Exam 3

Genetics Exam 3

1. chapter 10

   • central dogma
     • DNA -> RNA -> proteins transcription is major control point!
     • replication
       • DNA -> DNA
     • transcription
       • DNA -> RNA
     • translation
       • RNA -> proteins
   • DNA vs. RNA
     • both
       • -made of nucleotides joined by phosphodiester bonds
     • DNA
       • -deoxyribose sugar -T -usually double -more stable :)
     • RNA
       • -ribose sugar -has 2'-OH group -usually single, but can form intramolecular dbl strands -U
       • mRNA
         • messenger RNA in cytoplasm/nucleus carries genetic code for proteins
       • rRNA
         • ribosomal RNA in cytoplasm structural/functional component of ribosomes
       • tRNA
         • transfer RNA cytoplasm moves amino acids into polypep chains
   • beadle & tatum
     • made mutants -> crossed them w wt -> found missing proteins -> found arganine was needed  *ONE ENZYME ENCODED BY ONE GENE
   • khorana and nirenburg
     • found which codons encode for which amino acid 1 start 3 stop
     • jacob & monod
       • discovered mRNA
     • syndey brenner
       • said code was triplet was supported bcus only three base insertion/deletion could restore polypeptide order
       • CODON
         • set of 3 nucleotides responsible for coding an amino acid
   • transcription
     • 1. dsDNA template 2. DNA dependent RNAP 3. NTP + buffer
     • dsDNA
     • transcription unit
       • made of promoter (RNAP binds), structural gene (RNA coding), + terminator (stops).
       • 1. initiation
         • main control point RNAP + signma bind promoter (holoenzyme) -> DNA melted -> first NT added -> RNAP leaves starts @ +1 downstream
         • RNAP
           • I & II knows how to bind bcus of 12 base sequence at target site
       • 2. elongation
         • NTs add 5'-3' -> as RNAP moves down the pieces behind reanneal
       • 3. termination
         • stop signal signal = DNA sequence OR DNA sequence + termination protein
   • oscar miller
     • christmas tree thing
   • colinearity
     • # nucleotides amino acids in DNA = # of amino acids in proteins -tested by DNA:RNA hybridization
     • DNA:RNA hybridization
       • 1. RNA is compatible with more than one spot on DNA 2. ssDNA reanneals to other OR RNA FOUND INTRONS AND EXONS
       • introns
         • noncoding DNA
       • exons
         • coding DNA
   • post-transcription modification
     • 1. base addition (5' cap/3' polyA tail) 2. base modification (tRNA, hairpin) 3. RNA splicing (intron removal)
     • hairpin loop
       • when ssRNA folds in on itself during transcription
   • transcription vs replication
     • both
       • -use DNA template -5'->3' -products r antiparallel and complementary to template -substrates are nucleotide triphosphates
     • transcription
       • -unidirectional -initiation doesnt need primer -each gene transcribed separately
     • replication
       • -bidirectional synthesis -initiates from a replication origin

2. chapter 12

3. chapter 13

   • somatic vs germline mutation
     • somatic: only carrier has it, offspring don't germline: whole carrier has it, and half of offspring do
   • phenotypic level
     • lethal vs nonlethal
       • lethal conditional- death w certain environmental conditions nonlethal conditional - no death w certain environmental conditions
     • no phenotype change
       • 1. doesn't occur in gene 2. occurs in gene: silent/missense
       • silent mutation
         • no change in amino acid sequence
       • missense mutation
         • changes amino acid sequence if protein function doesn't change then it is NEUTRAL
     • change in phenotype
       • 1. morphological  2. nutritional 3. behavioral 4. regulatory (can be pleiotrophic)
   • genotypic level
     • point
       • change in one base
       • substitution
         • can have no change (silent/neutral) or cause nonsense mutation 
         • nonsense mutation
           • changes sense codon into stop codon
       • insertion
         • addition of nucleotide
         • frameshift mutation
           • can change the reading frame, usually causes loss of function
         • trinucleotide repeat
           • ex: FXS/huntington's...both can undergo genetic anticipation -fxs: x linked dominant, FMR1 not expressed -huntington's: autosomal dominant
       • deletion
         • removal of nucleotide
     • more than 1 base involved
       • reverse
         • wt is returned entirely
       • intergenic
         • 2 genes involved
       • intragenic
         • mutations are in the same gene
   • causes of mutations
     • 1. spontaneous 2. chemicals 3. radiation 4. transposable elements
     • spontaneous
       • 1. tautomerization 2. wobble/slippage (issues w incorporating enzymes n stuff) 3. recombination
       • wobble
         • nonstandard base pairing between third codon and first anticodon
     • chemicals
       • changing base chemical composition
       • intercalating agents
         • intercalate between dna bp -> dna contorts -> deletions/insertions happen
     • radiation
       • 1. UV - (5-300) cross links pyrimidines 2. X-ray - (.005-5) dna binds w free radicals and causes dna backbone to break
     • transposable elements
       • cause: insertions rearragement/duplicate of target site mobilizing surrounding DNA
       • transposon
         • mobile DNA due to nonrecombination 1.delineated by inverted repeats (>...<) 2. has gene encoding transposase 3. flanked by direct repeats in target
       • retrotransposon
         • transposes thru RNA intermediate
   • ames test
     • how to tell if smth is a mutagen not always valid for humans
   • DNA repair
     • xeroderma pigmentosum
       • autosomal recessive skin sensitivity to sunlight caused by defects in DNA repair

4. CRISPR

   • Cas9 based targeted genome sequencing
   • type of DNA damage
     • 1. single strand break 2. dbl strand break 3. base adducts 4. base mismatch/insertion/deletion

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