Dna Repair And Transcription

Front 1

Result of DNA Damage

Back 1

chromosomal rearrangements, deletions, block replication...> mutations>cancer

Front 2

Envioronmental Causes of DNA Damage
3 Kinds

Back 2

reactive O2 species- formationof hydroxyl radical
OH cleaves the deoxyribose or phosphate bckbne
UV light- abosrbed by pyrimidine dimers
Adduct formation- form covalent bonds which are short and cause distortion

Front 3

Biochemical Causes of DNA Damage

Back 3

Tautomerization during replication- misplaced proton, which may cause a bond in wrong place
Polymerase- contains EXONUCLEASE which normally removes incorrect nucleotide at end. (proofreading fail)

Front 4

BER

Back 4

Base Excision Repair- corrects base mis-match
1. glycosylase removes base
2. endonuclease cleaves backbone to remove sugar
3. DNA polymerase fills gap
4. Ligase seals

Front 5

NER

Back 5

Nucleotide Excision Repair- removes base with adduct
1. double excision removes oligomer containing damage
2. polymerase fills gap
3. ligase seals

Front 6

UV Sensitivity Defects
3 types

Back 6

Xeroderma pigmentosum- hypersensitive to UV, skin cancer, skin aging
cockayne syndrome- impaired nervous system development, hypersensitive to light, premature aging
Trichothiodystrophy- brittle hair and nails, some UV sensitivity

Front 7

Defects in other pathways
6 ways

Back 7

BRCA1 &2- predispose breast cancer
Werner's Syndrome- premature aging, retard growth
Bloom's ""- UV sensitivity, high incidence of cancers
Ataxia telangiectasia- sensitivity to ionizing radiation and chemicals
Fanconi anemia- short stature, skeletal anomalies, tumors, leukemias, mone marrow failure

Front 8

transcription

Back 8

produces single stranded RNA complement to DNA strand

Front 9

RNA Promoter
RNA Terminator

Back 9

recruits RNA polymerase to determine start site
induces RNA polymerase to stop synthesis and release transcript

Front 10

Chemistry of RNA vs. DNA
4 differnces

Back 10

1. Ribose triphosphates are the substrates
2. No primer required
3. UTP replaces dTTP
4. RNA polymerases do not proofread

Front 11

mRNA

Back 11

info to synthesize proteins
contain most of the sequence complexity of cellular RNA
only 5% of RNA mass

Front 12

rRNA
percentage?
3?
4?

Back 12

huge complex, translates mRNA sequences into protein sequences. carry out job of ribosomes
more than 60% of ribosome mass
3 rRNAs diff size in bacteria. 4 rRNAs diff size in euks

Front 13

tRNA

Back 13

small carriers of amino acids for protein synthesis
over 100 diff tRNAs per cell. only 5% of cellular RNA

Front 14

Small Nuclear RNA (snRNA)
Nucleolar RNA (snoRNA)

Back 14

small, highly abundant RNAs of eukaryotes
participate in reactions of RNA processing

Front 15

RNA interferance

Back 15

MicroRNAs (miRNA) combine with mRNA to control ability of mRNAs to be translated into proteins

Front 16

RNA Synthesis in Bacteria

Back 16

Core complex performs synthesis.
only one RNA polymerase in bacteria (4 core sub-units and sigma protein)
sigma binds promoter sequences> RNA polymerase to start site

Front 17

Consensus sequence

Back 17

idealized sequence representing the bases occurring with the highest frequency at each position in a functional nucleic acid site
bases that occur with high frequency are "conserved"
indicates how the DNA/protein interact. more conserved proteins= more efficiently protein will bind

Front 18

RNA Synthesis in Eukaryotes

Back 18

3 polymerases- transcribes specific types of RNA
polymerases bind only after recruitment by promoter binding proteins
RNA made in nucleus. transcripts must be shipped to cytoplasm to function

Front 19

Eukaryotic RNA Polymerases
3 types

Back 19

1- transcribes only a single gene (look up)
3- transcribes many small RNA's (tRNAs and small nuclear RNAs)
2- transcribes all the genes encoding proteins

Front 20

rifampicin (rifaldazine)
alpha- amanitin

Back 20

inhibits most bacterial RNA polymerases. treats mycobacterium tuberculosis
inhibits eukaryotic RNA polymerases

Front 21

cis-acting elements

Back 21

sequences involved in expression of a gene
1. dont move in the cell
2. only affect molecules to which they are attached
examples ( -10,-35, and TATA box sequences)

Front 22

trans-acting factors

Back 22

proteins that bind to cis-acting elements
1. move through cell and can affect multiple, unlinked targets
2. mutation of this, affects all genes that this interacts with
example( sigma protein and TATA box- binding protein)

Front 23

Other Cis-acting elements & trans-acting factors

Back 23

Slide 48. Look up