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51 Cards in this Set
- Front
- Back
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Who discovered nuclein and in what year?
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Frederic Meischer in 1869
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Where can the A form of DNA be found?
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DNA-RNA hybrids (a wider righ handed spiral helix)
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What is the Z form of DNA?
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the left hand DNA linked to initiation of transcription and extensive methylation
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Histones are basic or acidic?
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Basic, so they can bind to the acidic DNA
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The complex of DNA and histones is called what?
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nucleosome
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What is a a 30nm fiber?
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nucleosome formed into atubular coil called a solenoid
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Organization of DNA in chromatin is essential for what?
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controlling transcription…the compaction prevents easy access to the DNA to be transcribed
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How do you loosen the histones off the DNA
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Acetylation HAT: histone aceytyltransferasev(add negative charge to histones)
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What are HDATs associated with?
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Converts chromatin to silent (keeps the histone bound to DNA) histone de-acetylation
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What else is involved as a transcription factor with the histones?
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Histone Methylation: can silent or activate depending on where the modification occurs
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What percent of the genome is protein-coding exons?
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1.50%
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What is the technique called to determine diploid number of chromosomes and discern chromosomal abnormalities?
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Karyotyping
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What is the syndrome with only 1 X chromosome?
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Turner syndrome
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What is XXY called
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Klinefelter syndrome
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XXY has a high incidence of what?
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germ cell tumor and male breast cancer
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How abouts trisomy of chromosome 18?
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Edwards syndrome
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Down Syndrome is trisomy of what?
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Chromosome 21
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Trisomy of 13 and it leads to what?
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Patau syndrome; heart and kidney problems, microcephaly and abnormal genitalia
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What does RNAse P do?
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Cleaves off an extra sequence of RNA on tRNA molecules
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What do peptidyl transferases do?
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Activity of ribosome to form peptide bonds duing protein synthesis
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Cap on the 5' end of mRNA is required for what?
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For initiation of translation and put on during transcription
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What is the poly-A tail?
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On the 3'end and stabilizes the mRNA. This is added after transcription.
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What is the smallest RNA type
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tRNA
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What is the main function of tRNA
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bring the AA to the ribosome and recognize the codon where the AA should be on the growing polypeptide
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Other type of RNAs
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primers for DNA replication, snRNA (involved in splicing), Xist, miRNA
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What is Xist?
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Inactivates one of the two X chromosomes in vertebrates
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What is miRNA?
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small, non-coding, derived from endogenous genese and repress protein biosynthesis, usually by preventing the ribosome binding to mRNA
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What nucleotide analog resembles Thymidine?
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AZT
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What does AZT do?
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blocks replication by replacement of OH group by N3
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What nucleoside resembles deoxyadenosine?
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ddl (didanosine)
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Reverse transcriptase has a high affinity for what compared to what?
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AZT and ddl compared to normal DNA
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5-FU is an anaolog that inhibits what?
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Thymidylate synthase by blocking nucleotides that replicate it
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What is semiconservative replication
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Conserving what strand when making a new one, rather using a copy of a copy ya know
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In prokaryotes there is only one origin of replication? What about eukaryotes?
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Yep one in pro and multiple in eukaryotes
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Where does replication usually occur? What bases?
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AT rich sites
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DNA helicase uses ATP?
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Yes
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DNA replication starts with what that starts to separate the two strands?
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DnaA
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What do ssDNA-binding proteins do?
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They keep the strands apart and protect them from nucleases
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What removes the supercoils?
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DNA topoisomerases
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A mutation in DNA topoisomerases would do what?
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Kill the cell
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What other DNA enzyme requires ATP?
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DNA ligase
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Telomerase is active in what cells?
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Germ, stem and cancer cells
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What upregulates Telomerase
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Physical exercise, vitamin D
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How do X-rays damgage DNA?
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Indirectly by producing free radicals from H2O
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How do cigarettes damage DNA?
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Directly with benzo[a]pyrene; when oxidized in the body, it forms adducts with guanine residues
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How about UV light with DNA damage?
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UV light forms covalent dimer between two adjacent thymines on DNA strands
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What is an example of deficiency of DNA repair coupled with UV light exposure?
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Xeroderma pigmentosum (autosomal recessive) genetic defect in nucleotide excision repair
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What are the three types of DNA repair?
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Direct repair, Nucleotide excision repair, and base excision repair
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What is direct repair?
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removing damage directly: removing thymine dimer for example
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What is nucleotide excision repair?
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endonuclease cleaves abnormal chain and remove the distorted region, gap is filled by DNA polymerase and ands are joined by DNA ligase
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What is base excission repair?
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DNA glycosylases recognize the distortion and cleaes the N-glycosidic bond, then AP endonuclease cleaves sugar phosphate strand, then the normal pepes fill in the stuff correctly
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