Biochemistry – Nucleic Acids – Flashcards
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What are sources of purines occurring in nucleic acids or their metabolites?
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Adenine - A Guanine - A Xanthine - X Hypoxanthine - Hx
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What are dietary sources of purines?
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Caffeine Theophylline Theobromine
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What are the two types of pentoses?
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Ribose - occur in RNA (ribonucleicacid) 2'deoxyribose - occur in DNA (deoxyribonucleic acid)
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What is the structure of pyrimidines?
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1-ring heteronitrogen structure
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What are the pyrimidine nucleic acids?
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Cytosine - C (DNA and RNA) Uracil - U (RNA) Thymine - T (DNA)
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What is a nucleoside?
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nitrogen base + pentose
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What is a nucleotide?
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nucleoside + (Phosphate)n (n=1,2 or 3
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5-fluorouracil
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-synthetic nucleotide -blocks pyrimidine synthesis -cancer tx -thymine analog
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5-iodo-2'deoxyuridine
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-synthetic nucleotide -blocks thymidine kinase -cancer tx -thymindine analogue
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AraC
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-synthetic nucleotide -cancer tx (leukemia) -cytidine analogue
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Allopurinol
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-synthetic nucleotide -blocks uric acid synthesis -gout tx -purine analogue
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AZT
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-synthetic nucleotide -used to block replication of HIV (for prevention/delay of AIDS) -thymidine analog
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What is the difference between thymine and thymidine?
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Thymidine is the nucleotide whereas thymine is the nucleotide base
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What are synthetic nitrogen bases, nucleosides and nucleotide analogs?
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-synthetic bases have altered nitrogen bases or sugars -used as drugs to treat cancer, prevent immunological reactions in organ transplants or suppress viral growth -mechanisms of action: *inhibit enzymes of nucleic acid synthesis *incorporate into DNA and alter subsequent DNA synthesis
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What does the term nucleic acid often refer to?
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DNA or RNA
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What does the head and tail of DNA posses?
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Head: has a free phosphate called 5'phosphate or 5'end Tail: has a free -OH group on the 3'-carbon of the deoxyribose of the last nucleotide called 3'-hydroxy or 3'-end
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What type of bond connects the monomers of DNA and RNA together?
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Phosphodiester bond
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The double helix of DNA and RNA is maintained by __________ bonds between _________.
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-hydrogen -nitrogen bases
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How do the bases pair?
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A-T --> 2 hydrogen bonds G-C --> 3 hydrogen bonds (GCAT)
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What is a double helix?
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-two polymers twisted in helical form
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What makes up the backbone of DNA?
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sugar-phosphate backbone
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What does it mean when DNA is described as anti-parallel?
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5' to 3' matches up with the 3' to 5' of the antiparallel strand
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There are different forms of DNA with respect to their: a. primary structure b. secondary structure c. tertiary structure d. quaternary structure
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tertiary
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What form of DNA is predominant in humans?
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-B form -right handed -3.4 nm/turn
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What is melting temp of DNA strand dependent on?
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The number of GC and AT bonds
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How do you renature DNA
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incubate it with a rebuffer
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What happens at the A site of the ribosome?
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The PEPTIDE BOND is made
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What happens at the P site of the ribosome
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Protein is released
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What brings in the protein into the ribosome with the anticodon sequence corresponding to the mRNA codon?
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tRNA
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What is the methyl cap on mRNA?
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7-methylguanosine triphosphate (GmTP)
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What is the start codon? and what amino acid does it code for?
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AUG; methionine
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What is at the end of mRNA?
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Poly-A-tail which is a chain of adenosine
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What is a codon?
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3 monophosphate nucleotides that code for a particular amino acid
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The size of the mRNA varies according to the size of the respective _______.
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gene
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Gene
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segment of DNA that serves as a template for the biosynthesis of RNA
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Exon
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the gene DNA from which mature RNA is made
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Intron
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the RNA made from introns is removed
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How many base pairs are found in the human genome?
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3.1 billion base pairs
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What are the 3 types of RNA?
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rRNA - ribosomal RNA 75% mRNA - messenger RNA 5% tRNA - transfer RNA 20%
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What are the two strands that make a DNA double helix?
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Template strand Coding strand
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Template Strand
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for RNA synthesis "sense" strand
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Coding Strand
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the opposite strand called coding because its nitrogen base sequence is similar to that of the transcribed RNA "antisense" strand
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What are the 4 classes of rRNA based on molecular size?
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5S 5.8S 18S 28S
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How do rRNAs aggregate to for 80S ribosomes and what is their function?
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40S ribosomes (from 18S rRNA + PRO) 60S robosome (from 5S 5.8S and 28S rRNA + PRO) These aggregate to form 80S which anchors the mRNA, aminoacyl tRNA and the growing peptide (PRO)
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tRNA
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-very small 4S -cloverleaf structure -tRNAs transfer aa to the ribosomal site where protein synthesis is taking place -at least 20 tRNAs for the 20 amino acids used in proteins
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One arm has an ___________ : matches a codon on mRNA with an ________ to the bond.
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anticodon; hydrogen
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The 3' end has a _____ which carries a specific amino acid (dictated by the codon)
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CCA
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What is the start codon and what amino acid does it code for?
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AUG; Methionine
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What are the stop codons and what amino acids do they code for?
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UAA UGA UAG They don't code for proteins
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How many amino acids are there?
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20
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How many different three letter sequences can be made?
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64
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