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41 Cards in this Set
- Front
- Back
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What are the three functions of organic material? |
1) Replication 2) Expression 3) Mutation |
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What are the three compounds that make up nucleic acid? |
1) Nitrogenous base 2) Phosphate 3) Sugar |
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What are the four physical properties (functions) of nucleic acid? |
-Nucleic acids have four functions: 1) Base pairing 2) Form double helix 3) Provides stability 4) Superstructures (supercoils/grooves) |
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What are the two kinds of bases? |
-Purines: Aderine, Guamine -Pyrimidines: Cytosine, Thymine |
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What are the two purines? |
Aderine and Guamine |
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What are the two pyrimidines? |
Cytosine and Thymine |
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What bonds hold the sugar phosphate backbone together? |
Covalent bonds |
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What bonds hold the bases together? |
Hydrogen bonds |
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Does the phosphate backbone have a positive or negative charge? |
It has a negative charge |
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Does DNA have an overall positive or negative charge? |
It has an overall negative charge |
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Can highly condensed DNA be expressed? |
-No, DNA cannot be expressed when it is condensed -DNA is unwound by the addition of Acetyltransfere |
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What does Acetyltransfere do? |
It unwinds DNA when added |
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What does Histone Deactylase do? |
It reduces gene expression when it is removed |
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Is DNA replication semi-conservative? |
Yes. A parental strand binds with a filial strand. This helps prevents mutations during replication. |
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In which direction does replication occur? |
5´ to 3´ |
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What are the names of the two strands of DNA being replicated? |
-The leading or primary strand is continuously replicated -The secondary strand is replicated in segments called ¨Okazaki Fragments¨ |
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In general, what do DNA polymerases do? |
-DNA polymerase proofreads new DNA and replaces any incorrect nuceotide. |
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What is a nuclease? |
-Nucleases are nuleotide excision repair. They cut out the incorrect bases -Other enzymes replace the damaged DNA |
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What is the central dogma? |
Genetic info flows from DNA to RNA to protein, or from DNA to DNA. DNA>RNA>protein |
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What is transcription? |
-Transcription is the DNA directed synthesis of RNA -RNA is linked to the complementary strand of DNA -Uracil replaces Thymine |
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What are the three stages of transcription? |
1) Initiation 2) Elongation 3) Termination |
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The three stages of transcription are Initiation, Elongation and Termination. What happens in each phase? |
1) Initiation: a promoter establishes where RNA synthesis is initiated (TATA box) 2) Elongation: Transcription factors help eukaryotic RNA polymerase to recognise promoter sequences 3) Termination: Stops the reading of coding |
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What function does DNA ligase serve? |
DNA ligase seals breaks in the DNA strands |
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What is mRNA |
-messenger RNA -mRNA is the complimentary strand replicated from DNA |
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What is tRNA |
-transfer RNA -brings the amino acids to the ribosome to be made into a protein |
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What is rRNA |
-ribosomal RNA -Moves along the mRNA, and reads it whilst the tRNA links the amino acids into a protein |
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What is the -35, -10 and +1 sites and what do they do? |
-The -35 site is the binding site where the ribosome to the DNA -The -10 site is where the DNA starts to unravel to allow for reading -The +1 site is where the ribosome being reading the DNA |
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What is the ribosome? |
The enzyme which shifts along the DNA, replicating the RNA polymer (mRNA) |
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What is the process for transcription? |
1) Ribosome binds to -35 site 2) DNA starts unwinding at -10 site 3) Ribosome begins coding at +1 site, and continues along strand 4) The leading strand creates a continuous RNA chain. |
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What is the difference between DNA and mRNA? |
-RNA transcripts are antiparallel and complementary to the template DNA strand |
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What is the process of translation? |
1) tRNA reads the codons along the mRNA chain 2) tRNA brings the amino acids to the A site of the ribosome 3) the tRNA joins the amino acid to the polypeptide chain (P site) 4) the tRNA leaves the E site to retrieve another amino acid 5) Polypeptide chain termination occurs when the chain termination codon enters the A site of the ribosome |
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Why are frameshifts bad when they are not a multiple of three? |
-A frameshift is bad because it adjusts the reading frame of the codons. -If the frameshifts moves three bases, it is not so bad as the rest of the DNA stays in frame with the loss of only one amino acid. |
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What three things does DNA polymerase require to function? |
1) DNA polymerase requires a primer with a three 3´ -OH. 2) Template DNA to specify the sequence of a new strand 3) Substrates of dNTPs and Mg²⁺. |
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What does DNA polymerase III do? |
-DNApol III can add 3´ -OH to ends of DNA -3´ to 5´exonuclease cleaves errors from the DNA -DNApolll II has the ability to synthesise DNA, proofread and correct the synthesis if there are errors |
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What does DNA polymerase I do? |
-DNApol I can do three things: 1) polymerase (addition) activity 2) 3´ to 5´ exonuclease (remove) activity 3) 5´ to 3´ exonuclease activity (removal of RNA primers located on lagging strand) |
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What do helicases do? |
-Helicases are enzymes that untwist the helix at the DNA forks |
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What does topoisomerase do? |
-Topoisomerase goes ahead of the helicase (which is untwisting the forks) and removes the buildup of tension. |
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What does the enzyme primase do? |
-enzyme primase creates primer RNA
-a primer RNA is 5-10bp long and is paired to the template strand |
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Can DNA undergo spontaneous chemical reactions under normal cellular conditions? |
Yes. This is a spontaneous mutation. |
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Can DNA mutate after replication? |
Yes. Either by spontaneous mutation or by mutagens such as UV light. |
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What are thymine dimers? |
A mutation that causes DNA to buckle, and interferes with replication. |
