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16 Cards in this Set
- Front
- Back
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What is a gene? |
units of heredity: They are passed from generation to generation and are carried onchromosomes. Each gene provides an organism with some type of function. they are segments of DNA within a chromosome that allow a particular polypeptide to be made. Anearlier version of this idea was the 'one gene – one enzyme' hypothesis advanced by Beadle and Tatum |
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What did beadle and Tatum work with? Why did they treat it with xrays? What were they looking for? |
they worked with the bread mold Neurospora which can grow on a minimal medium w/ agar salts, glucose and biotin. X-rays cause damage to DNA, resulting in a loss of genetic information inrandom places throughout the genome. They then looked for mutants that were unable to grow onminimal media, but which could grow on a medium that was supplemented with all 20 essential aminoacids ('complete medium'). |
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What did Beadke and Tatum find? |
They found mutants that were unable to grow on MM, but were able to grow on MM + arginine. Hence,these mutants had a specific inability to make arginine: They could convert the precursors in MM to 19 ofthe 20 essential amino acids, just not arginine. |
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What did Beadle and Tatum conclude? |
arginine is synthesized in a series ofdiscrete steps, and that each step iscatalyzed by an enzyme – the productof a gene. If minimal medium is supplementedwith a chemical that is after the blockin the pathway, then the Neurosporamutant will be able to grow, becauseit now has arginine (or can make it). |
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what is the central dogma?? |
DNA-RNA- protein |
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in what step is the message on an mRNA created? when is it converted into an amino acid sequence? |
transcription. translation |
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What is the difference between prokaryotes and eukaryotes when it comes to transcription and translation? |
Prokaryotes: s, transcription andtranslation are coupled – anmRNA that is not yet completelymade can begin to be translatedby ribosomes |
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Transcription occurs when.. |
theenzyme RNA polymerase binds to the promoterregion, initiates transcription 5'-3 |
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expressions of genes can be regulated by proteins called ... |
transcription factors |
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What do transcription factors do? |
bind to the promoter and either blocktranscription or cause it to increase |
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what does rna polymerase do? |
initiate transcription byunwinding the DNA |
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Briefly summarize the three steps of transcription |
initiation- incorporation ofnew NTPs will occur using the bottom strand as atemplate. At termination, the RNA transcript is released, andRNA polymerase is no longer bound to the DNA |
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What are the 3 steps to priming an RNA. (Pre-RNA) |
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What is the genetic code? |
its the triplet code by which three bases (a codon) specify a single amino acid. Three basestogether generate a total of 64 possible codons, whose corresponding acids are shown on a genetic codetable. |
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codons read.. |
5->3 |
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How do you translate an mRNA |
Within each messenger RNA (either a mature mRNA in eukaryotes, or theprimary transcript in prokaryotes) is an open reading frame – a coding region that begins with a start codon(AUG), proceeds three bases at a time to specify amino acids, and then ends with one of three stop codons(UAA, UAG or UGA). Stop codons are also called nonsense codons. Surrounding the coding region areportions of the mRNA that are not used for specifying the amino acid sequence, called untranslated regions(UTRs). There is usually a UTR at the 5' and 3' ends. |
