Course book: Chapter 2 "Nucleic acids convey genetic information" Flashcards
What two findings were integral to Watson and Crick finding the structure of DNA?
- X-ray diffraction pattern of DNA.
- The fact that DNA was helical.
Not too many structures could fullfil the criterias, through trial and error, they eventually found the DNA structure.
Why did scientists conclude that there has to be an intermediary between DNA and protein?
They concluded it because they had visualized DNA to exist in the cell nuclei, while proteins are present primarily in the cytosol.
How did scientists conclude that rRNA were infact NOT tRNA?
- rRNA is ~1500bp.
- rRNA base pairs don’t reflect the gDNA ratio of AT/CG.
Is the following statement true?
1-5 ribosomes can translate an mRNA sequence at once.
False. <50 ribosomes can translate the same mRNA.
a. How many codons code for amino acids?
b. How many codons are stop-codons?
a. 61
b. 3
In what direction does polynucleotides grow?
5’ –> 3’. This means that the template is read
3’ –> 5’.
Describe how “pulse labelling” was used to figure out the directionality of polypeptide growth.
- Radiolabelled amino acids are added, and were briefly introduced to the ribosomes before stopping the protein synthesis.
- Cellular protein was extracted.
- Proteins were analysed with emphasis on radiolabelled amino acid incorporation. The probability of the radiolabelled aa being near the C-terminal was very high.
- Conclusion: the translation was interrupted when adding aas to the C-terminal.
Direction: N –> C.
Is the following statement true?
Start codons need to be preceeded by a GC-rich sequence, in eukaryotes and prokaryotes.
False. In prokaryotes, a GC-rich domain is required. In eukaryotes, the first ATG which is encountered is used.
Is the following statement true?
Start codons need to be preceeded by a GC-rich sequence, in eukaryotes and prokaryotes.
False. In prokaryotes, a GC-rich domain is required. In eukaryotes, the first ATG which is encountered is used.
