Topic 4- Protein synthesis Flashcards
Define gene
a length of DNA that codes for a polypeptide/protein
Define genome
the complete set of genes present in a cell
Define proteome
the full range of proteins that a cell is able to produce
Why is the proteome usually larger than the genome of the cell? (2 reasons)
-Due to the large amount of post-translational modification of proteins (often in the Golgi apparatus)
-Each gene is also capable of producing multiple different proteins via alternative splicing
Give 2 similarities between the structure of DNA and the structure of RNA
-is a polynucleotide – it is made up of many nucleotides linked together in a long chain
- RNA nucleotides contain the nitrogenous bases adenine (A), guanine (G) and cytosine (C)
Give 3 differences between the structure of DNA and the structure of RNA
-RNA nucleotides never contain the nitrogenous base thymine (T) – in place of this they contain the nitrogenous base uracil (U)
-contain the pentose sugar ribose (instead of deoxyribose)
-only made up of one polynucleotide strand (they are single-stranded)
What is the structure of an RNA nucleotide?
-made up of alternating ribose sugars and phosphate groups linked together, with the nitrogenous bases of each nucleotide projecting out sideways from the single-stranded RNA molecule
- sugar-phosphate bonds (between different nucleotides in the same strand) are covalent bonds known as phosphodiester bonds- forms the sugar phosphate backbone
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What is the structure of mRNA?
-single-stranded molecule
-made up of a sugar-phosphate backbone and exposed unpaired bases
-Uracil bases are present instead of thymine bases (which are found in DNA)
What is the structure of tRNA
-single-stranded molecule
-It has a sugar-phosphate backbone
-It has a folded shape-there are hydrogen bonds between some of the complementary bases
-Amino acids bind to a specific region of the molecule
-The specific anticodon found on the tRNA molecule is complementary to a specific codon on an mRNA molecule
Other than introns where can non coding DNA be found?
Between genes, as non-coding multiple repeats
What is alternative splicing?
-The exons (coding regions) of genes can be spliced in many different ways to produce different mature mRNA molecules
- means that a single eukaryotic gene can code for more than one polypeptide chain
he four bases found in RNA molecules (adenine, uracil, cytosine and guanine) have the ability to form how many codons?
64 different codons
What is the function of the stop and start codons
The START codon marks the start of the protein and therefore initiates the process of translation from the right location (this is always the amino acid methionine in eukaryotic cells, coded for by the codon AUG)
STOP codons cause translation to terminate at the end of the protein and do not code for any amino acids e.g. UAA
