Nucleic acids and protein synthesis Flashcards
What is a gene?
Segment of DNA which carries information about a certain trait.
Genes are transcribed and translated by the cell to make proteins
What is the function of mRNA
Carries the DNA message to ribosomes for protein synthesis
What is the function of tRNA
Transfers amino acids to the ribosome
What is rRNA
Ribosomal RNA make up the ribosome, which are protein factories of the cell.
What is the DNA sequence that defines there transcription of a gene by RNA polymerase begins?
It is called a promoter
Define coding sequence
RNA that actually encodes the polypeptide
What is the enzyme that synthesizes RNA molecules from a template of DNA through a process called transcription?
RNA polymerase
Describe the initiation phase of protein synthesis
The RNA polymerase recognizes the recognition sites causing it to bind to the promoter. Then the polymerase unwinds the DNA helix, and then starts building the pre-mRNA strand by using complimentary sequence of the template strand of DNA. The template strand is read from the 3’ to 5’ direction (but the RNA stand is built from 5’ to 3’ so that it matches the coding strand of DNA).
Describe the elongation phase of transcription
RNA polymerase adds the nucleotides to the pre-mRNA that are complementary to the template strand of DNA, and adds them in the 5’ to 3’ direction.
Describe the termination phase of transcription
When the RNA polymerase reaches the terminator, it signals the the RNA polymerase to stop and release from DNA. Once the polymerase is separated from the DNA, the DNA winds up into the double helix again, and the newly formed pre-mRNA is then released.
Describe RNA processing
The pre-mRNA must be processed into a messenger RNA.
A 5’ cap is added at the beginning of the RNA strand, and a 3’ poly-A tail is added to the end of the strand.
Splicing then takes place, where some parts of the strand are chopped off (introns). The remaining segment (exons) are stuck back together.
What is the function of the poly-A cap?
It increases stability for nuclear export (when the mRNA leaves the nucleus)
What is the advantage of Alternative slicing
Produces multiple mRNA’s from one gene
Describe translation
RNA binds to the small ribosomal subunit
tRNA binds to the start codon in the mRNA, using nucleotides that complement the codon. The tRNA brings with it an amino acid which matches the mRNA codon
-The large ribosomal subunit joins in, forming an initiation complex
-tRNA’s continue to bring amino acids coded for by the mRNA. This continues until a full polypeptide is formed
What is wobble pairing?
