Flashcards in Unit 1: human cells- Gene expression Deck (29)
The first stage of protein synthesis
happens in the nucleus
involves the formation of mRNA from a single strand of DNA
begins at the start of a DNA strand called the promoter region
RNA polymerase attaches to the DNA strand unwinding/unzipping it to separate the two strands
as it does this RNA nucleotides base pair with the exposed bases on the DNA strand
does this by joining Adenine to Uracil and Cytosine to Guanine
Any Thymine's on DNA strand pair with Adenine
transcription ends when the RNA polymerase reaches a terminator region
The mRNA strand which has now been formed is called the PRIMARY TRANSCRIPT
What does the primary transcript of mRNA undergo?
The primary transcript will now undergo splicing to remove non-coding regions called introns from the strand. This forms a MATURE TRANSCRIPT.
What does the mature transcript formed do?
The mature transcript formed of coding regions called exons will now leave the nucleus and head out into the cytoplasm towards the ribosome. The second stage called Translation will then occur at the ribosome.
What are the 3 types of RNA involved in gene expression?
Translation is the 2nd stage of gene expression
occurs at the ribosome
involves he synthesis of a polypeptide chain which will later become a finalised protein.
process of translation?
The mRNA attaches to binding site on the ribosome.
Every three bases on a messenger RNA is known as a codon. A second type of RNA (tRNA) is found in the cytoplasm and has a triplet of bases exposed at one end of the strand. This triplet is known as an anticodon. A the other end of the tRNA strand is an attachment site for an amino acid. Each anticodon acts as a code word for a particular amino acid. The tRNA will pick up the relevant amino acid and attach at the attachment site for transfer to the mRNA strand
What is the function of transfer RNA?
Picks up a SPECIFIC amino acid from the cytoplasm and brings it to the ribosome.
What is the function of messenger RNA?
Carries the genetic code from the nucleus to the ribosome.
What is the function of ribosomal RNA?
Along with protein it gives structure to the ribosome.
Where is mRNA made?
in the nucleus.
When is mRNA's function used?
The first stage of protein synthesis.
When is tRNA's function used?
The second stage of protein synthesis.
What does RNA consist of?
Units called nucleotides.
What are nucleotides made of in RNA?
A phosphate, a base and a ribose sugar.
In RNA what are the four types of bases?
Adenine, Cytosine, Guanine and Uracil.
What is the complementary base pair for Adenine in RNA?
What is the complementary base pair for Cytosine in RNA?
How are proteins made?
Proteins are made by joining together amino acids in a specific sequence.
What does the protein produced by the protein synthesis rely on?
The order of amino acids which is dictated by the order/ sequence of the bases on the DNA.
What are the two main stages of Protein synthesis?
Transcription and Translation.
What are the stages of transcription?
1) The section of DNA which codes for the desired protein (gene) UNWINDS and UNZIPS.
2) This is carried out by an enzyme called RNA PLYMERASE.
3) Free nucleotides enter the nucleus and RNA POLYMERASE joins them with their complementary DNA base starting at the 3' en.
4) Only one strand is copied.
What is the strand of mRNA produced by transcription called?
The PRIMARY TRANSCRIPT.
Why is only one gene transcribed to form mRNA?
So the PRIMARY TRANSCRIPT ONLY CODES FOR ONE PROTEIN.
What does the primary transcript contain?
It contains regions which CODE for the production of the protein called EXONS and regions which are NON CODING which are called INTRONS.
What are introns of the primary transcript?
INTRONS are NON CODING REGIONS which have to be REOMVED.
What are exons of the primary transcript?
EXONS are CODING REGIONS and are joined together to form a MATURE TRANSCRIPT.
What is DNA splicing?
DNA splicing is where INTRONS are REMOVED and the EXONS are joined together to form a MATURE TRANSCRIPT of mRNA.
What happens once the mature transcript is produced?
The MATURE mRNA leaves the nucleus and enters the cytoplasm.