Protein Synthesis D1.2 Flashcards
What is transcription?
the synthesis of RNA using DNA as a template. the GENE sequence of the DNA is copied in the mRNA.
Where does transcription take place?
the nucleus
What does a gene on the DNA sequence do?
specify the sequence of amino acids.
- DO NOT give any observable characteristics in an organism.
What actually give the observable characteristics in an organism?
proteins often directly or indirectly determine observable characteristics.
What is the RNA Polymerase?
an enzyme that is used in transcription and is responsible for:
- binding to the start of a gene in DNA
- separating the gene section of the DNA double helix
- pairing up and adding the RNA nucleotides complementary bases (uracil replaces thymine)
What is the first step of transcription?
the enzyme RNA polymerase binds to a site on the DNA at the START of a gene sequence.
What happens after the RNA Polymerase has bound to the DNA?
RNA polymerase moves along the gene sequence of the DNA and separates the double stranded DNA.
What happens after the RNA Polymerase has separated the DNA?
RNA polymerase pairs and adds RNA nucleotides with complementary bases along the template DNA going from 3’ to 5’.
- hydrogen bonds created between DNA and mRNA
- covalent bonds created between RNA molecules
What happens after the RNA Polymerase has paired the RNA nucleotides?
the mRNA is separated from the DNA at the END of the gene sequence and the DNA double helix reforms.
What is the antisense strand?
it is the template strand, the strand that the mRNA is bound to for creation of the mRNA strand. it is from 3’ to 5’.
What is the sense strand?
it is the non-template strand that does not partake in the copying process. it is the strand that the mRNA is actually trying to copy. it is from 5’ to 3’.
- identical to the mRNA strand (switch U with T)
What does it mean for DNA to be stable?
it does not change its code easily.
How is DNA stable?
stability is ensured by the sugar-phosphate backbone and hydrogen bonds between nucleotides.
What is the stability of DNA important for?
the conservation of the original code.
What do some somatic cells that do not divide to replace itself need to do?
must stay unchanged throughout life because they will be broken forever.
How can the stability of DNA be damaged?
free radicals,
chemicals,
cigarette smoke,
exposure to UV,
nuclear radiation.
What can instability of DNA lead to?
mutations (harmful or beneficial)
Why do DNA instability occur as a result of the ways of damage?
there are repair mechanisms to fix but not always successful.
What is gene expression?
the process by which the info carried by a gene is turned into an observable characteristic on an organism.
How does gene expression occur?
by transcription and translation.
What is the process of gene expression as it happens in the cell?
DNA –> mRNA –> polypeptide –> observable change
How come some genes are not expressed even when it is transcribed?
genes can be turned on and off and the expression of a cell depend on info from both inside and outside the cell. transcription, being the first stage of gene expression, is a key
stage at which expression of a gene can be switched on and off
What is genetic code?
the set of rules by which info encoded in mRNA sequences is converted to proteins by living cells.
What does genetic code do?
carries the message for the sequences of amino acids in a polypeptide.
