Transcription, RNA, and Genetic Code Flashcards
what are the 2 main stages involved in going from a gene to protein? what is their primary function?
- transcription - synthesis of RNA from a DNA template
2. translation - synthesis of polypeptide
when do transcription and translation occur in prokaryotes? Eukaryotes?
prokaryotes –> simultaneously
Eukaryotes –> transcription occurs while in nucleus, and
translation while in cytoplasm
what is RNA? what does it consist of? what are it’s main roles?
ribonucleic acid
- consists of a single strand of nucleotides
- main roles are coding, decoding, regulation and expression of genes
when are all RNAs produced? how are they produced?
- produced during transcription
- produced by copying one DNA strand of a gene (template strand)
what is the template strand? which strand is the template?
- the single DNA strand of the gene that is being copied.
- Which strand is the template varies with gene
Transcription builds from … end to … end; meaning that the template strand is copied from … end to … end.
Transcription –> from 5’ to 3’
Template –> copied 3’ to 5’
what is made from the template strand? how is this done?
- a complementary RNA molecule
- done by pairing complementary nitrogenous bases
if the following nitrogenous bases are present on the template DNA strand, what is the pairing nitrogenous base that will be produced in the RNA strand? (name the base and the pairing base)
- T
- A
- C
- G
- Thymine (not found in RNA) –> Adenine
- Adenine –> Uracil (not found in DNA)
- Cytosine –> Guanine
- Guanine –> Cytosine
what enzyme is responsible for carrying out transcription? what does it use as substrates?
RNA Polymerase
-uses nucleotide triphosphates: ATP, UTP, CTP, GTP
what are nucleotide triphosphates? what do those consist of?
- they are nucleotide monomers that have 2 additional phosphate groups (ATP, UTP, CTP, GTP)
- these consist of a nitrogenous base (adenine, uracil, cytosine, guanine), a ribose (5-carbon sugar), and 3 phosphates
what do the 2 extra phosphate groups in nucleotide triphosphates do?
- they’re used as energy sources to drive the energy requiring process of transcription
what are the three stages of transcription?
- Initiation
- Elongation
- Termination
during initition stage, what is the promoter?
it is the sequence (or region) of DNA at the beginning of the gene (where transcription of a gene is started)
what are the steps involved in initiation stage?
- RNA polymerase binds to promoter and separates DNA strands
- RNA polymerase Initiates transcription at start point (Initiation site)
- RNA polymerase synthesizes complementary RNA strand by adding complementary nucleotides on template strand
what happens during elongation stage? what happens to DNA strands?
-RNA polymerase adds RNA nucleotides at 3’ end of
the transcript –> causing the RNA transcript to elongate
-DNA strands reform double helix after RNA polymerase passes
what happens during termination stage?
- RNA polymerase stops transcribing RNA from DNA when it reaches terminator sequence on DNA
- RNA transcript is released
- RNA polymerase releases from DNA
- Double stranded DNA reforms
what is the terminator sequence?
it is the sequence (or region) of DNA at the end of the gene being copied (where transcription of a gene is finished)
what are the 3 types of RNA molecules required for translation (made during transcription)?
- Ribosomal RNA = rRNA
- Transfer RNA = tRNA
- Messenger RNA = mRNA
real quick, what is an amino acid? how many amino acids are there? what is a polypeptide?
amino acid –> protein monomer
-20 different amino acids
polypeptide –> protein polymer ie. chain of monomers
what is tRNA? what is it’s role? what does it do?
Transfer RNA = tRNA
- its role is to bring amino acids to the ribosome for assembly into polypeptides
- acts as an intermediate between mRNA and amino acids
- it translates a particular mRNA codon into a particular amino acid
tRNA structure:
- single stranded or double stranded?
- what shape does it take?
- how many nucleotides long is a tRNA strand?
- how does it physically act as an intermediate between amino acids and mRNA?
- single stranded (all RNA molecules are single stranded, silly)
- 2D shape drawn as cloverleaf structure to show “double stranded” regions (where it folds back on itself); actually 3D shape is folded L-shape
- ~80 nucleotides long
- carries an amino acid at one end and “attaches” to mRNA on the other
how does tRNA attach to mRNA?
-tRNA has an anticodon on one end
what is mRNA codon? what is tRNA anticodon? what is the function/purpose of these?
mRNA codon –> unit made up of a 3-base segment of an mRNA that will code for a specific amino acid in a ribosome
tRNA anticodon –> unit made up of 3 nucleotides that pair with complementary codon on mRNA
-function is to temporarily bind together so that the tRNA can translate that particular mRNA codon into a particular amino acid
what are the functions of a ribosome?
-to facilitate specific coupling of tRNA anticodons
with mRNA codons during protein synthesis
- by holding tRNA and mRNA in correct position it allows for the addition of a new amino acid to the end of the polypeptide chain
-catalyzes peptide bond formation
