GVR: RNA and protein synthesis Flashcards
Define genome:
All of the DNA of an organism within a cell
Define proteome:
The range of proteins a cell can produce.
In eukaryotic cells, where does transcription occur?
Nucleus
In prokaryotic cells, where does transcription occur?
Cytoplasm
Explain DNA transcription in eukaryotes:
1) Complementary RNA nucleotide bases align with DNA nucleotide bases.
2) RNA polymerase catalyses the formation of the phosphodiester bonds, forming the pre-mRNA strand.
3) Introns are removed, exons are spliced
4) mRNA exits through nuclear pores.
Explain the process of DNA translation in eukaryotes:
- mRNA attaches to the ribosome
- tRNA brings a specific amino acid to mRNA
- The specific amino acid is bound the a tRNA binding site
- Hydrogen bonds form between mRNA codons and tRNA complementary anticodons
- Peptide bonds are formed by condensation reactions between adjacent amino acids
- mRNA moves along the ribosome
- tRNA leaves the ribosome
-ATP is required, a polypeptide is formed
What bonds form between complementary base pairs?
Hydrogen
What bonds form between adjacent nucleotides in a DNA strand?
Phosphodiester
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation:
- tRNA brings specific amino acid to ribosome
- Anticodon on tRNA binds to codon on mRNA
- Amino acids join by condensation reaction using ATP
Describe how mRNA is produced from an exposed template strand of DNA:
- Free RNA nucleotides form complementary base pairs.
- RNA Polymerase forms phosphodiester bonds.
Give 3 differences between the structure of mRNA and tRNA:
- mRNA has codons, tRNA has an anticodon
- mRNA is linear, tRNA has a clover shape
- tRNA has a specific amino acid, mRNA doesn’t.
What does it mean if the genetic code is degenerate?
More than one codon codes for a single amino acid
What two molecules are ribosomes made from?
rRNA
Amino acids
Describe how mRNA is produced in a plant cell:
- Hydrogen bonds are broken, causing the DNA strands to separate
- One strand acts as a template
- Complementary base pairing occurs (adenine to thymine, cytosine to guanine)
- RNA nucleotides are joined by RNA polymerase.
- The pre-mRNA strand is formed
- Introns are removed, exons are spliced
Explain the role of ribosomes in the production of a polypeptide:
- mRNA binds to ribosome
- Two codons allow tRNA anticodons to bind
- Peptide bonds form between amino acids
- Ribosome moves along mRNA to next codon
Why might the base sequence of mRNA be different from the sequence of pre-mRNA in a eukaryotic cell?
Introns have been removed.
What are the 4 bases in DNA called (full names)?
Adenine
Thymine
Cytosine
Guanine
What are the 4 bases in RNA called (full names)?
Adenine
Uracil
Cytosine
Guanine
In RNA, what is thymine replaced with?
Uracil
RNA nucleotides join together as a result of a _________ reaction:
Condensation
What bonds form between RNA nucleotides during a condensation reaction?
Phosphodiester
In RNA why is uracil a better base than thymine?
- RNA goes outside the nucleus (into the cytoplasm)
- Thymine is quickly destroyed outside of the nucleus
In DNA why is thymine a better base than uracil?
- Uracil is more likely to mutate inside the nucleus than thymine is
The genetic code is _________, __________, and ___________.
- Universal
- Non-overlapping
- Degenerate
What does it mean if the genetic code is universal?
The same triplet codes for the same amino acid in all organisms.
What does it mean if the genetic code is non-overlapping?
- A base belongs to 1 triplet only
- Bases are read in sequence
What does it mean if the genetic code is degenerate?
More than one codon codes for an amino acid.
What are exons?
mRNA coding regions that code for amino acids.
What are introns?
Interrupting sequences that do not code an amino acid found in the middle of exons.
What does mRNA mean?
Messenger RNA
What does tRNA mean?
Transfer RNA
mRNA is made during ________.
Transcription
What is the role of mRNA?
Carries the genetic code from DNA to the ribosomes, where it is used to make a protein during translation.
What is transcription?
Where the DNA code is copied into a mRNA molecule.
What is translation?
Where the mRNA joins with a ribosome and the code it carries is used to synthesise a protein.
What is a codon?
A base triplet in DNA or mRNA that codes for an amino acid.
What is mRNAs nucleotide structure made up of?
- Base
- Phosphate group
- Pentose sugar
mRNA is _____-stranded.
Single.
tRNA is involved in ________.
Transcription.
What is the role of tRNA?
Carries the amino acids that are used to make proteins into ribosomes.
tRNA is a single __________.
Polynucleotide.
How does a tRNA molecule hold its shape?
It has hydrogen bonds between specific base pairs.
What is an anticodon?
A sequence of three nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon.
What is splicing?
When introns are removed and exons join together.
Why does prokaryotic DNA not undergo splicing?
There are no introns.
What happens in splicing?
mRNA strands containing introns are removed, and exons are joined together.
