DNA, RNA and protein synthesis Flashcards
What is a gene?
The base sequence of DNA that codes for either, the amino acid sequence of a polypeptide or a functional RNA.
What is the role of mRNA?
mRNA is a copy of one gene from DNA. The base sequence of mRNA is determined by the sequence of bases in DNA during transcription. It then leaves the nucleus through a nuclear pore and associates with a ribosome. There it acts as a template for protein synthesis.
What is the role of tRNA?
To attach to one of the 20 amino acids and transfer it to the ribosome to create a polypeptide chain. tRNA have a specific amino acid that attaches to them determined by the 3 bases found on the tRNA called the anti-codon.
Why is genetic code degenerate?
Some triplet or codons code for the same amino acids.
What is the role of rRNA?
It makes up the bulk of the ribosome which carries out translation.
What is the structure of mRNA?
A single stranded polynucleotide chain, so has no hydrogen bonds between complementary base pairs. Every three bases is called a codon and each is complementary to the triplets on the DNA template except uracil replaces thymine.
What is the structure of tRNA?
Made from a single stranded polynucleotide chain but is folded into a clover shape held in place by hydrogen bonds between complementary base pairs. It has an amino acid binding site and contains an anti-codon.
Why is genetic code universal?
The same triplet of bases codes for the same amino acids in all organisms.
Why is genetic code non-overlapping?
Each base in a gene is only part of one triplet that codes for one amino acid, the same base is not used for two or more triplets.
How is prokaryotic DNA different from eukaryotic DNA?
Prokaryotic DNA is not associated with proteins, eukaryotic DNA is associated with proteins called histones.
Prokaryotic DNA is short and circular, eukaryotic DNA is long and linear.
Prokaryotic DNA has genes that don’t contain introns, eukaryotic DNA has genes that may contain introns.
Prokaryotic DNA is found in the cytoplasm, eukaryotic DNA is found in the nucleus.
What is a genome and a proteome?
A genome is a complete set of genes in a cell.
A proteome is the full range of proteins that a cell is able to produce.
Describe the process of transcription?
RNA polymerase attaches to the DNA at the start of a gene.
The hydrogen bonds break between the two DNA strands by DNA helicase, exposing some of the bases.
One of the strands is used as a template to make a pre-mRNA copy of DNA.
Free RNA nucleotides line up alongside the exposed bases via complementary base pairing.
RNA polymerase moves along the DNA joining the RNA nucleotides to assemble the mRNA strand, until it reaches a stop codon.
Pre-mRNA is spliced to remove introns, forming a mature mRNA strand.
mRNA leaves the nucleus through a nuclear pore.
What is the difference between transcription in prokaryotes and eukaryotes?
In prokaryotes, mRNA is produced directly from the DNA as prokaryotic DNA does not contain introns.
In eukaryotes, both the introns and exons are copied during transcription producing pre-mRNA. The introns are then removed during splicing and the exons are joined to form mature mRNA.
What is the role of RNA polymerase in transcription?
To join adjacent nucleotides together by catalysing the formation of phosphodiester bonds.
What is polyploidy?
When an organism has three sets of chromosomes rather than the usual two. This is caused by the non-disjunction of all the homologous pairs of chromosomes in meiosis one or all the sister chromatids in meiosis two.
