DNA, RNA and Protein Synthesis Flashcards
What is DNA like in Eukaryotic Cells?
- linear existing in chromosomes
The DNA molecule in Eukaryotic cells is long, so what happens?
It has to be wound up so it can fit into the nucleus - it is wound up around proteins called Histones which help to support it.
Then the DNA had protein are coiled up very tightly to make a compact chromosome.
Mitochondria and Chloroplasts also have their own DNA, what’s different?
They’re circular and shorter like DNA in Prokaryotes.
What is DNA like in Prokaryotic Cells?
Shorter and circular - and the DNA isn’t wound around Histones.
It condenses to fit into the cell by supercoiling.
What is a gene?
A sequence of DNA bases that codes for either a polypeptide or functional RNA.
Different polypeptides have a different…
Number and order of amino acids - the order of bases in a gene determine the order of amino acids in a particular polypeptide.
Each amino acid is coded for by…
A sequence of 3 bases in a gene called a triplet.
DNA triplet = one amino acids.
What about genes that don’t code for a polypeptide code?
They code for a functional RNA instead - (molecules other than mRNA)
What is a cell’s genome?
The complete set of genes in the cell.
What is a cell’s proteome?
The full range of proteins that the cell is able to produce.
In Eukaryotic DNA, what can we find?
We can find sections of genes that don’t code for amino acids.
These are called INTRONS.
All the bits of a gene that do code for amino acids are called…
EXONS.
What happens to Introns during protein synthesis?
They’re removed so they don’t affect the amino acid order.
What else do Eukaryotic DNA contain?
Regions of multiple repeats outside of genes.
These don’t code for amino acids either = so they’re called non-coding repeats.
What are Alleles?
More than one form of a gene.
What is the order of bases in each allele like?
Slightly different so they code for slightly different versions of the same polypeptide.
Pairs of matching chromosomes are called…
Homologous pairs.
What’s a homologous pair like?
Both chromosomes are the same size and have the same genes although they could have different alleles.
Give 2 types of RNA:
mRNA
tRNA
Where is mRNA made and what does it do?
Made during transcription and it carries the genetic code from the DNA to the ribosomes where it’s used to make a protein during Translation.
mRNA is…
A single polynucleotide strand.
Where is tRNA involved and what does it do?
Translation - carries the amino acids that are used to make proteins to the ribosomes.
tRNA is…
A single polynucleotide strand that’s folded into a clover shape - H bonds.
Every tRNA molecule has…
A specific sequence of three bases at one end called and anticodon.
Every mRNA molecule has…
3 bases are called codons.
Transcription: (4)
1) RNA polymerase attaches to the DNA double helix at the beginning of a gene.
2) H bonds between DNA strands break = uncoils, exposing bases = one strand used as a template to make an mRNA copy.
3) RNA polymerase lines up free RNA Nucleotides alongside exposed bases on template strand =specific complimentary base pairing = joined together by RNA polymerase forming mRNA.
4) RNA polymerase moves along the DNA, separating the strands and assembling mRNA = hydrogen bands reform and goes into double helix.
What happens when RNA polymerase reaches a stop signal?
It stops making mRNA and detaches from the DNA.
What’s the difference between mRNA and pre-mRNA?
In EUKARYOTES
pre-mRNA contains both introns and exons = splicing takes place and introns aré removed and exons aré joined together forming mRNA strands.
SPLICING.
Does splicing take place in Prokaryotes?
No because there are no introns in prokaryotic DNA so there’s no need for it.
Translation occurs at…
The ribosomes in the cytoplasm.
What happens in translation?
Amino acids are joined together to make a polypeptide chain.
Translation: (4)
1) the mRNA attaches to a ribosome and tRNA carry amino acids to it - bond between amino acid and tRNA form.
2) a tRNA molecule with an anticodon complementary to the first codon on the mRNA attaches to mRNA = base pairing = happens again to next tRNA molecule.
3) the two amino acids attaches to the tRNA molecules are joined by a peptide bond = first tRNA molecule moves away leaving its amino acid behind.
4) a third tRNA molecule binds to the next codon on the mRNA = it’s amino acid binds to the first two and the second tRNA molecule moves away.
When does the process of translation finish?
When there’s a stop signal on the mRNA molecule.
Genetic Code is Degenerate:
There are more possible combos of triplets than there are amino acids.
Genetic Code is Universal:
The same specific base triplets Code for the same amino acids in all living things.
Genetic Code is Non Overlapping:
Each base triplet is read in sequence, separate from the triplet before it and after it.
