4A: DNA, RNA and Protein Synthesis Flashcards
How is DNA store in Eukaryotic Cells?
Wound around histones into chromosomes
How is DNA stored in Prokaryotic Cells?
a circular chromosome that is supercoiled to fit in the cell
What is a Gene?
a coding section of DNA that codes for a specific amino acid sequence forming a polypeptide chain
What is a Locus?
the fixed position where each gene can be found on a chromosome
What is non-coding DNA?
DNA that does not code for polypeptides called introns
Where are introns found?
Between exons in Eukaryotic DNA
What are Alleles?
different forms of the same gene
What are Homologous Chromosomes?
a pair of chromosomes that are the same size and have the same genes in the same locus
What is protein Synthesis?
the production of proteins from the information contained within a cell’s DNA
What is Transcription?
where the DNA code is copied into a molecule called mRNA
What is Translation?
where the mRNA joins with an organelle called a Ribosome and the code it carried is used to synthesise a protein
What is RNA?
a single polynucleotide strand used in Protein Synthesis
What is mRNA?
made during transcription, carries the genetic code from DNA to Ribosomes
What is tRNA?
carries Amino Acids that are used to make proteins to the Ribosomes
Describe Transciption
- mRNA associates with a ribosome / ribosome attaches to mRNA;
Idea of association is required - Ribosome moves to / finds the start codon / AUG;
- tRNA brings / carries (appropriate / specific) amino acid;
Must be explicitly stated and not inferred. - Anticodon (on tRNA complementary) to codon (on mRNA);
- Ribosome moves along to next codon;
OR
Ribosome ‘fits’ around two codons / can fit two tRNAs;
Must be explicitly stated and not inferred. - (Process repeated and) amino acids join by peptide bonds /
condensation reaction (to form polypeptide);
OR
(Process repeated and) amino acids joined using (energy from) ATP
(to form polypeptide);
Describe Translation
- mRNA attaches to ribosome
- codon on mRNA
- binds to an anti-codon on tRNA
- each tRNA brings a specific amino acid
- sequence of codons/bases on mRNA determines the order of amino acids
- formation of peptide bonds OR amino acids joined by condensation reactions
Describe the function of Ribosomes in Protein Synthesis
- Translation/construction of polypeptide(s)
- Provide a binding site for mRNA OR mRNA attaches to ribosome
- Provides binding sites for (two) tRNA molecules
- Two amino acids are held close together
- Formation of peptide bond(s)
- (allows) assembly of amino acids into the sequence/primary structure
Describe the role of tRNA in Translation
- tRNA attaches to (specific) amino acids
- tRNA (with amino acid) moves to the ribosome
- The anticodon of tRNA binds to/forms hydrogen bonds with (a complementary) codon of mRNA
Describe the role of ATP in Translation
- It activates the tRNA with an amino acid OR binds a specific amino acid with tRNA
- The phosphorylation of tRNA OR creates a high energy bond which is transferred to the tRNA
How is pre-mRNA turned into mRNA?
Introns are removed and Exons are spliced together before it exits nuclear envelope
What are three characteristics of the genetic code?
Degenerate
Non-overlapping
Universal
What does degenerate mean?
there are more possible triplet combinations that amino acids to be coded for
What does non-overlapping mean?
triplets don’t share bases
What does universal mean?
same specific base triplets code for the same amino acids in all living things
