8. DNA, genes and protein synthesis Flashcards
how many bases code for one amino acid
3
how many naturally occurring amino acids are there?
20
why is genetic code described as;
degenerative?
non-overlapping?
Universal?
degenerative, most amino acids are coded by more than one triplet
non-overlapping, each sequence is only read once
Universal, same bases code for the same amino acid across different species
what are introns?
non coding sequances
what is a genome
complete set of genes in a cell
what is a proteome
full range of proteins produced by genome
how many tRNA molecules can attach to one mRNA
2
what is pre-mRNA
mRNA that hasn’t been sliced
what is a homologous chromosome
chromosomes that share the same structural features, the same genes at the sames loci.
Describe the structure of tRNA
- single-stranded chain
- ‘clover-leaf shape’
- extended codon for amino acid
- anticodon loop on opposite side
What is transcription
process of making pre-mRNA using part of the DNA as a template
Explain the steps of transcription
- DNA unwound by DNA helicase exposing bases
- One chain acts as a template
- free mRNA nucleotides align with complementary bases on template
- RNA polymerase joins RNA nucleotides
Give three differences between eukaryotic and prokaryotic DNA
eukaryotic is;
- longer
- linear (pro is circular)
- associated with histones (pro isn’t)
What sets chloroplast and mitochondria DNA apart from other eukaryotic cells
they are;
- short
- circular
- not associated with histones.
(like prokaryotes)
How many amino acids is a tRNA complementary to?
one
Why is mRNA shorter than DNA?
able to carry section of genetic code to ribosome.
What does DNA helicase do?
Breaks hydrogen bonds between bases
What is a spliceosome? what does it do?
Protein that ‘splices’ out non-coding introns
Do prokaryotes have introns?
no
Explain the steps of translation.
- mRNA attaches to ribosome
- ribosome attaches at the start codon
- tRNA molecule complementary to the start codon aligns, held in place by the ribosome.
- ribosome moves along one codon, to enable another tRNA to join
- amino acids are joined by a peptide bond req. enzyme and ATP
- … until stop codon, ribosome detaches
Where do proteins go after translation?
enter golgi body for folding and modification
Give two key similarities in prokaryotic and eukaryotic DNA.
- made of DNA nucleotides
- nucleotides joined by phosphodiester bonds to make a polymer chain
