DNA, genes and protein synthesis Flashcards
How is prokaryotic DNA different to that of eukaryotic
it is short
it is circular
it is not bound by proteins
Eukaryotic DNA structure
Long
Linear
Bound with histone proteins
Mitochondria and chloroplast DNA
Short, circular and not bound with histones
similar to prokaryotic DNA
What is a gene
a short base sequence of DNA that codes for the amino acid sequence of a polypeptide or functional RNA (rRNA + tRNA)
Where are genes found
they occupy fixed positions on a DNA strand called a locus
What is a codon
a triplet of bases that encode a specific amino acid
3 properties of genetic code and what do they mean
its universal ( the code is the same for all organisms )
its degenerate ( there are more codons than amino acids, so some codons code for the same amino acid )
Non overlapping ( each base is only part of one codon so all codons are a discrete unit )
Difference between introns and exons
coding parts of DNA are exons
non coding parts of DNA are introns
What is a genome
the complete set of genes in a cell
What is the proteome
full range of proteins that a cell can produce from the genome
What does transcription do
Converts DNA into pre-mRNA/mRNA
What is splicing and what cells does it occur in
Conversion of pre-mRNA to mRNA in eukaryotic cells
What is splicing and what cells does it occur in
Conversion of pre-mRNA to mRNA in eukaryotic cells
What is translation
Conversion of mRNA to proteins using tRNA
Structure of mRNA
Short, single stranded linear chain of ribonucleotides
each 3 adjacent bases are called codons
Structure of tRNA
Single polynucleotide strand with a clover shape
has an amino acid attachment site and an anticodon complementary to an mRNA codon
Stages of transcription
DNA helicase unwinds the two DNA strands by breaking hydrogen bonds between bases
Free RNA nucleotides align and pair with their complementary base
RNA polymerase joins mRNA nucleotides together to form pre-mRNA
Stages of splicing
Introns are removed
exons are attached back together by a condensation reaction
mRNA is formed which exits through nuclear pores into cytoplasm
Stages of translation
Ribosome attaches to start codon of mRNA
( AUG)
tRNA with complementary anticodon aligns with mRNA
ribosome moves along mRNA allowing tRNA to attach the the next codon along
the two amino acids attached to adjacent tRNA molecules are attached by peptide bonds
process is continued until ribosome reaches a stop codon, the ribosome then detaches and translation stops
