paper 1: DNA, Genes and Chromosomes, Proteinsynthesis Flashcards
(37 cards)
draw and label a diagram of a DNA nucleotide
what does DNA stand for
deoxyribonucleic acid
describe how a strand of DNA forms
- many DNA nucleotides join together to make a DNA polynucleotide
- these are joined between the sugar moecule of one nucleotide and the phosphate of another nucleotide with a phosphodiester bond via a condensation reaction
describe how a DNA double helix forms
- bases from 2 strands form complementary base pairs joined together with hydrogen bonds
- the 2 strands twist and form a double helix
- the strands are anti-parallel
why can you describe DNA strands as being anti-parallel
DNA base sequence is read one way on one strand and the opposite way on the other strand
fill in this table
define a gene
DNA base sequence which codes for the amino acid sequence of a polypeptide
define a gene locus
fixed position on a particular DNA molecule/ chromsome which a gene occupies
define a genome
the complete set of genes in a cell
define a proteome
full range of proteins a cell is capable to produce
the genetic code is univeral. what does this mean
the same triplets code for the same amino acids in all living organsims
genetic code is non-overlapping. what does this mean
the DNA triplets do not share bases
genetcic code is degenerate. what does this mean
more than 1 triplet can code for the same amino acid
why might there be more codes than there are amino acids
- if there is a mutation in DNA then the amino acid sequence will be less likely to change so you still get a functional protein
how can a mutation in the DNA lead to a non-functioning protein or enzyme
- if there is a mutation in the DNA, this can change the primary structure of the protein
- can change the position of the hydrogen, ionic and disulfide bonds in the protien
- whihc changes the tertiary structure of the protein
- can lead to a non-functioning protein
define an exon
DNA base sequences within genes that code for an amino acid sequence
what are non-coding multiple repeats
DNA base sequences which do not code for an amino acid sequence
what are introns
DNA base sequence within genes which dont code for an amino acid sequence
describe the stages of transcription in a eukaryotic cell
- the DNA strands separate by breaking the hydorgen bonds between complementary base pairs
- only one strand acts as a template strand
- RNA nucleotides are attracted to the exposed bases and bind by complementary base pairing (A to T, T to A, C to G, G to C)
- the enzyme RNA polymerase joins the RNA nucleotides together by forming phosphodiester bonds
- this forms pre-mRNA
- introns are removed by splicing to form mRNA
how does transcription differ in prokaryotes compared to eukaryotes
prokaryotes have no introns so splicing does not take place and mRNA is directly formed
describe the stages of translation
- a ribosome attaches to the mRNA molecule and moves to find the start codon
- 2 codons fit into the ribosome at any one time
- the tRNA molecules carry specific amino acids to the pribosome and the anticodon binds to the codon by complementary base pairing
- the 2 amino acids form a peptide bond in a condensation reaction using energy from the hydrolysis of ATP
- the first tRNA is released to pick up another amino acid
- the ribosome moves along to the next codon
- when the stop codon is reahed translation stops
- polypeptide is released and ribosome detaches
what is the role of mRNA
carries template of DNA code for onne gene to the ribosome for proteinsynthesis
what is the role of tRNA
carries specific amino acids to the ribosome during proteinsynthesis
where is mRNA found
nucleus/ cytoplasm
