structure of DNA & protein synthesis Flashcards
(32 cards)
what is DNA?
a polymer made from four different nucleotides
what does a nucleotide consist of?
a common sugar and phosphate group with one of four different bases attached to the sugar
what are the four bases?
A, C, G, T
which bases pair with which?
A and T
C and G
what is nucleotide an example of?
a monomer
what does the order of bases control?
the order in which amino acids are assembled to produce a particular protein
what codes for an amino acid?
a sequence of three bases in the gene, a codon
mRNA
messenger ribonucleic acid
DNA
deoxyribonucleic acid
what is DNA made up of?
repeating nucleotide units
list 3 examples of proteins
- enzymes: amylase
- hormones: insulin
- structural proteins: collagen
describe protein synthesis
- the base sequence of the gene is copied into a complementary template molecule (mRNA)
- the mRNA passes out of the nucleus and into the cytoplasm
- the mRNA molecules attaches to a ribosome
- amino acids are brought to the ribosome on carrier molecules (tRNA) to add to the growing protein chain
- the ribosome reads the triplet of bases on the mRNA and uses it to join together the correct amino acids in the correct order
- when the protein chain is complete it folds up to form a
unique shape, enabling the proteins to do their job
where does transcription take place in?
nucleus
where does translation take place in?
cytoplasm
what do the long strands of DNA consist of?
alternating sugar and phosphate sections
explain how the structure of DNA affects the protein made
the order of bases in DNA determines the sequence of amino acids in proteins
what is a mutation?
a change in the base sequence of DNA
when do mutations occur?
continuously, can occur spontaneously
what do mutations do?
- change the sequence of the DNA bases in a gene, which produces a genetic variant
- as the sequence of DNA base codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for
what effect do mutations have on the protein?
- usually very little or not effect
- some can seriously affect as it can change the shape of proteins, affecting their abilities to function
3 types of mutations
- insertions
- deletions
- substitutions
describe insertions
- where a new base is inserted into the DNA base sequence where it shouldn’t be
- an insertion changes way the groups of three bases are read which can change the amino acids they code for
- they can have a knock on effect on the bases further on in the sequence
describe deletions
- when a random base is deleted from the DNA base sequence
- they change the way that the base sequence is read and have knock-on effects further down the sequence
describe substiutions
- substitution mutations are when a random base in the DNA base sequence is changed to a different base
