DNA Structure Flashcards
All 8 cards in this deck
What is a DNA nucleotide made of?
A common sugar and a phosphate group, with one of four bases (A, C, G or T) attached to the sugar.
What are the base pairing rules in DNA?
e.g. one strand reads A–C–GA always pairs with T, and C always pairs with G, so the complementary strand reads T–G–C.
How many bases code for one amino acid, and what does the order of bases control?
Three bases (a triplet) code for one amino acid; the order of bases controls the order in which amino acids are assembled to make a particular protein.
Where are proteins synthesised in a cell, and what brings the amino acids?
On ribosomes, using a template from the gene; carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.
How can a change (mutation) in the base sequence of a gene change the protein made?
It can change the sequence of amino acids, which changes the protein's shape — e.g. an enzyme's active site may no longer fit its substrate, so the protein cannot do its job.
True or false? All of the DNA in a cell codes for proteins.
False. Some DNA is non-coding; variations in non-coding DNA can switch genes on and off and so affect how genes are expressed.
What mass of DNA does a human sperm cell contain compared with a human body cell?
e.g. a body cell containing g of DNA
Half as much, because a gamete has one set of chromosomes.
e.g. the sperm cell contains g
To change a length of DNA given in nanometres (nm) into metres (m), what do you divide by?
(), because 1 nm m.