locating & sequencing genes Flashcards
what 2 methods are used to find location of certain genes in DNA molecule
DNA probing
DNA sequencing
what are DNA probes
short single stranded sections of DNA
either fluorescently or radio-activelly labelled
used locating genes
how are DNA probes used
has complementary bases to DNA sequence wanted to locate
DNA strands separated, 1 strand mixed with probe
probe binds to complementary bases
binding site identified either by radioactivity or fluorescence from probe
what is DNA sequencing
sanger method of locating DNA
involves terminators = modified nucleotides that end synthesis of DNA strand
2 roles of primers in DNA sequencing
carriers radioactive label used in identification
started process of DNA synthesis by making DNA double strand
process of DNA sequencing
4 test tubes each containing: single strand parts of DNA mixture of nucleotides with bases small quantity of 1 of 4 terminators primer DNA polymerase
what is DNA polymerase used for in DNA sequencing
to catalyse DNA synthesis
why do DNA fragments in each test tube of DNA sequencing vary in length
depends where terminator nucleotide binds to DNA template
why are singe strand parts of DNA put into test tube in DNA sequencing
acts as template for synthesis of its complementary strand
what is gel electrophoresis
technique used to separate out the different length fragments of DNA
what happens during gel electrophoresis
DNA fragments put on agar gel
voltage applied across it
DNA fragments move and separate
sheet of photographic film placed over it
radioactivity from fragments expose on the film, showing where its placed on gel
why do DNA fragments become separated during gel electrophoresis
gel creates resistance
large fragments move more slowly
so smaller fragments move further along
how many bases long can a DNA fragment be before no longer able to use DNA sequencing
500 bases
what is restriction mapping
method of cutting DNA with series of different restriction endonucleases
what happens during restriction mapping
restriction endonucleases used to cut DNA
fragments separated by gel electrophoresis
pattern produced determines distance between recognition sites
