chapter 21- manipulating genomes

Question 1

what does pcr stand for and what is it and why is it done

Answer 1

polymerase chain reaction and it is a way of amplifying dna by repeating dna replication in a lab

making a small piece of dna into a large sample so that dna profiling can be done on it

Question 2

what is the first step of pcr

Answer 2

high temp (90-95) for 30 secs, denatures the dna by breaking the hydrogen bonds that hold the strands together

Question 3

what is the second step of pcr

Answer 3

decrease temp to 55-60 and primers (anneals) bind to strands, this is needed for replication

Question 4

what is the third step of pcr

Answer 4

increase temp to 72-75 for 1 min, allowing dna polymerase to add bases to the primer to make the complentary stands, the primers are extended to make the dna double helix.

taq polymerase is used as it can within stand the high temp, it is from hot springs

Question 5

after a pcr is done what can happen next and what is it used for

Answer 5

gel electrophoresis, used for dna analysis

Question 6

what are the steps of gel electrophoresis

Answer 6

small fragments of dna are added to a gel containing a buffer

dna of a none length is used as a comparative

an electrocurrent is passed through the gel and the and the dna moves from cathode end to anode end

Question 7

is gel electrophoresis why does the dna move the anode (positive) side

Answer 7

because the phosphate groups on the nucleotides are negatively charged

Question 8

in electrophoresis what does the rate of movement of the dna depend on

Answer 8

mass and length of the dna

smaller ones move through easier, small move further than larger

Question 9

in electrophoresis, once the smallest dna fragments have reached the end what happens

Answer 9

gel goes into alkaline buffer and the fragments are denatured, the strands separate and the bases are exposed

the fragments are then fixed onto paper using uv or heat into the same relative positions as they were from the gel.

Question 10

outline the role of the polymerase chain reaction in sequencing a genome (2)

Answer 10

to amplify/make many copies of dna at a range of different lengths

Question 11

outline the role of electrophoresis in sequencing a genome (2)

Answer 11

to put dna pieces in size order

to read base sequence/order of bases

Question 12

outline the role of digestion of dna by restriction enzymes in sequencing a genome (2)

Answer 12

to cut genome dna into smaller fragments

to cut vectors/BACs/plasmids for gene library

not from ms: cutting dna with restriction enzymes, at different places > dna fragments

Question 13

suggest why a genome has to be fragmented before sequencing (2)

Answer 13

genome is too big

accuracy is better/fewer errors with smaller fragments

divide job over time/different labs

Question 14

what is genomics

Answer 14

the study of a whole set of the genetic instructions in the form of dna base sequences that occur in the cells of an organism of a particular species

Question 15

what did the human genome project identify (dktk?)

Answer 15

approx 20,000-25,000 genes in human dna - 2% of total dna

determined the base sequence of 3 billion base pairs

Question 16

what are introns

Answer 16

the non coding dna within a genome

Question 17

what are exons

Answer 17

region of genome that ends up with an mRNA molecule

Question 18

what are didNTPs/ddNTP

Answer 18

dideoxynucleotide, they are chain-elongating inhibitors of dna polymerase used in dna sequencing

ddnTP - n being either A, T, C, G
it is random chance where it goes

they are modified nucleotides to halt dna synthesis, it has an oxygen atom removed from ribose and so it cannot form phosphate bridges so cannot bind to the next nucleotide

Question 19

what is dna profiling

Answer 19

producing an image of the patterns in the dna of an individual- familial relationships/paternity testing/crime solving

Question 20

in dna sequencing how is asection of human dna preserved

Answer 20

it is put into bacs (bacterial artificial chromosomes) and transfer it into ecoli cells where the grow (binary fission) produce many copies of each section, these are called clone libraries

Question 21

what cuts up the dna

Answer 21

different restriction enzymes, creates overlap and then whole genome can be assembled

Question 22

what is synthetic biology

Answer 22

area of research that aims to create new biological parts, devices, systems or redesign systmes that already exist in nature, involves large alterations to an organisms genome (eg microbe)

these dna sequences can be used to create new genomes

beyond genetic engineering as it involves alterations to an organisms genome (microbe)

assemble new genome using existing dna sequences

Question 23

example of synthetic biology artemisinin antimalarial

Answer 23

a plant that is difficult to cultivate so construct a dna sequence of a new metabolic pathway containing genes from a bacteria, yeast > precursor which is inserted into yeast cells wich produce artemisinic acid

so large scale production