1.2 Flashcards
(19 cards)
DNA strands are composed of repeating units called?
•nucleotides
describe the structure of each nucleotide
• a deoxyribose sugar
• a phosphate group
• a base
how many types of nucleotides are there and why?
•4 (since there are 4 different bases)
a strong chemical bond joins?
•a deoxyribose sugar of one nucleotide to the phosphate of the next
•these repeating units make up the sugar-phosphate backbone
bases (in base pair rule) are joined by?
•weak hydrogen bonds
(therefore the two strands are held together by weak hydrogen bonds)
what does each strand start and end with?
•starts with a deoxyribose sugar at the 3’ end
•ends with a phosphate group at the 5’ end
as the strands run in the opposite directions they are said to be?
•anti parallel
the two strands take the form of a twisted coil called a?
•double helix
what forms the genetic code?
•the base sequence of DNA
what does the genetic code determine?
•the organisms genotype (genes) and the organisms phenotype (physical characteristics)
why is DNA replication important
•before cell divide, the DNA must replicate to make an exact copy of itself (each chromosome is duplicated)
what does DNA replication ensure?
•each of the two daughter cells formed have a full set of genetic information and the diploid chromosome complement is maintained
describe the process of DNA replication
•DNA is unwound and hydrogen bonds between bases are broken to
separate the two template strands.
• DNA is replicated by DNA polymerase which needs primers to start
replication.
• A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing DNA polymerase to add DNA nucleotides.
• DNA polymerase adds DNA nucleotides, using complementary base pairings, to the 3’ end of the new DNA strand which is forming.
• DNA polymerase can only add nucleotides in one direction (5’ to 3’) resulting in the leading strand being replicated contiously and the lagging strand being replicated in fragments.
• Fragments of DNA are joined by ligase
what are the requirements of DNA replication
•DNA replication
•ligase
•polymerase
•energy (ATP)
•DNA template strands
•primers
what is PCR?
•technique used to amplify (copy) a region of DNA
what are primers in PCR?
•primers are short strands of nucleotides complementary to specific target sequences at the two ends of the region of DNA to be amplified
describe the steps of PCR
•First, DNA is heated to between 92° and 98°C to separate the two strands.
•It is then cooled to between 50°C and 65°C to allow priness to bind to the target
•It is then heated to between 70° and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.
•Repeated cycles of heating and cooling are used to amplify the target region of DNA.
what does the term “vitro” mean
•outside of the body/ in the lab
what are uses of PCR?
•help solve crime
•settle paternity disputes
•diagnose genetic disorders like cystic fibrosis
