Lab 3: Molecular Biology Flashcards
There are 2 methods to making many copies of a DNA sequence. List them and briefly summarise both.
- PCR (polymerase chain reaction): method of reproducing DNA copies that reproduces identical copies of specific segments quickly and is best suited for amplifying DNA from small samples
- DNA cloning using plasmids: sequence of DNA is inserted into a plasmid which is then inserted into a bacterial cell. the bacteria is allowed to divide and produce more DNA copies
define: restriction endonuclease enzymes
- an enzyme that cleaves DNA into fragments
define: gel electrophoresis
- a technique used to separate DNA fragments according to their size
define: allele
- a variant form of a gene (dominant (will be expressed) vs recessive (less likely to be expressed))
98/100 of the last 100 hamster killers in Burnaby all have the same DNA sequence. Have you found a hamster killer allele?
No, not everyone with this allele will kill hamsters. Their chances are higher if their allele is dominant as opposed to recessive. Their inclination to kill hamsters also depends on environmental factors such as upbringing, societal norms, etc.
define: purine base
- 2 ring structures
- adenine and guanine
define: pyrimidine base
- 1 ring structure
- cytosine and thymine
Explain why you would never see a purine base paired with another purine base or or a pyrimidine base paired with another pyrimidine base in a DNA molecule
- always purine and pyrimidine; purine-purine: not enough space to fit in between backbone; pyrimidine-pyrimidine: too much space
- AT
- GC
Explain why adenine doesn’t pair with cytosine usually and why guanine doesn’t usually bond with thymine even though these pairings would put 1 pyrimidine with 1 purine.
Cytosine can form three hydrogen bonds with guanine, and adenine can form two hydrogen bonds with thymine.
In one single strand of DNA how are the individual nucleotides joined together? What kind of bonds join 1 nucleotide to the other and which components of the nucleotides are bonded together?
- covalent bonds connect the bases, sugars and phosphate groups strongly
How are 2 DNA strands joined together? What kind of bonds connect them and which components of the strands are bonded together?
- hydrogen bonds; weak but collectively strong and connect the bases together of 2 nucleotides
What is the difference between the 3’ and 5’ end of a DNA strand?
The 5’ end of the DNA is the one with the terminal phosphate group on the 5’ carbon of the deoxyribose; the 3’ end is the one with a terminal hydroxyl (OH) group on the deoxyribose of the 3’ carbon of the deoxyribose.
Why is DNA described as an anti-parallel double helix
- 2 strands that run in opposite directions (3’ and 5
ends) - twisted strands form a “twisted ladder” structure known as double helix
- structurally it makes the molecule stronger and more stable to be twisted (becomes twisted to discourage bases from interacting with surrounding water molecules)
For DNA transcription, what determines the leading and lagging strand?
The leading strand is determined by which original strand is in the 3’–>5’ orientation because the leading strand is made 5’—> 3’
Define: template and coding strand
- template: the one that will compliment the RNA strand you will create
- coding: the other DNA strand that compliments the template you’re using to code the RNA. will be almost identical to the new RNA strand except use U instead of T
