Lecture 16-18 Flashcards
Where is the genetic information of most living organisms stored
in deoxyribonucleic acid (DNA)
In some viruses, where is genetic material present
in ribonucleic acid (RNA)
What are nucleic acids composed of
nucleotides
What are the components of a nucleotide
nitrogen-containing bases
sugar (pentose)
phosphate (phosphodiester bond)
What is the difference between a ribose and a deoxyribose sugar
on carbon two a hydroxyl is seen in a ribose
on carbon two a hydrogen is seen in a deoxyribose (loss of the oxygen molecule)
What are purines
adenine and guanine
What are pyrimidines
cytosine thymine and uracil
What bond joins nucleotides
phosphodiester
Where does the phosphodiester bond connects two sugars
connects C3 of one to the C5 of the other
What is Chargaffs rule
purines = pyrimidines
%A = what
%T
%G = what
%C
How much of DNA is made up of purines
50%
How much of DNA is made up of pyrimidines
50%
How many H bonds are formed between A and T
2
How many H bonds are formed between C and G
3
With more G-C bonds, what occurs with melting point
melting point increases, more bonds to break
What are restriction enzymes and how are they used
group of endonucleases produced in bacteria as a means of destroying foreign DNA, by cleaving DNA at restriction sites
- restriction sites are often palindromic
- sticky ends are cut horizontally, blunt ends are cut vertically (refer to slide 25 for a visual)
What three components are required by a cloning plasmid
a multiple cloning site (MCS), an origin of replication, and a selectable marker
What are the four steps of cloning plasmids
digestion: restriction enzymes form complementary sticky ends
ligation: DNA fragment and plasmid join at sticky ends and form phosphodiester bonds to close the nicks
transformation: the ligated plasmid is mixed with bacterial cells under given conditions to optimize transformation
selection: cells containing the plasmid will grow on plates and form colonies
What is PCR and how does it work
polymerase chain reaction
step 1: denaturation of protein to split strands apart
step 2: primer annealing
step 3: polymerases attach and elongation occurs by replication of strands
What is the pattern in PCR production
2^(number of cycles) = number of copies
How does a forward primer work
anneals to the BOTTOM strand and has the same sequence as the top strand
How does a reverse primer work
anneals to the TOP strand and has the same sequence as the bottom strand
In vivo and in bacteria/viral DNA, what is the coiling pattern
supercoiled
What type of enzyme seals the nicks in DNA
ligase
How many approximate domains are the circular DNA molecules segregated into
50 domains
What is more extensive about human DNA structure
eukaryotes have very large genomes, so the DNA must be extensively folded and packaged into multiple chromosomes
What does each eukaryotic chromosome consist of
large linear molecule of DNA
large amounts of 2 protein types; 5 histones and many non-histone proteins
*essentially chromatin = DNA + histones + protein
Why are histones important to DNA
DNA is very negative and histones are very positive
What is the first level of DNA packaging in chromatin
nucleosomes
- DNA wraps around histones to form nucleosomes (11nm) (DNA wraps around histones 1 and 3/4 rotations)
- the segments not wrapped around histones, between nucleosomes, are called “linker DNA”
What does the nucleosome core consist of
octamer of histones (4 types of histone, 2 of each)
What is a complete nucleosome made up of (not just the core)
octamer of histones, histone H1 (fifth histone that acts as the glue), and wrapped DNA
What is the second level of DNA packaging in chromatin
30 nm chromatin fiber
- the scrunching together of the string of nucleosomes within a 30 nm width
What is the third level of DNA packaging in chromatin
inter-phase chromosomes
- 30 nm chromatin fibres are tethered to the chromosome scaffold (non histone proteins)
