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Biology Unit 2 DNA
Terms in this set (43)
DNA Structure: a nucleotide has three parts?
nitrogen base (4)
what nitrogen bases have a double ring structure?
what nitrogen bases have a single ring structure?
describe the ladder configuration
alternating phosphate/sugar groups forms on sides of ladder
rungs composed of nitrogen bases
complimentary base pairing, purine with pyrimidine
ladder coils to form a helix
why does complimentary base pairing occur?
because of hydrogen bonds
holds the sides of the ladder together
what is chargaffs rule?
percent of a equals percent of t
percent of g equals percent of c
how are nitrogen bases connected by hydrogen bonds?
3 hydrogen bonds c and g
2 hydrogen bonds a and t
describe the 2 ends of DNA
3 end where first sugar chain is
5 end where last phosphate chain is
semi conservative replication
where daughter molecules produced consist of one new chain of nucleotides and one from parent molecule
results in 2 daughter molecules that will be identical to parent molecule
requirements for semi conservative replication
supply of nucleotides to form new dna strand
template, a strand of dna to make a copy of
enzymes to read the template and assemble new dn strands
step 1 of semi conservative replication
enzyme helicase unwinds/unzips double stranded dna
exposes bases by pulling them apart
both strands act as templates
Step 2 of semi conservative replication
rna primase lays a primer set of nucleotides binding them to template strand
Step 3 of semi conservative replication
new dna nucleotides fit into place along template strands by complimentary base pairing
dna polymerase 3 helps to position new nucleotides
Step 4 of semi conservative replication
dna polymerase 1 replaces rna primer pieces with actual dna nucleotides
Step 5 of semi conservative replication
dna liagase repairs breaks in sugar phosphate backbone
daughter dna molecules identical to original
what direction does dna helicase unwind?
dna polymerase 3 can only build in that direction too
what direction does the leading strand build in?
builds in 5'3 and makes continous strand
what direction does lagging strand build in?
builds in 3'5 direction
what are okazaki fragments?
chunks of dna
made up of single strand
made up of nucleotides like dna
made of phosphate groups, ribose not deoxyribose
nitrogenous bases A, G, U, C
What are the major types of rna?
mrna: carries genetic info from dna to ribosome
trna: delivers amino acids to ribosomes
rrna: major component of ribosomes helps assemble new proteins
process where a gene on one strand of dna is used to produce a single strand of mrna
enzyme rna polymerase binds to dna template strand
rna nucleotides start to base pair with template strand
rna polymerase joins rna nucleotides together into a complete strand of mrna
junk mrna called introns and are cut out
useful mrna called exons are spliced together
poly-adenine tail added to end of mrna strand
process of using the code carried by mrna to create proteins
chain initation: ribosome subunit attaches to mrna at the start codon AUG, trna with matching anticodon UAC binds to start codon and brings first amino acid
Chain elongation: amino acids added to protein one at a time during this stage, amino acid from new trna forms a peptide bond with amino acid
chain termination: ribosome arrives at stop codon, instead of new trna release factor arrives at a site, new protein cleaved off, ribosome subunit breaks apart
how many mrna codons are there?
61 codes for amino acids, code for same amino acid
3 are stop codons and stops process of translation
what are the 4 tiers of protein structure?
primary, secondary, tertiary, quaternary
describe primary structure?
while mrna is being translated amino acids are brought in according to codon sequences and leave a long chain of amino acids
describe seconadary structure?
folding that occurs due to attractions between amine and carboxyl group
results in a coiled shape (alpha helix) or sheets (beta pleated sheets)
describe tertiary structure?
folding that occurs due to unique r group structures of amino acids
describe quaternary structure?
not seen in all proteins, some stop at tertiary
some proteins made of multiple amino acid chains
chains can be brought together to make a larger protein
when multiple chains combine
what groups are attached to a central carbon?
whats a gene mutation?
change in a sequence in the nitrogen bases within any given gene
change in dna means mrna changed too
if mrna affected final protein is too
describe errors in dna replication
sometimes new dna contains mismatched pairs of bases
however very rare since dna polymerase proof reads by checking originial strand
1 mistake per every billion bases copied
whats a mutagen?
error in dna replication
anything like chemicals, viruses that can induce a mutation
includes radition or organic chemicals
rate of this is low since dna repair enzymes constantly checks and repairs dna
radiation/chemicals can damage genes and make them unreadable
whats a transposon?
dna sequences that jump from one chromosome to another or to other spots on the same chromosome
can disrupt other genes
what is a point mutation?
occurs when one nucleotide carrying a certain base
what is a silent mutation?
is replaced by another carrying a different base
if the new codon still creates the same amino acid there is no change
this is a silent mutation
what is a nonsense mutation?
if the mutation causes a new stop codon to form the protein could end up too short or dysfuntional
what is a missense mutation?
if mutation causes a different amino acid to end up in the protein it will affect shape and functionality
what is a frameshift mutation?
occurs when there are more nucleotides and bases are inserted or deleted from the strand
this changes the ordering of the codons causing the ribosome to use the wrong amino acid to put the protein together
it changes the reading frame of mrna
describe how cells act in cancer
divide uncontrollably and invade tissues and disrupt regular body function
the result of specific mutations
normal cells stop dividing when they come into contact with neighbouring cells
tumor cells do not stop dividing
what are oncogenes?
they created proteins that move the cell cycle along
if mutated they can override anything stopping the cell cycle
what are tumor suppressor genes?
makes proteins to slow/stop cell cycle and cause cell death, apoptosis
mutations can damage these genes and cause them to no longer create proper proteins
what is metostasis?
enzymes created wher tumor cells can leave their original spot and travel throughout the body
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