DNA Replication…Notes
Steps:
1. A section of the DNA molecule unwinds and becomes a
___________________ladder.
2. The 2 nucleotide chains are separated by
__________________enzymes, which break the
hydrogen bonds between the bases.
3. DNA polymerases bind to the 2 sides of DNA moving
along in opposite directions, attaching free
___________________to the existing DNA chain.
4. Covalent bonds join sugars and phosphates,
__________________bonds join base pairs.
• The process of replication happens at many
different locations along the DNA
________________________, not just from
one end to the other.
• Result: 2 new strands of DNA that are exact
copies of the original, and the cell is ready
to undergo cell division
(_______________!).
Picture:
(see in your book 12-2,
pages 333-334)
Let’s watch an
animation of how
this happens!
Mutations…
• When the bases mis-match themselves in
base-pairing, this is one type of
____________.
• There is about one error in every 10,000
paired nucleotides but DNA can proof-read
itself and repair the mutation, helping keep
the error rate to about one error per 1
__________nucleotides.
• This has serious effects in new ___________.
• Mutations can be bad or good…
Good and Bad…
• Mutations drive _______________to happen!
• Good mutations – help the organism survive
longer so that their ___________can be passed
down
– Examples: camouflage, drug resistant bacteria (good
for them, bad for us!)
• Bad mutations – cause the organism to
__________and not allow those genes to be
passed down
– Examples: genetic disorders that cause early death,
cancer
Transcription and Translation
Protein Synthesis
• What is it?
– Transcription happens when DNA is
transcribed (making a ________________)
into RNA
– Translation is when the information is
translated into a ________________
Transcription: the process by which genetic
information is copied from DNA to _______.
Steps:
1. RNA transcription starts on the DNA strand (the
template) at the “____________” (initiator or
start) gene.
2. RNA polymerase binds to the promoter gene and
travels down one side of the
____________________(original DNA) attaching
complementary RNA bases and nucleotides.
3. The base pairing rules are the same except U replaces
T on the _________strand.
4. This continues until it reaches a DNA region called the
“termination signal” (or _________).
5. The RNA polymerase _________________both the
DNA molecule and the newly formed RNA molecule
(travels to cytoplasm).
6. DNA _______________back up!
This newly formed strand is called mRNA or
messenger RNA.
After mRNA is formed
• We are able to make a protein in the cytoplasm.
(______________________)
• Remember…
– The amount and kind of ___________that are
produced in a cell determine the structure and
function of the cell.
– In other words, proteins carry out the genetic
__________________________(genes) encoded in
our DNA.
• mRNA is now grouped into letters of ______ (a group
of 3 letters is called a codon).
– Each codon will code for one amino acid (AA).
– AAs are the __________________blocks of proteins.
– A few codons do not code for an AA, instead they
signal for translation of an mRNA to
______________(initiator/start codon/promoter) or
stop (stop codon/ termination signal).
• mRNA is ready to be “_____________” by 2 other
types of RNA…
rRNA or ________________RNA
• When the mRNA gets to the cytoplasm, rRNA
(which is in __________________form) will
attach itself over the strand.
• It helps attach the __________to the mRNA
• This is where ribosomes are made!
__________ or Transfer RNA
• tRNA will locate the start ___________on the mRNA
strand and will form the appropriate AA for that
codon
• tRNA travels down the mRNA to the next codon and
forms the appropriate ________ for that codon
• The second AA attaches to the 1st & the tRNA
molecule ________________from the 1st mRNA
codon
• This continues until a string/chain of AA are formed =
a _________________is made!