CDM Bio #3 Flashcards
Define DNA replication
The process in which a copy of a DNA molecule is made
Define mutation
A randomly produced, permanent change in the nucleotide sequence of DNA.
T/F Although mutations occur randomly, they are more likely to be detrimental than beneficial
True, the cell survival depends on keeping DNA changes to a minimum.
How high can DNA replicate? (in nucleotides per second)
Up to 1,000 nucleotides per second (in bacteria) about 100 per second in humans, the equivalent of about 1000 books per 8 hours
T/F DNA acts as a template for its own replication
True
Dna replication is said to be __________
Semi conservative
DNA sequences at replication origins are recognized by ______ ______-
initiator proteins
The process of DNA synthesis is begun by initiator proteins that bind to specific DNA sequences called _____ ______
replication origins
- Here individual hydrogen bonds are pried apart by initiator proteins
T/F separating a short length of DNA a few base pairs at a time requires a large energy input
False, it requires relative low energy input because the initiator proteins can readily unzip short regions of the double helix at normal temperatures.
Replication origins in simple cells (bacteria or yeast) span approximately ____ nucleotide pairs
100
What do replication origins
in simple cells contain?
DNA sequences that attract the initiator proteins and are especially easy to open.
For this reason AT rich sites are often found at replication origins (adenine thymine bonds are easier to pull apart than cytosine/guanine bonds)
How many replication origins are found in circular bacterial genomes?
One
How many replication origins are found in humans?
about 10,000 or 220 origins per chromosome.
This is because beginning DNA replication at many places at once greatly shortens the time a cell needs to copy its entire genome
Need to know:
Once an initiator protein binds to DNA at a replication origin and locally opens up the double helix, it attracts a group of proteins that carry out DNA replication. These proteins form a replication machine, in which each protein carries out a specific function.
What year did watson and crick publish their famous two page paper describing a model for the structure of DNA?
1953
What did watson and crick propose in their 2 page paper?
- complementary bases pair with one another along the center of the double helix, holding together the two strands of DNA
How many replication forks form at each replication origin?
two
What are replication forks?
Y shaped junction at the site where DNA is being replicated
What happens at the replication forks?
At each fork, a replication machine moves along the DNA, opening up the two strands of the double helix and using each strand as a template to make a new daughter strand. The two forks move away from the origin in opposite directions, unzipping the DNA double helix and copying the DNA as they go
DNA replication - in both bacterial and eukaryotic chromosomes - is termed __________.
Bidirectional
T/F in DNA replication, the forks move very slowly
name the rate in both bacteria and humans
False, the forks move very rapidly at about 1000 nucleotide pairs per second in bacteria and 100 nucleotide pairs per second in humans
Why is DNA replication slower in humans?
This could be due to difficulties in replicating DNA through the more complex chromatin structure of eukaryotic chromosomes
T/F the two replication forks found at ORI’s move in the same direction
False, they move in opposite directions
What synthesizes DNA using a parental strand as a template?
And how?
An enzyme called DNA polymerase
DNA Polymerase catalyzes the addition of nucleotides to the 3’ end of a growing DNA strand, using one of the original, parental DNA strands as a template.
