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What are leading strands?
Leading strands are one of the two newly synthesized DNA strands during DNA replication. They are synthesized in a continuous manner in the 5' to 3' direction, following the replication fork. The leading strand is synthesized in the same direction as the replication fork is moving, allowing for continuous synthesis.
What is genome and state what major events must occur during cell division for the entire genome to be passed on to daughter cells?
Mitosis
What determines the nucleotide sequence of the newly synthesised strand during DNA replication?
It must be the mirror image of the original half strand. (and the other strand, which is the mirror of the first is making the mirror of the mirror ... the original !)
What events must occur during division in both prokaryotic and eukaryotic cells?
Replication of DNA,segregation of the "original" and its "replica" follow, and cytokinesis end the cycle.
Why are two different primers required for the polymerase chain reaction?
Must use the forward and reverse primers to bind to complementary sequence at the 3' end of the template strand - each NEW strand is built in 5' to 3' direction. They flank the targeted gene region - must attach one to each strand of the target DNA.
What is the definition of a lagging strand?
A lagging strand is one of two strands of DNA found at the replication fork, or junction, in the double helix; the other strand is called the leading strand. A lagging strand requires a slight delay before undergoing replication, and it must undergo replication discontinuously in small fragments.
What fragments of DNA produced from the lagging strand that must be joined called?
Okazaki fragments
Why is the leading strand considered continuous?
The leading strand is the correct orientation, so it can be replicated continuosly - meaning the DNA Polymerase can continue to add new nucleotides without stopping. New DNA strands can only be created in a 5' to 3' direction. This is different to the lagging strand - which must be looped and copied in small, non-continuos segments. These segments are known as Okazaki fragments.
Why lagging strand is fragmented?
Think of DNA as a zipper. The left one labelled 5' on the top and 3' on the bottom. The right one labelled 3' on the top and 5' on the bottom. ex. left 5'-------------------------3' right 3'-------------------------5' As you 'unzip' (with helicase), the teeth of the zipper are exposed. The copying mechanism moves along the original strand in a 5' to 3' direction ex left 5'------ .....................\ .......................--------------------3' .......................--------------------5' ....................../ right 3'------ (periods are merely space holders ignore them) On the 'left' strand, the DNA Polymerase attaches to the free 5' end and moves toward the helicase On the 'right' strand, the DNA Polymerase must attach near the helicase (zipper-handle) and move towards the top. It must start several times therefore lagging strands are fragmented.
Two disjoint events in which one or the other must occur are called?
Complements or complementary events
Why is replication on one strand of DNA continuous while on the other strand the replication must be discontinuous?
New strands of DNA can only be created in one direction - 5' to 3'. This is because only the 3' end of the DNA is able to join to a new nucleotide. The two strands of DNA are antiparallel - meaning they run in different directions. Therefore only one strand (called the leading strand) is running in the correct direction for continuous replication. The other strand (called the lagging strand) must first be looped around so that small sections can be replicated in the correct direction.
If two events are mutually exclusive then they must be dependent?
No, if two events are mutually exclusive, they cannot both occur. If one occurs, it means the second can not occur.
Describe the significance of Okazaki fragments?
Okazaki fragments are created during DNA replication because DNA Polymerase can only add nucleotides in a 5' to 3' direction. This means that one strand (the leading strand) can be continuously created, but the other strand (the lagging strand) runs in the opposite direction. This means that loops must be created and shorter parts of DNA replicated one at a time. This creates fragments on the lagging strand. The RNA primers on this strand are later replaced with DNA by DNA Polymerase I, and joined together with DNA ligase.
What are leading strands?
Leading strands are one of the two newly synthesized DNA strands during DNA replication. They are synthesized in a continuous manner in the 5' to 3' direction, following the replication fork. The leading strand is synthesized in the same direction as the replication fork is moving, allowing for continuous synthesis.
What must be broken for the strand to separate?
Hydrogen Bonds Must be broken
What are the Situations wherein poisson distribution is applied?
The Poisson distribution may be used when studying the number of events that occur in a given interval of time (or space). These events must occur at a constant rate, be independent of the time since the previous occurrence.
Why are there many replication forks?
A replication fork is the mechanism by which a strand of DNA is synthesized. If you can imagine a strand of DNA unwound, then it would resemble a ladder. Unzip the DNA and it now looks like a fork, ie fork in road, not eating fork. There is a Leading strand, which is synthesised easily. USing DNA polymerase which 'reads' along the strand in the 3' to 5' direction on the strand, producing a replication strand in the 5' to 3' direction. The opposite strand is called the lagging strand, and this is slightly more complicated. DNA polymerase cannot read in the 5' to 3' direction on the template strand. Thus DNA primase is used to read the strand and replicate small RNA segments, called Okazaki fragments. The lagging strand has no been copied into many small strands of RNA, or Okazaki fragments. Next DNA polymerase comes along and replaces all the RNA nucleotides with DNA nucleotides. ANd finally DNA ligase 'stitches' all the small fragments into one long strand.
