semi conservative DNA replication Flashcards
What does semi conservative replication mean
how DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand. One old strand is conserved in each new molecule.
Why is DNA described as “semi conservative”
One old strand is conserved in each new molecule.
Why does DNA have to be replicated
Every time a cell divides, the DNA has to be copied so that each new daughter cell receives a full set of instructions. Each molecule of DNA replicated
When does DNA replication take place
This replication takes place during interphase, before the cell actually divides.
What’s the product of DNA replication in eukaryotes
This results in each chromosome (a chromosome being one molecule of DNA) having an identical copy of itself. Although,at first they are joined together at the centromere, forming two sister chromatids(find video).
What happens to DNA in mitochondria and chloroplasts while these organelles divide(organelles divide in interphase)
It replicates each time these organelles divide, which is just before the cell divides.
What happens to DNA every time a cell divides
DNA is copied so that each new daughter cell receives the full set of instructions.
Draw a chromosome
Does DNA replication use the whole DNA molecule
Yes
What is DNA gyrase
Enzyme that catalyses the unwinding of the double helix
What is DNA helicase
enzyme that catalyses the breaking of hydrogen bonds
henveen the nitrogenous pairs of bases in a DNA molecule.
What is DNA polymerase
enzyme that catalyses formation of DNA from activated deoxyribose nucleotides, using single-stranded DNA as a template
What is DNA ligase
Enzyme that catalyses the joining of short sections(Okazaki fragments )of the lagging strand.
1)What does DNA gyrase enzyme do first to the DNA molecule so it can make a new copy of itself
unwinds - the double helix is untwisted, catalysed by a DNA gyrase enzyme
2)What does DNA helicase enzyme do to the DNA molecule so it can make a new copy of itself
catalyses the breaking of the H bonds between nucleotide bases and unzips the double helix.This results in two single strands of DNA with exposed nucleotide bases.
3)What do phosphorylated
nucleotides do in DNA replication
free phosphorylated nucleotides bond to the exposed bases, following complementary base-pairing rules.
Why does it have to be PHOSPHORYLATED nucleotides that bond to exposed base pairs
Normal nucleotides are not activated
4)What’s does the
DNA polymerase enzyme catalyse
It catalyses the addition of the new nucleotide bases, in the 5’ to 3’ direction, to the single strands of DNA it uses each single strand of unzipped DNA as a template
5)Is the leading strand synthesised discontinuously
No, the leading strand is synthesised continuously whereas the lagging strand is in fragments (discontinuous) that are later joined, catalysed by ligase enzymes
6) what’s the final step in dna replication
hydrolysis of the activated nucleotides, to release extra Phosphate groups, supplies energy to make phosphodiester bonds between sugar residue of one nucleotide and the phosphate group of the next nucleotide.
What’s the product of
DNA replication
two DNA molecules, identical to each other and to the parent molecule. Each of these molecules contains one old strand and one new strand(semi-conservative replication).
How do the loops of DNA in prokaryotes, and inside mitochondria and chloroplasts replicate
semi-conservatively, a bubble sprouts from the loop and this unwinds and unzips, and then complementary nucleotides join to the exposed nucleotides.
Eventually the whole loop is copied.
How are point mutations caused (and please revise the other types of mutations , ask berg )
During DNA replication, errors may occur and the wrong nucleotide may be inserted.
How often do mutations occur
This is estimated to occur in 1 in 10^8 base pairs.
