D1.1 DNA Replication Flashcards
DNA replication is?
DNA replication is the production of exact copies of DNA with identical base sequence
what are the purposes of DNA replication?
- Cell division
- new cells need new DNA for growth and tissues repair
- Reproduction
- gametes require DNA to pass on genetic information
what does “semi conservative” mean?
- “Semi-conservative” means that:
One strand of the ‘parent’ DNA is kept in the ‘daughter’ molecule. This is called the template strand.
The other half is determined by the code on the template strand and is built up from free nucleotides in the nuclear space around the chromosomes. This takes place in the nucleus.
- During this process:
Nucleotides are added one by one to the new strand according to the rules of complementary base-pairing
If an adenine is the next exposed base on the original strand, a thymine nucleotide is added and vice versa
If a cytosine is the next exposed base on the original strand, a guanine nucleotide is added and vice versa
How does semi-conservative replication work? (5 steps)
- hydrogen bonds between the nitrogenous bases are broken
- free nucleotides are present in the nucleus
- free nucleotides pair up with complementary exposed bases
- the new strand is linked together
- there are now two DNA molecules. each one contains one old strand and one new one
During semi-conservative replication, when are hydrogen bonds formed?
Hydrogen bonds can only form between the template strand and the new strand if the correct bases are paired up
the output of semi-conservative replication?
The new DNA molecule has kept half of the parent DNA and then used this to create a new, daughter strand
what is the role of complementary base pairing in DNA replication?
It ensures that DNA is copied accurately.
The specific pairing of bases on the two strands ensures that the new strand is an exact copy of the original.
(otherwise, you’d have a mutation ㅠㅠ)
the only correct method of DNA replication is?
a semi-conservative method!
there were other ideas throughout history, but they’re not correct
why must DNA strands be separated prior to replication?
They must be separated before replication so that they can be copied and new DNA replicas can be made (so that they can act as templates)
The two strands of the DNA double helix are held together by their bases, and are very stable under normal conditions. SO, to replicate, enzymes break them apart.
what is the role of helicase in DNA replication?
it unwinds and unzips the DNA by breaking the hydrogen bonds between bases
