Bite-Sized Morsels of Biology that are Good and Good For You
Replication
DNA codes for proteins, and proteins make up everything important about an organism. Every time a new cell is made, it must have the correct instructions for all of the proteins in the body. Replication is the process of copying DNA.
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It occurs during interphase
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It is "semiconservative" - each side of the molecule is used as a template to make the other side correctly.
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It involves many enzymes and steps that may require a deeper dive
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Sometimes, mistakes are made: mutations.
Copying DNA
Replication takes place in the nucleus during the "S" phase of interphase when a cell starts preparing to divide.
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At many points along a chromosome, Helicase enzymes attach to the DNA and start to separate the weak hydrogen bonds between the bases.
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As they move away from each other, they create a bubble in the DNA
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This exposes all of the bases that would like to form hydrogen bonds with their complementary nucleotides
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DNA polymerase is an enzyme that will attach to the middle of the bubble and start reading the exposed bases.
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As it reads each base, it brings in the complementary nucleotide (A with T and G with C) and builds the opposite side of the molecule.
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Each original strand is saved as a new strand is built on the other side, so the process is called "semi-conservative" (semi- half; conserve - to save)
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Eventually, all of the helicase enzymes will meet and release, and all of the polymerase enzymes will finish their sides of the new molecules resulting in two identical copies of DNA.
Mutations
A mutation is a change in DNA. Sometimes DNA polymerase will make a mistake that can be anywhere from deadly to beneficial to not noticeable. The effects of mutations may require an understanding of Transcription and Translation.
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Substitution mutations - the wrong nucleotide is added on the new strand
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Missense mutations - code for the wrong amino acid when making a protein
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Nonsense mutations - code for stopping the protein before it is finished
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Silent mutations - code for the same amino acid, so the protein is not affected
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Frameshift mutations - the new strand has the wrong number of nucleotides which causes all amino acids to be changed
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Addition - an extra nucleotide is put into the new strand
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Deletion - a nucleotide is skipped, and the new strand comes up short
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