Genetics : 9/10. What bases are used to make DNA and RNA? How does a complimentary base pairing stabilize the DNA double helix? How is DNA structurally organized in a cell? What is “ semiconservative ” DNA replication?
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What bases are used to make DNA and RNA?
How does a complimentary base pairing stabilize the DNA double helix?
How is DNA structurally organized in a cell?
What is “semiconservative” DNA replication?
Review of organelles that make it possible to produce a functional protein from DNA.
How is your Genetic Info turned into your unique proteins? Genetic Info is contained in a the DNA double helix of chromosomes located in the nucleus that is “transcribed” into mRNA. The mRNA is “translated” into protein in the cytosol after associating with ribosomes.
-Uracil can’t hydrogen bond very well and hydroxyl-group also prevents double helix
DNA forms a double helix when complimentary bases on two strands hydrogen bond to each others bases. RNA cannot form a double helix because uracil can’t form hydrogen bonds to adenine and the hydroxyl-group of Ribose (RNA) blocks the formation of a RNA double helix ! Watson and Crick elucidated the double helix DNA structure in 1953
Histones: wound into nucleosomes
Helix must also be “unwound” to make new DNA or RNA
DNA on nucleosomes: wound into chromatids, supercoiled, and wound onto chromatin
Chromatids and Chromatin must be unwound to make new DNA or RNA
Chromosome is a massive structure of tightly wound/compact dsDNA
Chromosomes must be unwound at cell replication
Parts of chromosomes must be unwound for RNA to be produced
Degrees of DNA Organization:
1) Primary base
DNA is a huge molecule. All the DNA in the 10 trillion cells of your body put end to end would reach to the sun and back 65 times! How does all the DNA fit inside a tiny nuclei of a cell?
How do we organize this long strand into a structure that will fit inside a cell? Could you describe these structures from DNA to Chromosome (from smallest to largest)?
Shown in blue. This cell is undergoing cell division into two new cells. The new DNA in the two new cells is shown in RED.
Semiconservative DNA replication in original cell!
Each strand of DNA is used as a “template” to make
the next strand of new DNA that becomes a new ds DNA helix.
Two new cells, each with
a ds DNA (1old/1new)
Four new cells:
Two cells contain
the original two DNA
strands (blue), two contain entirely new (red) DNA.