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DNA structure, function and replication - Coggle Diagram
DNA structure, function and replication
Function of DNA
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Contains the instructions to construct other components of the cells such as proteins and RNA molecules
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Structure of DNA
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nucleotides
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consists of sugar molecules, a phosphate group and a nitrogenous base
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4 bases
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adenine always forms weak hydrogen bonds with thymine on the adjacent DNA strand of the double helix
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DNA in Eukaryotic cells
wound tightly around globular proteins called histones, forming DNA- proteins mixture called chromatids
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Chromosomes
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karyogram- taken when chromosomes are condensed and visible. The chromosomes in the photo can be cut out, arranged in order of size, numbered and pasted to produce a composite photo.
Genes are located in specific positions on a chromosome. These positions are called gene's locus or gene loci
DNA in prokaryotic cells
single, circular chromosome located in a region of the cytoplasm called the nucleoid
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Prokaryotes do not contain histone but do have proteins that assist in the spatial organisation of the chromosome in the nucleoid
DNA replication
DNA in parent cell is replicated before cell division occurs to ensure that ensure that each daughter cell receives an exact copy of the genetic information
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The sequence of bases on DNA makes up a code of instructions called the genetic code. The code provides the information needed to instruct the cell to carry out its functions. This code can be passed on to new cells
DNA replication is described as a semi-conservative process as the new DNA molecule each consist of one original strand and one newly synthesised strand.
Steps
- The complementary strands of the double helix are unwound and separated to expose the bases
- A enzyme named helicase breaks the weak hydrogen bonds between the original DNA molecule
- Free DNA nucleotides are added to the exposed bases on the exposed strands, Hydrogen bonds are formed between the free nucleotides and the bases on the exposed strands.
- DNA polymerase joins the sugar and phosphate groups of adjacent nucleotides creating the sugar-phosphate backbone of the newly synthesised polynucleotide strand
- DNA polymerase checks that the new sequence is complementary to the original sequence and removes and replaced misplaced nucleotides