How We Store Genetic Information

How We Store Genetic Information

1. Chromosomes

   • Consist of 2 arms (chromatids) joined by a specialised structure at the centre called a centromere.
   • Karyotype - the array of human chromosomes.
   • 22 homologous pairs of chromosomes.
   • Sex chromosomes - Female XX, male XY. Autosomes - all other chromosomes.
   • Each chromosome contains a single molecule of DNA.

2. Genes

   • Allele - known variations of a particular gene.
   • DNA: a. carries genetic information that is used to synthesise proteins; b. it's structure can be easily duplicated/replicated; c. is relatively stable.
   • DNA is a double-stranded molecule, the strands are made up of nucleotides (sugar, base and phosphate). Base pairings - A:T (U in RNA), C:G.
   • Dominant disorders - requires only one defective copy (allele) of the gene.
   • Recessive disorders - requres two defective copies (alleles) of the gene.

3. Each cell contains 23 pairs of chromosomes (46 total).

   • Each of the 24 (22 of the same, 23 (X) and 24 (Y)) different types of chromosomes contain different genes.
     • Each homologous pair of chromosomes (22 autosomes, and X chromosomes in females) contain the same genes in the same order - so each gene is present twice in the nucleus of every cell.

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