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.
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.
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.