Biology 1201A Lecture Notes - Lecture 4: Seedless Fruit, Noncoding Dna, Allele
22 Dec 2016
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Ploidy of a cell or species - number of chromosome sets in a cell"s nucleus (humans n=23) n, being # of chromosomes. Liver cells tetraploid or octaploid -> no cytokinesis, just divides and replicates. Humans are typically diploid (2n = 46) - 2 sets. Not all body cells are diploid, some are polyploid. Polyploid human cells: liver cells (4n, 8n, megakaryocyte (16n - 128n) Polyploid - contain more than two sets of chromosomes: some organisms are polyploid, especially plants (2n, seedless fruit are triploids (3n) Plants are more flexible so they can handle being polyploidy. As humans we have generated gametes into plants and fuse them to create a tetraploid -> We"ve do(cid:374)e this (cid:271)e(cid:272)ause polyploidy (cid:373)akes (cid:271)igger fruit. The seeds do(cid:374)"t for(cid:373) (cid:271)e(cid:272)ause they"re triploid * re(cid:373)e(cid:373)(cid:271)er i(cid:374) (cid:373)eiosis* Aneuploidy - an abnormal number of chromosomes in a cell, missing or extra chromosomes. Missing chromosome 21 -> cause of down syndrome : tolerable aneuploidy, the zygote will develop.
