Chromosome Structure Review Gene – DNA is a large molecule broken down into hereditary units called genes DNA is organized & packaged into chromosomes Chromosome – DNA wound or coiled tightly around proteins (histones)

Structure – fully condensed, duplicated A chromosome is made of 2 identical halves called a chromatids. A centromere holds 2 chromatids together DNA is packaged as a chromosome only during cell division, after it has been copied. When a cell is not dividing, its DNA is packaged more loosely as chromatin.

Chromosome #’s Review- each species has a different number of chromosomes Sex Chromosomes – and X or Y chromosome Autosomes – all remaining chromosomes Homologous Chromosomes – a pair of similar chromosomes (1 from mom, 1 from dad)

Diploid Cells Are cells having all homologous pairs and 2 sex chromosomes body cell, or somatic cells Diploid cell are abbreviated as 2n, where n = # of 1 set of chromosomes. The chromosomes of diploid cells can be arranged and studied using karyotypes.

Haploid Cells Cells that contain only 1 chromosome from the pair of homologous chromosomes and 1 sex chromosome. Haploid cells are abbreviated as n. Haploid cells are gametes.

Mitosis in a Plant Cell

Mitosis in an Animal Cell