CHAPTER 8 Chromosomes pp. 151-153

Chromosomes: coiled and compact DNA in nucleus DNA wrapped tightly around proteins called histones Chromatids: two halves of a dividing chromosome Chromatids joined by a centromere

Chromosome number: each organism has a specific number of chromosomes Sex chromosomes: determine sex of the organism (X or Y) female: XX male: XY Autosomes: all other chromosomes All organisms have two copies that are homologous

Haploid vs Diploid Haploid (n): only 1 set of chromosomes (n=23) like egg or sperm cells Diploid (2n): having 2 sets of chromosomes (2n=46) morphologically similar: homologous one set from mom and one set from dad 2 haploid cells (sperm and egg) can combine to make a diploid (zygote)

Karyotype: photo of chromosomes Block cells in cell division and stain the condensed chromosomes with dye Thinnest bands contain over a million base pairs and hundreds of genes Bands can be used to identify chromosomes and possible genetic disorders due to the wrong number of chromosomes