Download Chapter 6-1 Notes: Chromosomes:

Chapter 6-1 Notes: Chromosomes:
Cells are formed by cell division, which can occur 2 ways:
1. Asexual
 Only requires 1 organisms
 Occurs in prokaryotic cells
 Example: Binary fission
2. Sexual
 Requires 2 parents
 Occurs in eukaryotic cells
 Forms gametes
o Egg - females
o Sperm - males
 Before eukaryotic cells divided, they form chromosomes
o Made up of:
 2 chromatids
 1 centromere
 Each segment = gene
2 types of cells & chromosomes in our bodies
1. Somatic cells: anything except egg or sperm
o Chromosomes = autosomes
o In each somatic cell there are 46 chromosomes (23 pairs)
o They are know as diploid (2n)
 2 sets of chromosomes
 These pairs are known as Homologous chromosomes
 Chromosomes similar in shape, size, and genetic make-up
o 1 set of 23 comes from mom, the other from dad
o The 23rd pair of chromosomes determines your gender
 XX = female
 XY = male
 Male determines gender of future offspring
2. Sex cells: egg or sperm cells
o Chromosomes = Sex chromosomes
o In each cell there are 23 chromosomes
o They are known as haploid (n):
 1 set of chromosomes (half)
Mutations can occur:
 Karyotype: a picture of what are chromosomes look like
o Arranges chromosomes into their homologous pairs from biggest to smallest.
 23rd chromosome – sex chromosomes.
 Down’s Syndrome, XXX, Klinefelter’s Syndrome