• Defined: Tightly coiled DNA • Forms during cell division – New chromosomes created for new cells • 2 Parts: – 1) Chromatids: two identical parts of a chromosome – 2) Centromere: Joins chromatids together • Defined: Picture of an individuals chromosomes – Identify sex & chromosome defects • Size of final pair identifies sex – Same size: XX = female – Different size: XY = male • Normal human will have 46 chromosomes • Diploid Cells = Cells with the full set of chromosomes – Paired chromosomes • Half of our chromosomes come from each parent (23 from each parent) • Somatic (non-sex) cells are diploid • Created by mitosis • Ex: Skin, Muscle, Nerve, Blood Cells Humans have 46 total chromosomes. What is the human diploid chromosome number? Remember…Diploid = total number of chromosomes Answer = 46 Humans have 46 total chromosomes. What is the human somatic chromosome number? Remember…Somatic cells are non-sex cells… …Somatic cells are diploid… …Diploid cells have the full set of chromosomes Answer = 46 Humans have 46 total chromosomes. How many chromosomes are in brain cells? Remember…Brain cells are non-sex cells… …Somatic cells are non-sex cells… …Somatic cells are diploid… …Diploid cells have the full set of chromosomes Answer = 46 • Haploid Cells = Cells with ½ the total number of chromosomes • Gametes (sex cells) are the only haploid cells – Ex: Sperm, Egg, Pollen • Chromosome number is reduced by meiosis • How do humans get 46 chromosomes? Haploid sperm cell (23) + Haploid egg cell (23) = Diploid zygote (46) Humans have 46 total chromosomes. What is the human haploid chromosome number? Remember…Haploid = half number of chromosomes Answer = 23 chromosomes Humans have 46 total chromosomes. What is the human gamete chromosome number? Remember…Gamete cells are sex cells… …Sex cells are haploid… …Haploid cells have ½ the set of chromosomes Answer = 23 Humans have 46 total chromosomes. How many chromosomes are in female egg cells? Remember…Egg cells are sex cells… …Sex cells are gametes… …Gamete cells are haploid… …Haploid cells have ½ the set of chromosomes Answer = 23 Down Syndrome: What’s Wrong? • Writing notation: – 1st: total chromosome # – 2nd: Sex chromosomes – 3rd: extra or missing • Down Syndrome: 47, XY, +21 Turner’s Syndrome: What’s Wrong? • Write the notation for Turner’s Syndrome. 45, X, -23 or 45, XO, -23 Patau’s Syndrome: What’s Wrong? • Write the notation for Patau’s Syndrome. 47, XY, +13 Klinefelter’s Syndrome: What’s Wrong? • Write the notation for Klinefelter’s Syndrome. 47, XXY, +23 • What is the diploid chromosome number? 42 • What is the haploid chromosome number? 21 • How many chromosomes would be in somatic cells? 42 • How many chromosomes would be in brain cells? 42 • How many chromosomes would be in gamete cells? 21 • How many chromosomes would be in egg cells? 21 • How many chromosomes would be in muscle cells? 42 • How many chromosomes would be in sperm cells? 21 • Is this a male or female rat? male Quick Review • Chromsomes are tightly coiled strands of DNA • Diploid (somatic) cells contain the entire set of chromosomes • Haploid (gametes) cells contain only ½ the total number of chromosomes