1. Cell Reproduction Notes Day 1 Warm Up Where are your genes located?

2. http://people.na.infn.it/~nicodem/research/cell_genes.jpg

3. DURING MOST OF THE CELL’S LIFE, DNA FORMS A TANGLED MASS CALLED CHROMATIN. CHROMATIN LOOKS LIKE A PLATE OF SPAGHETTI. RIGHT BEFORE A CELL DIVIDES, THE CHROMATIN FORMS INTO CHROMOSOMES (X- SHAPED).

4. MOST OF THE TIMEONCE IN A WHILE CHROMATIN CHROMOSOMES

6. Cell Division Chromosomes = Tightly coiled, rod-shaped DNA Chromosomes are made of chromatin Human body produces 2 trillion cells per day & 25 million per second Cells are formed by cell division of older cells 1.When a cell divides, DNA is first copied & then distributed 2.Each cell ends up with a complete set of DNA

7. Chromosome Number Each human somatic cell has 2 copies of 23 different chromosomes –Total 46 –Somatic = any cell that is NOT a sex cell –(also called body cells or autosomes)

8. Sets of Chromosomes Each pair is made up of 2 homologous chromosomes –Homologous chromosomes = chromosomes that are similar in size, shape, & genetic content –Each homologue comes from one of the parents One from mom One from dad

9. Cells Can Be Diploid or Haploid Diploid = a cell that contains 2 sets of chromosomes (2n) Haploid (monoploid) = a cell that contains only 1 set of chromosomes (1n or n)

10. Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes 22 pairs are autosomes (chromosomes NOT directly involved in determining sex) 1 pair are sex chromosomes (contain genes that WILL determine the sex) –X & Y chromosomes

11. X & Y Chromosomes Male = XY Female = XX Male (dad) can donate an X or a Y to offspring Female (mom) can ONLY donate an X So-Which parent determines the sex of the baby?

12. MALE XY

13. Gametes Gametes are reproductive cells –Males = sperm (n = 23) –Female = egg (n = 23) Combine in fertilization to make a: –Zygote (2n = 46)

14. Karyotype Karyotype = a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size.

15. Karyotype cont’d Each of an individual’s 46 chromosomes has thousands of genes so the presence of all chromosomes is essential for normal functioning –Humans who are missing a chromosome don’t survive –Humans with more than two copies of a chromosome, called trisomy, may survive but will not develop properly.

16. What is wrong?

19. The Cell Cycle Repeating sequence of cell growth and division during an organism’s life 90% of cell life is spent in INTERPHASE Then it may go into MITOSIS & CYTOKINESIS

20. INTERPHASE (divided into mini-phases) G1(first growth) phase = Cell grows rapidly S (synthesis) phase = DNA copied G2 (2 nd growth) phase = Nucleus prepares to divide

21. http://publications.nigms.nih.gov/insidethecell/ch4_interphase_big.html