1. CHROMOSOMES AND CELL REPRODUCTION SECTION 1: CHROMOSOMES Chapter 6 Grade 10 Biology Fall 2010

2. Bell Ringer 1. What is the difference between prokaryotes and eukaryotes? 2. Do all cells divide in the same manner?

3. Objectives Identify four examples of cell division in eukaryotes and one example in prokaryotes Differentiate between a gene, a DNA molecule, a chromosome, and a chromatid Differentiate between homologous chromosomes, autosomes, and sex chromosomes Compare haploid and diploid cells Predict how changes in chromosome number or structure can affect development

4. Formation of New Cells About 2 trillion cells are produced by an adult human body every day New cells are formed when older cells divide  Cell division, aka cell reproduction

5. Formation of New Cells Different types of cell division The type of cell division differs depending on the organism and why the cell is dividing  Prokaryotes: bacteria reproduce asexually  Eukaryotes: undergo growth, development, repair, or asexual reproduction, formation of gametes

6. Formation of New Cells Gametes: are an organism’s reproductive cells  Sperm or eggs

7. Formation of New Cells Regardless of the type of cell division occurring, information stored in DNA must be present in each of the resulting cells  DNA directs cells activities and determines its characteristics When a cell divides, DNA is first copied and then distributed Each cell ends up with a complete set of the DNA

8. Prokaryotic Cell Division DNA- circular, attached to inner cell membrane Reproduce by binary fission Binary Fission: form of asexual reproduction that produces identical offspring  Single parent passes exact copies of all of its DNA to its offspring

9. Prokaryotic Cell Division Binnary Fission Stages: 1. DNA is copied 2. Cell divides  Adds new cell membrane to the point on the membrane between the two DNA copies  New cell wall forms around membrane  Pinch in two

10. Eukaryotic Cell Reproduction Genes: segments of DNA that codes for a protein or RNA molecule Single molecule of DNA has thousands of genes lined up like train cars

11. Eukaryotic Cell Reproduction Chromosomes: consists of DNA tightly coiled around proteins, condensed form of DNA  DNA and proteins become visible Chromatids: the 2 exact copies of DNA that make up each of the chromosomes Centromere: the point where two chromatids of a chromosomes are attached

12. Activity Time! Design a chromosome of your own. Label and colour:  Chromosome  Centromere  Chromatids  2 Gene regions

13. Eukaryotic Cell Reproduction 2 chromatids get separated during cell division and placed into each new cells  Ensures that each new cells will have the same genetic information as the original cell

14. Chromosome Number and Structure Somatic Cell: body cell, any cell other than sperm or egg  Has 2 copies of 23 different chromosomes  Total of 46 chromosomes  23 chromosomes differ in size, shape and set of genes

15. Sets of Chromosomes Homologous chromosomes: chromosomes that are similar in size, shape, and genetic contents Each of 23 pairs of chromosomes consists of two homologous chromosomes Each homologue in a pair of homologous chromosomes comes from one of the two parents

16. Sets of Chromosomes Diploid: contains 2 sets of chromosomes, somatic cells  2n = (23 x 2) = 46 Haploid: contains 1 set of chromosomes, gamete cells  n = 23  Each organism has characteristic number of chromosomes

17. Sets of Chromosomes Fertilization: fusion of 2 haploid (n) gametes (sperm and egg)  Forms diploid (2n) zygote Zygote: a fertilized egg cell

18. Sex Chromosomes Autosomes: chromosomes not directly involved in determining the sex of an individual  22 pairs in humans Sex Chromosomes: contain genes that will determine the sex of an individual  1 pair out of 23 in humans

19. Sex Chromosomes Human sex chromosomes:  X  Y- genes that cause fertilized egg to develop into a male located here  XX- female  XY- male  Sex determined by male since females only have X XX XXX YXYXYXYXY

20. Change in Chromosome Number Presence of all 46 chromosomes is essential for normal development and function Trisomy: humans with more than two copies of a chromosome  Will not develop properly

21. Change in Chromosome Number Karyotype: a photo of a chromosome in a dividing cell that shows the chromosome arranged by size

22. Change in Chromosome Number Down syndrome:  Trisomy 21  Short stature, round face with slanted eyes, varying degrees of mental retardation  How does this happen?

23. Change in Chromosome Number Disjunction: if one or more chromosomes fail to separate properly  One new gamete ends up receiving both chromosomes and other gamete receives none Trisomy occurs when gamete with both chromosomes fuses with a normal gamete

24. Activity Time! Karyotype activity with a friend! Label:  Haploid number  Diploid number Indicate:  Autosomes  Sex cells  If male or female

25. Change in Chromosome Structure Mutation: changes in chromosome structure

26. Change in Chromosome Structure Deletion: a piece of chromosome breaks off completely  After cell division the new cell will lack a certain set of genes

27. Change in Chromosome Structure Duplication: chromosome fragment attaches to its homologous chromosome  Carries two copies of a certain set of genes

28. Change in Chromosome Structure Inversion mutation: chromosome piece reattaches to the original chromosome but in a reverse orientation

29. Translocation mutation: if the piece reattaches to a nonhomologous chromosome

30. Activity Time! Modeling Chromosomal Mutations  11 note cards  Label:  1 – 5  Centromere  1 – 2  6 – 8  Demonstrate the 4 types of mutations