Goal 3

1. Goal 3 Learner will develop an understanding of the continuity of life and the changes of organisms over time

2. Reproduction • Asexual Reproduction: • Produces identical cells • Chromosome number stays the same • Mitosis is an example • Sexual Reproduction: • Produces genetically different cells • Chromosome number changes • Meiosis is an example

3. Mitosis *BE ABLE TO PUT IN ORDER! • Interphase = period of cell growth, DNA replication occurs (doubles DNA) • Cell divides once to make 2 identical cells • Helps make more cells for your body

4. Mitosis • Advantages = injury repair • Disadvantages = cancer • Cancer = uncontrolled cell division • “Differentiation” of cells • All cells start as “stem cells” – then they become any type of cell in the body by mitosis

6. Meiosis • Chromosome number decreases by half (46 chromosomes become 23) • Cell divides twice to make 4 genetically different cells • Makes egg and sperm cells (gametes)

7. Why Meiosis?

8. Variation Meiosis produces cells that are different… why? • Chromosome number changes • Crossing over occurs • Some of “dad’s” chromosome switches with some of “mom’s” chromosome producing a mix • “Random assortment” of chromosomes

9. Random Assortment of Chromosomes • The random distribution of chromosomes from mom and dad into gametes

10. DNA • DNA = Deoxyribonucleic Acid • DNA is made of nucleotides • A nucleotide has 3 parts: • Deoxyribose (a sugar) • Phosphate group • A nitrogenous base

11. DNA Bases • There are 4 nitrogenous bases in DNA: • Adenine (A) • Thymine (T) • Guanine (G) • Cytosine (C) • Complementary Base Pairing: • A with T ; G with C • Bases are bonded with WEAK hydrogen bonds

12. DNA Practice • If one side of DNA reads: T A C G A what does the other side read?

13. DNA Shape • DNA is double stranded • Backbone = sugar and phosphate group • Inside = bases are joined with hydrogen bonds • Double helix shape discovered by Watson and Crick

14. DNA Replication • Two new strands of DNA are created = each with one OLD DNA strand and one NEW DNA strand • Allows new cells to have an exact copy of DNA from parent cell • Occurs during INTERPHASE of the cell cycle

16. Transcription • Happens in the nucleus • Makes RNA as a copy of DNA • RNA is single stranded • RNA has Ribose instead of Deoxyribose • RNA has Uracil (U) instead of Thymine (T) http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

17. 3 Types of RNA • mRNA = “messenger” – takes DNA message from nucleus to ribosome • rRNA = “ribosomal” – makes up the ribosome • tRNA = “transfer” – transfers amino acids to the ribosome

19. Transcription Practice • What mRNA will be formed? DNA: ATG CAT GCA • From this mRNA, what does the DNA read? mRNA: CGU AGC AUC

20. Translation • Happens at a ribosome • RNA is turned into a protein • Amino acids are joined by peptide bonds to form proteins • Proteins are also called “polypeptides” http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html

21. Translation • Codon = a set of 3 bases on mRNA • Each codon “CODES” for an amino acid • Use your Genetic Code wheel to see which amino acid it codes for • START Codon = AUG • STOP Codons = UAA, UAG, UGA

22. Problems with Proteins • Mutations = mistakes in the DNA • Can cause the wrong protein to be made • Can occur during replication or transcription • Cancer = uncontrolled cell division • Can be caused by making too many, too little, or making proteins at the wrong time

23. Translation Practice mRNA: AUG CAU GGA CAG UAG mRNA: AUG GCA UGC ACU UAA