What makes us who we are? What determines what we look like, etc?

1. What makes us who we are? What determines what we look like, etc? Made of nucleotides (phosphate, sugar, base) Copies itself through replication DNA Organized into chromosomes mRNA • Cells divide by: • Mitosis (growth & repair) • Meiosis (reproduction) Proteins

2. Another way to think of it… http://video.pbs.org/video/1506740590 What do these things in the video stand for? Castle: Book: Scribe: Recipe: Cook:

4. Heredity • Is it possible for two parents with blue eyes to have a brown eyed child? • Is it possible for two parents with brown eyes to have a blue-eyed child? Why or why not?

5. Chromosomes have genetic information and are passed to offspring Human chromosomes stained with a special chemical and viewed under a high-powered microscope

6. Chromosomes come in pairs

7. Review – what are chromosomes? • Chromosomes = long pieces of DNA

8. Genes • Parts of chromosomes are called genes • Genes help determine your characteristics • what are some example characteristics? • Human chromosome # 7 • Contains about 1,800 genes • Contains over 150 million nucleotides Link to view genes and DNA sequence

9. Trait – Gene – Allele –

10. Trait – a characteristic of an organism • Example: “flower color” • Gene – part of a chromosome that helps determine a specific trait • Example: “flower color gene” • Allele – a form of a gene • Example: • One allele is the “blue” form of the gene • One allele is the “red” form of the gene

11. How many chromosomes? • Humans = 23 chromosome pairs, or 46 total. (about 20,000 genes) • Pea plant = 7 chromosome pairs (14 total) • Potato = 24 pairs (total 48) • Horse = 32 pairs (total 64)

12. Chromosomes come in pairs • For each pair - one copy came from Mom; the other came from Dad. • This pair of chromosomes is called a “homologous pair” because they have the same genes on them - flower color gene Flower chromosome 3 From Dad From Mom

13. Chromosomes come in pairs • IMPORTANT: homologous pairs have the same genes, but they are NOT IDENTICAL • Alleles can be different flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene From Dad From Mom

14. Original cell Sperm or egg cells But wait…if parents have two copies of each chromosome, how do they pass on one to their kids? • MEIOSIS is the process of cell division that decreases the number of chromosomes to make sperm or egg cells

15. The purposes of Meiosis: • Split the total number of chromosomes in half so that only ONE chromosome from each pair is inherited from each parent. • Produce variation in offspring by randomly sorting the chromosomes.

16. Meiosis • Original cell • Diploid • (pairs of chromosomes) • Sperm or egg cells • Haploid • (single chromosomes)

17. Fertilization Sperm Egg Gametes: (haploid sex cells) Zygote: (diploid embryo) Fertilized egg

18. Overview of the process of Meiosis

24. Yarn modeling of meiosis • Pink & green “chromosomes” • Paper clips = centromeres • Chalk = draw cells on table • Follow the steps on your worksheet • Same groups as Tuesday • Earliest birthday = facilitator; next birthday = resource monitor; next = clarifier; next = equity monitor Meiosis step 1 Meiosis step 2 Meiosis step 3

26. Plan for today • Consent forms • AQP handoff • Solidify meiosis understanding – explanation, dance • Genetics & Punnett squares • TOMORROW – Ms. Reeve gone; unit review & genetics practice (10 participation points!)

27. AQP Handoff • System 17 – water change? • System 7 – thanks for harvesting! Keep it up!

28. AQP Handoff • System 8 – nothing in binder this week? • Water level low today • Time to replace beans? • System 18 – lettuce, basil, others ready to harvest!

29. We left off Friday - Meiosis What is the purpose??

30. Homologous chromosomes have the same size and banding pattern

31. Activity: Owning meiosis • Work alone or in groups of 2-3 • Two choices: • Write in your own words a complete explanation of meiosis 1 & 2; include diagrams as necessary • Create a dance/act out meiosis 1 & 2; you will share this for the class & get feedback • Must include all phases (PMAT 1 & 2) • 15 minutes

32. Variation from meiosis: Independent Assortment • How many different combinations could there be with 3 chromosome pairs? • How many different combinations with 23 chromosome pairs? (humans)

33. Now let’s add in crossing over during prophase I… HUGE amount of possible variations!!

34. Karyotype • A picture of a person’s chromosomes (taken during mitosis). • Helps identify diseases caused by extra, missing, or broken chromosomes

35. Gender determination • Females have 2 “X” chromosomes. • Males have 1 “X” and 1 “y” chromosome. X X Female X y Male

36. Chromosomal Abnormalities • Caused by problems in Meiosis • Cannot be detected until after fertilization • “Nondisjunction”

37. Amniocentesis • High-risk mothers may get an Amniocentesis (“amnio”) • A sample of the amniotic fluid that surrounds the baby. This fluid contains the baby’s cells.

38. Amniocentesis • From the Amniocentesis, a karyotype can be made.

39. Normal (complete set of chromosomes) Disease (extra chromosome)

40. Chromosomal Abnormalities • Some chromosomal abnormalities are linked to maternal age (Down Syndrome)

43. How do we know which chromosomes are homologous? • Size • Pattern of bands - stain with a dye • Position of the centromere Centromere Animated karyotyping

44. Chromosomes have genetic information and are passed to offspring Dividing onion cells chromosomes chromosomes cell wall nucelus