1. You need: Mar. 18, 2019 Clean paper (2)/ pencil Meiosis puzzle/notes
Warm Up:
Mental Math – be ready
I CAN: determine how/why traits are passed from one generation to the next.

2. PUZZLE TIME!!
MEIOSIS

3. Starting point:
You want to start with one cell that has 100% of the genetic information (like a normal body cell). To keep things simple, we will work with a cell that has 4 chromosomes in a normal body cell.

4. Your goal:
To create FOUR cells that only have 50% of the genetic information. These would only have TWO chromosomes (NOT 4).

5. Puzzle check
Knowing if you have the right process is tricky. Let’s try watching the steps.
Cells Alive! (meiosis)

6. Starting point:
You want to start with one cell that has 100% of the genetic information (like a normal body cell). To keep things simple, we will work with a cell that has 4 chromosomes in a normal body cell.

7. After we start…
Before we can split to smaller groups, we need to copy the information. This reminds me of mitosis!

8. Once copies have been secured (copy and original are sticking together
Once copies have been secured (copy and original are sticking together!), then we line them up…
Metaphase

9. After lining up in the MIDDLE, we have to split
After lining up in the MIDDLE, we have to split. This is different than MITOSIS, though. How?
In MITOSIS, the chromosomes line up in the middle vertically and all four would split in half. But in MEIOSIS, they have split the total in half – not the chromosome and it’s copy!

10. After the ONE nucleus splits into TWO nuclei, we still need to split the original chromosome from it’s copy.

11. Lining up in the MIDDLE – like Metaphase…AGAIN!!
This time they are ready to separate the original chromosome and it’s copy.

12. Each chromosome (copy and original is separated
Each chromosome (copy and original is separated. Now the TWO look like they are becoming FOUR.

13. Did you reach the goal? Four cells and each has only ½ of the genetic material? Is the genetic material the same as each of the other cells?
If not all of these cells have the same genetic information, is that bad or good? Why?

14. Cheat / Hint:

15. Meiosis NOT Mitosis Used to create a cell that has ONLY 50% of DNA
Happens in the SEX ORGANS
Allows for different combinations of DNA

16. MITOSIS MEIOSIS -my-TOES-es -happens all over the body
-start with a “normal” body cell (100%) and end with TWO “normal” cells (100% each)
-exact copy
-my-OH-sis
-happens only in ONE place (sex organs)
-start with a “normal” body cell (100%) and end with several sex cells (50% each)
-allows for different combos of genes…and that helps strengthen the species.
-Sperm = boys; egg = girls

20. B.
Nucleus C.
Chromosome A.
CELL D.
DNA E.
A gene

22. Chromosome = a package of genetic information that can be passed from parent to offspring.
Gene = one SET of alleles (one from each parent) about a given trait…example: eye color.

23. Pheno (physical expression) Trait Genes/Alleles Height A a Tall
Chromosomes contain the genetic material of an organism. This genetic material is organized into packets of information called genes. Genes give the instructions for an organism’s traits or physical features.
Pheno (physical expression)
Trait
Genes/Alleles
Height A a
Tall
Stem shape D d
Spiral
Branched-hairy
Root texture G G

24. Mendel: Understanding Inheritance
Gregor Mendel
“The father of genetics”

25. What is Genetics?
GENETICS - is the science of how traits are inherited. In other words, how traits pass from parent to offspring.

26. What are TRAITS?
TRAITS are characteristics (the way we look, are, or think).
For example, being tall or short, blond or dark-haired, brown eyes or blue eyes, light or dark skinned, funny or serious, etc…
Traits are genetic and are passed down from parent to offspring.

27. Who was Gregor Mendel?
Gregor Mendel was an Austrian monk, who lived in the 1800’s.
Mendel conducted thousands of experiments on pea plants to see how traits (shape, color) were passed from generation to generation.
Mendel is known as the “Father of Genetics” for figuring out the basic rules of how traits are inherited.

28. What type of experiments did Mendel do?
Mendel crossed pea plants with different traits (eg. tall & short).
He started with PUREBRED plants (showed same trait for many generations – short parents had short offspring)
He crossed a tall parent with a short parent to see what the offspring plants would look like.

29. What happened? The 1st generation of offspring were ALL tall!
The short trait was “lost” – it had disappeared.
In the 2nd generation, the “lost” short trait reappeared in ¼ of the offspring. (Even though neither parent was short!)

30. Mendel tested MANY traits – and found that one form of the trait was always “dominant” in the first generation of offspring, but that the “hidden” trait re-appeared in 25% of the second generation.

31. So, what are Mendel’s rules of inheritance?
Mendel figured out that:
Traits are controlled by PAIRS of “factors” (genes) that are inherited from your parents (one from mom, one from dad).
Some factors are “dominant” - they mask or hide the other factor.
(For example, the tallness gene hides the shortness gene in pea plants.)

32. Let’s get the new vocabulary straight…
GENES - are the factors that control an inherited trait.
ALLELES – are the different forms of a gene.
(the TALL and SHORT alleles are the 2 forms of the HEIGHT gene in pea plants)
*We inherit one allele (or form of a gene) from our mom and one allele from our dad, so we have 2 alleles for every gene.

33. Let’s get the new vocabulary straight…
DOMINANT ALLELE - is one whose trait always shows up when the allele is present.
It can mask or hide the other form of the trait.
It is shown with an upper-case letter, for example “T”.
Example: Tall stems = TT or Tt

34. Let’s get the new vocabulary straight…
RECESSIVE ALLELE – is one whose trait is hidden whenever the dominant allele is present.
It will only show up if BOTH alleles are recessive.
It is shown with a lower-case letter, for example “t”.
Example: Short stems = tt

35. Let’s get the new vocabulary straight…
HOMOZYGOUS - Organisms with 2 same alleles.
HETEROZYGOUS - Organisms with 2 different alleles. Tt Tt

36. Let’s review… TT tt Tt Tt
When you cross the tall and the short plant, the offspring get a Tall allele (T) from the tall plant and a short allele (t) from the short plant.
In the first generation, the dominant TALL allele hides the recessive SHORT allele, so ALL the offspring are tall.
They are all heterozygous. TT tt Tt Tt

37. What happens if heterozygous plants cross?
In the SECOND generation, the heterozygous plants cross and it’s possible to have an offspring with the 2 recessive alleles.
With 2 recessive alleles, the plant will be SHORT, not tall. TT tt Tt Tt TT Tt Tt tt

38. SUMMARY
When studying genetics, we need to take 2 things into account:
PHENOTYPE - an organism’s PHYSICAL appearance.
(3 plants are tall, 1 is short)
GENOTYPE – an organism’s
GENETIC makeup (alleles).
(1 plant is TT, 2 plants are Tt,
and 1 plant is tt) TT Tt Tt tt

39. We will add more as we go. Review and vocabulary Pedigree Parent
Filial / offspring
Generations
Traits
Chromosomes
Dominant (gene)
Recessive (gene)
Always good to remind folks of vocabulary (words for the word wall), but it isn’t necessary to post here.
We will add more as we go.