The Dance of the Chromosomes

Good to be back!
Big day for most of us yesterday, and so it's taking me a little bit to get the homework up, but if you want to get started, read in your textbook from Ch.3, section 3 - Meiosis (my-O-sis), just pages 68-72 (not the whole chapter.)

Also, hopefully you have not lost your CD, or should I say, See-D! This is to observe over the next week or two.  Remember to water carefully.  Please take notes/pictures/diagrams of the progress your seed is making. 

We have already learned, so very thoroughly, about mitosis, which is when the cell divides, forming an exact copy of itself with an identical set of DNA. Mitosis happens to make new cells to replace old ones, and for growth,  so those new cells  need to be just like the old ones. The question may have  arisen, how then do we get cells to start a new person, who is not exactly like the parent, who is an original creation?  These cells must be different--they need to be halved, with only one of each type of chromosome from each parent, so that when they combine the offspring will have the right number, and the right kind, of chromosomes.  This is MEIOSIS. And so the next lesson is about the chromosomal dance which creates these amazing cells which create  a one-of-a-kind person who is loved by God.

The two vocabulary words you need to know are... HOMOLOGOUS CHROMOSOMES
MEIOSIS

The Big Idea you need to grasp is the purpose of meiosis, which is variety and uniqueness.


And here are three videos:

1, 2, 3...

Here's some vocabulary you need to know:
Copy this to your lab book:
gene - a section of DNA which codes for a particular inherited trait (makes a particular protein which leads to a particular trait)
allele - a "flavor" of a gene
dominant - an allele which will express itself (we use a capital letter)  BOLD
recessive - an allele which will take a back seat if a dominant allele is present (use a lower case letter)  SHY
homozygous- both alleles are the same (BB or bb)
heterozygous - the alleles are different (Bb)
genotype - the genetic makeup
phenotype - the observable traits or appearance

1.Now watch the video:

2.Now do the Punnett Square Worksheet Print out both pages Punnett Square Worksheet

3.Read through Chapter 3, section 2 - Traits and Inheritance

This should keep you busy on your vacation!  But here's a hint: if you want to do your homework speedily, learn the vocabulary first!  It might be obvious, but it bears repeating: When you know what the words mean, you understand the paragraphs so much better! 

Enjoy your week.

Heredity...

This week's homework will be to review Chapter 3, section 1, this time answering all the review questions and doing the math.  (Yea, math!)

1. Know the vocabulary -- any word written in bold type or italicized.  Heredity, Dominant Trait, Recessive Trait, self-pollinating, true breeding, cross-pollinating, characteristic, trait, first generation, ratio.

2. School to Home activity, page 57. Describing Traits

3. Describe step-by-step Mendel's experiments.

4. Math Practice, page 60.  Also fill out the 4th column in Table 1: Mendel's Results  (find the ratios)

5. Answer section review questions 1-7

0

For reference the video we watched in class is here: Mendel's Peas: Experiments that Changed the World

Good Friday...

It's Good Friday today, and not just because there's no science homework.

I hope you get some time to reflect on the goodness of God and his amazing love for each of us, and his determination to face unspeakable suffering for the sake of bringing salvation and reconciliation to the world.  "Behold, what manner of love the Father has given unto us, that we should be called the children of God!" 

...and a joyful Easter to you as well.

Stop and smell the...

Flowers are an important part of many plants. Plants use flowers to make other plants – to reproduce. Flowers have special parts, called stamens and pistils. When pollen from the stamen finds its way down through the pistil, the flower is pollinated, and seeds start to grow. The seeds eventually find their way to the ground, the seeds sprout, and more plants are born.

Plants have all different styles of flowers. Some flowers have patterns on them that guide bees and other insects to the pollen. Wheat flowers are long and stringy, so when the wind blows, pollen can float easily from stamen to pistil. Some flowers even smell like rotting meat to attract flies. The flies land, pick up pollen on their legs, and dust some of it onto the flowers’ pistils. Although flowers have different shapes, colors, and smells, all flowers make seeds to keep the plant population growing.

Every flower consists of a set of adaptations that help to ensure successful reproduction. For example, flowers often have bright colors, attractive shapes, and pleasing aromas. These traits help them attract insects and other animals that
will carry pollen grains from flower to flower. Pollination also occurs by means other than animals carrying the pollen. For some flowering plants, the wind plays an important role in transferring pollen from plant to plant.

The seed-bearing plants that produce flowers are called angiosperms. The flower produces the seeds, each of which contains a new plant embryo. The parts of the flower are usually found in four whorls, or rings. Petals are one of the four whorls. They attract pollinators. Sepals lie outside the petals. They protect the bud.

The reproductive organs, the stamens and pistils, make up the third and fourth whorls and lie inside the petals. A stamen is a male reproductive part. It consists of an anther that is held up by a filament. The anther produces pollen grains. A pistil is a female reproductive part. Its top is called the stigma. It is sticky to ensure that when pollen grains land on it, they stick to it. The middle supporting structure is the style, and the large base is the ovary, where the eggs are produced.
1. Bill Nye - Flowers! video
23 minutes - 23 points!

2.  Go outside and find 7 flowers (different kinds!) -- locate the stamen and the pistil on each flower. 7 points.

3.  Read Chapter 3, section 1 - about Gregor Mendel and his famous flying peas.    20 points.

50 points possible!  

[Do you crave more science videos? Here's "The Biggest Flower in the World": https://www.youtube.com/watch?v=FHaWu2rcP94&list=PL47D0521D98A9EF1D&index=8]

Worksheet & Review

Homework: Using the handout of onion root tip cells under the microscope, cut  the paper into individual cells and sort them into IPMAT [ Interphase, Prophase, etc...] Don't write on the cells, and skip the cells that are really too blurry to tell! Glue them into a circle --around the edges of the circle, like a clock face, in the order of the cell cycle.  This will give us an idea of how much time this plant spends in each stage. Make it neatly done, label each stage, use good paper, and if you do not understand the directions, CALL me!  Do it right or do it over!

 ALSO - READ CAREFULLY!
Count up how many cells are in each stage, and make a table with 3 columns, like this:

	Number  of cells	% time in this stage
Interphase
Prophase
Metaphase
Anaphase
Telophase

 + Cytokinesis

To find the percentage of time in each stage, divide the "Number of cells" by the total number of cells on the page, and multiply by 100.

Add a Title at the top of the page, and a sentence or two of Summary at the bottom.

When you are done, check to see if you followed the directions completely.
 [If your copy of the handout gets messed up, go here: mitosis onion cells image.]

For reference: here is a website that has good pictures and descriptions.  http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html

ALSO< Please turn in your chapter 3 review question & answers on Monday. [note to moms of the younger kids: Feel free to modify the lesson according to your own judgement and time constraints.]

Multicellular organisms constantly need to make more cells!

• Each minute your body needs to make ...oh...about 300 MILLION NEW CELLS! A cell spends most of its life working and growing, breaking down sugars, synthesizing proteins, enzymes, and other macromolecules, but cells inevitably wear out, break down and suffer injuries.
• In addition, as organisms grow and change, they need new cells to make more skin tissue, bone tissue, muscle tissue. These new cells can only come from one place: OTHER CELLS - through the process of cell division, or mitosis.
• For multicellular organisms (like us) cell division allows an organism to grow and develop from a single cell to trillions of cells, and also  to repair and replace cells worn out and used up by everyday life

On Thursday we will finish off our Mitosis unit by looking at photographs of real cells and trying to figure out which stage the cell is in.  By looking at the pictures above, you can see the difference between a diagram and the real thing.

HOMEWORK: Review chapter two - re-read sections 1-3 and answer the end of chapter review questions.  This chapter has covered the cell membrane and how materials pass through it, photosynthesis and respiration, and the cell cycle- how a cell duplicates itself.