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Sunday, November 21, 2010

Apologia Biology, Module 7, Cellular Reproduction and DNA

Quizlet Vocabulary Game, M7 
M7 Recap Blog Post at Sahm-I-Am

(1) p. 197-198, Experiment 7.1, DNA Extraction
Our class did this experiment last year.  (See our results)
Here are instructions if any other blog readers need them, and an instructional video.
►And just for fun, you can try this DNA Extraction Virtual Lab.

This is Applie's video below from when her class did this, and here is her Module 7 post.


(2) p. 198b-200, Protein Synthesis - Part 1: Transcription
"Synthesis" means the making of or production
The point of the next 2 sections is to show how proteins are made from DNA.
Cells synthesize, or make, proteins that result in the traits that DNA gives us.  The cell's genes determine what kinds of protein a cell will make, which determines the job of that particular cell.

A scribe is someone who writes down a copy. You can see the word scribe in transcribe, and script in transcription. Transcription means to copy or transcribe. 
Something called RNA is what helps make the copy of DNA, which is in the nucleus of the cell.   RNA looks like DNA, but it ends up being only a single strand of nucleotide bases. 

The differences between DNA and RNA are:
DNA: has nucleotide base pairs of cytosine & guanine, and adenine & thymine.
►See diagram of DNA strand. (source)
RNA: has individual nucleotide bases of cytosine, guanine, adenine, and uracil, but they are not in any particular order yet.  They will match up to corresponding DNA nucleotides so they will be in the correct order for transcription (copying)
--There are two nucleotides that are different - uracil in RNA, and thymine in DNA.
Uracil in RNA will match up to adenine in DNAAdenine in RNA will match up to thymine in DNA, so U-A, and A-T.
DNA: has deoxyribose (on the "rail" of the "ladder").
RNA: has ribose.
DNA: is twisted in a double helix of paired nucleotides.
RNA: usually in a single strand of joined nucleotides.

►See diagram of DNA and nucleotides.
Only a certain section of DNA will be copied.  As this section of the DNA strand unwinds, individual RNA nucleotides match up to compatible DNA nucleotides and take a "negative snapshot" of the DNA code.  For example, if the DNA has a nucleotide of guanine, an individual nucleotide of RNA cytosine will match to it.  If the DNA has a nucleotide of adenine, an individual nucleotide of RNA uracil will match to it.
Before, the RNA nucleotides were individuals, and not in a strand since they had to match up to the DNA in the correct order.  Now they are a "negative" copy of the DNA, and will be used by the ribosome to make a protein.
This is copying, or transcribing the DNA code.


(3) p. 201- 204, Protein Synthesis - Part 2: Translation

Transcription and Translation.  A polypeptide is a chain of amino acids.  Poly means many.

After the RNA "negative" of the DNA is made, the RNA takes this negative out of the nucleus and into the cytoplasm to a ribosome.  Because of this, it is called messenger RNA, or mRNA
Near the ribosome is a different kind of RNA called transfer RNA, or tRNA.  This tRNA contains a special sequence of three nucleotides called an anticodon.
A special sequence of three nucleotides on mRNA is called a codon.
The codon and anticodon aren't just any three nucleotides, but certain various combinations.

The tRNA is bonded to an amino acid, but only a certain type of amino acid will bond to a certain sequence of three nucleotides in the tRNA.
For example, if the three-nucleotide anticodon is made up of uracil, uracil, and cytosine, the tRNA is bonded to the amino acid lysine.  (p. 202 shows a few more combinations).
A codon on mRNA attracts a specific amino acid.  Then the tRNA links up to the mRNA.

After the tRNA links up to the mRNA, the amino acids on each of the tRNA anticodons bind together to make a protein.
The chain of amino acids that make a protein is called a polypeptide. (poly- means many)
(The first 30 seconds of this video are the same as a video already posted, but good to see it again.)

Learn the difference between mRNA codon and tRNA anticodon, and how a chain of amino acids form a protein.  A stop codon is a special codon that signals the stopping point for translation.
Learn which codon is the starting point for Translation (which 3 letters).

Through studying DNA, a man realizes only God could have created all this!

►To practice what you've learned, go to the DNA Workshop
Click on DNA Workshop Activity, then in the pop-up window on the top right, click on Protein Synthesis.
Follow the directions to first build RNA, then match tRNA anticodons to mRNA codons to build proteins from the amino acids.
If you don't understand this, go back and watch all the above videos, and re-read the textbook.   


(4) p. 205-211a, Mitosis: Eukaryotic Asexual Reproduction

Exp. 7.2, Mitosissince we do not have a microscope, watch/read what is posted here.

Mitosis is the process of cells splitting and multiplying, for repair of cells, or growth of new cells from existing cells.  
This is asexual reproduction.

Mitosis is the growth of new cells, either to replace damaged cells, or for a growing person or unborn baby.
But before Mitosis begins its 4 stages, the DNA that is in the nucleus must duplicate itself into sister chromatids, then coil up into chromasomes.

Exp. 7.2, Mitosis
►Watch this video of Mitosis.  Click Animation.
[If you need to, press your F11 key to make the screen larger. Sometimes clicking F11 while in a different tab works better.]

►After watching the animation, click Tutorials at the bottom.
Below that, 5 Interactive Tutorials are listed:   
Roles of Mitosis, Overview of Mitosis, Cell Cycle, Stages of Mitosis, and Summary.    
Do all except the middle one, the Cell Cycle.  Mastering these is important.

Learn the 4 phases of Mitosis, and briefly what each one does.  You can remember their order by the acronym PMAT.  (Interphase is not a phase of mitosis; it is an 'in-between' phase.)  
After completing the Summary, click on each cell to see descriptions of each cell.
►Fill in this printable Study Sheet for Mitosis.

►This will help you understand what you are drawing & labeling in Fig. 7.6, p. 208 which is also your assignment for today.
If you don't understand this, go back and watch all the above videos, and re-read the textbook.   


(5) p. 211-213a, Diploid and Haploid Cells
--All living things have different numbers of chromosomes.  An onion has 16 chromosomes in each cell; a horse has 64; and a carp has 104.
--Humans have 46 chromosomes in each cell.  The chromosomes are in pairs, so humans have 23 pairs in each cell.
Each pair consists of similar types of chromosomes, and therefore they are called homologous chromosome pairs, or homologous pairs.  Homo- means same, but homologous means similar, but not identical.
Each chromosome is attached to its sister chromatid (its duplicated chromosome) at the centromere, giving them their X shape.  Two sets of these make a pair of similar, homologous chromosomes.  XX.
--The 23rd pair of chromosomes are chromosomes that determine sex.  In a female these are both X chromosomes, or XX, but in a male, they are XY.  So in males, the 23rd pair is not homologous.
►See image of Human Chromosomes

Read carefully.
--When a cell's chromosomes come in pairs, it is called a diploid cell.  XX, XX, etc.
--Cells with chromosomes that do not come in pairs are called haploid cells.  A haploid cell has only one representative of each chromosome pair.  X, X, etc.
Cells can have 23 pairs of chromosomes, or 23 chromosomes, depending on what phase the cell is in.

There is also a diploid number and a haploid number.  This can be rather confusing, but read carefully:
--The diploid number represents the total number of chromosomes in 1 cell or counting both partners in the pair.  In other words, the total number of chromosomes in a diploid cell.  46.
--The haploid number is the number of chromosomes in a haploid cell.  23.  Makes sense, right?
But it is also the number of homologous pairs in a diploid cell.  23.

►►So how can a diploid cell have a haploid number?  A diploid cell has homologous pairs, but a haploid cell does not have any pairs.  So how can this be?
►It's like saying there are 46 people at the party, and 23 couples.  But 23 is also the number of boys.

This is not a haploid cell, but a haploid number.  A haploid number is the number of chromosomes represented by one chromosome from each pair in the organism.  So in a human haploid cell, there is only one chromosome from each pair, equaling 23; in a human diploid cell, one chromosome from each pair will still be 23.
(Thanks to the teachers at Apologia for being willing to email me several times until my brain finally got it!)


(6) p. 213-218a, Meiosis: The Cellular Basis of Sexual Reproduction
The purpose of meiosis is for sexual reproduction.  
It is the process by which a diploid cell forms a haploid cell called a gamete (eggs and sperm are gametes).

►Watch this video of Meiosis.  Click Animation.
[If you need to, press your F11 key to make the screen larger. Sometimes clicking F11 while in a different tab works better.]

--After watching the animation, click Tutorials at the bottom.
--Below that, 5 Interactive Tutorials are listed:   
Homologous Chromosomes, Meiosis I, Meiosis II, Comparing Mitosis and Meiosis, and Summary.
Mastering the first 4 are important.
►Use this comparison printable Study Sheet for Meiosis.  You will be able to fill this in after you complete Comparing Mitosis and Meiosis, but you should do all the first 4 Interactive Tutorials to be able to understand this.
►Watch this video to be able to answer the last question about Recombination.
This is why parents can have children that look so different from one another.
These haploid cells (that were produced by diploid cells) will have only 23 chromosomes (one from each pair), and are the cells that determine sex.  These are called gametes.  Gametes are the eggs and sperm.
After an egg and sperm unite, the resulting cell is called a zygote.  The zygote now is a diploid cell with 46 chromosomes (or 23 homologous chromosome pairs).
The zygote will multiply again and again by mitosis (not meiosis), forming a baby.

After you understand meiosis, here is a fun video to watch.  =)
The DNA first coils up into chromosomes (see image or Fig. 7.4, p. 205).


(7) p. 218-222, Viruses
Learn The Lytic Pathway (or Lytic Cycle) for cells in general, (not just the one for bacteria in Fig. 7.14).
►Read the paragraph on p. 219 that ends in "This process is called the lytic (lih' tik) pathway."
Sorry about the green flashes, etc.  This video must have a virus, hehe!

The virus transcribes and translates.  Transcription and Translation.
This is how the cell reproduces the virus.  The virus cannot reproduce itself.

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