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Thursday, May 1, 2014

Biology 101, Chapter 7, The 6th Day – Biology History, Cells, Genetics [post 2/3]

We made DNA! =)
Blog Posts for Chapter 7:
• Post 1/3 Cells
• Post 2/3 - DNA
• Post 3/3 - Genetics

In addition to Biology 101:
• Apologia Biology Exp 7.1, DNA Extraction
Here are instructions if you don't have an Apologia Biology book, and a video.
• Have Your DNA and Eat it Too! (click the pdf links), Our class has done this twice (diff students), so even tho I have 3 new kids, I have 3 who have already done this so we aren't doing it this year.

Other Study Links
 DNA Extraction Virtual Lab.

2. DNA

Four criteria for life:
If something fails to meet even ONE of these, it is not alive.
  1. All life forms contain DNA.
  2. All life forms can take energy from their surroundings and convert it to usable energy for themselves.
  3. All life forms can sense and respond to changes.
  4. All life forms reproduce.
DNA - deoxyribonucleic acidHear pronunciation.  Click on the little speaker.

Apologia Biology Experiment 7.1, DNA Extraction
My previous biology class did this experiment about 3½ years ago.  (See our results)
If you don't have an Apologia Biology book, here are instructions (with explanations of why), and a video below.  (I always like to look at several sources to get a good idea of how and why to do things.)
(1) Pea DNA Extraction

►And just for fun, you can try this DNA Extraction Virtual Lab.
►Read how another blogger's class did this experiment.  Her posts are always fun to read! =)

Of course this DNA is in clumps, or we would never be able to see anything.
In fact, it takes a powerful microscope to even be able to see the chromosomes, which are long strands of DNA in the nucleus that are coiled up and compacted.  See image. (source)

(2) DNA Structure
Note that A and T are linked together, and C and G are linked together.  These letters represent the names for the nucleuotides in DNA.  In DNA, Adenine always links to Thymine, and Cytosine always links to Guanine.
Apples in a Tree, Car in the Garage.  A-T, C-G

How proteins are made from DNA
All the writing below and three videos make up this section.

Part 1: Transcription of DNA
"Synthesis" means the making of or production.  
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. 

(3) Transcription and Translation Overview
polypeptide is a chain of amino acids.  Poly means many.

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.
(Apples in a Tree, Car in the Garage.  A-T, C-G)
►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)

►►DNA vs RNA image (source)◄◄ Read below↓

--There are two nucleotides that are different - uracil (in RNA), and thymine (in DNA).
Uracil in RNA will match up to adenine in DNA.  
Adenine in RNA will match up to thymine in DNA, so A-U, and A-T.
(For RNA, remember Apples Under the tree) 

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 (source).
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. 

Part 2: Translation of DNA
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.

Transfer RNA strands will link to a messenger RNA strand on a ribosome in order to make a protein chain.
Here is how:
The tRNA is already bonded to an amino acid, but only a certain type of amino acid will bond to a certain sequence of three nucleotides in the mRNA.
For example, if the anticodon (a three-nucleotide sequence on tRNA) is made up of guanine, adenine, and adenine, the tRNA is bonded to the amino acid leucine.  This anticodon will only link to a portion of mRNA that has a codon with the sequence of cytosine, uracil, and uracil.  
Each codon (3-nucleotide sequence) on mRNA attracts a specific amino acid. 
So then the tRNA links up to the portion of mRNA that will accept the anticodon that is on the tRNA.

After the tRNA links up to the mRNA, the amino acids on each of the subsequent tRNA anticodons bind together one by one to make a protein. 
►The chain of amino acids that make a protein is called a polypeptide. (poly- means many)

(4) From RNA to Protein Synthesis - how proteins are made

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).
(5) Protein Synthesis: Translation Process

And that is how proteins are made from DNA

(6) DNA Double Helix
How one man realizes through studying DNA that only God could have made all this! =)
"Without DNA there is no self-replication, but without self-replication, there is no natural selection. So you can’t use natural selection to explain the origin of DNA without assuming the existence of the very thing you’re trying to explain!"

Two Types of Cell Reproduction:

A) Mitosis - asexual  reproduction of cells

Mitosis is the growth of new cells, either to replace damaged cells like when you have scraped your arm, or for a growing child, or an unborn baby as it grows.
The replicated cells are identical.  Skin cells replicate skin cells; muscle cells replicate muscle cells, etc.
This is asexual (nonsexual) reproduction.

(7) The Cell Cycle and Cancer - how cells multiply by Mitosis

(9) How DNA is Packaged  After DNA that is in the nucleus duplicates itself into identical sister chromatidsthen it coils up into chromosomesThe X shape you may be familiar with.

(10) Mitosis  He says, "having already replicated..." Because before Mitosis begins, the DNA that is in the nucleus must duplicate itself into identical sister chromatids, then coil up into chromosomes.

(11) Mitosis Animation - also G1, S, and G2 that occur during Interphase.

B) Meiosis - the purpose of meiosis is sexual reproduction. 

-All living things have different numbers of chromosomes.  An onion has 16 chromosomes in each cell; a horse has 64 in each cell; and a carp has 104 in each cell.
--Humans have 46 chromosomes in each cell.  The chromosomes are in pairs, so humans have 23 pairs in each cell. 

The cool process of meiosis is why all humans do not look alike.  =)
Each pair of chromosomes determines many different traits (hair color, hair texture, curly, straight, etc, just to name a few).  There are hundreds of genes on each chromosome!  When parents have children, they contribute one chromosome from each pair, which "cross over" with each other to form new combinations.  The results of crossing over are random, and give more possibilities for each trait a child will have.  Since there are many, many kinds of traits, the possibility of having a child who doesn't look exactly like a parent is great.

Things to know:
--When a cell's chromosomes come in pairs, it is called a diploid cell.  XX, XX, etc.
--Cells with chromosomes that are not 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.

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 that is in a pair is attached to its sister chromatid (its duplicated chromosome), 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

Mitosis results in 2  identical diploid daughter cells, 
and meiosis results in 4 genetically different haploid cells.

►►These videos only show a few pairs of chromosomes in the cells, but know that there are 23 pairs, all exchanging information to produce varied traits.

(12) Meiosis - This is why parents can have children who look so different from one another. 

Mitosis results in 2 identical diploid daughter cells, 
and meiosis results in 4 genetically different haploid cells.

So what happens to the extra haploid cells?  In females, randomly, one of the gametes (eggs) takes up most of the cytoplasm and organelles.  As a result, what gets produced are 3 tiny gametes and one large gamete called the egg.  Only the large one will function properly, and that is the one that gets successfully fertilized by the male gamete (sperm).  The others, if fertilized, will quickly degenerate and die.
►The haploid sperm cell and haploid egg cell fuse to form a diploid cell with 23 pairs of chromosomes, totaling 46.
►This diploid cell, now called the zygote, will begin to multiply and produce many cells by mitosis, forming a baby.  =)

(14) Phases of Meiosis  2²³ = 8,388,608 possibilities! WOW!

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

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