Tuesday, December 8, 2009

DNA/GENETICS/PROTEIN SYNTHESIS

GENETICS
IS THE STUDY OF HOW TRAITS ARE PASSED ON.


HEREDITY
IS THE PASSING OF TRAITS FROM PARENTS TO OFFSPRING OR BABIES.


DNA - What is it?- (Deoxyribonucleic acid) is the master molecule that contains all the information about the organism's traits and it is found in the nucleus.
-
Your traits are your proteins
- The information found on your DNA is used to make your proteins or your traits.



Mutation-What is it?- any permanent change in the DNA

Possible consequences of mutation- a mutation can lead to illness, can lead to death or no change in the organism

Traits - WHAT ARE THEY?
- your characteristics, for example your eye color, your height, the shape of your nose… Note: Most of your traits are not visible.


DNA -
How is it made?
- DNA is made by linking smaller molecules called nucleotides.

DNA - What does it look like?
- is described as a double helix or twisted ladder.
- DNA is a polymer. A polymer is a large
molecule that is made by linking smaller molecules.
- (Examples of other biological polymers are: starch is made by linking glucose, protein is made by linking amino acids.)


DNA model


Nucleotides
- Each nucleotide is made up of a phosphate, a sugar (deoxyribose) and a base.
- It is the bases that hold together the two strands of DNA using weak hydrogen bonds.
- There are four bases in DNA adenine, thymine, guanine and cytosine.
- Adenine is paired with thymine and guanine is paired with cytosine.

( A---T, G----C)

CHECK OUT THIS ILLUSTRATION OF A DOUBLE STRANDED DNA!




DNA - What is it made up of?
- The DNA is not one continuous molecule.
- It is made of pieces called chromosomes, and each chromosome has thousands of genes.



CHROMOSOME - WHAT IS IT?
- is one molecule of DNA, usually contains thousands of genes and proteins.



GENE - What is it? 
-is a segment or piece of your DNA or your chromosome that is responsible for one of your traits. For example, you have the gene for eye color, the gene for heights.


It is estimated that the average person has about 50 to 100,000 genes!


CHECK OUT THE RELATION BETWEEN GENES AND CHROMOSOMES

GENES ARE FOUND ON THE CHROMOSOMES AND CHROMOSOMES ARE FOUND INSIDE THE NUCLEUS.


Sexually reproducing organisms
- Have a pair of chromosomes that contain genes for the same traits.
- One chromosome received from the mother and the other chromosome from the father.
- On each of your chromosomes, you have two genes for each of your traits.


REMEMBER: at interphase during the cell cycle, before (cell division) mitosis or meiosis, DNA replication occurs or the DNA copies itself.
- This event is very important in order for the CELL to have a new set of chromosomes for the new cell(s).


During DNA replication
- an enzyme breaks the hydrogen bonds between the nitrogen bases that hold the the two strands together, thus opens up the DNA molecule.
- Each side of the DNA molecule serves as a template or pattern for copying a new strand.

Let us check out this event. BUILD A DNA MOLECULE. Click the link below!!


"INTERACTIVE DNA REPLICATION 1"




CHECK OUT THIS ANIMATION

"DNA REPLICATION" (advance)


How is DNA replication initiated?
- DNA replication begins when an enzyme opens the DNA and each of the old strands is used as a template or a pattern to copy a new strand. (A----T, G----C) Replication is necessary during interphase before the cell undergo mitosis or meiosis when the cell is replicating.


Question: If information on the DNA is information on how to make your proteins, how does this information get to the protein factory or the ribosome?

Answer: This information is sent through a mRNA.

mRNA - What is it?
- The DNA makes a copy of the gene that it wants to express and this copy is called mRNA. It is the mRNA that leaves the nucleus and carries the genetic information to the ribosome for protein synthesis.

AMAZING!!! This DNA is making an RNA copy of one of its genes.
(transcription)















Check this out!
  • The RNA has three bases in common with the DNA. Like DNA, RNA has A (adenine), G (guanine) and C (cytosine. However, the RNA does not have T (thymine), instead it has U (uracil).
  • DNA has deoxyribose as sugar and RNA has ribose.
  • DNA is double stranded and RNA is single stranded.



A FEW QUESTIONS ABOUT WHAT YOU'VE LEARNED.....

What is a mutation?

  • A mutation is any change in the DNA.

Are all mutations bad?

  • Most mutations are deadly. However, some mutations can help the organism survive changes in the environment.
  • According to the theory of evolution, the diversity of living things that exist today is the result of mutations and sexual reproduction.


What happens to the information on the DNA?

  • The information on the DNA is used to make the organism's proteins


How does the DNA get the information for protein synthesis to the protein factory or the ribosome?



  • The DNA makes a mRNA copy of a gene it wants to express and send this copy to the protein factory, the ribosome. (Although the DNA has the information on how to make all of your proteins, it is not making them all at the same time. The DNA is very conservative; it only makes what it needs when it needs it.)


Why doesn't the DNA itself carry the message to the protein factory or the ribosome?

  • The DNA contains thousands of genes it is much too big to fit through the pores or the holes of the nuclear membrane.
  • If the DNA migrates or moves to the cytoplasm, it can be attacked by special enzymes called nucleases.
  • Additionally, if the mRNA gets damaged, the master copy, the DNA simply makes another mRNA.

Most of the time, the cell is not replicating or copying its DNA. It is expressing its genes or making its genes' products. That is, the information on the DNA is being converted into proteins.



DNA to RNA to ProteinsBold- Transcription is the copying of a DNA into mRNA and this takes place in the nucleus.- Note: RNA does not have the base thymine instead it has uracil. This is the order of the base pairing. (A------U, G------C) The RNA has ribose as sugar and is single stranded.

- Translation is converting the mRNA into an amino acid sequence or protein and this takes place at the ribosome.
- Every three bases or letters represents a CODON. Each codon codes for or represents particular amino acid. For example, UUU codes for the amino acid PHE
- Information on the DNA is information on how to make your proteins.
- Example of proteins are: enzymes, antibodies and hormones.

"INTERACTIVE PROTEIN SYNTHESIS"



Remember: All
proteins have specific shape. An enzyme that breaks down starch will not be able to break down protein because they have different shape. An antibody against the measles will not fight chicken pox because they have different shape. The sex hormone testosterone will not interact with the receptor for the hormone insulin because they have different shape.

Traits - WHAT ARE THEY?
- your characteristics, for example your eye color, your height, the shape of your nose…
- However, the expression of your traits can be modified by environmental conditions.

- EXAMPLE: two identical twins one grows up in America and the other grows up in Jamaica. With little knowledge in genetics, it is very easy to infer that these twins will not look identical. The one who grows up in Jamaica will be darker because of the sun and may be shorter and slimmer because of availability and types of food. While the one in the US will be lighter because of less exposure to the sun and may be taller and chunky because food in the states have growth hormones.


Questions:

What is DNA?
  • DNA is the master molecule that has all of the information about the organism's traits.

How are the bases paired in DNA?

  • A___T, G____C

Where do you find DNA inside the cell?
  • DNA is found in the nucleus.

Why is necessary for the DNA to make a RNA copy?
  • The DNA is too big and it cannot fit though the pores or the holes of the nuclear membrane and also this is done to prevent the DNA from being attacked by nucleases or enzymes that break down DNA.

What is the relation between genes and chromosomes?

  • On each chromosome, there are thousands of genes. A gene is a piece of your chromosome that codes for one of your traits.





How are the bases paired in RNA?
  • A___U, G____C

Explain transcription.
  • Transcription is the process where the DNA is being copied into RNA. This event takes place inside the nucleus.


Explain translation.
  • Translation is when the mRNA is being converted to an amino acid sequence or protein. This event takes place at the ribosome.

Explain differentiation.

  • Differentiation is when your cells become specialized. For example, your bone cells and your skin cells they both have the same DNA. However, they each focus on different genes and this allows them to become different cells.

Who do we get our genes from?
  • We get our genes from our parents.

List three differences between DNA and RNA.
  • DNA is double stranded and RNA is single stranded.
  • DNA has thymine as a base and RNA has uracil.
  • DNA has deoxyribose as a sugar and RNA has ribose.

NOTE
Information in the DNA is information on how to make your proteins. Any change in the DNA can lead to a change in the protein.


LET US TAKE A SLIGHT DETOUR.
-Restriction Enzymes are bacteria enzymes that are used to cut double stranded DNA at specific locations called restriction sites. The locations of restriction sites on the chromosomes are not the same for everybody. However, since we inherit our chromosomes from our parents, we also inherit our restriction sites from our parents.


Restriction enzymes are the cutting tools in genetics! 

What does that mean?
-If the same restriction enzyme is used to cut your DNA and your parents DNA, the size of the pieces that are generated or made will be the same or similar.


How does this information help anybody?
-This information is used to help determine relationship. It is used to determine paternity. (Who’s the baby's daddy?) It is also used in crime scene investigation. It is commonly known as the DNA test.

This is how it works.
-DNA samples are collected from both the father and the baby. Both samples are treated with the same restriction enzymes. Then they are placed in a special apparatus (machine) called gel electrophoresis, which separates the pieces of DNA based on their size and create visual pattern. If this is the father of the baby, the patterns that are created by the baby's DNA and the father's DNA will be similar.

Gel electrophoresis separates molecules based on their sizes.

Want to learn more?


Check out this link!


"RESTRICTION ENZYMES/GEL ELECTROPHORESIS"


2 comments:

Maya Omeragic said...
This comment has been removed by the author.
Maya Omeragic said...

nice