DNA: The Regulation of LifeDNA: The Regulation of Life

Master Program of the CellMaster Program of the Cell

DNA – Deoxyribonucleic DNA – Deoxyribonucleic Acid – The molecule Acid – The molecule found in the nucleus that found in the nucleus that contains the genetic contains the genetic code for an organism.code for an organism.

1953 – James D. 1953 – James D. Watson and Francis H. Watson and Francis H. C. Crick made the model C. Crick made the model of the DNA molecule.of the DNA molecule.

Watson and Crick Watson and Crick figured out the model by figured out the model by using research done by using research done by Rosalind Franklin.Rosalind Franklin.

Gene – A section of the Gene – A section of the DNA that has the genetic DNA that has the genetic code that controls a code that controls a particular traitparticular trait

Fun Fact: If the information Fun Fact: If the information in your DNA were written out in your DNA were written out in English it would fill in English it would fill 400,000 pages of print with 400,000 pages of print with an average of 500 words per an average of 500 words per page. page.

That is about 1,000 books That is about 1,000 books full of information. Even full of information. Even though a Chimpanzee’s though a Chimpanzee’s DNA is 97% the same as DNA is 97% the same as a human’s, how much a human’s, how much information is in that 3% information is in that 3% difference?difference?

Even though it contains Even though it contains all this information, it all this information, it consists of 0.0007% of consists of 0.0007% of your body’s weight.your body’s weight.

Nucleus – The control Nucleus – The control center of the cell. It has center of the cell. It has to store, maintain, and to store, maintain, and retrieve DNA.retrieve DNA.

Double Helix – The Double Helix – The twisted ladder structure twisted ladder structure of DNAof DNA

Chromatin – All the DNA in Chromatin – All the DNA in the Nucleus. The double the Nucleus. The double helix DNA molecule wraps helix DNA molecule wraps around protein “spools” to around protein “spools” to take up less space (A). take up less space (A).

This is the form of DNA This is the form of DNA for most of the cell’s life.for most of the cell’s life.

Chromatid – The Chromatid – The identical copies of the identical copies of the chromatin that the cell chromatin that the cell makes in s-phase of makes in s-phase of interphase.interphase.

Chromosome – An Chromosome – An individual chain of individual chain of chromatin that is coiled in chromatin that is coiled in long tube-like structures long tube-like structures (B), (B),

… … those tubes are then those tubes are then coiled into another tube-coiled into another tube-like structure (C), and like structure (C), and coiled again to make up coiled again to make up the chromosomes (D) that the chromosomes (D) that we see under the we see under the microscope during mitosis. microscope during mitosis.

The letters A-D denote The letters A-D denote the four different coiling the four different coiling of the DNA to make it as of the DNA to make it as compact as possible compact as possible during mitosis.during mitosis.

The “legs” of the ladder The “legs” of the ladder are made of a phosphate are made of a phosphate “backbone” and a sugar “backbone” and a sugar base. Each “rung” of the base. Each “rung” of the ladder is made of 2 ladder is made of 2 nitrogen bases.nitrogen bases.

The 4 nitrogen bases The 4 nitrogen bases are Adenine (A), are Adenine (A), Thymine (T), Cytosine Thymine (T), Cytosine (C), and Guanine (G).(C), and Guanine (G).

Adenine (A) ALWAYS Adenine (A) ALWAYS pairs with Thymine (T)pairs with Thymine (T)

Cytosine (C) ALWAYS Cytosine (C) ALWAYS pairs with Guanine (G)pairs with Guanine (G)

These bases are put These bases are put together to make up the together to make up the “genetic code.” Each “genetic code.” Each group of three represents group of three represents an amino acid. an amino acid.

Special groups indicate Special groups indicate a start or end of the a start or end of the sequence.sequence.

The Activities of DNAThe Activities of DNA

DNA ReplicationDNA Replication – The – The copying of DNA before the copying of DNA before the cell splits through mitosis. cell splits through mitosis.

This needs to be exact This needs to be exact and if it is not, the cell and if it is not, the cell will not work as efficiently will not work as efficiently or die.or die.

StepsSteps

The double helix is The double helix is “unzipped” by separating “unzipped” by separating the bond between the the bond between the nitrogen bases nitrogen bases (nucleotides). (nucleotides).

This is done by, the This is done by, the enzyme, DNA helicase.enzyme, DNA helicase.

The appropriate nitrogen The appropriate nitrogen bases (nucleotides) are bases (nucleotides) are placed in the correct placed in the correct pairing (A-T and C-G). pairing (A-T and C-G).

This is done by, the This is done by, the enzyme, DNA enzyme, DNA polymerace.polymerace.

All of the missing parts All of the missing parts of the phosphate-sugar of the phosphate-sugar backbone are filled in. backbone are filled in. This is done by, the This is done by, the enzyme, DNA ligase.enzyme, DNA ligase.

This results in two This results in two identical molecules of identical molecules of DNA. DNA.

RNARNA – Ribonucleic Acid – – Ribonucleic Acid – Performs various tasks that Performs various tasks that need the information on the need the information on the DNA and is a single strand DNA and is a single strand instead of a double strand.instead of a double strand.

RNA uses three of the RNA uses three of the same bases, but it uses same bases, but it uses Uracil (U) instead of Uracil (U) instead of Thymine (T)Thymine (T)

RNA Transcription – RNA Transcription – The copying of a portion The copying of a portion of DNA into a RNA form of DNA into a RNA form

StepsSteps

The DNA is untwisted The DNA is untwisted and “unzipped” and “unzipped”

This allows the copy of This allows the copy of the DNA, which is called the DNA, which is called RNA, to be made. This RNA, to be made. This is done by, the enzyme, is done by, the enzyme, RNA polymerace.RNA polymerace.

The DNA is “zipped” and The DNA is “zipped” and re-twisted.re-twisted.

Types of RNATypes of RNA

Messenger RNA (mRNA) Messenger RNA (mRNA) is used to carry a particular is used to carry a particular genetic code from the DNA genetic code from the DNA to a ribosome to make a to a ribosome to make a protein.protein.

Transfer RNA (tRNA) Transfer RNA (tRNA) collects free amino acid collects free amino acid molecules and carries molecules and carries them to the ribosome.them to the ribosome.

Ribosomal RNA (rRNA) Ribosomal RNA (rRNA) are part of the structure are part of the structure of the ribosome of the ribosome themselvesthemselves

Constructing a ProteinConstructing a Protein

When there is a need for When there is a need for a certain protein, the cell a certain protein, the cell “looks up” how to make “looks up” how to make that protein (on the DNA)that protein (on the DNA)

The cell makes a copy The cell makes a copy of this code in the form of of this code in the form of mRNA by the process of mRNA by the process of transcription.transcription.

The mRNA is The mRNA is transported out of the transported out of the nucleus to a ribosome.nucleus to a ribosome.

The mRNA is fed The mRNA is fed through the slot in the through the slot in the ribosome.ribosome.

The tRNA brings the The tRNA brings the amino acids that amino acids that correspond to the code correspond to the code on the mRNA.on the mRNA.

The ribosome links the The ribosome links the amino acids together into amino acids together into a protein chain.a protein chain.

Translation - The Translation - The process of synthesizing process of synthesizing proteins from the RNA proteins from the RNA pattern pattern

After the protein is After the protein is assembled, other assembled, other proteins fold it into its proteins fold it into its proper shape. proper shape.

The average protein is The average protein is made of 300-450 amino made of 300-450 amino acids and can be made acids and can be made in about 3 minutes. Is in about 3 minutes. Is this a random process?this a random process?

We know what all of the We know what all of the coded sequences on the coded sequences on the DNA are (A, T, C, G), but DNA are (A, T, C, G), but we still do not know what we still do not know what they do.they do.

Errors in ReplicationErrors in Replication

Mutations – Small Mutations – Small random changes in the random changes in the DNA codeDNA code

PolydactylyPolydactyly

Albino AnimalsAlbino Animals

Two-headed CowTwo-headed Cow

Webbed ToesWebbed Toes

Skin PigmentSkin Pigment

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These occur during These occur during replication when there is an replication when there is an extra nucleotide, a extra nucleotide, a nucleotide forgotten, nucleotide forgotten, improper base pairing, or improper base pairing, or physical damage.physical damage.

If this occurs in a vital If this occurs in a vital gene it will cause death of gene it will cause death of the cell, but if it is not it the cell, but if it is not it could cause a deformity in could cause a deformity in the organism or the organism or malfunction in the cell.malfunction in the cell.

What do DNA and RNA stand for?What are the names of the two scientists

who made the model of DNA? Who was the scientist that provided all the information for the model?

What is the difference between chromatin, chromosomes, and chromatids?

What are the names of the four nitrogen bases that make up DNA? Which ones go together?

What are the steps of DNA replication.Which nitrogen base is NOT used in RNA?

What replaces it?What are the steps to transcription (the

making of mRNA)?

What does mRNA do? (Where does it move to and from to do this?)

What does tRNA do?What are the steps for translation (the

making of a protein)?