Searching for the “Secret of Life”

Searching for the “Secret of Life”

1. What is the fundamental unit of all living things?

The cell2. Which cellular structure controls

the cell and carries the hereditary information?

The nucleus3. What molecule in the nucleus

carries the code of life?

DNA

1. What is the fundamental unit of all living things?

The cell2. Which cellular structure controls

the cell and carries the hereditary information?

The nucleus3. What molecule in the nucleus

carries the code of life?

DNA

Nucleic AcidsI. DNA

A. Background Info1. DNA is stored in the _______ of a cell2. DNA is the basic substance of heredity.

Heredity is the passing of traits from parent to offspring (baby).

Traits are your physical characteristics (eye, skin and hair color, height, etc)

3. DNA is a molecule that stores and passes on genetic information (traits) from one generation to the next

It is why you look like your parents!

B. Structure1. DNA is made of repeating units

called nucleotides.2. Nucleotides have 3 parts:

a. A nitrogen containing baseb. A 5-carbon sugar called

deoxyribosec. A phosphate molecule

What do you think DNA stands for?DeoxyriboNucleic Acid

Phosphate group

Deoxyribose

Nitrogen-containing base

NUCLEOTIDE (Draw Me!)

3. DNA has 4 different nucleotide bases.

a. Adenine (A)b. Cytosine (C)c. Guanine (G)d. Thymine (T)

Adenine Guanine Cytosine Thymine

Phosphate group Deoxyribose

C. DNA Discovery1. Mid-1800s: scientists knew the

nucleus contained a nucleic acid molecule

2. By 1950, scientists knew what DNA was made of, but didn’t know what it looked like until…

3. 1952, a woman named Rosalyn Franklin took the first pictures of DNA using X-ray diffraction

4. Using the work of Franklin, James Watson and Francis Crick made a model of DNA…

THE DOUBLE HELIX!

D. The Double Helix1. The overall shape of DNA is

described as a double helix (a twisted ladder)a. The “rails” of the ladder are made of

deoxyribose and phosphate molecules.b. The “rungs” of the ladder are made of

the bases A, C, G, T.

2. A simple model of DNA

What holds the bases together to make the “rungs”

of the ladder?

What holds the deoxyribose and

phosphate molecules

together to make the “rails” of the

ladder?

E. Principles of Base Pairing (Chargaff’s Rule)

A. The opposing bases always pair the same:

Adenine (A) pairs with Thymine (T) Guanine (G) pairs with Cytosine (C)

What would be the complementary base sequence for

the strand of DNA below?A C G G T T A C A A T G AT G C C A A T G T T A C T

II. How does DNA control living organisms?

A. DNA contains the instructions to make proteins.

What is so important about proteins?1. Made of 20 different amino acids2. Control many reactions in living organisms3. Used for growth and repair of cells4. Make hormones, enzymes and toxins5. Make you, YOU!

II. A section of DNA that has the instructions to make a specific protein is called a gene

III. RNA: The Other Nucleic Acid What does RNA stand for?

Ribonucleic AcidA. Differences between DNA and

RNA1. RNA contains the sugar ribose

instead of deoxyribose.2. RNA is found in both the nucleus

and cytoplasm. DNA is only in the nucleus.

3. RNA contains uracil (U) instead of thymine (T)

B. Three Kinds of RNA

1.Messenger RNA (mRNA)

a.Copies the DNA code in the nucleus and carries the message to the ribosomes

2. Transfer RNA (tRNA)a. It transfers amino acids to the ribosome

and places them in the correct position in the protein.

2. Transfer RNA (tRNA)a. It transfers amino acids to the ribosome

and places them in the correct position in the protein.

3. Ribosomal RNA (r-RNA)a. Part of the ribosome that is involved in making tRNA

IV. Protein Synthesis Summary (Steps to make a protein)

1. Instructions to make proteins gets copied from DNA to mRNA.

2. The mRNA molecule leaves the nucleus and goes to a ribosome.

3. tRNA brings amino acids to the ribosome where they are joined together to make a protein using the instructions on the mRNA molecule.

V. Mutations1. Mutation is any change in the DNA2. Mutations can happen when:

a. Chromosomes are copiedb. Nondisjunction (chromosomes go the

wrong way in meiosis)c. Exposure to chemicals, X-rays, sunlight

3. Mutations can cause the wrong protein to be made, which usually kills the organism or…