DNA

Chapter 4 section 3 DNA
Challenge problems. (extra credit if you figure them out! Type it up and pass it in)
Why can wolves and coyotes still mate even though they are different species?

Where is the difference between chimps and humans on their chromosomes?

Objectives: Identify parts of DNA.

Explain how DNA copies itself.

Describe RNA and each type of RNA.

Vocab: DNA

RNA (mRNA, tRNA, rRNA)

Gene

Mutations

Nitrogen base

• When a cell divides the chromosomes are duplicated so each cell has a full copy.
• DNA or deoxyribonucleic acid is located on the chromosomes. See picture on page 112. DNA is super-coiled to fit into very compact chromosomes.

Discovery of DNA, History:

• Rosalin Franklin took a picture of DNA through X-ray.
• DNA is like a twisted ladder called a Double helix.
• 1953- Watson and Crick made a model of DNA after discovering the structure.

What is DNA made up of?

• 1) Nitrogen bases
• Guanine G can only pair with C.
• Cytosine
• Adenine A can only pair with T.
• Thymine

o 2) Phosphate- The sides of the ladder or the backbone of DNA

o 3) Sugar- The sides of the ladder or the backbone of DNA

What would pair with the sequence AATGCCGTC?

How many nitrogen bases?

Because G always pairs with C and A always pairs with T we can find out how much of each nitrogen base is in a given segment of DNA.

What are the percentages of A, T, and C if the percentage of G is 20%?

Copying DNA

• The DNA unzipps- the two strands separate
• Each side becomes a pattern for the new strand
• The new DNA is identical to the parent strand

Genes- Brainstorm- What is a gene? What do we know about genes?

Definition-

• A gene is a section of DNA code that instructs your proteins to assemble in a certain way. (genes build proteins)
• Proteins do everything in your body and give you your traits. Genes are responsible for what kind of protein is built.
• What might happen if the protein was made wrong?

Making Proteins-

• Genes are found on chromosomes (in the nucleus.)
• Proteins are made on ribosomes (outside of the nucleus)
• The code needs to be transferred from the nucleus to the cytoplasm (to the ribosome)
• RNA carries the code

RNA-

• Like DNA but only one strand, one side of the ladder.
• In DNA the sugar is deoxyribose
• In RNA the sugar is just ribose
• In RNA Thymine is replaced with Uracil
• If one side of a DNA strand was ATCTACTTC, what would that be in RNA?

3 kinds of RNA-

• mRNA- messenger RNA

-directs the order that amino acids are assembled to make proteins

• t RNA- transfer RNA

-brings amino acids (the pieces of proteins) to the ribosomes

• rRNA- ribosomal RNA

-Ribosomes are made of r RNA

What happens-

• Protein production begins when mRNA moves into the cytoplasm
• 3 ribosomes then attach
• tRNA brings amino acids (the pieces of proteins) to the ribosome
• In the ribosome 3 nitrogen bases (UAG or C) on mRNA temporarily match with 3 nitrogen bases on tRNA.
• The code carried on the mRNA directs the order in which the amino acids bond.
• This process repeats and repeats till the protein is made.
• The order in which amino acids bond gives each protein a specific role or job. Different orders of amino acids will give the protein a different function.
• There a great picture of the process on page 115. Figure 17.

Controlling Genes

• Not every cell uses all the genes coded in the chromosomes.
• Cells turn off or turn on genes they need or don’t need.

Mutations

• Mistakes in copying DNA (Happens mostly in sex cell formation, meiosis)

Results- Non-function of genes

• Extra chromosomes
• Advantage (the protein could work better)
• Mutations are the raw material for natural selection

How do we get mutations?

· Natural mistakes in copying

· X-rays, sunlight (UV rays), chemicals, carcinogens