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Antibiotic Resistance:
Case Study



UNIT 5: DNA Replication and Protein Synthesis

What you should know:

DNA is made of two strands of nucleotides twisted into the form of a double helix. Each nucleotide in DNA is made of the sugar deoxyribose, a phosphate group, and one of four nitrogen bases. The two strands of DNA are complementary. Adenine pairs with thymine, and cytosine with guanine. Before a cell can divide it must replicate it's DNA so that when it splits, each daughter cell can have a copy of the DNA. In DNA replication, enzymes split the double helix apart and add nucleotides to the new copy of DNA. After DNA has replicated there are two identical strands of DNA.

The instructions needed to make proteins are coded in the nucleotides that make up a gene. The instructions in the genes are transferred to an mRNA moleucle during transcription. The mRNA molecule is complimentary to the gene on the DNA. mRNA is a messenger that carries the genetic code out of the nucleus to the cytoplasm where a ribosome attaches to the mRNA and translates the code into a protein. During translation, tRNA molecules bring the specific amino acid that the mRNA coded for. tRNA molecules have anticodons that are complimentary to the codons in mRNA. By combining amino acids in the order that the mRNA coded for, a protein is made. The genetic code used by most organisms to translate mRNA is used by most organisms.

Alterations in your DNA are mutations. Mutations can arise from errors in replication, or cell division. Mutations are also caused by chemical agents such as radiation or carcinogens. Mutations can have no effect, change the type of protein, or make the protein non-functional. Mutations can be passed on to children. Cancer is a type of mutation that can be caused by radiation or exposure to chemicals such as the carcinogens found in cigarette smoke.

How you make sense of things:

Initial EPE before lab

Observations you make
in your daily life:

Patterns you notice:
Explanations for the patterns:

You look like your family members.

You have some traits that your mom has, and other traits that your dad has.

Identical twins look exactly the same.

If you don't wear sun screen and stay in the sun too long you are at risk for skin cancer.

Smoking often leads to lung cancer.


Your traits are controlled by your DNA that you get from your parents.

Cigarette smoke contains harmful chemicals that give people cancer.

Cancer claims the lives of many people and is difficult to cure.

You look like your family because you have similar DNA.


Goal EPE after lab

Observations you make
during lab:

Patterns you notice
in your data:

Explanations for the patterns:

Making DNA Models
DNA is made up of sugar, phosphate and nitrogenous bases which we represented with cut-outs of construction paper.

The nitrogenous bases (made with construction paper) have different shapes that only allow adenine to pair with thymine, and cytosine to pair with guanine.

DNA is a double helix.

To copy the DNA the two strands of DNA separate and new nucleotides (made of construction paper) are brought in to match up with their complimentary bases to create two identical DNA molecules.

The DNA double helix splits apart and RNA nucleotides are matched up to their complimentary bases to form an mRNA.

tRNA molecules match their anticodons to the codon on the mRNA and drop off their amino acid to the growing polypeptide chain that will become the protein.

Sci-Fly Mutation Activity
Changing one of the nitrogenous bases in the DNA makes that strand mutated.

When the codon is translated into an animo acid it may not be the same amino acid that the original DNA would have coded for.


Making DNA Models
The complimentary nature of DNA allows it to replicate an exact copy of itself and also allows it to make mRNA.


Sci-Fly Mutation Activity
Mutations in DNA can have no effect on the amino acid or can change the amino acid.

Fly's with mutations may still appear normal, or may also appear abnormal if the mutation caused a change in the amino acid that was coded for.

Making DNA Models
DNA replication must occur before a cell splits to ensure that each daughter cell gets a copy of the DNA.


Sci-Fly Mutation Activity
Mutations occur when DNA is altered which can result in a non-functional or altered protein.



What you should be able to do:

1. Describe the structure and funciton of DNA.
2. Propose possible effects of exposing an organism to radiation and toxic chemicals.
3. Demonstrate how the genetic information in DNA molecules provides instructions for assebmling protein molecules and that this is virtually the same mechanism for all life forms.
4. Describe the processes of replication, transcription, and translation and how they relate to each other in molecular biology.
5. Describe how inserting, deleting, or substituting DNA segments can alter a gene. Recongnize that an altered gene may be passed on to every cell that develops from it and that the resulting features may help, harm, or have little or no effect on the offspring's success in its environment.