The most astonishing thing about life is…

Every single living thing on the face of the earth is made of the same 20 amino acids organized and directed by variations of the same molecule, DNA.

Life Science CONTENT STANDARD C:

As a result of their activities in grades 9-12, all students should develop understanding of

1. The cell2. Molecular basis of heredity3. Biological evolution

THE CELL

Cells store and use information to guide their functions.

The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires.

If just one of the 10 to 100 trillion cells in your body were the size of a baseball park, the average bacterium would be the size of a pitcher’s mound, and the average virus would be the size of a baseball.

E.COLI

THE CELL

Cell functions are regulated. Regulation occurs:

through changes in the activity of the functions performed by proteins

through the selective expression of individual genes.

This regulation allows cells to respond to their environment and to control and coordinate cell growth and division.

THE DNA MODEL

DNA model alone can be used to show (or to allow for the discovery of) all the features of DNA that are important in grades 5-12:

That DNA is made up of four different nucleotides

The nucleotide parts: sugar, phosphate, and base

DNA model alone can be used to show (or to allow for the discovery of)

That the double helical structure: derives from the shapes and bonding of the nucleotides , and occurs only when two DNA chains join base to base and are antiparallel

QuickTime™ and a decompressor

are needed to see this picture.

Replication of DNA

by strand separation and laying down ofnew nucleotides along the separated strands.

DNA model alone can be used to show (or to allow for the discovery of) …

The weak bonds that form between complementary bases

The strong bonds that form between the sugar and phosphate molecules in the DNA backbone

That the helices unzip readily due to the weak bonds between complementary bases while the strands remain intact due to the strong bonds of the backbone.

The Energetics of bond breaking and bond formation

DNA model can be used to show (or to allow for the discovery of)…

Transcription of DNA message into an RNA copy (mRNA or messenger RNA)

Its coding function - how sequences of nucleotides can act as a code for sequences of amino acids in protein molecules

Each combination of threenucleotides (A G C or U)is the code for a particularamino acid.

Either UUU, or UUC, is the code for the topleft amino acid, phenyl-alanine

SCALE

It can be used to dramatize scale: e.g. if all the DNA in only one human cell were stretched out in one long strand it would be about 1 meter long. If the same amount were represented by the model and similarly stretched out, it would be about 149,668 km (or 93,000 miles) long.

The antiparallel directionality of the complementary DNA strands

QuickTime™ and a decompressor

are needed to see this picture.

Mutation - how information is encoded in DNA molecules and how it is modified by mutation: how its language changes – evolves – over the generations

NUCLEOTIDE TO GENOME

The model can be used to demonstrate or elicit several of the Basic Science Process Skills

Grades 5-8

OBSERVING

USING SPACE-TIME RELATIONSHIPS Symmetry, mirroring, describe directions, spatial arrangements

MEASURING Estimation of size, scale

COMMUNICATING

PREDICTING Based on observations measurements and inferences about relationships

INFERRING

THE INTEGRATED PROCESSES

FORMULATING HYPOTHESES DEFINING OPERATIONALLY EXPERIMENTING