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DNA

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Goals and Standards

After completing all activities and assignments in this unit, students will be able to:

• Describe mitosis and meiosis and explain their importance.• Construct and identify the parts of a model of a DNA molecule.• Describe how DNA copies itself.

PA Science and Technology Standards covered in this unit:• 3.1.7B Describe the use of models as an application of scientific or

technological concepts.• 3.3.7C Know that every organism has a set of genetic instructions

that determines inherited traits.

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Vocab: DNA, gene, replication

• DNA – Deoxyribonucleic acid – a chemical in the nucleus of cells that codes and stores genetic information.

• Gene – A segment of DNA on a chromosome that directs the making of certain chemicals, controlling traits that are passed to an offspring

• Replication – creation of new exact copies of DNA to be used in newly made cells

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Vocab: Mutations

Mutation – a mistake that is made when DNA is copied. This may or may not show a problem in the individual

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Vocab: Mitosis, chromosome, asexual and

sexual reproduction• Mitosis – process that divides the nucleus to

make 2 identical cells• Chromosome – threadlike strands of DNA in the

nucleus that carry the information for all the characteristics of an organism

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Vocab: Meiosis, fertilization, RNA

• RNA – ribonucleic acid – similar to DNA, but one stranded. Leaves the nucleus to make proteins at the ribosomes.

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Vocab: Transcription, translation, amino acid, protein

• Transcription – DNA is copied into RNA

• Translation – RNA is copied into proteins

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What does DNA look like?

A

A

A

T

T

C

GC

G

T

T

A

C

G

Sugar

Phosphate Group

Thymine

Adenine

Guanine

Cytosine

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Characteristics of DNA:1. The sides or “handrails” of the DNA “ladder” are made of sugar and phosphate molecules.2. The “stairs” are made of molecules called nitrogenous bases.3. The 4 nitrogenous bases are:Adenine thymine cytosine guanine4. The nitrogenous bases always match up like this:Adenine and thymineCytosine and guanine5. The two strands of DNA are to each other.

DNA Model Notes

complimentary

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Materials Key

Material DNA Structure

Beads Blue = Adenine

Yellow = Thymine

Green = Guanine

Purple = Cytosine

Red = Sugar

Pipe Cleaners Serve to anchor everything else together

Straws Phosphate groups

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Making your DNA model

First, build a half strand of DNA that looks like this.

Then, match the nitrogenous bases and build the other half of the DNA strand.

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Interphase: When the cell is doing its work

Cell membrane

Cytoplasm

Centrioles

DNA – 2 copies

Nuclear membrane

8 – top left box

Nucleus

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Prophase – DNA starts to appear as chromosomes

ChromosomesNuclear envelope dissolving

Spindle

Centrioles

8 – top right

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Metaphase: Chromosomes line upChromosomes lined up on equator of cell

spindle

centriole

8 – middle left

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Anaphase – Spindle pulls the copies of the DNA to opposite poles

8 – middle right

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Telophase – New nuclear membranes start to appear

8 – bottom left

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Cytokinesis – 2 separate, identical cells

8 – bottom right

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Meiosis vs Mitosis

Mitosis

1. 1 division of the nucleus

2. Makes all other types of cells

3. New cells are identical to original

Meiosis1. 2 divisions of

the nucleus2. Makes sperm

and egg cells only

3. New cells have ½ the number of

Chromosomes as original

A. Involve chromosomes

B. Use prophase, metaphase, anaphase and telophase