DNA Structure and Function Target 3 1 I












- Slides: 12

DNA: Structure and Function

Target 3 -1 �I can describe and model DNA by correlating its structure and its functions.

What is DNA? �DNA is a huge molecule that contains biological info �Genes = instructions for how to make new cells �Ex) Eye color, height, ear shape, how to digest food �All cells of all living things contain DNA �DNA is shaped like a long, twisting ladder (double helix shape). Inside our cells it clumps itself up into a blob.

DNA Molecule • “Double Helix” shape • Very, very long ladder

Structure of DNA �Nucleotide = building block of DNA molecule � 1 sugar � 1 phosphate � 1 nitrogenous base � 4 types of bases: A, T, G, C �Produced in cells �Link up because of their charges �Sugar = positive �Phosphate = negative

Structure of DNA 1. Backbone - Made of sugar and phosphate parts - Long chain to support the molecule 2. Base pairs - Nitrogenous bases pair up: A/T and C/G - Criss-cross to hold the two half-strands together

DNA Replication �We have the exact same DNA in every cell because DNA is able to replicate itself into exact copies 1. Strand splits down the middle (unzips) 2. Loose nucleotides link up with their complementary pairs 3. End with 2 identical strands

Examples �What would a complementary strand look like in order to match this strand?

Examples • The nucleotides can rebuild the complementary strand by matching up their bases!

Examples �Complete the segments of DNA below by completing the base pairs. 1. AGTTACCCCGCT 2. G C C A T A G G G C 3. G T A A G T A C A A

DNA in Individuals �Only about 0. 01 % of our DNA contains genes �Genes are basically the same for everyone � 99. 9 % of our DNA is “filler” �Repeating sections of base pairs �Repeats are basically the same for everyone, but they will repeat a different number of times �We can identify individuals by looking at how long the repeating filler sections are

Exit Ticket 1. Sketch a strand of DNA and label the backbone and the base pairs 2. Sketch a nucleotide and label the sugar, phosphate, and nitrogenous base 3. Describe how DNA replicates itself 4. Write the complementary strand for: CCAGTAG 5. Do we use genes or filler DNA to identify individuals?