DNA Replication

What does DNA stand for? D = deoxyribo + N = nucleic + A = acid Put it all together and it spells- deoxyribonucleic acid

What is DNA Replication? Process by which- a cell makes a copy of the DNA in its nucleus.

When does DNA Replication occur? Before Mitosis begins- Interphase Cell Division: Stage1- Interphase

Why is DNA Replication an important cell process? Ensures that each daughter cell will have all of the genetic information it needs to carry out its activities. Forming daughter cell DNA (genetic information) Forming daughter cell DNA (genetic information)

History of DNA’s Discovery * 1950’s scientists showed DNA carries all cell’s instructions. * Learned DNA passed from parent cell to its daughter cells. * 1953 James Watson and Francis Crick discovered structure of DNA by stealing and using Rosalind Franklin’s lab notes and pictures. - Revealed important information about how DNA copies (replicates) itself.

Appearance of DNA Looks like spiral staircase or twisted ladder Often called “double helix” helix- shape that twists like threads of a screw

Structure of DNA Sides (DNA Ladder) Rungs (DNA Ladder) Phosphate Sides (DNA Ladder) Alternating molecules of Deoxyribose sugar Phosphate Rungs (DNA Ladder) Made up of pairs of nitrogen bases adenine thymine cytosine guanine Deoxyribose sugar Nitrogen base

Ladder Rungs Letters A, T, G, C Used to represent the four bases that make up ladder’s rungs Nitrogen bases on one side of ladder “match up” in specific way with bases on the other side. Adenine always pairs with Thymine (A-T) Guanine always pairs with Cytosine (G-C) Nitrogen Base Nitrogen base

Pairing pattern of the nitrogen bases key to understanding how DNA replication occurs.

Replication Process Step 1: Two sides of the DNA molecule unwind and separate between paired nitrogen bases on each rung. Like a zipper unzipping

Replication Process Step 2: Nitrogen bases floating in nucleus pair up with bases on each half of the DNA molecule. A always pairs with T G always pairs with C

Replication Process Step 3: Once new bases are attached, two new DNA molecules formed. Order of bases in each new DNA molecule exactly matches the order in the original molecule.