Chromosomes & DNA Replication

DNA & Chromosomes Prokaryotes Eukaryotes circular chromosomes DNA is found in cytoplasm Eukaryotes Located in nucleus 1000x more DNA than prokaryotes Number of chromosomes varies (human has 46, fruit flies has 8)

DNA Length Very long DNA in one human cell is one meter long Ex: Imagine stuffing 300m of rope into your back pack

Chromosome Structure Contain DNA & protein (histones) packed together called chromatin Not visible until cell division

Chromosome Structure

DNA Replication Before a cell divides it copies its DNA (replication) Each new cell now has a complete set of DNA The DNA molecule separates into two strands Two new strands follow the rules of base pairing (C with G, A with T) EX: a sequence of base pairs with TACGTT would have a complimentary strand of ATGCAA

DNA Replication

Cell Reproduction Facts Adults produce about 2 trillion cells a day Replacement cells are exact copies of the old cells Some cells, like hair & nails, are replaced constantly Other cells, like brain & nerve cells are rarely replaced Replicating DNA provides both daughter cells with a complete set of DNA.

Cells divide because Large cells an inefficient. (diffusion of wastes/nutrients take too long) Growth & Development Replace old cells Replace damaged cells