5.1 Cell Cycle and Mitosis Science 9

What causes growth?

Questions… What is cell growth? Why are adults bigger than babies? Do bigger animals (ie: elephant versus mouse) have more cells or bigger cells?

The Cell Cycle 1 2 3

1. Interphase Longest stage in cell cycle Growth = cell size increases, proteins and molecules are made, some organelles duplicate DNA replication = DNA makes a copy of itself

DNA Replication 1.Hydrogen bonds break to unwind DNA 2.Original strand acts as a “template” for complementary base pairing with free nitrogenous bases 3.Hydrogen bonds form between template and new strand to form two DNA molecules

DNA Replication

2. Mitosis Produces two identical daughter cells with the same number of chromosomes as the original cell Allows for growth in multicellular organisms Shortest stage of cell cycle Sister chromatids are joined by a centromere

Prophase Early: replicated chromosomes coil to X shape and nuclear membrane breaks down Late: spindle fibres (tube like structure) attach to chromosomes at their centromeres

Metaphase Spindle fibres pull chromosomes to cell equator

Anaphase Spindle fibres pull sister chromatids to opposite poles of cell (once separated, each sister chromatid = a chromosome)

Telophase Spindle fibres disappear Nuclear membrane forms around each set of chromosomes

Ch. 5.1: Mitosis Continued

3. Cytokinesis Separates two nuclei and cell contents into two daughter cells by pinching cell membrane together in animal cells In plant cells, a plate forms along the centre to divide cell into two daughter cells

Concept Questions Tiny tube-like structures made of protein are called A) spindle fibres B) chromosomes C) nucleolus D) DNA

Which stage is the longest in the cell cycle? A) mitosis B) DNA replication C) interphase D) cytokinesis

The phase of mitosis where chromosomes line up across the middle of the cell is A) anaphase B) metaphase C) prophase D) telophase

The phase of mitosis in which the duplicated chromosomes form into an X shape is A) anaphase B) metaphase C) prophase D) telophase

The phase of mitosis in which duplicated chromosomes move apart to opposite ends is A) anaphase B) metaphase C) prophase D) telophase

The phase of mitosis in which the nuclear membrane reforms is A) anaphase B) metaphase C) prophase D) telophase

What Causes Growth? which cells divide more frequently? how does a cell “know” when to divide (how is cell division controlled)? enzoeOM enzoeOM