KEY CONCEPT DNA replication copies the genetic information of a cell.

Replication copies the genetic information. A single strand of DNA serves as a template for a new strand. The rules of base pairing direct replication. DNA is replicated during the S (synthesis) stage of the cell cycle. Each body cell gets a complete set of identical DNA.

Proteins carry out the process of replication. DNA serves only as a template. Enzymes and other proteins do the actual work of replication. Enzymes unzip the double helix. Free-floating nucleotides form hydrogen bonds with the template strand. nucleotide The DNA molecule unzips in both directions.

DNA polymerase enzymes bond the nucleotides together to form the double helix. Polymerase enzymes form covalent bonds between nucleotides in the new strand. DNA polymerase new strand nucleotide

DNA replication is semiconservative. Two new molecules of DNA are formed, each with an original strand and a newly formed strand. DNA replication is semiconservative. original strand new strand Two molecules of DNA

Replication is fast and accurate. DNA replication starts at many points in eukaryotic chromosomes. There are many origins of replication in eukaryotic chromosomes. DNA polymerases can find and correct errors.

Questions What does "semiconservative replication" mean? What is the goal of DNA replication? What is the function of DNA polymerase? What feature of replication ensures that DNA is copied quickly? How does a cell ensure that no errors are introduced during replication?

KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

The cell cycle has four main stages. The cell cycle is a regular pattern of growth, DNA replication, and cell division.

The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. Gap 1 (G1): cell growth and normal functions DNA synthesis (S): copies DNA Gap 2 (G2): additional growth Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) Mitosis occurs only if the cell is large enough and the DNA undamaged.

Cells divide at different rates. The rate of cell division varies with the need for those types of cells. Some cells are unlikely to divide (G0).

Cell size is limited. Volume increases faster than surface area.

Surface area must allow for adequate exchange of materials. Cell growth is coordinated with division. Cells that must be large have unique shapes.

Questions During which stage of the cell cycle is DNA copied? Which part of the cell cycle takes the longest amount of time? Which cell type divides at the highest rate? What limits how large a cell can grow? Which kind of cell undergoes mitosis least often?

KEY CONCEPT Cells divide during mitosis and cytokinesis.

Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA

DNA plus proteins is called chromatin. chromatid telomere centromere One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes. Condensed, duplicated chromosome

Interphase prepares the cell to divide. Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell centrioles spindle fibers centrosome nucleus with DNA Interphase prepares the cell to divide. During interphase, the DNA is duplicated.

Mitosis divides the cell’s nucleus in four phases. During prophase, chromosomes condense and spindle fibers form.

Mitosis divides the cell’s nucleus in four phases. During metaphase, chromosomes line up in the middle of the cell.

Mitosis divides the cell’s nucleus in four phases. During anaphase, sister chromatids separate to opposite sides of the cell.

Mitosis divides the cell’s nucleus in four phases. During telophase, the new nuclei form and chromosomes begin to uncoil.

Cytokinesis differs in animal and plant cells. In animal cells, the membrane pinches closed. In plant cells, a cell plate forms.

Questions What term describes a structure that protects the ends of a chromosome? What term describes a loose organization of DNA and proteins? How is DNA organized in the cell? In what phase of mitosis do chromosomes become attached to spindle fibers? How does the number of chromosomes in the daughter cells compare with the number of chromosomes in the original cell?

Specialized cells perform specific functions. Cells develop into their mature forms through the process of cell differentiation. Cells differ because different combinations of genes are expressed. A cell’s location in an embryo helps determine how it will differentiate. Outer: skin cells Middle: bone cells Inner: intestines

KEY CONCEPT Gametes have half the number of chromosomes that body cells have.

You have body cells and gametes. Body cells are also called somatic cells. Germ cells develop into gametes. Germ cells are located in the ovaries and testes. Gametes are sex cells: egg and sperm. Gametes have DNA that can be passed to offspring. body cells sex cells (sperm) sex cells (egg)

Your cells have autosomes and sex chromosomes. Your body cells have 23 pairs of chromosomes. Homologous pairs of chromosomes have the same structure. For each homologous pair, one chromosome comes from each parent. Chromosome pairs 1-22 are autosomes. Sex chromosomes, X and Y, determine gender in mammals.

Body cells are diploid; gametes are haploid. Fertilization between egg and sperm occurs in sexual reproduction. Diploid (2n) cells have two copies of every chromosome. Body cells are diploid. Half the chromosomes come from each parent.

Haploid (n) cells have one copy of every chromosome. Gametes are haploid. Gametes have 22 autosomes and 1 sex chromosome.

Chromosome number must be maintained in animals. Many plants have more than two copies of each chromosome. Mitosis and meiosis are types of nuclear division that make different types of cells. Mitosis makes more diploid cells.

Meiosis makes haploid cells from diploid cells. Meiosis occurs in sex cells. Meiosis produces gametes.

Be able to calculate generations For example: Given the length of cell cycle (eg 24 hours) Be able to figure out the number of cells after so many hours (eg 96 hrs) On hour 1-1 After 24 hours-2 After 48 hours-4 After72 hours-8 After 96 hours-16