Cellular Growth & Reproduction Biology 1B Ms. Morris
Friday, February 7, 2014 Warm Up: Look around at the other people in the classroom. What types of variation (differences) do you see? What similarities do you see? List at least 3 examples of each. WHY do you see the variation that you do (why don t we all look the same)? Announcements: Your projects are graded. TAKE THEM HOME by 3pm today. PLEASE.
Standard Update: SB2. Students will analyze how biological traits are passed on to successive generations. e. Compare the advantages of sexual reproduction and asexual reproduction in different situations.
Human cells Humans have two types of cells: Somatic cells (also called body cells) Sex cells (also called sperm and egg cells or gametes)
Human Somatic Cells 23 pairs of chromosomes = 46 total chromosomes Diploid number of chromosomes is 46 The 2 chromosomes in a pair are called homologous chromosomes or homologs Contain genes for the same trait (blood type, organ functioning, height, etc)
Human Gamete Cells 23 chromosomes not pairs!! 1 egg (23) + 1 sperm (23) = zygote (46) Meiosis/sexual reproduction results in genetic variation differences in members of the same species
The cell cycle: Somatic vs. Sex Somatic Cells All cells except sex cells Reproduce through mitosis 2 new identical cells Diploid contain two of each chromosome Sex cells (gametes) Egg and sperm cells Produced through meiosis 4 new nonidentical cells Haploid contain half the number of chromosomes
Asexual Reproduction Overview Only one organism as a parent One or more cells from the parent organism form an offspring that is genetically identical to the parent Sometimes the offspring is referred to as a clone
Types of Asexual Reproduction Mitosis: Process by which the nucleus copies itself then divides Ex. Most eukaryotic cells Binary Fission: Prokaryotic Cells -> Happens VERY quickly Step 1: DNA Replicates Step 2: Cell Pinches and Divides Budding: A small area of cells attached to the parent starts to grow and then detaches when it is a separate organism Ex. Fungi Vegetative Propagation: Send out runners that allow a new plant to grow, or cuttings from a plant can be rooted Ex. Plants
Advantages of Asexual Reproduction FAST Creates IDENTICAL cells Ex. If you cut yourself, its nice that your new skin cells will be identical (or almost identical) to the skin you damaged
Sexual Reproduction Overview Type of Reproduction that creates sex cells called GAMETES (sperm and egg) Both plant and animal cells produce gametes by a process called MEIOSIS
Sexual vs. Asexual Reproduction Why is genetic variation important? Adaptation and evolution over time would not happen Negative genes would stay in the gene pool forever Offspring would be clones of their parents
Sexual Reproduction & Chromosomes It is because of sexual reproduction that we see the variation we do Traits are located on genes, which are DNA segments DNA makes up chromosomes Each chromosome has thousands of genes that code for proteins that make us, US!
Why does DNA form a chromosome? (Whole Structure) (Holds 2 halves together to make the whole) (Half Structure)
Monday, February 10, 2014 Warm Up: Why do you think cells have to divide? Of what do cells need to make copies before they divide? (Make a guess if you do not know).
Foldable Eukaryotic Asexual Cell Cycle Cover: The Cell Cycle ** Flaps 1-6 should have a written description AND a simple diagram** Flap 1: Interphase Flap 2: Mitosis ~ Prophase Flap 3: Mitosis ~ Metaphase Flap 4: Mitosis ~ Anaphase Flap 5: Mitosis ~ Telophase Flap 6: Cytokinesis Flap 7: Cellular Growth, Cell Cycle Regulation, Cancer, and Stem Cells
Cells grow until they have reached their limit, then either stop growing or divide The smaller the cell, the more efficient the cell Cell division easier Cellular transport easier Cellular Growth Cellular communication easier (Last Flap)
The Cell Cycle (on back of the cover) Cells reproduce by a cycle of growing and then dividing into identical cells Eukaryotic Cells: Entire cycle takes 12-24 hours 3 Stages Interphase ~ Growth & Development Mitosis ~ Nuclear Division Cytokinesis ~ Cytoplasm Division
Which phase of the cell cycle is the longest? What is happening during this phase? Why do you think it is so long?
Flap 1 Interphase Interphase (3 phases) G 1 : Gap 1 Growing and carrying out normal functions S: Synthesis Cell copies DNA in preparation for cell division G 2 : Gap 2 Cell prepares for division of nucleus Cell takes inventory, making sure the cell is ready for division
The Cell Cycle Mitosis (4 Phases): See pg. 141 Prophase (Flap 2) Metaphase (Flap 3) Anaphase (Flap 4) Telophase (Flap 5) What do you notice about the differences between the plant and animal cells?
Flap 2 Prophase The Cell Cycle: Mitosis Nuclear membrane dissolves Nucleolus disappears Chromosomes condense from chromatin In animal cells, spindle fibers form from centrioles (Review: WHY do we need centrioles in animal cells?)
Why does DNA form a chromosome? Review (Whole Structure) (Holds 2 halves together to make the whole) (Half Structure)
Tuesday, February 11, 2014 Warm Up: Yesterday, we began to talk about the asexual cell cycle in somatic cells (mitosis). Today, answer: What do you think would happen if cells just kept dividing over and over again without any type of regulation or control? Why? Announcement: If you are taking the ASSET test Thursday morning and are missing class, you MUST make up the missing work ASAP. New edmodo code: rgcjut While we re working on the warm up, let s listen to a little song
Flap 1 Interphase Interphase (3 phases) G 1 : Gap 1 Growing and carrying out normal functions S: Synthesis Cell copies DNA in preparation for cell division G 2 : Gap 2 Cell prepares for division of nucleus Cell takes inventory, making sure the cell is ready for division
Prophase The Cell Cycle: Mitosis Nuclear membrane dissolves Nucleolus disappears Chromosomes condense from chromatin In animal cells, spindle fibers form from centrioles (Review: WHY do we need centrioles in animal cells?)
Flap 3 The Cell Cycle: Mitosis Metaphase Chromosomes attach to spindles and align along the equator (Middle) of the cell
Flap 4 The Cell Cycle: Mitosis Anaphase Chromosomes split into chromatids and are pulled to opposite ends of the cell Cell is elongating (getting longer)
Flap 5 Telophase The Cell Cycle: Mitosis Chromosomes at the poles and relax back into chromatin New nuclear membranes begin to form New nucleoli form All nuclear information has been copied Cell ready to divide **1 CELL -> 2 NUCLEI
Cytokinesis Cytoplasm divides, creating 2 new IDENTICAL daughter cells In animal cells: cell pinches inward In plant cells: new cell wall is formed The Cell Cycle Flap 6
Now A surprise for you!!
Questions about the Asexual Cell Cycle?
LAST FLAP Regulation of the Cell Cycle Cyclins regulate the cell cycle Checkpoints at G1, G2, and Metaphase If the cell does not pass the checkpoints, the cell will not divide; apoptosis (cell suicide) will occur
Cancer
Friday, February 14, 2014 Warm Up: What are 2 advantages of mitosis and other forms of asexual cell reproduction? Clicker Pop Quiz! Log into your Clickers. Announcements: Winter Break: Monday-Wednesday next week New edmodo code: rgcjut
LAST FLAP What is cancer and why does it happen? It is a mass of uncontrolled cells that are dividing Cancer can be benign (non harmful) or malignant (potentially harmful) Happens because of (MANY reasons): Apoptosis Failure Cells are programmed to commit cell suicide when they get too old; cancer could result when this does not happen Lack of Control of the cell cycle Cells continue to divide uncontrollably and form a mass
LAST FLAP In general, what causes cancer? Random mutations (no known reason) Environmental influences Chemical carcinogens (cancer-causing agent) X-rays High frequency radiation Viruses (only a few, don t worry) Special tumor viruses Ex. HPV human papillomavirus (HPV), Hepatitis B, Epstein Barr Virus, Herpes 8, etc
Stem Cells
Stem Cells BBC Video Most cells have a specialized function Stem cells are unspecialized cells that can develop into specialized cells under the right conditions 2 types Embryonic right after fertilization, before the system is an embryo, these cells have not yet specialized Adult cells of a certain tissue type may be able to help replace cells of that type Ex. Nerve cells replacing brain tissue
Questions so far?
Thursday, February 20, 2014 Warm Up: How is sexual cell reproduction (meiosis) different from asexual cellular reproduction? What is the major advantage of sexual reproduction? Announcements: New edmodo code: rgcjut Your mitosis vs. meiosis review worksheet is due TOMORROW at the beginning of class (I ll hand it out today.) While we re working on the warm up, let s listen to a little song
Stem Cells BBC Video Most cells have a specialized function Stem cells are unspecialized cells that can develop into specialized cells under the right conditions 2 types Embryonic right after fertilization, before the system is an embryo, these cells have not yet specialized Adult cells of a certain tissue type may be able to help replace cells of that type Ex. Nerve cells replacing brain tissue
The SEXUAL cell cycle: Meiosis Chapter 6 (Sections 6.1-6.2)
Meiosis The process of forming gametes (sex cells ~ egg and sperm). Gametes have half the number (n) of chromosomes as regular body cells (somatic cells/autosomes, 2n). At fertilization, the gametes (haploid, n) join to form diploid cells (2n).
Meiosis Cell reproduction where the number of chromosomes is reduced by half. Called reduction division. Has 2 main stages Meiosis 1 Meiosis 2
Meiosis I Interphase: Cell growth & copying of organelles/genetic information
Meiosis I Prophase 1 Chromosomes become visible and pair with their homologue When homologous chromosomes pair up to form tetrads, crossing over or synapsis occurs (chromosomes segments are exchanged forming new combinations of genetic information)
Meiosis I Metaphase 1 Homologous chromosomes pair up along equator
Meiosis I Anaphase 1 Homologous chromosomes split apart at the centromere and start to move towards the poles of the cell.
Meiosis I Telophase 1 & Cytokinesis I New nuclear membranes form Each pole has only 1/2 of the original genetic information Have 2 new cells, genetically different from parent cells (2n)
Meiosis I
Interphase II Chromosomes do NOT duplicate NO S PHASE!!
Prophase II Nuclear membrane disappears Spindle forms
Metaphase II Chromosomes align at the equatorial plate
Anaphase II Sister chromatids separate at the centromere and are pulled to opposite poles of each cell
Telophase II and Cytokinesis II Original cell is divided into four haploid cells Each new cell contains half the number of original chromosomes
Meiosis II 2 cells from meiosis I divide again, creating haploid gametes (n; sex cells: sperm and egg) Prophase II, Metaphase II, Anaphase II, Telophase II ~~ SAME things happen as in Meiosis I (except NO crossing over) THEN cytokinesis occurs SUMMARY
Meiosis vs. Mitosis