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CELL CYCLE INTERPHASE CELL DIVISION (cell is getting ready to divide) G1 Cell begins to grow S DNA is copied (cell is dividing) G2 Cell finishes growing M Phase (MITOSIS) Prophase, Metaphase, Anaphase, Telophase Cytokinesis Cytoplasm divides CHROMOSOMES: • • • • • Usually, DNA is in a loose form called chromatin When the cell is going to divide, it coils up nice & tight to form a chromosome A piece of a chromosome is called a gene A chromosome is made up of 2 sister chromatids, each containing many genes These sister chromatids are joined together at the centromere Label the diagram using the terms below: Centromere Chromatid Chromosome Gene 1. 2. ______________________ 3. _______________ 4. ______________ Chromosomes (continued) • Humans have a total of 46 chromosomes in MOST of their cells. 46 is the human diploid number- “2 sets of chromosomes” • We get 23 chromosomes from mom (1 set) & 23 chromosomes from dad (1 set) • The only cells that DO NOT have 46 chromosomes are our sex cells (gametes), which are either sperm cells (in males) or egg cells (in females) • These cells have ½ the amount of chromosomes; a total of 23 chromosomes. 23 is the human haploid number- “1 set of chromosomes” • When the sperm (haploid) & egg (haploid) join during fertilization, the resulting cell (called a zygote) contains a total # of 46 chromosomes (diploid) Nucleus of the egg cell containing 23 chromosomes Nucleus of the sperm cell containing 23 chromosomes 2 types of chromosomes: 1. Autosomes: • chromosomes that determine EVERYTHING about you EXCEPT your gender (sex) Q: What are some things that autosomes would determine about you? A: height, hair color, eye color, freckles, skin color, hair texture, etc. • Out of the 46 chromosomes humans have, 44 of them are autosomes (chromosome pairs #1- #22) 2. Sex chromosomes: • chromosomes that ONLY determine your gender • you have 2 sex chromosomes (pair #23) Q: What are your sex chromosomes if you are a MALE? A: XY Q: What are your sex chromosomes if you are a FEMALE? A: XX KARYOTYPE: this is a picture of all of someone’s chromosomes • it’s used to determine genetic disorders • Pairs #1- #22 are called autosomes • Pair #23 (last pair) are the sex chromosomes • Each pair of chromosomes are called Homologous Chromosomes- they are ‘identical’ to each other (1 is from mom; 1 is from dad) Answer the following questions based on the information in the Karyotype. Q1: How many chromosomes are in the picture? A1: 46 Q2: Why are the chromosomes in pairs? A2: Because 1 chromosome came from mom and the other came from dad Q3: Is the person below a male or female? A3: male Cell division in Prokaryotes: •Happens very quickly because these cells are very simple •Remember- prokaryotes are bacteria cells •The process is called Binary Fission • this creates clones Cell division in Eukaryotes: •Happens much slower because these cells are very complex •The process is called Mitosis, which involves many detailed steps CELL CYCLE: • The cycle begins with Interphase • The cell spends most of it’s time in Interphase • Interphase is divided into 3 parts: 1. G1 2. S • Cell division is divided into 2 parts: 1. Mitosis 2. Cytokinesis 3. G2 INTERPHASE: •G1- stands for Gap 1 •in this phase the cell begins to grow •S- stands for Synthesis •in this phase DNA is copied •G2- stands for Gap 2 •in this phase the cell finishes growing -Remember: There is a total of 46 chromosomes in these cells (somatic cells- “body cells” - examples: muscle cell, bone cell, skin cell, kidney cell, liver cell) -The centrioles (“scissors”) are also copied in interphase! Q: Do you remember what the centriole looks like? Draw a picture: Now the cell contains 2 sets of centrioles! CELL DIVISION: • Cell division is divided into 2 parts 1. Mitosis 2. Cytokinesis 1. MITOSIS: • Is made up of 4 phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase http://player.discoveryeducation.com/index.cfm?guidAssetId=D80AF785-7629-4AEB-975D04B82CDBBC9C&blnFromSearch=1&productcode=US •You will be required to know ALL stages of the cell cycle IN ORDER!! **HINT: to help you learn this, take the 1st letter of each phase and write a sentence that will help you remember them in order!!** •Here are the phases: Interphase, Prophase, Metaphase, Anaphase, Telophase & Cytokinesis MY sentence: I Picked More Apples Than Carrots MITOSIS (continued): PROPHASE: •In this phase, the nuclear envelope breaks down •The chromosomes become visible •The centrioles („scissors‟) begin to move to opposite sides of the cell •Spindle fibers, which are long strands of protein begin to form Label the following in the picture: - Chromosome - Nuclear envelope - Centrioles - Spindle fibers MITOSIS (continued): METAPHASE: •The centrioles are at the poles of the cell •In this phase, the chromosomes attach to the spindle fibers •The chromosomes line up in the MIDDLE of the cell •The spindle fibers will play “tug of war” with the chromosomes Label the following in the picture: - Chromosome - Centrioles MITOSIS (continued): ANAPHASE: •In this phase, the cell gets a little bit longer in shape •The chromosome will split in half: •1 chromatid will go to one side of the cell •the other chromatid will go to the other side of the cell •Each chromatid is now called a CHROMOSOME!! Label the following in the picture: - Chromosome - Centrioles - Spindle fibers MITOSIS (continued): TELOPHASE: •In this phase, the chromosomes finish separating •The spindle fibers break down •The nuclear envelope comes back •The chromosomes become LESS VISIBLE •The 2 cells are ALMOST completely separated Label the following in the picture: - Chromosomes - Nuclear envelope - Centrioles 2. CYTOKINESIS •In this phase, the CYTOPLASM (gel) divides •Now there are 2 identical cells •These cells are called daughter cells •Each cell has a total of 46 chromosomes (Telophase) Label the following in the BOTTOM picture: - Chromatin - Centrioles - Nuclear envelope - Nucleolus 2 Daughter cells http://www.neok12.com/php/watch.php?v=zX645478027c03150f647502&t=Cell-Division