For example: You are constantly loosing skin cells, in order to keep your skin healthy, your body needs to be constantly making new skin cells.

Transcription

1 Name: Cells and Reproduction A. The Cell Life Cycle The many cells in your body are constantly and. For example: You are constantly loosing skin cells, in order to keep your skin healthy, your body needs to be constantly making new skin cells. QUESTION: Where do new skin cells come from? YOUR ANSWER: OFFICIAL ANSWER: New skin cells come from. THE CELL CYCLE STEP 1: After cell is born, it eats and grows (G1 or 1 st growth phase) nucleus stringy DNA Eat food and grow Eat food and grow AND make extra copies of the organelles cell Golgi Body In your body, your cells get food from your. When you eat food and digest it, the nutrients (vitamins, minerals, amino acids, and other things) go into your blood and travel to all the cells in your body. After a growing for a while, the cell starts getting ready to divide in two. First it needs to make extra copies of all the. By the end of step 1, all the organelles have been copied. Cells And Reproduction Page 1

2 STEP 2: Keep growing and start making an extra copy of the DNA (S phase) Eat food and grow AND start making an extra copy of the DNA. Eat food and grow AND finish making an extra copy of the DNA. At the start of this step, the cell has already made extra copies of all the organelles and starts to make an extra copy of the that is inside the nucleus. REPLICATION = the of making an of the DNA in a cell. To make a copy of the DNA, the double helix match up with each half of the DNA molecule. and extra Cells And Reproduction Page 2

3 By the end of this part of a cell s life, there are two copies of all the DNA in the nucleus. AND the DNA gets and packaged up into. REMEMBER FROM EARLIER LESSON: During most of the cells life, DNA is and. DNA that is loose and stringy is call. By the end of step 2, the DNA is all twisted up and packaged into X shape called a. Cells And Reproduction Page 3

4 PARTS OF A CHROMOSOME Chromatid = chromosome. of the X shape of a Centromere = the of the X. The centromere is important because it is where the chromosome gets during cell division (we will learn more about this later) IMPORTANT IDEA: The X shape of a chromosome actually contains the DNA of the cell. of STEP 3: Keep growing bigger (G2 or 2 nd growth phase). STEP 4: MITOSIS the separates the two DNA copies and divides We will learn about Mitosis tomorrow. Summary of the cell cycle: NOTICE: Cell division (step 4) is only a _ of the cell s life most of the cells life is spent doing steps 1 through 3. Steps 1 through 3 are often refered to as INTERPHASE. Cells And Reproduction Page 4

5 B. MITOSIS: Cell Division to make more cells that are the same. Things that the cell has done before starting mitosis: 1. eat food,, and make extra copies of all _ except the (G1) 2. make an extra copy of the DNA ( ) and package up the DNA into chromosomes. (S) Mitosis part 1: Prophase 1 st THING THAT HAPPENS: starts to break apart. WHY? In order to get the two copies of the DNA into separate cells, we have to get them the nucleus. The _ start getting into position and _ start forming.. By the end of mitosis part 1 (Prophase), the nuclear membrane has the have attached to and of the the chromosomes. _ of Cells And Reproduction Page 5

6 The have also moved to of the cell. How do you know that prophase is over? Once the Why is prophase important? It is the starting of cell division, the nucleus has completely disappeared, prophase is over. so that the chromosomes are free to in the. If prophase did not happen, the chromosomes would be the. in Mitosis Part 2: Metaphase The picture here shows a cell at the end of the part 2 (called Metaphase) Before metaphase, the chromosomes are the cell (not any way). in _ Once the nuclear membrane disappears (at the end of ), stretch out from the. The spindle fibers (the little strings) attach to the (the middle part of the X shape). Once all the chromosomes are attached to spindle fibers, the chromosomes start into position. By the end of metaphase, the chromosomes are all in a line (as shown in the picture above). When is metaphase officially over? Cells And Reproduction Page 6

7 As soon as the chromosomes start getting in, metaphase has ended. Why is metaphase important? When the cell is dividing, it is important that each new cell gets a of all the metaphase, all the chromosomes are getting the next part happens properly. instructions. During so that If metaphase did not happen properly, the chromosomes might get and not get into the new cells properly. Mitosis Part 3: Anaphase The picture shown here, shows a cell in the of mitosis). of anaphase (the 3 rd part At the start of anaphase, all the chromosomes are all. As soon as the chromosomes start getting ripped in has started., anaphase Once the chromosomes reach the detach from the. of the cell, they When is anaphase over? Anaphase is officially over when the the. let go of Cells And Reproduction Page 7

8 Why is anaphase important? It is during this part of mitosis that the so that each of the new cells that will be formed get the gets evenly divided of DNA. If anaphase does not happen, the new cells will not get the correct amount of DNA and won t be healthy they may die (or at least not be normal or healthy). Mitosis Part 4: Telophase Telophase officially starts when detach from the spindle fibers. The picture, shown to the left, shows a cell in the middle of telophase. During telophase, the nucleus to. and the cell starts For a brief period the cell actually has two nuclei but very soon after the nuclear membranes reform, the cell divides into two. Telophase officially ends when the reforms. Once telophase is over, the cell. cytokinesis = a fancy word meaning _ = the process of the cell becoming after telephase Cells And Reproduction Page 8

9 C. Controlling Cell Division and getting rid of unhealthy cells. The Cell Life Cycle The controls the cell. It is constantly _ what is happening inside the cell and makes about what needs to happen. There are main places where the nucleus decides whether the cell will continue to or should. checkpoint#1: at the end of the 1 st growth phase. At this point in the cell s life, the nucleus checks the following 2 things: i. did the cell get enough _ ii. is the DNA in healthy (not too many bad, no missing ) If the cell is not healthy enough, the nucleus will checkpoint#2: at the end of the 2 nd growth phase. the cell At this point in the cell s life the nucleus checks the following thing: i. did enough get (during replication) If the DNA did not get copied properly, the nucleus can try to order on the DNA to get it copied properly, or the nucleus will the cell. checkpoint#3: mistakes that happened during mitosis. _ If don t get attached to the properly during they won t get pulled apart properly during. Cells And Reproduction Page 9

10 If the chromosomes don t get properly, the two new cells that get made won t have a normal amount of (one cell will have DNA and one cell will enough). If this happens, the nucleus will notice this mistake and that cell Sunlight has UV radiation in it which can cause. REMEMBER: mutations are when there are in the DNA. If there are mistakes in the DNA, the nucleus will this and _ the cell. This is why your skin peels when you get sunburned. The skin has been damaged (by the radiation) and the nuclei of the effected cells order their cells to death. Cells And Reproduction Page 10

11 D. Different types of reproduction. Remember Mitosis: cell at the start. A bunch of steps (PMAT) Becomes cells that are the _ as the ones in the beginning (assuming no happen) This type of reproduction is call Remember Human reproduction: reproduction. Your mom is genetically from your dad. This means: The mom is the in your from in your dad When your parents got together the result was that they reproduced to make. the DNA in your body comes from your and half comes from your. Cells And Reproduction Page 11

12 This kind of reproduction, where two living things mix their DNA together to reproduce is called reproduction. Reproduction = to make of something (cells, animals, plants) Asexual reproduction = any type of reproduction that involves _ organisms being made that are genetically to the original organism. Sexual reproduction = any type of reproduction that involves new organisms being made as a result of a of so that the new organism is to the parent organism but has a _ mixture of DNA. QUESTION: In science fiction movies, there have been situations where people have cloned copies of themselves. Would cloning be considered sexual or asexual reproduction? Explain your answer. YOUR ANSWER: OFFICIAL ANSWER: If you made a clone of yourself, the clone would look pretty much the as you. Since it looks the same as you, it must have the same instructions on how to your body. Since the clone would have the same DNA as you, making clones would be considered reproduction. Cells And Reproduction Page 12

13 TYPES OF ASEXUAL REPRODUCTION: 1. : PROCESS: Parent cell One living thing grows and divides into two This process is basically the same as. parts EXAMPLES OF THINGS THAT DO THIS: Several _ organisms reproduce this way. The name of the organism picture to the left is the paramecium (you don t need to remember this for grade 9) Two daughter cells The textbook shows an amoeba reproducing by binary fission (see pg 168) Most types of reproduce this way. _ 2. _ PROCESS: A part of the living organisms starts to get The lump continues to _ on it. and eventually becomes a of the original organism and. _ Cells And Reproduction Page 13

14 EXAMPLES OF THINGS THAT DO THIS: The hydra (pictured above) as well as several types of sea sponges reproduce in this manner. 3. Fragmentation Pictures of different types of sea sponges. 3. PROCESS: Similar to budding, a piece of the organism and _ into a whole new. Fragmentation is different from budding in that, for fragmentation, the piece is breaking off because of an. For example: some Star fish Cut a piece off If a star fish is injured and has a piece of its body chopped off, if the piece is big enough, the chopped off piece will grow into a whole new star fish (and the original starfish will heal). Plants can also reproduce in this way. You can cut parts of a plant off and have it grow into a whole new plant. Cells And Reproduction Page 14

15 4. : PROCESS: A type of reproduction done _ by plants. Involves a or _ growing away from the main plants that then develops into a _ plant. 5. : PROCESS: Similar to how plants can make, many molds and mushrooms produce. _ Spores are similar to seeds in that they are and can often float in the air (as some seeds can). The spore has all the instructions on how to grow a whole mushroom (just like a seed can grow a whole plant). If the spore lands in a place where it has enough food to grow, it will develop into a whole. An important difference between spores and seeds, is that spores result in making mushrooms that are to the mushroom they, whereas seeds in plants come from a of _ between two separate plants ( reproduction). Cells And Reproduction Page 15

16 REMEMBER: All 5 forms of asexual reproduction involve making new organisms that are to their. The kids will be exactly the same as their parents unless (mistakes in copying DNA) happen. _ Cells And Reproduction Page 16

17 E. More details on sexual reproduction. Living things that are made by sexual reproduction contain a of DNA from their parents. _ A normal cell in your body would have _ chromosomes. 23 of them come from your and 23 of them come from your. A picture of a complete set of chromosomes for a human To make understanding things easier, I am going to pretend that a human cell has 4 chromosomes, 2 from dad and 2 from mom. Human Mitosis DNA Replication Mitosis (PMAT) Notice: one cell turns into two cells that are the as the original Cells And Reproduction Page 17

18 HOW YOU WERE MADE: + Egg Fertilized Egg (Zygote) Sperm Fertilization = the process of a (or pollen) the resulting in the formation of a. Zygote = a a sperm (or pollen) cell that forms from with an egg. NOTE: the zygote is what grows and eventually becomes a. Gamete = a cell that is especially used for reproduction are the gamete are the gamete Cells And Reproduction Page 18

19 QUESTION: Why won t mitosis work for making sperm cells (in men) or egg cells (in women)? YOUR ANSWER: OFFICIAL ANSWER: Mitosis results in cell becoming cells that are the same as the cell. A sperm and an egg each have only the amount of of a normal living animal. A special type of cell division is needed in order to make gametes (sperms and eggs). Meiosis = a different kind of cell division that creates cells that have much division is needed to make as the original cell this type of cell (sperms and eggs). (we will go over this tomorrow) Cells And Reproduction Page 19

20 Cells And Reproduction Page 20

21 F. Advantages of Sexual and Asexual Reproduction Biologists (scientists who study living things) think that the success of an organism depends on several things: i. The ability to get and (nutrients) ii. The ability to find a and place to live iii. The ability to produce offspring that produce their own offspring (ie make grandchildren) to It is the third item above we want to focus on in this lesson. An organism that is successful in reproduction means that it s offspring will do better than the offspring of other organisms. There are a variety of ways to succeed in nature. We will examine some differences between sexual and asexual reproduction in order to think about situations where one may or may not be better than other. There is no clear right or wrong way to reproduce because it depends on the situation. Let s look at the following examples Cells And Reproduction Page 21

22 DIFFERENCES IN SEXUAL AND ASEXUAL REPRODUCTION: Asexual Reproduction Large number of offspring are produced very quickly Sexual Reproduction Fewer offspring are produced in a longer period of time. For example: Bacteria can reproduce by binary fission anywhere from 12minutes to 24hours. For example: People usually only have one or two kids at a time and it takes 9months for a egg to develop into a baby. This makes asexual reproduction better than sexual because: This makes sexual reproduction better than asexual because: Asexual Reproduction Can have babies without needing another organism. For example: When a bacteria is ready to have kids, it just divides into two. Sexual Reproduction Need to find a mate before having babies. For example: For people, a man needs to find a woman, and a woman needs to find a man, in order to have a baby. This makes asexual reproduction better than sexual because: This makes sexual reproduction better than asexual because: Cells And Reproduction Page 22

23 Asexual Reproduction All offspring (babies) are the same as the parent For example: When a bacteria divides, it creates more bacteria that are the same is the original. Sexual Reproduction Offspring are similar to but not exactly the same as the parents. For example: When people have kids, the kids look the same and have similar health conditions to their parents. This makes asexual reproduction better than sexual because: This makes sexual reproduction better than asexual because: Sex in bacteria.. sex without reproduction!! Cells And Reproduction Page 23

24 G. Understanding Stem Cells The picture below shows the development of the embryo after. In humans, the events shown in the picture take about two weeks to happen. During this entire time (the first two weeks after fertilization) all the cells are as each other. All the different cells in your body come from these cells but in the first two weeks, the cells have yet been told what they will become. QUESTION: As the fertilized egg (the zygote) develops, the cells divide again and again. Do they divide by the process of mitosis or by the process of meiosis? Explain how you know. YOUR ANSWER: OFFICIAL ANSWER: Cells And Reproduction Page 24

25 The picture below shows the next part in the life of what will become a baby. The blastula becomes a gastrula. What is important to notice in the picture above, is that all the cells are. There are 3 kinds of cells now. In the first two weeks, there is only one kind of cell but eventually the cells start to differentiate. To differentiate means that the cells start what kinds of cells they will. tell the cells from the blastula to start changing so that the cells will choose one of the 3 possible paths. Once a cell has been told what path to take, the blastula (from the last step in the picture on pg 27) turns into the gastrula (pictured above). A video showing the stages from fertilization to the first existence of the embryo A video showing the later stages of embryonic development Cells And Reproduction Page 25

26 WHAT IS A STEM CELL? Stem cell = a cell from the fertilized egg that has yet what to become. WHAT MIGHT WE USE STEM CELLS FOR IN THE FUTURE? Since stem cells have not yet been told what kind of cell to become, they can possibly become. This can be useful when it comes to replacing certain. FOR EXAMPLE: If you are diabetic because the cells that make up your pancreas do not produce. A scientist (doctor) can grow stems cells in a lab and give a chemical signal to the stem cell to make the stem cells turn into normal insulin producing. Cells And Reproduction Page 26

27 The doctor can then put the new pancreas cells into your pancreas so that your pancreas will be able to make insulin. Scientists don t really know all the possible uses for stem cells yet. They are still learning all the details on how to get them to work. If scientists can learn more about how to get stem cells to work properly, we could potentially avoid people needing to wait for an organ transplant. Someday, we might be able to grow whole organs from stem cells in the laboratory. WHY DO PEOPLE GET UPSET ABOUT WORKING WITH STEM CELLS? Stem cells come from mixing sperm and eggs in a laboratory to create the ). that develop into blastula (a ball of cells that are all Some people believe that once a sperm and an egg meet each other (fertilization) that the zygote is the beginning of and deserves to stay alive. Other people feel that the ball of cells is not truly a and since the work with stem cells could potentially help so many people, that it is worth researching further. What you believe is up to you, there is no right answer it is a matter of personal belief and opinion. Cells And Reproduction Page 27

28 I. Understanding Cancer (basically) HOW DOES THE NUCLEUS CONTROL THE CELL? The nucleus has the instructions on how to work the cell (called ). The DNA is used to make. The proteins do a lot of different things for the cell including nucleus what is inside the cell. the If there are too many or in the DNA, the proteins made from the DNA properly and won t be able to tell the nucleus the information. If the nucleus gets the information about what is happening in the cell, the nucleus will make decisions about what needs to happen next. The nucleus might think its time to when its not. Cells And Reproduction Page 28

29 When a cell has lost control and starts to divide when its not supposed to, it is called a cancer cell. Cancer cells continue to divide and eventually make a big lump of cells call a. If a tumour continues to grow, it will eventually come into contact with a. This is bad because cancer cells can _ of the tumour and travel through the blood stream. The cancer cells that flake off can move to another place in your body and cause a to grow in other places in your body. Cancers are caused by. mutations are needed in order for a cell to become cancerous. Since your body has some ability to mutations, and you hopefully don t expose yourself to or (that increase the chance of mutations), you don t usually get cancer. Cells And Reproduction Page 29

30 But as you live your life, some mutations don t get fixed which is why cancer is more common in people it takes some time for mutations to build up to cause cancer. Also it is possible that the genes in that you got from your parents might make you more prone to cancer than other people. Scientists (doctors) don t really understand a lot of the details about cancer and cells. A lot of scientists are studying cells to learn more about them this is why we do not have a cure for cancer yet. Terry Fox was born in Manitoba but grew up in Port Coquitlam. He had cancer in his knee and had to get his leg amputated when he was 18 years old. When he was 21, he decided to start his Marathon of Hope where he wanted to raise money and awareness for cancer research. Cancer ended up taking his life when he was 23 years old. He is buried in a Port Coquitlam cemetery. THE END Cells And Reproduction Page 30