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The Cell Cycle and Control 1. As you know cells are very small. We need microscopes __________ to help us see cells to study them. There are reasons that cells are small. Certain limitations keep a cell __________________. from growing too large Instead of continually growing, when a cell grows to a certain size it _______ divides (reproduces). Cell Size Limitations 2. ________-is fast and efficient over short Diffusion distances, but becomes slow and inefficient as distances become larger. For example: A mitochondrion at the center of a hypothetical cell with a diameter of 20 cm would have to wait months before receiving molecules entering the cell! 3. _____DNA DNA is responsible for coding for proteins in our cells. The larger the cell the more protein needs it would have. The cell’s DNA could not keep up with the protein needs of a large cell. proteins 4. __________________________Surface area to volume ratio As the cell increases, the volume increases much faster than the surface area. As the cell increases it needs more _________ _______ to nutrients and has more wastes excrete. This means it needs more plasma membrane in which to release wastes and diffuse nutrients. Cell Reproduction-All cells come from ______________. preexisting cells (Cell Theory) 5. Scientists discovered that chromosomes ___________, which contain DNA and proteins become darkly colored when stained, are responsible for passing genetic information from one generation to another. These chromosomes are located inside the _______ nucleus and become visible just before the cell divides. 6. Before a cell divides, the DNA is unwound into _________ chromatin to carry out cell functions. The Cell Cycle The cell cycle is the sequence of growth and division of a cell. _________________ 8. Most of the cell's life is spent in the period of growth called _________. interphase 7. 9. Following interphase, a cell enters mitosis its period of division called ______. Mitosis is broken into four phases: ________, metaphase _________, _________, prophase anaphase and ________. telophase After mitosis, a short period called _________ cytokinesis occurs in order to divide the cytoplasm. 10. During interphase the cell is in a resting phase. It carries out __________, cell functions grows, copies its DNA and makes new ________. organelles 11. Interphase is divided into three G1 phase phases. ___ is the first growth S period of the cell, __ phase is the time to copy DNA, and ___ G2 phase is the second growth of the cell. 12. Prophase- first phase of mitosis Chromosomes become visible Chromosomes are made of two sister chromatids _________ (B) connected by a __________ centromere (A) Centrioles move to opposite poles of cell Spindle starts to form Nuclear membrane breaks down ____________ 13. Metaphase Chromosomes line up along ______ equator of the cell Spindle attaches to centomeres 14. Anaphase Chromosomes ____________ divide Chromatids separate and move sides to opposite ______ of the cell 15. Telophase Chromosomes unwind into _________ chromatin Nuclear membrane forms around chromatin 16. Cytokinesis- is different in plant and animal cells. In animal cells, the plasma membrane pinches _______ in separating two new cells. This is cleavage and the fold is called the called _________ ______________. Cleavage furrow b. In plant cells, vesicles containing cell wall material line up in the center of the ______________ cell and fuse together forming a ________. cell plate The cell plate then connects with the existing cell wall creating two new cells. a. 17. Label the cell cycle. G1 B. S C. G2 D. Metaphase A. Results of Mitosis 18. When mitosis occurs, __________ unicellular organisms remain unicellular-they have simply multiplied. In __________ multicellular organisms, cell division results in groups of cells that work together as _______. tissues 19. Tissues form ______, organs organs form _____________, organ systems and organ systems form __________! organisms Control of the Cell Cycle 20. Biologists believe that a series of ________ enzymes called cyclins control the cell’s progress during the cell cycle. There are enzymes that tell the cell when to start mitosis as well as controlling it throughout the phases. 21. The production of these enzymes is done by genes _____. Genes are a segment of DNA ____ the controls the production of a protein. 22. Cells can lose control of the cell cycle and start dividing uncontrollably. The results may be cancer ______. Cancerous cells Normal cells Meiosis There are two types of cells in your body: cells 1) Somatic ___________—body cells 2) _________—sex cells (germ cells) Gametes Haploid __________ cells cells have ½ the number of chromosomes in a species. They are designated by 1N or N. (Sex cells) What is the haploid number for humans? 23 ___ Diploid cells cells have the correct __________ number of (paired) chromosomes for a species. They are designated by 2N. (Body or somatic cells). What is the diploid number for humans? 46 ___ The 2 chromosomes that make up a pair are called homologous __________ chromosomes. Each _____________ sister chromatid in the pair has information about the same ____. gene The combination they form together results in a particular trait being expressed. The process that forms new somatic cells is _______. mitosis Human sex cells in the female are the egg cells. In the male, they are the ____ ______ sperm cells. Each has ___ 23 chromosomes or the haploid number for humans. Female sex chromosomes are represented by an ___ X and males are represented by a ___. Y Since XX results chromosomes are paired, _____ in a female offspring and _____ XY is male. The cell division that forms new sex cells is called _______. Meiosis haploid cells. Meiosis produces ______ Meiosis is divided into two distinct parts: ________ Meiosis I and _________. Meiosis II Each ends with cell division. Meiosis I consists of _________I, Prophase Metaphase _________I, __________I, Anaphase and _________I. Telophase What happens immediately after Telophase I? _________ Prophase II Meiosis II consists of ________ Prophase II, Metaphase Anaphase II and _________ II, _________ ________ Telophase II. It occurs immediately after ________. Meiosis I No replication of ______occurs DNA before prophase II. Asexual _______ reproduction does not involve the exchange of genetic material (DNA). It can be accomplished by cellular ______ division. This reduces genetic _______ variation because the resulting daughter cells are _______. identical Bacteria reproduce by a mitotic division called _______ Binary _______. fission They have circular _______ that copies itself and DNA then a new cell wall forms dividing the cell. Other types of asexual reproduction are: Budding which is often used by fungi, and _______, ________ Vegetative__________, propagation which is used by a lot of plants. Sexual reproduction increases _______variation within a species genetic because it involves the exchange of DNA _____, which is the genetic material of a species. There are ____ four sperm produced in meiosis of sperm cells, which is called ______________. spermatogenesis Egg cells undergo meiosis that is called _________. oogenesis It produces one ___ egg cell, which receives most of the cytoplasm, and _____ three small cells that are called polar __________. bodies ____________ Nondisjunction is when chromosomes do not separate correctly and offspring end up with one chromosome too many or one too few. This causes birth defects. When a gamete with an extra chromosome is fertilized by a normal gamete the result is called ________. trisomy Trisomy zygotes have an extra st chromosome and they will develop ______________ 21 into a baby with _______________. Down syndrome missing a chromosome If a zygote is ________ the result is called monosomy _________. This is usually a lethal defect, but one result is called _______________, Turner syndrome Females will have only one ___ X chromosome instead of two. When a whole extra set of chromosomes ___________ is present in the zygote the condition is called ________. polyploidy This is lethal to animals, but is desired in plants. Polyploidy leads to larger flowers or fruit. ___________________.