Mitosis and Meiosis Unit 5 Study Guide Answers

Biology Unit 5 – Reproduction: Mitosis & Meiosis Study Guide Questions 1. a. What is the function of DNA? Has the information for making proteins b. What is the difference between chromatin and chromosomes? Chromatin – unorganized DNA Chromosomes – long organized strands of DNA 2. Identify the names of A-D. Define each of theses terms: a) Chromosome – condensed structures of DNA strands b) Centomere – attaches the two sister chromatids c) Chromatids – Identical copies of the DNA d) Homologous chromosomes – chromosomes which contain the same gene sequence, but are not identical (one came from mom, the other from dad) 3. a. Explain the difference between autosomes and sex chromosomes. Autosomes = normal chromosomes Sex chromosomes = determine gender b. What sex chromosomes determine male? Female? Male = XY Female = XX 4. a. Use the karyotype below to determine the number of autosomes, number of sex chromosomes, the gender of this individual and the total number of chromosomes in a human cell. Autosomes= 44 sex chromosomes = 2 gender = male total #= 46 b. Why are there two of each chromosome? One from Mom and one from Dad c. Where did they come from? Mom and Dad 5. A karyotype shows an individual with 45 autosomes and two X chromosomes. What can you determine from this karyotype? Has one extra autosome (abnormal) and is a female 6. Explain the difference between somatic cells and gametes, using the terms haploid and diploid. Somatic cells are diploid and gametes are all haploid 7. Why is a cell’s life described as a “cycle”? Draw & label a diagram showing the cell cycle and its 5 phases. It begins in G1 and then goes through the 5 phases and after it complete cytokinesis the two new cells are right back in G1 8. Why would some cells stay at G1 (G0) in the cell cycle? Give one example. If they go through S and G2 and Mitosis and Cytokinesis they stop their normal function… nerve cells, heart cells… don’t want those to stop function… that would be bad….  9. What would result if a cell completed mitosis, but failed to complete cytokinesis? Two nuclei in one cell 10. Cytokinesis in an animal cell is different than cytokinesis of a plant cell. Explain how this process must be different in each cell type. Plant cells have to form a new cell wall to complete the separation into two new cells after the membrane pinches in. 11. What cells undergo mitosis? List at least 3 cells in your body and explain the reasons they would undergo mitosis. Describe how you are now comprised of over 1 trillion cells, when you began as just a singe cell. Somatic cells/Diploid cells. Skin – to replace and repair Lung – to replace and repair Bone – to replace, repair, grow more Mitosis adds more cells = growing 12. When does DNA replicate (copy itself)? Why does this stage take so long? In S phase. Replication (helicase and DNA polymerase) takes time to open and add the new nucleotides to the millions of nucleotides in our cells 13. Complete the following table regarding Mitosis: Question What types of cells are produced in this process? How many chromosomes are in a human cell before this process? How many chromosomes are in a human cell after this process? How many cells are produced in this process? (starting with one cell) MITOSIS Diploid/somatic/normal/2n 46 46 2 14. Complete the chart below regarding the 4 phases of mitosis: Prophase Metaphase Start to condense Chromosomes line ***Chromosomes*** description and become visible up in the middle to (chromatids the cell attached) (chromatids attached) Nuclear Envelope appearance Spindle Fiber description Draw a picture of each stage of mitosis showing 2 chromosomes. Present, but beginning to disappear Spindle fibers form & Centrioles move to opposite sides of the cell Not present Centrioles are on opposite sides of the cell & spindle fibers connect with centromeres Anaphase Chromatids pull apart to form unduplicated chromosomes & move to opposite sides of the cell Not present Centrioles are on opposite sides of the cell & chromatids move along the spindle fibers See Cell Cycle & Mitosis Practice Activity 15. What is the only purpose of meiosis? What are the only cells produced in meiosis? The purpose of meiosis is to produce gametes (haploid cells). Telophase Un-duplicated chromosomes begin to unwind and return to chromatin. Reform around each nucleus formed Centrioles are on opposite sides of the cell & spindle fibers are no longer present 16. Describe what is happening with the chromosomes during meiosis I compared to what happens in meiosis II. Meiosis I – Homologous chromosomes separate Meiosis II – Sister chromatids separate 17. How are the events of Metaphase I of meiosis different than Metaphase of mitosis. Draw a picture to illustrate. In metaphase I of meiosis chromosomes line up in homologous pairs (tetrads). In metaphase of mitosis, chromosomes line up alone. Mitosis Meiosis 18. Define and DRAW Crossing-over. When does crossing over occur? Define Independent assortment. When does independent assortment occur? Crossing-over: recombines genes on chromatids, mixing maternal and paternal genes on a single chromatid Independent assortment: maternal and paternal chromosomes separate randomly during meiosis I, gametes receive a mixture of maternal and paternal chromosomes Both of theses events “shuffle” the genes so that each gamete receives a unique combination of genes. 19. What is genetic diversity? How do Crossing-over and Independent Assortment lead to so many different possible combinations of genes? Be specific for each one! Crossing Over: this mixes up maternal and paternal genes, so that the resulting chromatids are not identical copies of the maternal and paternal genetic material. Makes new genetic combinations and ensures that no gamete will be alike, meaning no offspring (except identical twins) will be alike. Keeps a variety of different gene combinations in a population. Independent Assortment: this means that the chromosomes will be assorted into gametes independently of one another, providing multiple different combinations for the gametes (over 8 million possible combinations for humans!). No two gametes will be exactly alike. 20. For a diploid cell with 4 chromosomes (shown to the right), how many different combinations of chromosomes are possible in the haploid gametes formed during meiosis? Which process accounts for these possible combinations? There would be 4 possible combinations of chromosomes in the haploid gametes formed (see diagram in #19). This is due to independent assortment of chromosomes. 21. What is 1 advantage and 1 disadvantage of asexual reproduction? What is 1 advantage and 1 disadvantage of sexual reproduction? In oogenesis, why is only 1 of the 4 products used as the egg? How many of the cells produced in spermatogenesis are functional gametes? An advantage of asexual reproduction is that the organism is able to pass on all of their genes to their offspring. A disadvantage of asexual reproduction is that all individuals in a population will be genetically identical and would be equally affected by a change in the environment. An advantage of sexual reproduction is that a population of sexually reproducing organisms will have a greater genetic diversity and would be able to respond differently to changes in the environment, allowing the population to adapt. A disadvantage of sexual reproduction is that organisms are only able to pass on ½ of their genes to their offspring. In oogenesis only 1 egg cell is produced due to an unequal division of the cytoplasm during cytokinesis. The cell that receives the majority of the cytoplasm (and organelles) will be the egg cell. In spermatogenesis, all for gametes will be functional. 22. Explain how nondisjunction during meiosis can lead to abnormal offspring. Give 2 examples of nondisjunction disorders. Nondisjunction is the failure of chromosomes to separate during anaphase I or anaphase II. This causes some gametes to inherit an extra chromosome and others to be missing a chromosome. If these gametes are fertilized by a normal gamete, the zygote will suffer from trisomy (an extra chromosome, 3 instead of a pair) or monosomy (missing a chromosome, 1 instead of a pair). 23. Complete the following table regarding Mitosis and Meiosis: Question MEIOSIS What is the purpose of this process? Growth, Repair/replacement of damaged cells, asexual reproduction What types of cells are produced in Gametes this process? How many chromosomes are in a 46 human cell before this process? How many chromosomes are in a 23 human cell after this process? How many cells are produced in this 4 process? (starting with one cell) How are the daughter cells produced They are genetically identical in this process different or similar to (clones). the original cell? MITOSIS Formation of gametes Somatic cells 46 46 2 They are each genetically unique. 24. Define differentiation and explain why cells in a multicellular organism would differentiate. Differentiation is the process of cells developing different structures & functions. Cells in multicellular organisms differentiate to become the many different types of cells that make up various tissues and organs. 25. How many chromosomes are there in each of your body cells? If each of your cells contains a complete set of all of your genes, why do you have so many different types of cell? Each of your body cells has 46 chromosomes. Only the genes that code for traits needed by each cell are expressed (“turned on”/transcribed & translated). These different patterns of gene expression lead to differentiated cells.