Biology Unit 6 Study Guide Answers

Name ______________________ Date ______ Biology Unit 6 Study Guide: Chromosomes, The Cell Cycle, and Mitosis • Chromosomes 1. What is a chromosome? What is it made of? A structure made of DNA and proteins where genes are located. 2. What are genes? Where are the located? What important role do they play in humans? Genes are segments of DNA that code for proteins or RNA molecules. They are located on chromosomes. Genes play an important role in how a person’s body develops and functions. 3. Understand that a single chromosome (X-shaped) is made of 2 chromatids (V-shaped). 4. True/False: When the two chromatids of a chromosome separate, they become individual chromosomes. True. 5. What is the structure that holds the chromatids together? The centromere. 6. Why is it important that chromosomes split during mitosis? To ensure that each cell has the same genetic information. 7. How many pairs of chromosomes do humans have? 23. 8. How many total chromosomes do humans have? 46. 9. What is the difference between haploid and diploid cells? Haploid cells have one set of chromosomes. Sex cells, or gametes, are haploid. Diploid cells have two sets of chromosomes. Somatic cells, or body cells, are diploid. 10. What is the difference between somatic cells and gametes? Somatic cells are diploid body cells with one chromosome from each parent. Gametes are haploid sex cells. 11. What is a zygote? The fertilized egg that is diploid. This results when the haploid sperm fuses with the haploid egg. 12. What does homologous mean? A chromosome of similar size, shape, and genetic content. In other words, the other chromosome in a diploid pair. 13. How many pairs of autosomes and sex chromosomes do we have? We have 22 pairs of autosomes and 1 pair of sex chromosomes. 14. Which adult determines the gender of the child and why? The male because males can have an X or Y gamete and females always have a Y gamete.

Name ______________________ Date ______ Males- XY Females- XX 15. What is a karyotype used for? To examine an individuals chromosomes? 16. What is the common name of Trisomy 21 and what is the cause? The common name is Down Syndrome. The cause is fusion of a diploid gamete with a haploid gamete. 17. List and briefly describe the four types of gene mutations. Deletion – piece of chromosome breaks of completely Duplication – fragment attaches to its homologous chromosomes Inversion – fragment reattaches on to the opposite side Translocation – fragment attaches to a non homologous chromosome • The Cell Cycle 18. What is the cell cycle? A repeating sequence of cellular growth and division. 19. List the 5 stages of the cell cycle. G1, S, G2, Mitosis, Cytokinesis 20. What stages make up interphase? What happens during each of these stages? G1 – growth, most of cell’s life S – DNA is copied. Chromosomes consist of two chromatids. G2 – Prepares the nucleus to divide 21. What is mitosis? The process during cell division in which the nucleus of a cell divides into two nuclei. In other words a process that makes an identical copy of a cell. 22. What is cytokinesis? Process in which the cytoplasm divides. 23. What are the three checkpoints for division? Be able to identify them in order. Cell growth checkpoint (G1) – if good moves on to S DNA synthesis checkpoint (G2) – if good moves on to mitosis Mitosis checkpoint – if good moves to G1 • Mitosis and Cytokinesis 24. What are spindles and what are they made of? Structures made of centrioles and microtubule fibers that move chromosomes apart during mitosis. 25. What is the structure of a centriole? A 9 triplet arrangement arranged in a circle. 26. Describe how the ‘reeling’ of spindle fibers occurs: Spindle fibers are attached to the centromere. They shorten bit by bit, pulling chromatids towards the poles.

Name ______________________ Date ______ 27. When chromatids finally arrive each pole has ____ ____________ ____ of chromosomes. One complete set. 28. What are the stages of mitosis (in order)? Prophase, metaphase, anaphase, telophase. Think PMAT

29. What is the stage before mitosis? Interphase 30. What is the stage after mitosis? Cytokinesis 31. What happens during prophase? Chromosomes coil up and become visible. The nuclear envelope dissolves and spindle forms. 32. What happens during metaphase? Chromosomes move to the center of the cell and line up. Spindle fibers link the chromatids of each chromosome to opposite poles. 33. What happens during anaphase? The centromeres divide and the two chromatids of the chromosome split apart and move toward opposite poles as spindle fibers shorten. 34. What happens during telophase? A nuclear envelope forms around the chromosome at each pole. Chromosomes uncoil and the spindle dissolves. 35. What happens during cytokinesis? The cytoplasm is divided in half. The cell membrane grows to enclose each cell. 36. Be able to identify a diagram of every stage of mitosis. 37. What is the difference in cytokinesis in plant cells and animal cells? In animal cells the cell is pinched in half by protein threads. In plants, a cell plate is formed by fusing of the Golgi apparatus.