Solution Manual for Method and Practice in Biological Anthropology: A Workbook and Laboratory Manual for Introductory Courses, 2nd Edition

Chapter 2: Cell Biology and DNA Reading Questions 1. Which of the following individuals was responsible for coining the term “cell”? (a) Hooke, (b) Darwin, (c) Wilkins, (d) Watson. 2. Prokaryotic cells are distinguishable from eukaryotic cells because prokaryotes do not contain: (a) organelles, (b) a plasma membrane, (c) DNA, (d) a nucleus. 3. Chromosome strands are called (a) centromeres, (b) alleles, (c) chromatids, (d) homologues. 4. Alternate forms of a gene are called (a) alleles, (b) sister chromatids (c) homologues (d) replicated DNA. 5. Sister chromatids separate during nuclear division in (a) mitosis, (b) meiosis I, (c) meiosis II, (d) both a and c. 6. Who won the Nobel Prize in 1962 for identifying the structure of DNA? (a) Hooke, (b) Meischer, (c) Watson and Franklin, (d) Watson, Crick, and Franklin. 7. Which of the following is a possible base pairing in DNA? (a) adenine-cytosine, (b) adenine-thymine, (c) cytosine-thymine, (d) thymine-guanine. 8. Transcription in DNA (a) results in the formation of an identical DNA strand, (b) results in the formation of mRNA, (c) happens in the nucleus, (d) requires the assistance of tRNA anticodons. 9. True or False: DNA replication occurs in the ribosome. 10. True or False: Crossing over is an important source of variability. In-Class Exercises Exercise 1 Why do gametes have only 23 chromosomes, one of each pair? Because when they combine during fertilization the zygote will have the correct number of chromosomes, one of each pair from mom and the other of each pair from dad. Chimpanzees have 48 chromosomes in their somatic cells. How many chromosomes do you think are found in their sex cells? 24 Exercise 2 *Exercise requires karyotype and answers will vary * Exercise 3 *Exercise requires microscope and answers will vary depending on phases present* Exercise 4 Compare and contrast mitosis and meiosis in the human with the following matching questions. a 1. happens in the body cells b 2. produces 4 daughter cells c 3. begins with 46 chromosomes a 4. produces 2 daughter cells a 5. one nuclear division c 6. one chromosome replication b 7. happens in the testes and ovaries b 8. daughter cells have 23 chromosomes each b 9. two nuclear divisions a 10. daughter cells are diploid a. mitosis b. meiosis c. both mitosis and meiosis Exercise 5 Draw a homologous pair of chromosomes. Use one color (e.g. pink) for one member of the pair and use a second color (e.g. blue) for the second member of the pair. Next, draw the two chromosomes crossing over, so that the two colors are touching. Third, draw the two chromosomes after the crossing over is completed and they have shuffled their gene pairs, exchanging genes (colors) between them. Have at least one exchange. Compare your drawing to others in the class and see the amount of variation that might be possible. *Answers will vary but may look like the following:* Exercise 6 Practice DNA base pairing: Consider the following DNA strand: ATCCTAGGTCAG Identify the complementary bases: TAGGATCCAGTC Now, practice DNA replication. Consider the following double stranded DNA molecule. Notice that the DNA bases are paired accordingly. Separate the strands and replicate them, identifying which strands are original and which are the new complementary strands. Write the complementary bases for the top strand above the strand and the complementary bases for the bottom strand below the strand. New strand: ATGCCGTTGACTCGA Top strand: TACGGCAACTGAGCT _______________________________________ Bottom strand: A T G C C G T T G A C T C G A New strand: Exercise 7 TACGGCAACTGAGCT The following chart lists all possible mRNA codons and the 20 amino acids they code for. Note that there is some redundancy in the code. Also note that some codons code for start or stop, which tells the cell where to start or stop making the protein. Using this information, fill in the blanks below the chart for the amino acid each codon calls for. UCA Serine GUA Valine UGG Tryptophan AGA Arginine CUC Leucine GCC Alanine CAU Histidine AUG Start (Methionine) Exercise 8 The following is a template strand of DNA: ACGGTTCATGCA a. What is the complimentary mRNA strand? UGCCAAGUACGU b. What are the complimentary tRNA anticodons? ACG; GUU; CAU; GCA c. Using the chart from the previous exercise, what is the sequence of amino acids for this peptide chain? Be sure to use the mRNA codons when reading the chart! UGC: Cysteine; CAA: Glutamine; GUA: Valine; CGU: Arginine Post-Lab Questions 1. Describe the difference between the autosomes and the sex chromosomes. Answers should include some or all of the following: Autosomes are always homologous pairs and contain information pertaining to body structure and function; they comprise pairs 1-22 in humans. The sex chromosomes (pair 23) are homologous in females but not in males, since the X and Y chromosome are different lengths and the Y chromosome carries information primarily pertaining to the biological sex of the individual. 2. How many chromosomes were there in your karyotype set? Was this the normal number for humans? *Depends upon the student’s karyotype*. 46 is the normal number. Some kits offer mutations. 3. Referring to your lecture textbook, or the Internet, discuss the clinical symptoms associated with any anomaly you identified in your karyotype. *Student activity, answers will vary.* Some karyotype kits offer Turner’s syndrome, Klinefelter’s syndrome, Down Syndrome, and XYY Males. 4. How do you determine the sex of an individual when examining their karyotype? By looking at the sex chromosomes – if there are 2 identical chromosomes, the individual is XX and female. If one of the chromosomes is small and the other is large, the individual is XY and male. 5. How are the different types of chromosomes identified for a karyotype? Based on size, length of arms and position of the centromere. 6. If the chromosome number for an organism is 22 before mitosis, what is the chromosome number of each daughter cell after mitosis has taken place? 22 7. Why does DNA replicate prior to mitosis? So that each daughter cell has the complete complement of chromosomes. 8. What do you think might happen if a cell underwent mitosis but not cytokinesis? The cell without the cytoplasm and associated organelles would not survive (this is common in females, one gamete gets all cellular contents, the ovum, while the other three get little/none and are called polar bodies, which resorb). 9. If a cell in an organism had 16 chromosomes before meiosis, how many chromosomes would exist in each nucleus after meiosis? What is the diploid number? What is the haploid number? 8 after meiosis, 16 is diploid, 8 is haploid. 10. From a genetic standpoint, what is the significance of fertilization? It is when the egg and sperm meet allowing the 23 chromosomes from the mother to unite with the 23 chromosomes from the father (in humans) creating a zygote. 11. Describe the differences between haploid and diploid cells. Where are haploid and diploid cells found? Diploid cells have the full complement of chromosomes with all the homologous pairs. Haploid cells have only half of the complement of chromosomes, with only one of each chromosome from each homologous pair. Body cells are diploid, sex cells are haploid. 12. Discuss the differences you observed when comparing your crossing over diagram to others in the class. How many different combinations did you see? *Student activity – answers will vary because each person’s diagram will be at least slightly different.* 13. What does it mean when we say DNA replication is semiconservative? One parental strand remains intact, while a new complementary strand is formed. 14. Describe the differences in DNA and RNA structure. DNA is double stranded while RNA is single stranded. DNA has a deoxyribose sugar, RNA has ribose sugar; DNA has thymine, RNA does not, but has Uracil. 15. To transcribe means “make a copy of”. Is an exact copy of DNA made during the process of transcription? Why or why not? No, because RNA does not have thymine, so it replaces it with Uracil. Also, because of the law of complementary bases, the RNA strand is actually a “mirror image” of the DNA strand that is being copied. Also the sugar molecules differ between DNA and RNA. 16. Where does transcription happen? What about translation? Transcription happens in the nucleus, translation occurs in the ribosome. 17. What amino acid would be produced if transcription took place from the DNA sequence CAT? (mRNA would be GUA), amino acid is Valine. • If a genetic mistake took place during replication and the new DNA strand has the sequence CAG, what is the new mRNA, and which amino acid would this result in? (mRNA is GUC), amino acid is Valine. • What if the genetic mistake resulted in a DNA strand with the sequence GAT? (mRNA is CUA), amino acid is Leucine. • Explain these results. Because there is some redundancy in the codons versus amino acids some genetic mistakes will not result in a change of amino acids, while other mistakes will.