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Name____________________________ Per____ Ch. 6 Meiosis, Chromosomes, & Karyotypes STUDY GUIDE DUE_______ Directions: Use the terms in the word bank to complete the paragraph below. Some words will not be used. Diploid Meiosis Gamete Haploid Homologous chromosomes Gene Fertilization Crossing over A segment of DNA on a chromosome that controls the production of a protein is called a _____________. A ________________ cell contains two copies of each chromosome. A sex cell, or ______________________, is ________________________ meaning it contains one copy of each chromosome. ______________________________ are pairs of chromosomes, one from each parent. _____________________________ creates genetic variation by providing new combinations of genes that are different from the parents. Directions: Compare meiosis and mitosis by filling in the chart below with the correct answer Mitosis Meiosis Number of times cell is in interphase Number of DNA replications Number of cell divisions Number of daughter cells Chromosome number of daughter cells (n or 2n) Directions: Use the word bank to correctly complete each sentence. Some words may be used more than once. Diploid Haploid Meiosis Mitosis Homologous chromosomes 1. In meiosis, one ____________________ cell divides to make four ________________ cells. 2. A ____________________ cell has half the chromosomes of a __________________ cell. 3. Pairs of chromosomes that have genes for the same trait arranged in the same order are _______________________________________. 4. During __________________________, two divisions of the nucleus and the cytoplasm occur. 5. Prophase I and prophase II are stages in ______________________. 6. In ____________________ two identical somatic cells are made. 7. In ____________________ four different gametes are made. 1 Directions: Complete the table below and answer the questions that follow Organism Somatic Cells (2n) Gametes (n) Human 46 23 Garden Pea 14 Fruit Fly 16 Tomato 12 Chimpanzee 78 Dog 48 Leopard Frog Corn 1. 2. 3. 4. 39 13 20 What is the diploid number for a chimpanzee? ____________ What is the haploid number for a fruit fly? _______________ Which organism has 24 chromosomes in each of its body cells? ____________________ Which organism contains 24 chromosomes in each of its egg cells? _________________ Directions: Answer each question on the lines provided. 1. If a male organism has 40 chromosomes in each body cell, how many chromosomes does a female of the same species have in each body cell? _____________ 2. How many homologous pairs of chromosomes does the male have? _____________ 3. How many chromosomes would be in a sperm cell and in an egg cell? ____________ 4. How many chromosomes would be in an offspring? ____________ 5. How many pairs of homologous chromosomes would be in an offspring? _____________ Directions: Complete the table by checking the correct column(s) for each description Mitosis Meiosis Involves in the production of gametes Involves in growth and repair Promotes genetic variation in organisms Consists of one nuclear division (nucleus divides once) Produces daughter cells that are genetically identical Involves two sets of nuclear division (nucleus divides twice) Produces daughter cells that are not identical Occurs during sexual reproduction Occurs during asexual reproduction Results in four haploid gametes 2 Chromosomal Alterations Read and annotate the following article to answer the questions and complete the coloring diagrams on the back. Permanent changes in chromosomes known as mutations may be passed to the offspring of a mating pair if they exist in cells that produce sperm or egg cells. One kind of mutation affects only a single gene, while other types of mutations involve the rearrangement of several of them. For instance, pieces of chromosomes may be lost or exchanged between nonhomologous chromosomes. When altered chromosomes are passed to offspring, variation increases. The diagram (on back of page) displays four different types of alterations that can occur in chromosomes. Focus on the first two alterations, entitled Deletion and Inversion. The first chromosomal alteration we will discuss is deletion, which is illustrated in the upper left portion of the diagram. You should begin by coloring the normal chromosomes with genes A to G using seven distinct colors. When gene deletion occurs, a portion of the chromosome is lost, usually from the end. In our diagram, the chromosome that has undergone deletion is missing gene A. The remainder of the chromosome should be colored with the same colors that were used in the normal chromosome. A deletion sometimes results in the loss of an important gene, with severe consequences to the organism. We will now turn to the second chromosomal alteration, called inversion. You should continue to use the same colors for the genes. We will now show how inversion differs from deletion. We will start again by looking at the normal chromosome, which contains genes A through G (A to G). When an inversion takes place, a segment of chromosome turns around 180°. Notice that genes C and D have inverted, so that the sequence of genes in the altered chromosome is different. At first glance, it may seem that the chromosome is not affected because the genes are present, but the position of a gene in a chromosome is very important. For example, a gene may be separated from its nearby regulatory gene as a result of inversion, so its rate of expression may be altered, or it may cease to be expressed at all. Scientists believe that chromosomal inversion may be a factor in developing cancer cells. We will now focus on a third type of alteration called Translocation, in which two chromosomes are involved. Continue your coloring as you read below. A translocation involves the movement of a chromosomal segment from one chromosome to another. The two chromosomes involved are nonhomologous, which means that they are chromosomes from different chromosomal pairs. Begin by coloring genes A through G with the colors you used above, and then color the genes of the second chromosome, genes H to N, with different colors. ( Note: if you do not have enough different colors, feel free to use green stripes, green dots, red squiggles, etc. to differentiate the gene colors.) Now take a look at the point at which translocation has taken place. Genes F and G from the first chromosome have moved to the second chromosome, and genes M and N have moved from the second chromosome to the first. Chromosomes 1 and 2 are now considerably different than they were originally. Certain translocations have been linked to cancer, and abnormal gametes can result from this alteration. The final type of chromosomal alteration that we will consider is Duplication. Focus on the lower right portion of the diagram. The same colors that you used for the genes labeled before should be used here. In duplication, a chromosomal segment doubles itself. For instance, here we see the normal chromosome with genes A to G on the left, but genes D and E appear twice after duplication occurs in the abnormal chromosome. Duplication occurs when a broken segment of one chromosome attaches to its homologous chromosome. One effect of the repeating genes may be duplicate proteins in an individual. For example, there are two alpha chains in hemoglobin molecules in human red blood cells. The two molecules may result from a single gene that duplicated in an ancient ancestor so that the modern descendent now produces two proteins instead of one. Therefore, duplication may be a factor in evolution. Helpful hints: COLOR the KEY at the bottom of the next page as you color the genes. Also, if you have run out of colors, feel free to use colored symbols (i.e. solid red, red dots, red stripes, red squiggles, etc.) to give you multiple “colors” from one color. Questions: 1. What are mutations? 2. What is a deletion mutation? What could be the result? 3 3. Explain what an inversion mutation is. 4. What is one abnormality that may result from a chromosomal inversion? 5. What is a translocation mutation? 6. Duplication mutations are thought to possibly be a factor in _____________________, which is when species change over a long period of time. Color the chromosomal mutations and the key below as described in the reading on the previous page. 4 Biology Student EQ: Do I carry deadly genes? Karyotype Study Guide Targeted Skills analysis Enduring Understanding Nucleic acids transfer genetic information from generation to generation. Broad Brush Knowledge chromosomal disorders Concepts Important to Know and Understand Heredity Core Objectives 9. Interpret the role of genetics in determining heredity and as it applies to biotechnology. BACKGROUND INFORMATION Problems in the number of chromosomes (called chromosomal abnormalities) can be detected in an organism. In order to do this, cells from the organism are grown in a laboratory. After the cells have reproduced a few times, they are treated with a chemical that stops cell division at the metaphase stage. During metaphase, the chromosomes are at the best length for identification. Each chromosome has two identical chromatid pairs attached at the centromere. The appearance of each chromosome resembles an Xshape. The cells are treated further, stained, and then placed on a glass slide. The chromosomes are observed under the microscope where they are counted, checked for abnormalities, and photographed. The photograph is then enlarged, and the chromosomes are individually cut out. The chromosomes are identified and arranged in homologous pairs. Homologous chromosomes are identical, or matching, chromosomes. One chromosome in a homologous chromosome pair comes from the mother, the other from the father. The arrangement of homologous chromosome pairs is called a karyotype. Humans have 46 chromosomes, 23 pairs. A human karyotype would show 23 pairs of homologous chromosomes, lined up from largest to smallest. The most common chromosomal abnormalities are caused when the chromosomes do not separate properly during meiosis (called nondisjuction). A monosomy is when only one homologous chromosome is present in the organism and a trisomy is when the organism has three copies of a homologous chromosome. The following are examples of three of the more common nondisjunction chromosomal abnormalities. If there is a nondisjunction at chromosome 21, the result could be trisomy 21 (3 #21 chromosomes) also called Down Syndrome. If there is a nondisjunction at chromosome 23, the result could be trisomy 23 with XXY also called Klinefelter’s Syndrome. If there is a nondisjunction at chromosome 23, the result could be monosomy 23 with XO also called Turner’s Syndrome. Define 1. karyotype ___________________________________________________________________________ _____________________________________________________________________________________ 2. homologous chromosome ______________________________________________________________ _____________________________________________________________________________________ 3. centromere __________________________________________________________________________ _____________________________________________________________________________________ 4. chromatid pair _______________________________________________________________________ _____________________________________________________________________________________ 5. chromosomal abnormality ______________________________________________________________ _____________________________________________________________________________________ 5 6. nondisjunction _______________________________________________________________________ _____________________________________________________________________________________ 7. two types of nondisjunction a) monosomy ________________________________________________________________________ _____________________________________________________________________________________ b) trisomy __________________________________________________________________________ _____________________________________________________________________________________ 8. Define Down Syndrome _______________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 9. Define Klinefelter syndrome ____________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 10. Define Turner syndrome ______________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ Directions Use the attached pictures to complete the table below. Figure Number of Autosomes Number of Sex Chromosomes Gender Normal or Abnormal Type of Abnormality Which Chromosome has the Abnormality? 1 2 3 4 6 Figure 1 Figure 3 Figure 2 Figure 4 7