Bio Homework 7 PDF

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Post-Lab Questions 1.In order for photosynthesis to occur in green plants, the following must be present: a. __sunlight_ as the energy source. b._ CO2__as the carbon source. c. __Chlorophyll_ for the absorption of light energy. d. _NADP__ as the electron donor. 2.According to your spectrophotometric data in Exercise B, which colors of light are used in photosynthesis? Red and Violet 3.Why do plants contain so many pigments? Multiple pigments absorb different wavelengths of light, allowing the plant to capture the maximum amount of energy from the sun. 4.When using the I2KI test in Exercise C, why did you extract the pigments from the leaf before adding I2KI? The pigments removed are similar to the color that would stain the leaf if there was starch present. Data Exercise A: Modeling the Cell Cycle (Interphase) 1.Why are the activities of G1 important for a cell that is preparing to divide? Cells increase in size in Gap 1, produce RNA and synthesize protein and the first check point occurs here. 2.Why is it necessary for DNA to duplicate before cells divide? DNA replication is important since it creates a next copy of DNA that have to go into one of the two daughter cells when a cell divides. Without replication, each cell lacks adequate hereditary fabric to give instructions for creating proteins vital for bodily purpose. Exercise B: Simulation of Interphase, Mitosis, and Cytokinesis 1.What is the significance of using two different colors for the two homologous chromosomes? They could have different alleles. 2.Could you have used two red strands, one short and the other long? Why or why not? 3.Why do you need to replicate the centrioles? Centrioles help to arrange the microtubules that move chromosomes during cell division to ensure each daughter cell receives the appropriate number of chromosomes. 4.Why is it important that the chromosomes line up in single file during metaphase? This is where they organize and finally begin to separate. It plays an important role because it allows the cell to assemble and then divide the chromatids. 5.During mitosis, when would you change the description of DNA strands from chromatids to chromosomes? Metaphase 6.How many helices of DNA are in each of the daughter chromosomes after telophase? 2

7.How many chromosomes do you have in each of your daughter nuclei? 30 8.How does the number of chromosomes in the two daughter cells that you formed in your simulations compare with the number of chromosomes in the parent cell? The two daughter cells have half as many chromosomes per cell. 9.How do the two cells that you formed in your simulation compare with the parent cell with regard to which chromosomes are present? The parent cell is divided into two separate, but identical, daughter cells. Then the Homologous pairs are separated, and the two resulting daughter cells have half as many chromosomes per cell. 10.Would the constitution of the daughter cells be any different if you had lined up the metaphase chromosomes in a different order? No, the chromosomes need to be in a line in the middle so they can split correctly. the order doesn't matter because the chromosomes still split and travel to the opposite poles of the cell 11.If the red chromosomes represent paternal chromosomes and the yellow chromosomes represent maternal chromosomes, what can be said about the genetic constitution of the daughter cells? The genetic makeup would be a combination of both. 12.Keeping your answer to the previous question in mind, briefly describe how mitosis maintains a constant chromosome number and why daughter nuclei are always genetically identical. Interphase allows for the duplication for each chromosome which accounts for an equal number of chromosomes in each daughter cell. metaphase splits identical chromosomes in the middle to split off correctly. Exercise C: Mitosis in Living Tissues-Onion Root Tips 1.Describe what you observed. You could see Miotic processes in the root tip. 2.What might be the purpose of the root cap? The root cap protects the actively dividing cells. 1.The relative amount of DNA in a cell can be represented graphically over time. Label the line segments which show G1, S, G2, and mitosis.

2.Complete the following table and summarize the events of interphase in the following figure: Phase of Cell Cycle

Number of Chromatids per Chromosomes

G1 S G2 Prophase Metaphase Anaphase Telophase

46 92 92 92 92 92 92

1.How do protein kinases and cyclins regulate the cell cycle? Cyclins drive the events of the cell cycle by partnering with a family of enzymes called the cyclin-dependent kinases. A lone Cdk is inactive, but the binding of a cyclin activates it, making it a functional enzyme and allowing it to modify target proteins. 2.What role does cell division play in the growth of an organism? The growth of plant cells is dependent on the addition of new cells. 3.What is the function of the centromere region of a chromosome? Centromere function includes sister chromatid adhesion and separation, microtubule attachment, chromosome movement, establishment of heterochromatin and mitotic checkpoint control. 4.What is a centrosome? How are centrioles and centrosomes related? A centrosome is an organelle that is found close to the nucleus within the cytoplasm of cells. Centrosomes are key to the division of cells and produce the spindle fibers that are required during metaphase of mitosis. Each centrosome consists of two centrioles that are orientated at right-angles to each other. 5.What is the function of spindle fibers? How do they lengthen and shorten? Spindle fibers shorten and pull sister chromatids toward spindle poles. Separated sister chromatids move toward opposite cell poles. Spindle fibers not connected to chromatids lengthen and elongate the cell to make room for the cell to separate. 6.When does a chromatid become a chromosome? Anaphase 7.You have a diploid cell containing eight chromosomes (2n = 8). What would this cell look like at metaphase? How many chromosomes would each of the daughter cells have? At metaphase, there would be 4 chromosomes which consist of 4 sets of sister chromatids aligned at the middle of the cell. 8.You are given two dishes of beads, one containing red beads and the other yellow. Describe how you would simulate the chromosomes of a diploid cell for which 2n = 4. The red bead would describe one parent and yellow bead would describe the other parent and the daughter cells would have an equal genetic composition of both parent cells. 9.Can a haploid cell undergo mitosis? Why or why not? If you had a haploid cell with four chromosomes (n = 4), what would it look like during metaphase? Yes, because 4 chromosomes can be duplicated into 8 which is the function of Mitosis. 10.Indicate the stage of mitosis (interphase, prophase, metaphase, anaphase, telophase) during which each of the following events occurs. Prophase Nuclear membrane disappears.

S phase Centrioles replicate. Metaphase Chromosomes are arranged in single file between the poles of the cell. Anaphase Chromatids separate. Prophase Spindle fibers form. Telophase Cell plate forms. S phase DNA replication occurs. Prophase Chromosomes first become visible as long thin strands. Anaphase Chromosomes move to opposite poles of the cell. Data and Questions Exercise A: Simulation of Chromosomal Events During Meiosis 1.How many cells are formed during meiosis? Are the cells haploid or diploid? 4 daughter cells: haploid 2.How many cells are formed during mitosis? Are the cells haploid or diploid? 2 daughter cells: diploid 3.List 3 major differences between meiosis and mitosis: The number of daughter cells produced, Mitosis produces diploid cells and Meiosis produces haploid cells, and Mitosis only has one stage and Meiosis has two. 4.Place a single short strand of red beads and a single long strand of yellow beads on your table. a. Could a cell like this exist? Yes b. Would it be haploid or diploid? Diploid c.Is it possible for this cell to carry out mitosis? No d.Is it possible for this cell to carry out meiosis? No 5.Place a single long strand of red beads and a single long strand of yellow beads on your table. a. Could a cell like this exist? Yes b. Would it be haploid or diploid? Haploid c.Is it possible for this cell to carry out mitosis? No d.Is it possible for this cell to carry out meiosis? No Exercise B: Mendel’s First Law: Alleles Segregate During Meiosis 1.Why was it important that the two chromatids of the chromosome you created had the same alleles (A and a) on one dyad? So there are no genetic deformities. 2. Diagram the products of meiosis in the space provided below. Use colors to indicate individual chromosomes. Be sure to indicate (A) and (a) as they appear during the simulation.

3.Do your observations support Mendel’s "first law? Explain. Yes, because Mendel’s law states that there must be equal separation and there was in my diagram. 4.Consider the hybrid corn and answer the following questions: a. What color seeds would corn with the genotype (RR) have? Purple b. What color seeds would corn with the genotype (rr) have? Yellow c.What alleles can the parent with the genotype (RR) contribute? The dominant seed color which is purple. d.What alleles can the parent with the genotype (rr) contribute? The recessive seed color which is yellow. e. Create a Punnett square for the cross of RR with rr:

f. What genotype will the F1 offspring have? Rr g. What phenotype will the F1 offspring exhibit? Purple h. What alleles can F1 offspring contribute to gamete formation 3 Purple and one yellow i.Create a Punnett square for the cross of two F1 individuals:

j. What genotypes are possible in F2? Indicate the % likelihood of each. Rr, rr k. What is the expected ratio of purple: yellow kernels in the F2 generation? __3___:__1___

l.Counts observed from the hybrid cross corn: Purple Kernels: ___3_____Yellow Kernels: ___1____ m.What is your observed ratio of purple: yellow kernels? __3___:__1___ n. How do your counts compare to the expected ratio? Spot on lol o. Is it possible to determine the genotypic ratio from your phenotypic observations of the ear of corn? Explain. Yes, the genotype of the corn determines the color of the corn as well. Exercise C: Mendel’s Second Law 1.Given two pairs of homologous chromosomes, there are two possible alignments during metaphase I of meiosis. Draw both possibilities and indicate the alleles present on each chromosome.  Gametes  Gametes

2.Draw the chromosomes as they appear for both possibilities at all stages indicated in the procedure using colors to differentiate the chromosomes. Remember to indicate the alleles present. Shown above. 3.How many possible combinations of alleles exist? 4 4.Given an individual with the genotype AaBb, what are the possible gametes? aB, Ab, AB, ab 5.Using Mendel’s second law, trace the path of two unlinked genes through the following crosses: Gene #1: Seed Color (P and p); PP or Pp genotype results in a purple color; pp results in a yellow color. Gene #2: Seed Shape (S and s); SS or Ss genotype results in a smooth seed; ss genotype results in a wrinkled seed.

PPSS

PPSS

PpSS

PpSS

PPSS

PPSS

PpSS

PpSS

PPSs

PPSs

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PpSs

PPSs

PPSs

PpSs

PpSs

a. Which alleles are present in the gametes of these parent types: i. RRSS (purple, smooth)? ii.rrss (yellow, wrinkled)? PPSS(Purple Smooth), PpSS (Purple Smooth),PPSs (Purple Smooth), PpSs(Purple Smooth). b. What F1 generation genotype(s) are possible from crossing the two individuals listed above? Use a Punnett square to determine. Shown Above.

c.What phenotype will F1 individuals exhibit? Purple and Smooth d.Cross two heterozygous individuals from the F1 generation with each other; what are the possible genotypes of the F2 generation (offspring)? Use a Punnett square to determine. Use colored pencils to identify each of the different phenotypes produced by this cross. Circle all genotypes that result in a particular phenotype with the same color.

PPSS

PpSS

PpSS

ppSS

PPSs

PpSs

PpSs

ppSs

PPSs

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ppSs

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ppss

e. What is the expected proportion of each genotype in the F2 generation? PPSS, PpSS,ppss,PPSs,PpSs,ppSs,Ppss 6.Complete the following table with your expected and observed results for the F2 generation of the cross above: Phenotypic Ratio Expected (Purple: Yellow) __12_____: ___4____ 7.Do your observations match the expected values? Explain. Yes, they match. 8.Would you expect to see the same genotypic to phenotypic ratios if the alleles/genes were linked? Explain. Yes, it doesn’t change the genetic makeup....