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Assignment 3 KEY Spr 20201

BIOL 151 – Spring 2020
Dr. Gulrud
Assignment Key Unit 3 Review of Chapters 10-12 - KEY
Instructions: Read the corresponding textbook chapters, listen to the lecture recordings and
animations, and check your understanding with Kahoot. Then answer all of the following questions and
submit your completed worksheet to the D2L dropbox before 11:59 pm on April 11th. Late
assignments will only be accepted in excusable circumstances verified with documentation.
Assignments can be submitted into a dropbox on D2L before 9 am on the due date. An answer key will
be posted on D2L Brightspace on April 12th. You are strongly encouraged to review the answer key to
help prepare for your unit exam. Be sure to include your name and lab section.
1. Place the following phases of the cell cycle in order, beginning with G1
(M phase, Cytokinesis, S phase, G2)
G1 → __S phase_____→ __G2__________ → ___M phase____ → __cytokinesis__ → G1
2. Describe each of these proteins and their roles in genome organization and cell division. Be sure to
indicate which domain of life (Bacteria, Archaea, or Eukaryotes) they function in.
a. Histones/Nucleosomes-small, eukaryotic proteins around which the DNA double helix
wraps to compact the DNA into chromatin.
b. Synaptonemal complex –structure that holds two homologous chromosomes together in
prophase I, so that crossing over can occur.
c. Kinetochore proteins-eukaryotic proteins that bind to the centromere of chromosomes and
attach to microtubules.
d. Cohesin – eukaryotic protein that holds sister chromatids together after they are created by
DNA replication
e. FtsZ-bacterial and archaeal protein monomer that polymerizes to form microtubule-like
tubes, forming a ring that “pinches off” the septum during binary fission.
f. Tubulin-structures composed of tubulin that push and pull chromosomes during anaphase.
Also part of spindle fibers/spindle apparatus
3. Label sister chromatids, cohesin, and homologous chromosomes in the following electron
micrograph of 2 human chromosomes.
Homologous Chromosomes
Sister Chromatids
4. Place the following phases of Mitosis in order as they occur during mitosis and state the key events
that occur during each phase.
(Anaphase, Metaphase, Prometaphase, Telophase, Prophase)
Key Events
1. Prophase
Chromosomes begin condensing and become visible, mitotic spindle begins
to form, nuclear envelope breaks down, golgi and ER disperse
Microtubules attach to kinetochores, chromosomes continue to condense
2. Prometaphase and begin move to center of cell
3. Metaphase
Chromosomes align at middle of cell
4. Anaphase
Cohesin is cleaved and sister chromatids separate in 2 phases (A and B)
5. Telophase
Mitotic spindle disassembles, nuclear envelope reforms, chromosomes
5. Name the phase of MITOSIS that each of the following cells represents. Note that this cell is a diploid
eukaryote that has 2 pairs of chromosomes for a total of 4 chromosomes (analogous to humans
having 23 pairs of chromosomes for a total of 46 chromosomes).
Chapter 11 Meiosis
6. What is separated during each of the following phases of Meiosis?
a. Anaphase I: Homologous Chromosomes
b. Anaphase II: Sister Chromatids
7. In what phase of Meiosis does crossing over occur? Prophase I
8. Circle the correct answer. Meiosis I / Meiosis II is most similar to Mitosis.
9. Fill in the blank with a number.
Mitosis in diploid cells produces ___2____ identical cells, each with __2___ copies of every
gene/chromosome while Meiosis produces ___4_____ non-identical cells, each with __1____ copy
of every gene/chromosome.
10. What cells undergo meiosis? Germline cells that are specialized cells in the testes and ovaries of
animals for example that produce gametes.
Chapter 12 Inheritance
11. Monohybrid crosses helped Mendel develop the principle of __segregation__ while dihybrid crosses
helped him develop the principle of _independent assortment_.
12. Explain how the white flower color trait was able to “Hide” in the F1 generation of Mendel’s
monohybrid cross of pea plants. The white flower trait needs 2 copies to create the phenotype. The
F1 generation contained just 1 copy so it was present but hidden by the presence of the purple
13. Mendel’s monohybrid crosses yielded an F2 phenotypic ratio of __3:1_______ while his dihybrid
crosses yielded a phenotypic ratio of ____9:3:3:1______.
14. During his experiments with pea plants, Mendel referred to the trait that was expressed in the F1 or
first filial generation as _________ .
a. Dominant
b. Recessive
c. Homozygous
d. Codominant
15. Juvenile Glaucoma is a human condition that results in blindness and is caused by a dominant allele.
Draw a Punnett Square to determine the expected genotypic and phenotypic ratios of a cross
between a Heterozygous blind individual and a normal individual (use G = Glaucoma allele and g =
normal allele).
a. Genotypic Ratio: 1Gg : 1gg
b. Phenotypic Ratio: 1 Glaucoma : 1 Normal
c. Describe what percentage of this couples children would be expected to have Glaucoma.
1 out of every 2 children or 50%
d. If this couple has 4 children, is it possible for all 4 of them to have normal vision? Why?
Yes, although unlikely it can happen because with a small sample size this can happen by
random chance just like you can filp “Heads” 4 times in a row when flipping a coin.