SCI 135 - Third Exam Spring 2018
Answer Key


On the line to the left, place the letter of the choice that best answers the question.
Three Points Each. NOTE: "e" answers are never the correct answer.

        1. During fertilization,

___B___    a. Diploid cells get together                                b. Haploid cells get together
                c. One diploid cell joins one haploid cell               d. All of these can happen
                                    e. Fertility is, umm, made fertilaceous...

        ...haploid (1 set of chromosomes) fuse to form the 2 sets (diploid) for the offspring.

        2. Which cell function is closely associated with the presence of Golgi bodies?

___B___    a. Storage         b. Secretion        c. Reproduction         d. Movement        e. Golgi-something

        ...match the organelle to its use.


        3. Which is made up mostly of RNA and RNA components?

___A___    a. Nucleolus         b. Chromosomes         c. Nucleus        d. Endoplasmic reticulum         e. RNA bisque

        ...again, match the organelle to its use.

        4. What is done with a cell by endoplasmic reticulum is done by a human with their

___C___    a. Muscle system         b. Nervous system        c. Circulation system         d. Digestive system
                                                                    e. Credit cards

        ...they both are the transport system for materials to get where they have to.

        5. Under normal conditions, rare sodium ions move slowly from fresh-water into plant cells,
                            where the concentration is higher. This is done by

___B___    a. Osmosis         b. Active transport         c. Diffusion        d. Passive transport         e. Plant elves

        ...if it's going low-to-high, it's got to be active.

        6. In a double-stranded chromosome, a telomere can be found

__D____    a. Holding each strand together                    b.  Side-by-side - it is the name of the strands
                c. Only during telophase                               d. At the end of each strand
                                e. Only if you really really want to find it

        ...that's where telomeres are - they are the "caps" on the strands.

        7. For humans, which number of chromosomes would be polyploidy?

___B___    a. 47         b. 92         c. 23         d. 46         e. 18 and-a-half

        ...multiple sets, when humans have 23 pairs in a cell (this would be 4 sets).

        8. The best explanation for why most genetic diseases are recessive involves

___B___    a. Two DNA codes that can’t be used                b. Two DNA codes for non-working proteins
                c. DNA codes that don’t get passed on                d. All of these are involved
                                                e. Explaining what recessive means

        ...if only non-working proteins can be made, that job won't get done.

        9. Histones are closely associated with

___A___    a. DNA         b. Spindle fibers         c. Chlorophyll        d. Cell membranes         e. Lowstones

        ...they are the packaging proteins that allow a lot of DNA to fit into tiny chambers.

        10. In dividing cells, actual cell division (cytokinesis) occurs

___D___    a. Only in telophase            b. In anaphase or telophase            c. In telophase or interphase
                d. In interphase, telophase, or anaphase            e. When cell parts get really angry with each other

        ...once the strands are apart, it can be done at any time up to prepping the next division.

        11. Cells usually secrete materials using

___B___    a. Pigments         b. Exocytosis         c. Endocytosis         d. Spindles         e. Cell slime

        ...moving stuff out using vesicles flowing onto the membrane.

        12. Position effects refers to where _____ are.

___D___    a. Chloroplasts         b. Mitochondria         c. Ribosomes        d. Genes         e. The things I studied

        ...translocation mutations can move genes to where they are easier or harder to use, changing expression.


Answer any eight of the following questions for 4 Points Each.
Note: if you answer more than eight, only the first eight will be corrected.
You can get partial credit on these answers.

1. What two abilities must an HIV escape mutant have to be truly dangerous?
Must be a working virus (can attack new cells) Has surface antigen that host's antibodies can't attach to

2. What are the two typical components of cytoskeleton?
Microtubules Microfilaments

3. For high chromosome numbers (compared to low numbers), give one specific -
ADVANTAGE-    More variation in sexual reproduction DISADVANTAGE -  More errors when cells divide

4. What two areas of well-funded medical research are focused on telomerase?
Aging (restore telomerase for better damage repair) Cancer (take away a chemical that helps cancers progress)

5. The spindle fibers are made up of what particular cell structure?


6. What are two different ways that living things keep osmotic pressure from hurting them?
Cells in casings that osmotic pressure can't break

Pump out excess water
Waterproof every surface that can be waterproofed

7. Give two things whose formation would be driven by HOX genes.
Any basic layout (front/back, right/left, structure placement) features

8. Some radiation can have huge effects on cells, even producing cancerous changes. What particularly does the radiation do inside the cells? can break DNA in multiple places, so it's hard to repair properly (and often leaves pieces loose)

9. For the fluid mosaic model of cell membranes, describe the -
FLUID      The free-flowing PHOSPHOLIPID
part -              molecules in 2 layers
MOSAIC      The other molecules, mostly proteins,
part -               in patterns in & on the membrane

10. What is the function of microvilli?

        ...they increase the surface area of a cell.

11. Of the point mutations, an addition is much worse than a substitution. Explain why.

        ...a substitution changes the codon it's in, but an addition "bumps" the beginning of every codon from there to the end of the gene, changing every one downstream.

12. What, technically, is a gene?

        ...a sequence of DNA that codes for a particular type of protein.

13. What are two major functions of centromeres?
Hold chromosome copies together Connect to spindle fibers during cell division

14. Briefly, what is the endosymbiont theory?

        ...the idea that some organelles were originally prokaryotes taken in as food but "put to work" with a really valuable function instead.

15. What is one thing that happens in Meiosis I that does not happen in mitosis?

        ...homologous pairs of chromosomes are put together during prophase, then the pairs, but not the copy strands, separate during anaphase.

16. Explain why a cell attacked by prions eventually stops working properly.

        ...prions take working proteins doing some important job in the cell and change them into prions, until there are no proteins doing the job anymore.


Answer any four of the following questions for Eight Points Each.
Note: if you answer more than four, only the first four will be corrected.
You can get partial credit on these answers.
1. Using this DNA code give the messenger RNA sequence and, using the chart available with the exam, give the coded amino acid sequence.
Strand     T A C A G C C A A C T G G G C C C G T A G A C G A C T

mRNA   A  U  G -U  C  G -G  U  U -G  A  C -C C G - G G C -A U C -U G C -U G A
               the dashes are just there to mark the codons.
Acids      Methionine - Serine - Valine - Glutamate - Proline - Glycine - Isoleucine - Cysteine

2. What are four different types of proteins that can be embedded in a cell membrane?
Pores / Channels Pumps
Receptors Connectors
Markers Enzymes

3. For the four phases of mitosis (so not the one between / INTERPHASE), name the phases in order and give one specific thing for each that happens particularly in that phase.
Prophase Chromatin, chromosomes appear.  Spindle forms and attaches to chromosomes, pulling them toward cell middle.  Nuclear envelope and nucleolus disappear.
Metaphase Chromosomes lined up in middle of the cell.  Chromosome strands separate.
Anaphase Chromosomes pulled away from each other.  Cell plate forms in plants.
Telophase Prophase steps reverse.

4. Give three sets of differences (other than the associated genders) between -
Much larger (holds food for offspring) Much smaller
Fewer made Many more made
Must be reached by sperm Have way to get to where the egg cell is
One starting cell makes one working egg cell (and 3 polar bodies) One starting cell makes 4 working sperm

5. Give three sets of differences between -
Larger Smaller
Rarely more than 12 on a cell Always many on a cell
May have add-on structures Don't have add-ons
Usually spin Usually stroke

6. For four different types of vesicles or vacuoles, give the name and function:
Lysosomes Contains digestive enzymes
Peroxisomes Recycles cell materials
Secretory vesicles Takes secretions out of the cell
Central vacuole Stiffens cells in small green stems
Contractile vacuole Pumps out water entering by osmosis
Food vacuole Brings larger items into the cell to be broken down

7. For the three basic layers of an early embryo, give -
ENDODERM Digestive, respiratory
ECTODERM Skin, nervous, exoskeleton
MESODERM Muscle, circulation, excretory, endoskeleton, reproductive


Answer as many as you are able. Wrong answers will not result in points being lost from the main exam. You can get partial credit on these answers.

What is a mosaic? Three Points.

Why don’t animals have cell walls? Three Points.

To study cell membranes, red blood cells are popped using what simple approach? Three Points.

Why is it called a nuclear envelope? Three Points.

What was the most convincing piece of evidence to convince folks about the endosymbiont theory? Three Points.

Why did Mendel do his genetics work on pea plants? Three Points.

What is a Barr body? Three Points.

What type of proteins can be made using the splicing function? Three Points.

When cells turn into cancer, they spend less and less time in interphase. Why? Three Points.

Why is it important that only the nucleus from the sperm, and no other organelles, get into the egg cell during fertilization? Three Points.



SCI 135 

Michael McDarby