SCI 135 - Third Exam Fall 2013
Answer Key

Links in each number connect to the pertinent sections of the online book.



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.   Position effect can change how

___C___                    a.  Cells reproduce
                                 b.  Cells relate to each other in multicelled systems
                                 c.  Genes get expressed
                                 d.  Materials get moved through a cell membrane
                                 e.  Easily your foot goes to sleep

                                  ... some mutations (translocations) move genes from "loosely-wrapped"
                                    parts of a chromosome to "tighter," harder-to-access parts, and the genes
                                    get used less there (or the opposite happens).


                        2.   In the fluid mosaic model, the phospholipid molecules are

___B___                    a.  Held tightly to each other          b.  Freely floating in 2 layers
                                 c.  Held in place by proteins           d.  Only a small part of the membrane
                                 e.  The things that are by the things when the things are there

                                  ... they are the "fluid" part of the model (embedded proteins are the "mosaic").


                        3.   A cell that specializes in absorbing materials most likely has

___D___                    a.  Cilia                       b.  Golgi bodies                    c.  Ribosomes
                                d.  Microvilli                         e.  Issues with self-image

                                  ... they increase surface for that absorption.


                        4.   Mitochondria are found in

___C___                    a.   Plants but not animals                   b.  Animals but not plants
                                 c.   Both plants and animals                d.  Neither plants nor animals
                                               e.   Books that only insane people read

                                  ... 99+% of eukaryotes (plants, animals, fungi, protists) do aerobic
                                    respiration, done in mitochondria.


                        5.   Water moves from soil, where the water is close to pure, to the cells of
                                                a plant’s roots.  This movement is

___B___                    a.  Performed by the lining cells of the root
                                 b.  Passive transport
                                 c.  Active transport
                                 d.  Only done if nutrients are carried in the water.
                                 e.  Not particularly interesting

                                  ... the movement is "downhill," from a higher-concentration area to a
                                        lower-concentration one.


                        6.   Which is an example of apoptosis?

                                 a.  A hand forms as a paddle;  cells between the bones die to separate
                                                the fingers

                                 b.  Some materials have to be helped to move through a membrane,
                                                even if they are going in the “right” direction
___A___                    c.  After digestion, leftover materials are ejected from the cell
                                 d.  Many places in DNA code for small functional RNA molecules
                                 e.  Somebody drops a really heavy rock on their bare foot

                                  ... cells dying because they need to, they do it to themselves.


                        7.   Which can change almost the whole sequence of a coded protein?

___D___                    a.  Radiation                b.  Substitution                c.  Translocation
                                 d.  Deletion                              e.  Scrambling with a whisk 

                                  ... if a nucleotide in a codon is lost, that codon changes and every following codon
                                        is shifted one spot down, potentially changing them all.


                        8.    Which starts with diploid cells and ends with haploid cells?

___A___                    a.  Meiosis               b.  Transcription                 c.  Mitosis
                                 d.  Translation                             e.  Is that even legal? 

                                  ... 2 sets of chromosomes reduced to one set each.


                        9.   A nucleolus  would contain a lot of

___C___                    a.  Membrane               b.  DNA                     c.  RNA
                                 d.  Carbohydrates                 e.   Cell slimey stuff 

                                  ... that's where a lot of RNA is stored and processed.


                        10.  Sectioning needs to be done to

___A___                    a.  Prepare tissues for the microscope
                                 b.  Figure out where genes are on a chromosome
                                 c.  Position chromosomes for a cell division
                                 d.  Subdivide eukaryote cells for different functions
                                 e.  Keep the drunks away from the nice customers at games 

                                  ... it's the thin-slicing so a transmission beam can go through. 


                        11.   Recessive traits show up with which allele combination?

___D___                    a.  Three recessives and a dominant             b.  Four recessives only
                                 c.  One dominant and one recessive             d.  Two recessives only
                                                e.  Time for rock, paper, scissors, shotgun… 

                                  ... alleles work in pairs, and recessives only show if no dominants hide them. 


                        12.   Materials are broken down for recycling in the

___B___                   a.  Pseudopod                b.  Peroxisome                c.  Golgi bodies
                               d.  Nucleus                                 e.  Recyclothingy

        ... one of those remember the name things.   




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

1.   What are two components of the cytoskeleton?
Microtubules Microfilaments
2.   Give the terms that go with each definition -


TYPES OF GENES            (one of two types)
3.    Give two different things that parts of our noncoding DNA might be -
Help in chromosome structure.

Old unused genes.

Functional RNA codes (not really non-coding, but not known until recently)

Regulators of gene expression.

Foreign genes.

DNA mini-parasites.

4.   Give the basic structural difference between -
Just membrane in lining Lining membrane has ribosomes embedded
5.   What is the function of histones?

        ...they are the proteins that DNA is packaged with to make chromosomes.

4.   It’s called a nuclear envelope, not a nuclear membrane.  Give one feature about it that makes it different from a “regular” membrane (other than it being around the nucleus).
 is 2 membranes thick.

7.   The two different medical research areas that are very interested in telomeres -
(telomerase to complete copied chromosome tips made less and less with aging, compromising repair functions)
(cancer cells require working telomerase to make lots of cells)
8.   Give one set of differences between -
Only one in the cell

Loop-shaped chromosomes

May make plasmids (little partial chromosomes)

Homologous pair(s)

2-ended chromosomes

Do not make plasmids

9.   Explain why HIV escape mutants are so dangerous.

         ...they still work to invade and kill cells of the immune system, but existing HIV antibodies can't attach to altered antigens.  By the time new antibodies are in production, the immune system can be too shut down to use them.

10a.  What is a Barr body?

10b.  Why do Barr bodies exist?

A deactivated X chromosome It "equals out" working X chromosomes between XX genders and XY genders.
11.  Give two pieces of evidence that supports the endosymbiont theory.  - That some cell organelles began as kidnapped prokaryotes that worked for the bigger eukaryote rather than being digested.
Structures and molecules in organelles almost identical to known prokaryotes.

Such kidnapping & use is found in some existing eukaryotes.

Organelles have partial but clearly prokaryote-type chromosomes inside them.
12.  For a low chromosome number (compared to a high chromosome number) -
ADVANTAGE –  Fewer mistakes during cell division DISADVANTAGE -  Less variety for sexual reproduction

13.  Briefly give the most common explanation for why cells seem to have a maximum size limit.

         ...growing cells increase volume (working chemistry) at a much faster rate than surface area (input / outgo for that chemistry).

14.  What are two Kingdoms of Life where all of the cells have cell walls?




15.  Give the names of two different types of vacuoles -
Food Vacuoles

Central Vacuoles

Contractile Vacuoles

16.  Explain how a prion can cause the malfunction of an entire cell.

        ...since the prions can turn working cell proteins into prions, the affected proteins stop doing whatever important function they were doing before being transformed. 



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

1.   Give three sets of differences (other than the associated genders) between -
Larger (hold food for offspring) Smaller
Comparatively fewer made Many more made
Must be reached by sperm Have way of getting to where egg cells are
One starting cell makes on egg cell and 3 tiny polar bodies One starting cell makes 4 working sperm
2.   Give three sets of differences between -



Larger Smaller
May have add-on structures Do not have add-on structures
Rarely more than 12 on a cell Always very numerous on a cell
Not usually very coordinated with other flagella Always highly coordinated with other cilia
Tend to spin Tend to stroke
3.   Give four rules from the Cell Theory.
All living things are made up of at least one cell. Cells are the smallest unit considered alive.
Cells only come from pre-existing related cells. Cells are more alike than different.
4.   Give the terms for each of the two groups in each microscope category -
(beam goes through)
(beam reflects off)
5.   What are three different ways that fresh-water organisms deal with osmosis?  Osmosis would continually move water into cells less dilute than the environmental water.

Pump excess water back out

Enclose cells to resist expansion Waterproof most surfaces

6.    Using this DNA code give the messenger RNA sequence and, using this chart, give the coded amino acid sequence.

T  A  C  C  C  A  T  G  G  T  A  C  C  G  A  T  G  A  A  A  A  G  C  G  A  T  T
                                                                 Codons marked:

mRNA  A  U  G -G  G  U -A  C  C -A  U  G -G  C  U -A  C  U -U  U  U -C  G  C -U  A  A

Amino  Methionine - glycine - threonine - leucine - alanine - threonine - phenylalanine - arginine (STOP)
  Acids    (start)

7.   Give four different functions for some of the proteins found embedded in cell membranes.
Allow materials through small holes (pores / channels) Move materials from one side to the other (carriers / pumps)
Pick up information from outside (receptors) Identification for other cells (markers)
Help bend the membrane to form vacuoles and pseudopods Attach the membrane to surfaces while crawling



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.

The resolution on light microscope hits a limit at about 1200X magnification.  Why can’t it be better than that?  Three Points.


Why do some specimens need to be coated with gold or platinum?  Three Points.


What common word applies to almost all prokaryotes (but not eukaryotes)?  Three Points.


For two points each, give up to three different materials that can easily pass through a typical cell membrane.  Three Points.


When a cancer becomes malignant, it turns on genes for what particular ability?  Three Points.


Cancers may begin when several different control systems malfunction.  For Two Points each, what systems might those be?


Mendel, the genetics monk, believed that he was not really successful as a scientist.  Why?  Three Points.


What particular feature is often true of proteins from recessive alleles?  Three Points.


What does the term “gender” mean, biologically?  Three Points.



SCI 135 

Michael McDarby





Hit Counter