Test 2

Question 1

The first experiment we discussed showed the
abiotic synthesis of small organic molecules from
inorganic compounds. Consider the early planet,
which was probably thick with water vapor and
stinky with methane, ammonia, and hydrogen
sulfide. What gas was missing from this early
mix? Why?

Answer 1

Oxygen was missing because this was before photosynthesis.

Question 2

How old is the planet? How old is the
earliest fossil evidence of life on Earth? .
What kind of organisms was the earliest fossil?

Answer 2

4.6 Billion years. Life is 3.5 billion years. Bacteria was the oldest fossil.

Question 3

flipping membrane picutre.

What do these images highlight as an important
step in the origin of life on earth?

Phospholipids are amphipathic. Explain what this
means.

The head is hydrophilic, and the tail is
hydrophobic. Now, use the sketch of
phospholipid bilayer structure of a plasma
membrane. Label the hydrophilic heads,
hydrophobic tails, and location of water.
Why are the tails all located in the interior?

Answer 3

It highlights that amphipatic molecules Spontaneously form vesicles when placed into water (lipid bilayers). It is critical to develop a cellular membrane and have an inside of the cell different from the outside.

Ampipathic: hydrophillic region and hydrophoic region.

Tails are in contant w each other and remote from water. Heads like water.

Question 4

What are ribozymes?

Answer 4

RNA molecules that catalyze reactions.

Question 5

Explain the evidence for the “RNA world
hypothesis”

Answer 5

RNA can replicate and perform catalytic action. RNA with greatest ability to replicate will reproduce. Occasionally, a copying error will result in a molecule that folds into a shape even better.

Question 6

Here is a figure that shows the structure of a
phospholipid. Label the sketch to show the
phosphate group, the glycerol, and the fatty acid
chains. Also indicate the region that is
hydrophobic and the region that is hydrophilic.

Answer 6

Phosphate group is P surrounded by Os.
Head is hydrophyllic. Fatty acid tails are phobic.

Question 7

This is the stressed
+ non stressed graph

What did this experiment show? How is it related
to the origins of life on earth?

Answer 7

It shows that competition among abiotic vesicles was possible.
Osmosis could lead to a lipid competition that was driven by cargo inside the vesicle. Cargo could be RNA which could explain how first cells evolved via natural selection. More RNA were more stressed and were better competitors.

Question 8

This is the early earth simulator. The tube thing

Explain this apparatus, how it works, what it is
trying mimic, and their results

Answer 8

It was used to simulate primitive earth. Modern air was removed and filled with hydroden, methane, ammonia. He applied heat to make steam and electricity. then steam cooled to liquid and r4epeated. amino acids were then produced,

Question 9

This is another nonstressed/stressed graph again with the orange line.

What is the difference between the results
presented both of these figures? What are
similarities in their results?

Answer 9

Top two created stressed vesicles by placing tRNA inside cell. this is more representative of the type of solutes that could have created osmotic pressure in the first cells on earth, compared to the sugar presented in. the four panel figure below. Both showed that abotic vesicles with more solutes inside and whose membranes were stressed could outcompete vesicles lacking solutes and therefore evolve via natural selection. both show that differences in osmotic pressure is enough to change outcomes of competitng for limited resources.

Question 10

What were Darwins inferences and observations
that led him to develop the theory of evolution
by natural selection? What are the tenants of
natural selection?

Answer 10

Variations in traits exist. these traits are heritable. Species overproduce. There is competition for resources. Differential survival, so not all offspring survive. Future generations will have greater frequencies of traits that increases fitness in a given environment.

Question 11

Explain the process of natural selection.

Answer 11

Individuals that have certain inherited traits survive and reproduce at higher rates. survival of the fittest.

Question 12

______ do not evolve, _________ evolve.

Answer 12

Individiuals do not evolve, populations evolve.

Question 13

Do antibiotics cause bacteria to become
resistant? Do antibiotic cause bacteria to get a
mutation to make them resistant? Explain your
response and how bacteria populations become
resistant to antibiotics

Answer 13

No, a drug doens’t create resistant pathogens. It selects for resistant individuals that are already in a population. over generations, populations will become more resistant because they will survive and reproduce.

Question 14

What is the definition of evolution
(microevolution)?
What is a population?

Answer 14

change in allele frequencies in a population over generations.

a pop is a group of individuals in SAME SPECIES that lives in SAME AREA and INTERBREEDS producing FERTILE offspring.

Question 15

What are the four main mechanisms that can
cause the evolution of populations?
Of the four mechanisms of evolution, what is the
only mechanism that is adaptive?
What is the definition of an adaptation?

Answer 15

NAtural selection, gene flow, genetic drift, mutations.

natrual selection is adaptive.

adaptation is a trait that improves the match between organisms and their environment, increasing their fitness in the environment.

Question 16

Several sources of genetic variation are available.
What is the ultimate source of new alleles and
genetic variation?

Answer 16

Random mutations

Question 17

Ph graph vs the surface area graph

Describe this experiment and how its results
improved our understanding of abiotic origins of
life.

Answer 17

it showed that growing abiotic vesicles could accumulate a lower internal PH (more protons), Abiotic vesicles store energy in absence of any proteins by flipping fatty acids to inner leaflet. This brings protons into the cell, creating a gradient, which is a form of potential energy that can perform cellular work. the internal pH dropped as the vesicle.

Question 18

light absorbance v time. montmorillonite, ceramic microspehres. (charged clay shit)
Describe this experiment and what its results
supported.

Answer 18

myristoleate congregates on clay called montmorillonite when mixed w water. fatty acids may have been limited in primitive earth, so negatively charged clay acted as a catalyst. RNA is negatively charged, so maybe it could have catalyzed vesicle formation.

vesicles still form with buffer alone, and without charged surfaces, but not as fast.

Question 19

What is the probability that a particular base pair
is conserved in at least 19 out of 20 ribozyme
sequences if the probability of conservation in a
single base pair is 0.70?

Answer 19

probablilyt that all 20 are conserved .70^20 = 0.00079.

probability that 19 of 20 are conserved (.70^19 * .3) *20 = .0068.

probability 20 conserved or 19/20. 0.00079 + 0.0068 = 0.0076 or 0.76%.

Question 20

If pH is on the log scale, what is the difference in
H+ ion concentrations between a solution with a
pH of 3 and a pH of 7?

Answer 20

A solution with a pH of 3 has 10,000 times more hydrogen ions than the solution a pH of 7. Multiples of 10 for each pH value change.

Question 21

The RNA bases graph and that G was not expressed as well

Explain this experiment and whether is supports
the RNA world hypothesis.

Answer 21

Ribozyme could add 3/4 RNA nucleotides to CCCCC primer. It polymerized RNA slowly. It highlights that a ribozyme has the potential to replicate RNA molecules and supports the RNA world hypothesis.

Question 22

The diagram that shows the bases in a curvy shape idk.

Pink bases and pink dashes represent bases and
base-pairs that were conserved across all 25 high
functioning ribozymes. If the probability of basepair conservation in any ribozyme sequence =
0.65, what is the probability that all 25 ribozyme
sequences have the same conserved base pair? If
the probability is low, what does that suggest
about the role of those sequences? If the
probability is high, what does that suggest about
the conservation of those sequences?

Answer 22

prob conservation = .65
prob of conservation in all 25 = .65^25 = 0.000021 or .0021%. Prob is very small, the shared base pairs were not due to random chance and they likely play an important role in ribosomal function.
If the prob was high, then conserved based were likely due to chance, not due to important function.

Question 23

6 pics of vesicles and stuff inside

All living cells have “cargo” inside of them. What
does this experiment show is possible in abiotic
vesicles?

Answer 23

Abiotic vesicles can spontaneously trap microspheres and other vesicles. They can entrap RNA and clay, which are negatively charged. Entrapping RNA could increase rate of vesicle formation because vesicles form more quickly on charged surfaces. Highlights entrapment of RNa or DNA inside abiotic vesicles does not need enzymes

Question 24

Vesicle radius graph with the tall one and the shorter one to the right

What aspect of living cells does this figure show
is possible in abiotic vesicles?

Answer 24

All living cells grow and reproduce. Vesicles can take fatty acids and incorporate them into membrane and grow. Abiotic vesicles grew spontaneously when fatty acids were available.

Question 25

The cell inside water with sucrose glucose and fructose

An artificial ‘cell’ is immersed in an aqueous
solution with the solute concentrations shown in
the diagram. The membrane is permeable to
water and monosaccharides (glucose and
fructose) and impermeable to disaccharides
(sucrose). Which direction will water move?

Answer 25

Solute conc inside cell = .05 (0.03+.02)
solute conc outside cell, in solution = 0.03 M (.01
+.01+.01)

water flows from low solute to high solute, so itll flow into the cell. Hypotonic. Cell will swell.

Question 26

What is an antigen?

Answer 26

A substance that elicits an immune response by binding to receptors of B cells, antibodies, or T cells.

Question 28

What is the relationship between an antigen
receptor and an antibody?

Answer 28

An antigen receptor is a general term for a surface protein, located on B cells that binds to antigens, initiating adaptive immune responses. An antibody is a protein secreted by plasms cells (differentiated B cells) that binds to a particular antigen. they have antigen receptors on the variable region.

Question 29

the primary v secondary response with the mutated bases.
What is presented in this figure? What is the
difference between primary and secondary immune
response? Are affinities for the antigen generally
higher in secondary or primary reponse antibodies?
Explain how the affinities changed in the secondary
immune response

Answer 29

due to hypermutations in lymph nodes, biding sites for secondary antibodies are genetically different. thye also have different affinity for some of the antigen. secondarfy response is the second response to same antigen. It is faster and stronger due to memory B cells and mutations. This B-cell mutation and cellular evolution highlights why allergies get worse as you age.

Question 30

Inversion v deletion genome graph

A dot plot compares two genetic seqeunces
(reference vs comparison). What do patterns such
as these on a dot plot suggest about the genetic
sequences that are being compared?
Is it possible to know if these two genomes are
different species?

Answer 30

first is a chormosomal inversion, where part of the genome flips 180 degrees in chromosome.

second is an insertion or deletion of genetic sequence. gap and shift show an insertion or deletion where vertical genome contains more DNA than horizontal genome. Not possible to know wheter difs in size was due to insertion or deletion because the pattern is the same.

not possible to determine if same speices or dif species based on dot plot or full genomnen sequence. def of species is vague.

Question 31

of primers and type of primer graph

Since the only difference in the three experiments
in Figure 5.1A was the amount of primer,
what can you conclude about the role of primer for
DNA polymerase? What did you learn in Figure 5.1B
about the characteristics of a primer used by E. coli
DNA polymerase?
While this data shows that DNA primers are best in
E. coli, what do we now know about the type of
primer that E. coli uses for DNA replication?

Answer 31

More primers, the more
DNA polymerized even with fixed amounts of dNTPs and DNA polymerase. Amount of primer determines how many new DNA strands can be formed.

For E coli, best primers are DNA based primers. they must 3’ OH group present becauswe that is where the next base will be added. E coli uses RNA primers.

Question 32

Young v old DNA polymerase table
What factors influence DNA polymerase ability to
replicate DNA accurately?

Answer 32

Older DNA polymerase made fewer nucleotide bases and made more errors. Cofactor ion also impacgts DNA polymerase activity and accuracy, but less than age.

Question 33

ions and their error ratesw

Heavy metals are a common environmental factor
known to cause genetic mutations (mutagens).
Which ion had the strongest impact on the error
rate of DNA polymerase?

Answer 33

Cd2+ has the strongest error rate of DNA polymerase. similar error rates with a tenth of the conc of nickel.

Question 34

Cancer graph and polidy thing in mice or whatever

WT normal
AB98 AB152 cancer

Describe the DNA content of mouse cancer cells
AB98 and AB152 in the Figure. Which cancer cell
type has more total DNA?
Why do cancer cells typically have more
chromosomes than normal cells?

Answer 34

AB98 cells are between diploid and tetraploid compared to wildtype. AV152 are tetraploid or higher. AB152 has more DNA as indicated by the shift to the right of its nuclear content.

Cancer cells escape cell cylfe. They ignore the checkpoints because of incorrect DNA replication or connection of spindle fibers to each chromatid. They get the wrong number of chromosomes (aneuploidy)

Question 35

What are paralogs? Why are there so many paralogs
in the pufferfish genome? What does that suggest
about the evolution of vertebrates?

Answer 35

Paralogs are duplicate genes within a single species.

every chromosome contains manyh paralogs, the data supports that entire genome was duplicated rather than just bits and pieces

the origin of vertebrates was a result of duplicated genome inb an invertebrate followed by additional mutations of redundant genes

Question 36

The graph below depicts the primary and secondary
immune response. The first arrow shows exposure
to antigen A. The second arrow shows exposure to
antigen A again, and antigen B. Use the graph to
explain the difference between a primary and
secondary immune response. Why is the secondary
response faster and stronger?

Answer 36

Primary response peaks 10-17 days after initial exposure, selected B and T cells give rise to effector forms. Secondary response occurs after subsequent exposure to same antigen. Secondary response is fater, of greater magnitune and more prolonged. It relies on memory B cells from first exposure.

Question 37

The graph with secondary v primary response

What does this figure show? Does exposure to one
antigen prime your immune system for a different
infection?

Answer 37

Each response for one antigen is unrelated to initial response for a dif antigen. primary response to new antigen is same as any other primary response.

Question 38

Cells with Bs insiede them and little antigen things

How does this figure explain adaptive immune
responses and why the secondary response is
stronger and faster than the primary immune
response? What is happening during primary
exposure? What are the two types of cells that are
produced?

Answer 38

Specific antigens bind to antigen receptors of B cells. B cells msut have irght antigen receptor.
Selected B cell divides, forming a clone of identical cells bearing receptors for antigen. some cells developed into short-lived plasma cells that secrete anibodies specific for antigen.

other cells develop into long-lived memory B cells that help with next exposure.

Question 39

Soomething about memory B cells and primary resonses and stuff with like the yellow bar and arrows and secon gen.

What is somatic hypermutation? Where does it take
place? Which cells experience it and what are the
outcomes? How is this an example of natural
selection?

Answer 39

Somatic hypermutation: secondary respose B cells mutate rapidly but only in a small segment of their heavy and light chain alleles. coding portions change, and so do B cell’s capacity to bind the antigen and receive survival signal. Some mutations increase affinity, and some decrease. It takes place in lymph nodes. Overproduction of B cells, varation in population due to mutations, so B cells with higher affinity survive and reproduce.

Question 40

The picture of the antibody with the A, b, c, and D region.

What is shown? Label the different proteins and
parts of this structure, Heavy chain, light chain,
variable region, antigen binding site
How many antigens can bind to this antibody?
Would it be the same antigen or two different
antigens?
Do antibodies kill the pathogen?

Answer 40

An anitbody is shown.l Heave chain B and D. Light chain A and C. Variable region
A and B. Antigen binding site A and B.

Two compies of same antigen can bind to one antibody.

no, antibodies help other cells in immune system identify and kill pathogen. They can also neutralize viruses, making it harder for viruses to infect cells.

Question 41

Describe how immunizations lead to immunity in
the patient.

Answer 41

immunity can develop thru intro of antigens into body by immunizaiton. immunizations induces primary response and immunological memory, an encounter with the pathogen from which the vaccine was derived trtiggers a rapid and strong secondary immune response

Question 42

What are allergies?

Answer 42

exaggerated responses to certain antigens called allergens

Question 43

What is your adaptive immune system? How are
vaccines and the adaptive immune response
related?

Answer 43

Adaptive immune system relies on pathogen specific recognition. Each B and T lymphocyte is specific for a particular antigen. Your adaptive immune response is also respionsible for immunilogical memory so you can;t get sick from the same pathogen more than once.

Vaccines are the inactive form of a pathogen and once injected they start an adaptive immune respionse to the weakened form of the pathogen which results in antibodies and memory cells for future infections.

Question 44

What is a genetic mutation? Why do mutations
impact the functioning of proteins?

Answer 44

A genetic mutation is a change in the DNA sequence. Sometimes it can change one nucleotide to another, sometimes mutations can be insertions or deletions of nucleotides.

by changing DNA sequence, you can change the mRNA and therfore the codons for the protein that is being made. changing amino acide order changeds shape of the protein which is critical for functionality.

Question 45

Draw what it looks like when DNA polymerase is
beginning to synthesize a new strand. What is
needed in order for DNA polymerase to start adding
new nucleotides?

Answer 45

It is synthesized starting on an RNA primer from 5’=3’. DNA polymerase needs a primer with nucleotides with a 3’OH available. DNA polymerase can only add 5’-3’ direction. We use an RNA primer.

Question 46

Brain size graphs among races

Are there any issues you can see from the top figure
compared to the bottom figure? What was the
purpose of the top figure?

Answer 46

The top only includes the average, not the variation included. The Y axis also range also amplifies any differences.

Question 47

This table shows genome differences between humans
and chimps. Which species has more genetic diversity
among individuals?
For humans, of the DNA differences are genetic
differences greater within or between human
populations?
How can you explain to people that race is real, but it
cannot be defined using biological criteria? Support
your answer with data.

Answer 47

On average, two unrelated
chimpanzee juveniles differ
by about 1.2%
On average, two unrelated
humans in the world differ
by only 0.1%
Human genetic differences
are greater within
populations (85%)
compared to between
(15%).
From your everyday life,
the data in Table 6.2, the
disproportionate number
of Black men in American
prisons, you know that
race is real and has
profound impact on
health. However, genomic
DNA and many other
rigorous scientific studies
since the 1960s have all
concluded that race cannot
be defined by any
collection of objective
criteria such a DNA or
phenotypes. Race is
defined subjectively by
individuals and cultures.
From these judgements,
people are treated
differently which causes
real and measurable
consequences.

Question 48

Based on this tree, what are the proposed ancestors of
mitochondria and chloroplasts?

Answer 48

Ricettsia sp. is a type of
aerobic, heterotrophic
bacteria alphaproteobacteria which are
thought to be the most
common ancestor to
mitochondria
Cyanobacteria are the
proposed ancestors to
chrlorplasts.

Question 49

Effective weekly doses of warfarin for different racial
categories and VKORC1 promoter genotypes. What
does this suggest about race based medicine?

Answer 49

The genotype of the
VKORC1 is a better
predictor of effective doses
of warfarin, compared to
race. Races with the same
genotype should be given
the same amount of
warfarin. Not every
individual within a race will
have the same genotype.

Question 50

Mutation (SNP) frequency for one location (rs1834640)
within the SLC24A5 gene, G is ancestral base and A is
the newer base.
Look at the African populations YRI and LWK. Do these
populations predominantly have the ancestral G base or the newer A base? Are there any African
populations who have less than 50% homozygous G?
Are there any non-African populations who have more
than 50% homozygous G? Are there any populations
who have more than 50% homozygous A? Where are
they located? All in Europe or north America or
Australia? What do you expect their skin tone to be?
What does this suggest about genetics of human skin
tones?

Answer 50

The Yoruba and Luhya
samples have mostly the
ancestral and darker SNP,
G. The Maasai samples
have about the same
number of homozygous G
as heterozygous
genotypes. All three
Chinese samples have
more than 50%
homozygous G despite
their skin tones being
much lighter than the
Maasai.
GIH and CEU both have AA
more than 50%. They likely
have lighter skin color, even in India.
These apparent
contradictions underscore
the complexity behind
human skin tone genetics.

Question 51

Are eukarya more closely related to Archaea or
bacteria? Or are they equally related based on this
tree?

Answer 51

Eukarya share a more
recent common ancestor
with archaea, so are more
closely related to archaea
than bacteria.

Question 52

Explain the hypothesis for the origin of eukaryotes
through endosymbiosis

Answer 52

At some point an ancient
archaea (maybe) engulfed
a bacteria that could use
oxygen to help make
energy. That bacteria did
not die and eventually
became the mitochondria.
Another eukaryote that
had a mitochondria
eventually ate a
cyanobacteria that could
perform photosynthesis.
This also did not die and
become the chloroplasts

Question 53

DNA evidence suggests that eukaryotes have some
genes and cellular characteristics derived from
archaea, and others from bacteria. Which functions
came from archaea and which from bacteria?
What is the “ring of life” showing?

Answer 53

Transcription, translation,
replication from Archaea
ATP production from
bacteria
Metabolism, detox, ion
homeostasis, both
ring of life,” represents
more accurately how the
three domains evolved due
to endosymbiosis. Bacteria
and archaea “merged” to
form Eukaryotes.

Question 54

What do these two figures show? Where did these two
structures come from and what is their role in eukaryotic cells?
What is endosymbiosis? What is the evidence that
these two organelles came from endosymbiosis?

Answer 54

A shows mitochondria.
Which is found in all
eukaryotes, including
plants. Mitochondria
generates ATP for cells
B. shows chloroplasts wich
is found in plants and algae
and other photosynthetic
eukaryotes. Chloroplasts
turn light energy into
chemical energy (sugars).
Endosymbiosis refers to
the process by which
formerly small bacteria
that began living within
larger cells.
Both organelles have two
outer membranes.
The inner membranes of both organelles have
enzymes and transport
systems that are
homologous to those
found in the plasma
membranes of living
prokaryotes.
Each of these organelles
contains circular DNA
molecule that, like the
chromosomes of bacteria,
is not associated with
histones or large amounts
of other proteins. These
organelles also have the
machinery (ribosomes,
etc.) needed to transcribe
and translate their DNA
into proteins.

Question 55

What is a bootstrap value? How is it used in
evolutionary trees?

Answer 55

The bootstrap process is
designed to reveal how
robust and reliable the
depicted relationships are
in the evolutionary tree.
Higher bootstrap values
means you should have
more confidence in that
evolutionary relationship
because even after
randomization and
resampling that
relationship was retained

Question 56

What is the out of Africa hypothesis? Does the tree
above support or refute the “out of Africa
hypothesis”?
Which individuals in the tree have more differences in
their mtDNA when compared to all others? Support
your answer with data.
Identify the MRCA that represents a bridge between
current Africans and current non- Africans. How
confident can you be in the data supporting this
shared ancestry?

Answer 56

Out of Africa Hypothesis
posits that all modern
humans (Homo sapiens)
originated from a single
population in Africa and
then migrated to other
parts of the world,
replacing local archaic
human populations such as
Neanderthals and
Denisovans
Based on this tree african
and non-african
populations share a
common ancestor that was
African. This supports the
out of Africa hypothesis. African populations have
greater genetic diversity
among populations, which
is indicated by the longer
branch lengths within
African populations. This
greater genetic diversity
indicates a longer period of
genetic evolution there. All
non-African populations
show a more recent,
smaller subset of this
genetic diversity,
suggesting they are
descendants of a
population that migrated
out of Africa.
The out-of-Africa theory
has been validated many
times by these data and
many more. Some of the
MRCA of west Africans and people currently living
outside Africa migrated
west where their
descendants live today,
whereas others migrated
east out of Africa.
Collectively, the two San
individuals have more
differences in their mtDNA
which is revealed by the
longest cumulative vertical
distance between them
and their most similar
match of #5, the Hausa
individual. Considering
only one person, Ibo #12 is
the most different
compared to Ibo #11
The MRCA at the branch
marked by 98 (the left one)
represents the shared
ancestors between current
Africans and all the current
non-African. The bootstrap
value of 98 indicates a very
high confidence in this
branchpoint (98%)

Question 57

Do the data from the Figure support or refute the
hypothesis that lower birth weight has a genetic
component? Support your interpretation with the
available data.

Answer 57

If we assume that the Black
African immigrants and
African Americans share
much of their DNA, then it
seems environmental
differences are the major
factor.

Question 58

What data in the Table indicate that ancient humans
and pre-humans of Africa evolved alleles in multiple
genes that produced light and dark skin color before
humans migrated out of Africa?
What is the oldest known H. sapien fossil?

Answer 58

The skin color alleles
evolved before H.
sapiens became a separate
species (200,000 – 300,000
years ago), and before a
subset of humans migrated
out of Africa about
100,000 years ago. Only
the SLC24A5 SNP evolved
after a subset of H.
sapiens migrated out of
Africa.
The oldest known fossils of
our species suggest that
Homo sapiens appeared in
Africa sometime between
195,000 and 160,000 years
ago.

Question 59

What does a phylogenetic tree represent?
Are polar bears more closely related to American black
bears or Asian black bears, or are they equally related
to these two species? Explain.

Answer 59

The evolutionary history of
a group of organisms can
be represented in a
branching diagram called a
phylogenetic tree.
Polar bears are equally
related to these two
species because polar
bears share the same
common ancestor with
both of these two species.

Question 60

Which of the trees shown here depicts an evolutionary
history different from the other two? Explain.

Answer 60

Figure C. Trees a and b
show that taxon C and D
share the most recent
common ancestor, and
that clade is most closely
related to the B lineage.
However, the C tree
suggests that C and B share
the most recent common
ancestor, and that clade is
closely related to the
lineage leading to D.

Question 61

Average warfarin dose requirements to achieve clinical
benefits, separated by race of patients. Adjusted
mean weekly warfarin dose (+/- 95% confidence
interval). What genetic information is missing here to
help explain variation in effective treatments?

Answer 61

There is a genetic variation
in each race, especially for
the VKORC1 promoter
genotypes. GG, GA and AA
are best for determining
effective treatments, not
race. Race-based medicine
assumes all individuals
within a race are the same
genetically. We know that
is not the case.

Question 62

Consider the intergenerational birth weight data from the Figure. Do immigrant Black and White mothers
deliver children with similar birth weights? What about
the immigrant’s grandchildren? What is the general
trend for G2 and G3 birth weights for each of the four
populations?

Answer 62

No, the White immigrant
mothers give birth to
heavier children than the
Black immigrant mothers.
However, with the small
sample size of 194 and the
lack of statistical measure,
we cannot be sure if these
two averages are
significantly different or
not. The G3 grandchildren
of immigrants have very different outcomes. The
White immigrants have a
significant increase in birth
weights whereas the Black
immigrant grandchildren
have a decrease in birth
weight. Only Black
immigrating to American
show a decline in birth
weights for children born
of mothers who were
raised in America.
Therefore is it highly
unlikely that genetics is the
major factor for the
decline. It is much more
likely that systemic racism
and its effects as seen in
Table 6.2 is the major
factor leading to this
decline.

Question 63

Someone says that humans evolved from
chimpanzees. Is that true? Use these trees to explain.
Are these trees showing the same or different
evolutionary relationships?

Answer 63

chimpanzees are our
closest living relative
meaning that we share a
common recent ancestor
with chimpanzees, but we
did not evolve from them.
We evolved from a
common ancestor that is
now extinct and was not a
chimp or a human. We
have been evolving
independently for the last
6-7 million years.
These trees are the same.
Humans closest relative
are chimps followed by
gorillas, then orangutans,
then gibbons. It’s the same
in both trees.

Question 64

What is shown in this figure? How many levels of
protein structure are there? Summarize each level
here.

Answer 64

A. Primary structure: Chain
of amino acids with a
unique sequence.
Polypeptide chain.
B. Secondary structure:
α helix or β pleated sheet:
Coils and folds resulting
from the hydrogen bonds
between polypeptide
backbone
C. Tertiary structure:
Overall shape (3D shapre)
of the polypeptide
resulting from interactions
between the side chains (R
groups) of the various
amino acids. All proteins
have primary, secondary,
and tertiary structure
D. Quaternary structure:
Overall protein structure that results from the
aggregation of multiple
tertiary structure proteins
(hemoglobin is a great
example)

Question 65

What is a covalent modulator vs an allosteric
modulator? Which figure shows allosteric modulation?
Which figure shows covalent modulation?

Answer 65

Both are different
mechanisms by which
molecules interact with
enzymes or receptors to
regulate their activity
Allosteric modulators are
ligands that bind to a
protein, usually away from
the functional site, which
alters the protein’s shape
and its function
A second way of altering
the shape of a protein is by
covalent bonding. The
most frequent reaction of
this type is accomplished
by the addition of a
phosphate group,
phosphorylation. Any
enzyme that mediates
protein phosphorylation is
called a protein kinase.
These enzymes catalyze
the transfer of phosphate
from a molecule of
adenosine triphosphate
(ATP) to a hydroxyl group
present on the side chain
of certain amino acids.

Question 66

What is shown in the figure? What is the difference
between these two structures? How are they similar?
Can we use both of these as a form of energy? What
organisms can use the structure on the right for
energy?
What is the most abundant organic compound on
earth?

Answer 66

The figure compares two
polysaccharides, starch
and cellulose. They are
both long chains of glucose
molecules, but starch has a
1-4 Alpha- bonds while,
cellulose has a 1-4 beta
bond. Due to the
difference in bond angle,
our enzyme amylase
cannot digest cellulose but
can use starch for energy.
Starch is on the left and
cellulose is on the right.
Humans enzymes digest
starch by hydrolyzing its
alpha linkages; however,
these enzymes cannot
hydrolyze the beta linkages
of cellulose because of the
distinctly different shapes
of these two. Some
microorganisms can digest
cellulose, such as bacteria
in a cow as well as some
fungal species.
Cellulose, which is found in
all plant cell walls!

Question 67

What is cytoskeleton? What are some of its functions?
What is the role of cytoskeleton in forming microvilli in
your small intestine? What function do microvilli serve
for cells lining the lumen of your intestine? What is adaptive about this shape instead of a flat surface?

Answer 67

The cytoskeleton is a
network of fibers
extending throughout the
cytoplasm. The
cytoskeleton gives
mechanical support to the
cell to help maintain its
shape, provides anchorage
for many organelles and
cytosolic enzymes, and
facilitates vesicle traffic by providing a scaffold upon
which motor proteins can
“walk.”
Microvilli are the surface in
which proteins are
embedded that bring
nutrients into intestinal
cells for delivery
throughout your body. By
having a wavy surface,
each intestinal cell can
have more import proteins
on its surface and thus
bring in more nutrients
without requiring the cell
to become substantially
larger.

Question 68

What does this figure show? Explain how tubes in the
endoplasmic reticulum form and explain how
differences in lipid composition can impact the
diameter of each tube being made.

Answer 68

Scientists wanted to
understand how the
endoplasmis reticulum
formed. They found that
microtuble tracks are used
by a motor protein called
kinesin to pull membranes
from the nucleus to form
many tubes. Kinesin moves
along each microtuble
track and can change
directions easily along each
track. Via this process the
volume of the vesicle plus
the tubes remains
essentially unchanged, but
the total surface area
grows rapidly as the tubes
are pulled from the vesicle

Question 69

What did this experiment show about how each tube
diameter varies?

Answer 69

lipid composition of the
large experimental vesicle,
changed the diameter on
the new tube being drawn
out by kinesin.
Three different lipid
compositions required
different amounts of force
to pull the tubes. The three
different tubes of
membrane also had
different diameters
depending on the lipid.

Question 70

What produced these membrane shapes? Are enzymes
or motor proteins needed?

Answer 70

Lipid vesicles
spontaneously adopt
varied shapes. Rigid lipids
were labeled blue, and
more fluid, relaxed lipids
were labeled red. Lipid
composition can
determined membrane
shape. Highlighting form
follows function.

Question 71

Which amino acids are hydrophilic, A or B?
Which amino acids are hydrophobic, A or B?
The folding of proteins is critical for its function. The
way that proteins fold is determined by the order of amino acids (primary structure). When proteins fold
into three dimensional shapes where are hydrophobic
amino acids found, on the surface or inside of the
folded protein?
What about hydrophilic amino acids, surface or inside
the folded protein?
What would happen to the functioning of a protein if a
mutation resulted in a hydrophilic amino acid replacing
a hydrophobic amino acid?
What would happen to the functioning of a protein if a
mutation resulted in a hydrophilic amino acid replacing
another hydrophilic amino acid?

Answer 71

A represents the
hydrophobic amino acids.
They are all non-polar R
groups. Many Cs and Hs
B represents the
hydrophilic amino acids.
They have many O, N, S, in
their side chain. All all
polar or some kind of
charged molecules. Hydrophobic amino acids
(only Cs and Hs) would be
folded inside of the protein
to avoid touching water.
During the folding (tertiary
structure) the hydrophilic
amino acids (charges, N, O,
S) will be placed on the
surface of the protein, in
contact with water.
If a hydrophilic amino acid
replaced a hydrophobic,
the protein would not fold
the same and it would
likely lose its functionality.
If a hydrophilic amino acid
replaced a hydrophilic, the
protein would likely fold
the same and it would
remain functional.