KIRSTIN MILKS: Hi, everybody Kirstin Milks from Bloomington,
Indiana back with another AP Daily video for AP Biology.
We are into the free response questions.
Today is question one.
Interpreting and evaluating experimental results.
Make sure you've got paper or writing implement
a calculator and a copy of the equation sheet handy.
You can also print out the PDF that accompanies this video.
Now I think the best way to use this video is to complete
the prompts in writing.
Don't just try to answer in your head.
It's really going to help further your learning
and help make it so that your time is better spent.
So let's go ahead and get started
while we look at what this question asks students to do.
You can take a look at these four parts here.
It's going to be really important
that we go back and forth between the information
and the question and the knowledge in our heads
to answer this type of question.
Note that sometimes explain, means
that you're explaining how, which
often has describing a process.
And sometimes you're explaining why
which often has describing the underlying reasons
or causal relationships that make something happen.
Sometimes you explain mostly using data in this question
and sometimes you explain by applying
the biology you've learned previously to this question.
So you ready.
Let's go ahead and practice.
Here's a sample FRQ1.
Please pause the video to read the beginning of the FRQ
and look over the figures.
OK.
Here's part A. Please pause to read the prompt
and then write down your answer on your scrap paper.
OK.
So the correct answer for identify,
is that luciferase is produced by ribosomes
in the you say cytoplasm or you could say cytosol.
And you have to describe the location of that component.
Right.
So it's both ribosomes and cytoplasm or cytosol.
If you don't get both you didn't get the point
and it happens in the lymphocytes.
What about the explain part?
Well, the sequences of nucleotides in the messenger
RNA dictates the amino acid sequence of luciferase.
But if you just said that you don't get the point
you have to explain it all the way through.
And that's what this highlighted text is doing there.
So make sure when it says explain that you
explain all the way through.
All right.
Here's part B pause to read the prompt
and then write down your answer on your paper.
We did that.
Cool.
Let's go ahead and answer the identify question
as we take a look here, you can see
that we're looking at different plasmids that
have different parts in them that shown here.
And the parts that are different are
these upstream regulatory sequences of CD3 gamma.
And you can see they're also in that figure 2
part they're shown as diagram here in yellow.
So the independent variable in the experiment
that you could say it's the particular plasmid that
was in the lymphocytes or you could
say it's the particular CD3 gamma regulatory sequence that
is introduced into the lymphocytes either one of those
is a correct answer.
For this next identify, which plasmid
was used as a negative control for luciferase activity?
You're expecting no activity.
So we look for in the graph of relative luciferase activity
what the lowest one was.
In this case, you could have said it was the parent plasmid
or you could have said it was the plasma
without any regulatory sequences inserted
or you could have written both of those and gotten credit.
OK.
Last but not least, this justify part.
We're justifying including the plasma with the non-CD3 gamma
active promoter.
So that's down here in yellow as you can see it
and you can see it meant quite bit of luciferase which
is an interesting thing to have happen here.
It's a positive control to make sure
that you've introduced the plasma into the T lymphocytes.
And it also lets you know that the assay is working
that you can use this luciferase assay to measure promoter
activity.
All right.
Next up we're going to take a look at C. Go
ahead and pause the video and write
your answer on your paper.
We have a couple of bolded words here.
First one is identify.
We want the one that contains the core promoter sequence.
And so we're going to look and see
what we can see here that's all of this stuff.
But we also want the one that has the fewest or no negative
regulatory sequences.
So a negative regulatory sequence
means you're going to end up with a decrease in something.
In this case in luciferase production and/or activity.
And so as we go through and see, that
means that we're looking for one where you didn't end up
getting luciferase.
So in that case, an increase because it
doesn't have negative regulatory sequences it's this one here.
So the correct answer it is, how I'm going to do it?
PCD3 gamma 15.
and it's an identified question.
So you don't have to justify it.
But again it's because this plasmid gives the greatest
luciferase activity.
They've changed the font here a little bit
but the question is the same.
We're going to describe the most likely cause of the variation
amongst some different plasmids cells that contain
those different plasmids.
So if we take a look at those I've highlighted them here
in the picture and you can see the difference between the DNA
sequence in them, is that they have different amounts
of the upstream regulatory sequences for the real life CD3
gamma gene.
So you can see this one has the first 419
and you can see they have different amounts.
When we look at the variation in luciferase activity
as I've shown here in yellow, it doesn't just
increase in cells that have less and less
and it doesn't decrease in cells that
have less and less of the upstream regulatory sequence.
Well, there's a hint back in the intro text
which I'll show you here.
So they might have positive or negative effects
on the expression of the gene, the different regulatory
sequences do.
And that means that you would see
positive or negative amounts of luciferase gene that
are expressed in this context.
And so the different sequences that
are cloned into the plasmids contain different combinations
of positive and negative regulatory sequences.
That's a correct answer here.
All right.
Last but not least, we're going to calculate
a little it's asking us for two specific plasmids which
I found here with the arrows.
And then we're looking to see what their luciferase levels
are, I've put that here.
And then we're going to make sure
that we're calculating this correctly it's
asking for a 5% increase between the one
I've marked in orange and the one I've marked in purple.
And so the percent increase is approximately 100%.
And again to calculate that the blank 59
bar ends at the two and the blank 149 bar ends at the four
on the axis that's labeled relative luciferase activity.
Cool.
Next up is D go ahead and pause the video
and write your answer on the paper.
Sweet.
So we're going to predict the most likely observed level
of luciferase activity if you take one of these plasmids
and you put it into non-lymphoid cells.
For example a line of kidney tissue cells.
Again we've got information in the original question,
that will help us answer that.
In this particular case, the protein that
gets made as a result of regulation
by these upstream regulatory sequences,
it only gets made in the plasma membrane,
or it ends up being in the plasma membrane
of immune system T lymphocytes.
And so what that means here is that we're not going
to get a luciferase activity.
So you'll say there will be little luciferase, activity
there'll be no luciferase activity,
if you introduce this plasmid 7, 8, 9 into non-lymphoid cells,
and the reasoning.
Well, this is something that you'll remember,
the parts of the upstream regulatory sequence
are what control whether or not a gene product or protein gets
made.
So in this particular case, you've
got all of these proteins which I'm representing here
as circles that land on those upstream regulatory sequences.
Those proteins are specific to the cell type.
So you can imagine that the types of cells that express
this like the lymphoid cells.
They have the purple proteins but kidney tissue cells
because this protein is only made
the protein we're thinking about CD3 gamma,
is only made in lymphoid cells.
Then kidneys might have this green set
of proteins totally different and they won't land on those.
So non-lymphoid cells won't contain the transcription
factors that bind to this focused
genes regulatory sequences.
Cool.
Here's another example of an FRQ 1.
Go ahead and pause the video and read through the prompts
or again, use the PDF that's attached to the video.
There's more.
Cool.
One thing that's difficult about this picture, by the way,
is that the error bars top is right on that 175 line.
But if you squint you can see it. .
Cool I put those graphs side by some graphs
that will be important for you up on top of each other here.
Here's part to go ahead and pause the video
and write your answer on your scrap paper.
All right.
Sweet.
Our first question prompt is about describing
why DNA replication is said to be a semi conservative process.
In this case one strand of DNA serves
as the template for the synthesis of a new strand
of complementary DNA.
This is just a definition.
It looks scary but if you know what some conservative means
then you can answer it.
Next up is our explain part--
it's explaining how random mutations may arise in the DNA.
And you'll remember you get errors in DNA replication
that can introduce or not correct errors
in nucleotide sequence or you can have changes in DNA repair
mechanisms.
Or you can have changes that are induced
by external factors like radiation or certain chemicals.
So all of that is stuff you're bringing from your brain
to this question.
Here's part B. Go ahead and pause the video
and answer the question on your paper.
All right.
We're going to identify a dependent variable
in the experiments it's right here on the graph.
It is indeed the number of colonies
produced by 10 to the 7 cells for each
of the strains analyzed.
Yeah.
You had to give them the whole thing.
Identify the reasoning the scientists
used when they took a look at two separate strains,
those strains are shown here in blue and in purple.
They are controls for the number of colonies
that are produced when only the plasma backbone is introduced
into the C3 and C6 strains respectively.
And then to justify this analysis
that they're talking about in the last part of the question,
they're thinking about growing on a growth medium that's
lacking the toxic chemical.
So there's not any and that means
the toxic influence isn't there that
means you expect an increase.
So analyzing the number of colonies
produced from each of the environmental and clinical
isolate strains when the strains were
planted on growth medium lacking the toxic chemical it's
a positive control to demonstrate
that all of the strains can grow and produce colonies.
That part about telling it's a positive control
isn't enough you do have to explain all the way through.
Here's part C. Go ahead and pause the video,
write your answer on your paper.
OK.
So for each strain there's information
in the question stem.
So we're looking at high frequency of DNA mutations
in this mutated phenotype.
And so those strains that produced
a relatively large number of colonies those are C3 and C6.
Those were strains with cells that contain DNA mutations that
make them less susceptible to damage by the toxic chemicals
than the others, which are all the strains that
start with E and C8.
So for each strain we have done that description here.
All right.
Part D, we've got some stating and some providing evidence.
Go ahead and answer it.
We're stating the null hypothesis here.
Let's take a look down here at this graph,
and you can think about these two parts of the graph.
It shows pretty clearly that mutations to this gene
are not responsible for the high mutation rate produced
by C3 and C6 strains in the presence of the toxic chemical.
You also could have said the large number of colonies
but you do need to have one or both of those ideas.
You also could have said that introduction
of a wild-type HMSH2 gene won't decrease the mutation rate
or will not reduce the large number of colonies that
would also be a correct answer.
Lots of ways to say a null hypothesis that works here.
So this question asks you to provide evidence based
on the rest of that claim.
Again, there's information in the question text for you
here if we take a look at figure 2.
You can see that when the MSH two gene was introduced
into C3 and C6 cells, the number of colonies that grew
from those cells was reduced.
And that gene encodes a DNA repair enzyme as we just
saw that suggests that the cells were now
able to repair the mutation to a gene encoding
a protein targeted by the chemical.
And you have to make sure you say,
this supports the scientists claim.
If the question asked you to support or review
make sure you sneak that in there.
All right.
Part D go ahead and pause the video and answer the question.
Last but not least, we're doing an explanation here
about why mutated phenotypes were found only
among the clinical isolate strains.
The mutated phenotype confers a selective advantage
to the strains that are isolated from infective individuals.
And so strains like C3 and C6 are
less likely to be killed by antifungal drugs
than our clinical strains without a mutation phenotype
or environmental strains that were not subject to selection
by antifungal drugs.
Cool.
Make sure when you are explaining
and you say more likely, less likely,
make sure you answer less than what,
more than what it's really important as we create these.
Three quick reminders about FRQ number one.
First off refer to the introductory test
throughout the FRQ.
It is your friend.
It will help give you some answers.
Number two remember that inhibiting and inhibitor
has an enhancing effect.
You want to draw those up arrows, down arrows,
make sure you're thinking about that appropriately.
Number three remember, you're going
to need your own biology knowledge, not just
the information given.
So don't feel panicky if you feel like a question doesn't
have the information you need.
All right.
Thank you so much for practicing with me.
I hope you learned a lot.
We'll see you back here for AP Daily as you continue to study.