biology passage graph

[yoyohomieg5432]

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This is from AAMC 11.







The graph makes absolutely no sense to me. In the top what does CatB -/- mean or CatL +/+? I've never seen this symbology.

Also, in the X axis what is the 'bacterial' entry? The other ones are genes that were introduced.

I attached the passage too if it helps at all.

does CatL +/+ mean they have the CatL gene? If so, why would you bother introducing CatL (the CatL entry on the x axis) if the cell already has the gene?

 

[Postictal Raiden]

This is from AAMC 11.

The graph makes absolutely no sense to me. In the top what does CatB -/- mean or CatL +/+? I've never seen this symbology.

Also, in the X axis what is the 'bacterial' entry? The other ones are genes that were introduced.

I attached the passage too if it helps at all.

does CatL +/+ mean they have the CatL gene? If so, why would you bother introducing CatL (the CatL entry on the x axis) if the cell already has the gene?

If I were you, I would increase the size of the font of the first sentence to make sure everyone realizes that this is one of the most important graphs that they will ever encounter in the preparation. Just a friendly suggestion 🙂

 

[AdmAckbar]

If I were you, I would increase the size of the font of the first sentence to make sure everyone realizes that this is one of the most important graphs that they will ever encounter in the preparation. Just a friendly suggestion 🙂

Do you mean that if I haven't taken AAMC11 yet I shouldn't look at it, b/c it'll affect my score? Because I saw that first sentence and haven't looked at the image/question yet.

 

[mcloaf]

Do you mean that if I haven't taken AAMC11 yet I shouldn't look at it, b/c it'll affect my score? Because I saw that first sentence and haven't looked at the image/question yet.

Yes.

 

[yoyohomieg5432]

bolded it. idk how to make it bigger.

would appreciate some help on this though.

 

[yoyohomieg5432]

last minute plea for help. taking mcat tomorrow morning

 

[mcloaf]

This is from AAMC 11.







The graph makes absolutely no sense to me. In the top what does CatB -/- mean or CatL +/+? I've never seen this symbology.

Also, in the X axis what is the 'bacterial' entry? The other ones are genes that were introduced.

I attached the passage too if it helps at all.

does CatL +/+ mean they have the CatL gene? If so, why would you bother introducing CatL (the CatL entry on the x axis) if the cell already has the gene?

last minute plea for help. taking mcat tomorrow morning

Yes, the +/- notation refers to the genotype of cells into which they are introducing these genes. + means they have the gene in question, - means they lack it. The bacterial entry is just a control introduced to show that whatever changes they are seeing are not a function of the physical process of introducing new genetic material, but rather that these changes are a function of the new genes themselves. Not really sure why they bothered to introduce exogenous CatL into a CatL +/+ genotype, but who knows.

Hope that helps.

 

[Bomikepa]

can someone help me understand this:

V. cholerae O395N1 were inoculated into LB (pH 6.5) with or without 40 mM malonate and shaken at 30°C for 6 hrs. Total RNA was extracted and analyzed by qRT-PCR. Gene expression levels were normalized between the samples by using 16S ribosomal RNA. All experiments were repeated three times. The error bars indicate standard deviations. P values were calculated by Student's t test and *indicates P≤0.05.

so O395N1 is the strain of virus?
LB- is the type of broth on the agar plate? what LB?
so the malonate is independent variable?
and the amount of gene expression is the dependent variable because it depends on if we have the malonate ?

"Gene expression levels were normalized between the samples by using 16S ribosomal RNA" what does this mean????

qRT-PCR

i know pcr...is rt reverse transrciptase? whats the q for?

on the graph....which one is the standard the one which did not have the malonate?

and the p range means what? i think it means that its significant?

thanks all

source: http://www.ncbi.nlm.nih.gov/pubmed/23675480

 

[mcloaf]

can someone help me understand this:

V. cholerae O395N1 were inoculated into LB (pH 6.5) with or without 40 mM malonate and shaken at 30°C for 6 hrs. Total RNA was extracted and analyzed by qRT-PCR. Gene expression levels were normalized between the samples by using 16S ribosomal RNA. All experiments were repeated three times. The error bars indicate standard deviations. P values were calculated by Student’s t test and *indicates P≤0.05.

so O395N1 is the strain of virus?

Yes.

LB- is the type of broth on the agar plate? what LB?

Yes: http://en.wikipedia.org/wiki/Lysogeny_broth

so the malonate is independent variable?

Yes.

and the amount of gene expression is the dependent variable because it depends on if we have the malonate ?

Yes.

"Gene expression levels were normalized between the samples by using 16S ribosomal RNA" what does this mean????

qRT-PCR

i know pcr...is rt reverse transrciptase? whats the q for?

on the graph....which one is the standard the one which did not have the malonate?

and the p range means what? i think it means that its significant?

thanks all

source: http://www.ncbi.nlm.nih.gov/pubmed/23675480

See bolded stuff above for the short answers.

qRT-PCR is quantitative reverse-transcription PCR. http://en.wikipedia.org/wiki/Real-time_polymerase_chain_reaction

In short, it's a method that uses fluorescence to quantify the amount of whatever gene you're looking for in your sample. If there's more mRNA for gene X, there is more fluorescence. However, in order to account for variation in the concentration of the different samples that you're loading you need to normalize to a housekeeping gene that you know will be present at a relatively constant level in all of your samples. In this case they've used ribosomal RNA, but often people will use something like Actin. Point is, once you've measured the housekeeping gene in all of your samples you can measure your gene of interest and then normalize your results by looking at the ration of [gene of interest]/[housekeeping gene]. This allows you to compare expression between samples without worrying that you're loading different amounts material.

There's something sort of similar going on with the graph. If you look at the y axis it's showing relative expression compared to wild type (i.e. without malonate), not absolute expression. So to make that graph they'd taken their gene expression measurements for all of those genes with and without malonate, then they've set the wild type expression equal to 1 on the y axis. The values they're showing with the bars are the relative expression in the presence of malonate, so if the value is 0.5, that means that expression is half that of the wild type.

Lastly, yes, generally P value less than 0.05 is considered significant. http://en.wikipedia.org/wiki/P-value


Hope that helps. Sorry if any of this is unclear as I'm on my way out the door to the airport. I'll point out that a lot of this you could have looked up on your own as far the definitions of things like qRT-PCR.