Biology SL/HL help

[Mahuta ♥]

Hello,

TOPIC 7 -- DNA replication, transcription and mRNA translation

Has a detailed explanation.

[Guest Juicebox]

I don't understand: during photosynthesis, when plants take up CO2 what happens to the pH?

[Mahuta ♥]

During photosynthesis, when plants take up CO₂, they will release H⁺ ions through the dissociation of H₂CO₃:

CO₂ + H₂O -------> H₂CO₃ ---------> H⁺ + HCO₃^-

^{EDIT: This is in Biology help thread now.}

[Rouge]

Good morning Maha,

I'm doing a lab report on the investigation of distribution of catalase in a soaked sprouted green bean and determining the effect of different temperature on its activity.

I'm not very sure what to do for the data processing and presentation part. Because, the effervescence of the beans in hydrogen peroxide is rated from a scale of 0 to 4. With beans at different temperature, 40 C,50-80 C, 100 C. 3 beans are boiled at 100 C while the other 3 is unboiled.

Thank you.

[Mahuta ♥]

Good morning Maha,

I'm doing a lab report on the investigation of distribution of catalase in a soaked sprouted green bean and determining the effect of different temperature on its activity.

I'm not very sure what to do for the data processing and presentation part. Because, the effervescence of the beans in hydrogen peroxide is rated from a scale of 0 to 4. With beans at different temperature, 40 C,50-80 C, 100 C. 3 beans are boiled at 100 C while the other 3 is unboiled.

Thank you.

Okay, I am not sure I have a clear idea about your experiment. I get how you determined the effect of temperature on the activity of catalase, but I don't understand how you are investigated it's distribution; your results don't show anything about it.

For the results you got, if I were you, I would first have two tables, one for the 3 boiled (to find the average) and one for the other 3. Then a big one with the boiled and unboiled to compare (though your investigation doesn't seem to investigate the effect of boiling or not boiling).

I can't really think of another way to present the data, perhaps you could use a line graph, but I remember doing that when I counted the bubbles rather than using a scale.

The following topic may help you: How to write a good biology lab report.

[Rouge]

I agree with you about the results being vague. Like you said, I'll just average all of the 3 trials of unboiled beans at different temperature and form a line graph.

Thank you so much for your insight, Maha.

[awebb]

This is so great you are willing to advise so many of us. Thanks you. My lab is on light intensity and photosynthesis. I changed the light intensity five times and did five trials for every minutes of exposure at each different wattage.I used the T test to compare each wattage against 250 in each trial. Does that sound like the right use of the T test?

[kiwi.at.heart]

This is so great you are willing to advise so many of us. Thanks you. My lab is on light intensity and photosynthesis. I changed the light intensity five times and did five trials for every minutes of exposure at each different wattage.I used the T test to compare each wattage against 250 in each trial. Does that sound like the right use of the T test?

T test is used usually just to determine whether there is a statically significant difference between two variable. Generally you only use it when you have only 2 variables that you are testing.

I would not use the t-test for your lab because what you want to look at is the trend of varying light intensities and the comment on it. All you would have done with the t-test is say that all the results are either significantly different to the 250 trial which isn't really showing anything. In Bio you don't need to process the data that much. For your lab, I would just plot your data averages on the graph, and in standard deviation, and then draw a line of best fit and that would be sufficient and what you want to show for a lab like yours.

[IBtank]

So the process of DNA Replication involves a primer, consisting of RNA nucleotides, being produced at the replication fork. After this happens DNA Polymerase III adds DNA in a 5' to 3' direction in order to grow the DNA strand. DNA polymerase I finally removes the primer and replaces it with DNA nucleotides.

So in my view the process of the primer is totally unnecessary isn't it?

Why do you first use RNA nucleotides and then remove them again?

I dont understand the necessity of this?

Anyone able and willing to explain?

Thanks

[LMaxwell]

Are you talking about the replication fork? If yes, then it's a process which occurs during the S phase in interphase (before mitosis or meiosis). From what I've learnt, there aren't ANY RNA nucleotides involved, simply DNA nucleotides, i.e. A, T, C and G.

So you know that there are two strands in DNA: one in the 5' 3' direction (the leading strand) and the other in the 3' 5' direction (the lagging strand), and DNA replication can ONLY go in the 5' 3' direction. Basically, the enzyme helicase unwinds/uncoils these two DNA strands. DNA polymerase III then adds nucleotides to the strand running in the 5' 3' direction (the leading strand). These added nucleotides will be complementary to the bases already there, e.g. T will pair with A and C will pair with G, or vice-versa.

OK, that was easy, right?

Where the problem arises is on the other strand, which is running in the 3' 5' direction. Thankfully, an RNA primase comes along and adds short RNA primers to the 3' 5' strand. DNA polymerase III can then add free nucleotide to these bases by the same mechanism of complementary base pairing. The nucleotides can be added due to the RNA primer because it allows the strand to be copied in the 5' 3' direction. This process of adding nucleotides creates short lengths of replicated DNA called Okazaki fragments. After this, the RNA primer is removed by DNA polymerase I, and ligase replaces the gaps between the Okazaki fragments with DNA.

I think you must have confused yourself with transcription which is a completely different process.

Key things to remember:

- strand can only be replicated in the 5' 3' direction

- 5 enzymes involved: helicase (unwinds DNA strands), DNA polymerase III (adds free nucleotides to complementary bases in 5' 3' direction), DNA polymerase I (removes RNA primer), RNA primase (adds short RNA primer), ligase (joins Okazaki fragments)

Watch this video or any other videos on YouTube (they're often quite good for biology, although they may not always contain enough information for IB biology - especially HL)

http://www.youtube.com/watch?v=teV62zrm2P0

Edited January 14, 2012 by brofessional

[IBtank]

Are you talking about the replication fork? If yes, then it's a process which occurs during the S phase in interphase (before mitosis or meiosis). From what I've learnt, there aren't ANY RNA nucleotides involved, simply DNA nucleotides, i.e. A, T, C and G.

So you know that there are two strands in DNA: one in the 5' 3' direction (the leading strand) and the other in the 3' 5' direction (the lagging strand), and DNA replication can ONLY go in the 5' 3' direction. Basically, the enzyme helicase unwinds/uncoils these two DNA strands. DNA polymerase III then adds nucleotides to the strand running in the 5' 3' direction (the leading strand). These added nucleotides will be complementary to the bases already there, e.g. T will pair with A and C will pair with G, or vice-versa.

OK, that was easy, right?

Where the problem arises is on the other strand, which is running in the 3' 5' direction. Thankfully, an RNA primase comes along and adds short RNA primers to the 3' 5' strand. DNA polymerase III can then add free nucleotide to these bases by the same mechanism of complementary base pairing. The nucleotides can be added due to the RNA primer because it allows the strand to be copied in the 5' 3' direction. This process of adding nucleotides creates short lengths of replicated DNA called Okazaki fragments. After this, the RNA primer is removed by DNA polymerase I, and ligase replaces the gaps between the Okazaki fragments with DNA.

I think you must have confused yourself with transcription which is a completely different process.

Key things to remember:

- strand can only be replicated in the 5' 3' direction

- 5 enzymes involved: helicase (unwinds DNA strands), DNA polymerase III (adds free nucleotides to complementary bases in 5' 3' direction), DNA polymerase I (removes RNA primer), RNA primase (adds short RNA primer), ligase (joins Okazaki fragments)

Watch this video or any other videos on YouTube (they're often quite good for biology, although they may not always contain enough information for IB biology - especially HL)

http://www.youtube.com/watch?v=teV62zrm2P0

thank you i know get it! but in my biology book there is something wrong then because my question was based on the book! hmm...

[Sandwich]

So the process of DNA Replication involves a primer, consisting of RNA nucleotides, being produced at the replication fork. After this happens DNA Polymerase III adds DNA in a 5' to 3' direction in order to grow the DNA strand. DNA polymerase I finally removes the primer and replaces it with DNA nucleotides.

So in my view the process of the primer is totally unnecessary isn't it?

Why do you first use RNA nucleotides and then remove them again?

I dont understand the necessity of this?

Anyone able and willing to explain?

Thanks

Essentially the RNA primer is there because DNA can only be added on to an existing strand; RNA does not require a pre-existing strand, it can make its own one (the 'primer') using the enzyme RNA primase. So this self-creating RNA strand is used in order to kick off DNA synthesis. Without it, that won't happen. No RNA primer = no pre-existing strand = no DNA can be added.

Just to clarify that bit a little more. Also, while youtube videos can be useful, they vary in quality/details/accuracy and IMO the best place to learn this stuff from is the textbook!

[whatthehell]

I'm having a lot of trouble with some hardy weinberg problems. I have to do a sheet about "fork birds" and I'm having difficulty finding the genotypic frequency. Can you help?

[Emmi]

I'm having a lot of trouble with some hardy weinberg problems. I have to do a sheet about "fork birds" and I'm having difficulty finding the genotypic frequency. Can you help?

Can you post an example problem please so we know what numbers we're working with?

Edited February 26, 2012 by emyski

[claudika94]

hi, I really dont get topic 4 and 10. Espetially 4.4 not. Can somebody please help me? I have a test on this topic next week.

does anyone have notes that they can post or something

[kim luffy]

Is that topic on genetics? Sorry i use the study guide so i'm not really sure which topics they are

Edited March 14, 2012 by kim luffy

[claudika94]

yeah, thats the topic of genetics. I m getting crazy

[kim luffy]

Cool so what exactly don't you get? the whole thing or is there something specific?

[claudika94]

I have the most trouble with how the genetic engineering works. can you please explain the PCR, gel electrophoresis and gene transfer?

And the next thing i dont understand is : 'explain how meiosis results in an effectively infinite genetic variety in gametes through crossing over in prophase 1 and random orientation in metaphase 1'

[kim luffy]

Well in the PCR, DNA is copied again and again to produce many copies of the original molecules. This is useful when small amounts of DNA is found and large amounts of it are needed. It's carried out at high temperature using a polymerase enzyme called Thermus aquaticus. It can be used at crime scence and such.

Gel electrophoresis is used to seperate mixtures of proteins, DNA or other molecules that are charged. The mixture is placed on a thin sheet of gel and an electric field is applied to the gel by placing two electrodes at both ends. the particles will move to the respective electrode depending on whether it is positively or negatively charged. The rate at which they move depends on the size and charge of the molecule. So let's say if the the particle is small and highly charged, it'll move faster compared to a particle that's large and less charged.

For gene transfer, you can take an example of how insulin is taken from a human and placed into a bacterium where it is left to multiply and later used for diabetic patients.

Basically, taking the example of insulin, the mRNA that codes for insulin is removed from the human pancreas and the DNA copies are made using the enzyme reverse transcriptase. Sticky ends are made by adding extra G nucleotides to the ends of the gene. At the same time, a plasmid (small loops of DNA found in bacteria) is cut open using a restrictive enzyme. Stciky ends are made by adding extra C nucleotides to the ends of the cut plasmid. The insulin gene and plasmid link through complementary base pairing (C-G) between the sticky ends. DNA ligase seals in the nicks by making a sugar-phosphate bond. A suitable host cell is chosen to receive the gene, in this case, E.coli bacteria. The recombinant plasmid (plamisd with insulin gene) are mixed with the host cells and are absorbed. The genetically modified E.coli is cultured in a fermenter and then the e.coli makes the human insulin whihc is purified and used by diabetics.

Bibliography: study guide I hope it helped. If you still don't understand, drop me a PM and i'll explain

Edited March 14, 2012 by kim luffy