Yacoubb's Bio 3+4 Questions

[simpak]

Gene expression is exactly what it sounds like: transcribing a gene to give an mRNA and translating the mRNA to give a protein is gene expression.  To remember the difference, remember that translation comes later than transcription.

DNA replication does not come 'first' because it's not related to gene expression.  DNA replication exists to make a copy of the genome right before a cell divides.  Most cells in your body don't replicate (much) anymore but for as long as they live they need to keep expressing genes because proteins are the functional components of the cell that allow it to carry out its role in the body.  So think of DNA replication and transcription/translation as separate entities even though the processes are somewhat similar.

Which enzymes are you talking about?  DNA replication involves a DNA polymerase (ie, something that makes DNA) while transcription involves an RNA polymerase (ie, something that makes RNA).  The only protein you should need to know about for translation is RNA polymerase (and potentially activators or repressors since you were asking about those in another thread).  Most all other enzymes you will discuss (primase, ligase, helicase, topoisomerases) are involved in replication.

RNA polymerase does not require a helicase to open DNA, it can do this itself.  RNA polymerase also doesn't require a primer so there would be no primase involved in transcription.

[Yacoubb]

whats gene expresssion?

and does dna replication come first?

where do all the enzymes come in ?

Genes are units of DNA that encode the set of genetic instructions to synthesise particular polypeptides. It is through these polypeptides (e.g. Enzymes) that a particular gene, for instance, eye colour, is expressed in appropriate regions of the body (in this case, the eyes). It's really alluding to protein synthesis, which involes the 2 stages:
1.) Transcription - where the template (antisense) strand of DNA is tramscribed to form mRNA.
2.) Translation - the mRNA is translated to synthesise a particular polypeptide.

DNA replication is part of the cell cycle - during the S-phase of interphase, the genetic material duplicates so that the genetic material can be divided into two diploid somatic cells in mitosis or recombined and assorted into 4 nuclei during meiosis.

The function of an enzyme is to increase the rate of a reaction by lowering its activation energy. So, the enzymes you should know about for DNA replication are:
* DNA helicase (unravels the double-helix DNA molecule and separates the two polynucleotide strands by breaking the weak hydrogen bonds between them).
* DNA polymerase which collects free DNA nucleotides and builds the complementary DNA strands according to the complementary base pairing rule.

The enzymes in Transcription:
* RNA polymerase that builds the pre-mRNA molecule using the DNA template strand, funnily enough, as a template, and building that pre-mRNA using collected RNA nucleotides which attach to complementary base pairs.
* Ligase - during post transcriptional modification, once introns and sometimes exons are removed, the remaining exons are joined by ligase enzymes to form a continuous mRNA strand.

[Smiley_]

thanks both of you
I feel like an idiot but I get it now

[Yacoubb]

thanks both of you
I feel like an idiot but I get it now

You're not an idiot You're smart for asking a question you need an answer to and therefore consolidating it! Don't be hard on yourself!

[vox nihili]

thanks both of you
I feel like an idiot but I get it now

Better to feel like an idiot here than on the exam right?

[simpak]

Haha don't worry you're not an idiot.  I got a 50 in Biology and I started off asking the same question about how replication and gene expression would tie together but they really need to be treated as separate but similar processes imo.  Learning is best helped by clarification!

[vox nihili]

Haha don't worry you're not an idiot.  I got a 50 in Biology and I started off asking the same question about how replication and gene expression would tie together but they really need to be treated as separate but similar processes imo.  Learning is best helped by clarification!

I love when the questions start off with "well this is probably a stupid question but..." then by the end of it I'm left thinking "oh god, I got a 43 and I'm studying BIOmedicine and I don't even know that".

[Yacoubb]

I'm studying Photosynthesis and I was wondering if someone could check whether my descriptions of photosynthesis are accurate. Thanks

Light-dependent Stage:
- Chlorophyll molecules absorb light energy.
- A H₂O molecule is split into H⁺ ions and O₂.
- ATP is formed from ADP + Pi.
- NADP molecules collect H⁺ ions to form NADPH+ molecules.

Light-independent stage:
- CO₂ reacts with H⁺ ions provided by NADPH+ to synthesis glucose.
- ATP provides energy to synthesise glucose.
- A H₂O molecule is formed when H+ ions are accepted by oxygen atoms.

[swagsxcboi]

I'm studying Photosynthesis and I was wondering if someone could check whether my descriptions of photosynthesis are accurate. Thanks

Light-dependent Stage:
- Chlorophyll molecules absorb light energy.
- A H₂O molecule is split into H⁺ ions and O₂.
- ATP is formed from ADP + Pi.
- NADP⁺ molecules collect H⁺ ions to form NADPH molecules.

Light-independent stage:
- CO₂ reacts with H⁺ ions provided by NADPH to synthesis glucose.
- ATP provides energy to synthesise glucose.
- A H₂O molecule is formed when H+ ions are accepted by oxygen atoms.

remember that when the CO₂ is split, the carbon is used in synthesising the glucose (obviously 6-C are needed) aka carbon fixation
light dependant- grana (contains chlorophyll, accessory pigments)
light independant - stroma (contains necessary enzymes)

[Yacoubb]

remember that when the CO₂ is split, the carbon is used in synthesising the glucose (obviously 6-C are needed) aka carbon fixation
light dependant- grana (contains chlorophyll, accessory pigments)
light independant - stroma (contains necessary enzymes)

Yeah I figured.

Carbon fixation is required to reduce carbon dioxide from its highly oxidised state as carbon dioxide and reduce it to carbon that can be used to synthesise organic glucose.

Carbon Fixation:
* CO₂ reacts with RuBP (ribulose bi-phosphate) to form a unstable 6-C compound. The reaction between carbon dioxide and ribulose bi-phosphate is catalysed by RuBisCO.
* The unstable 6-C compound splits into two 3-C compounds.
* Once of these 3-C compounds continues through the Calvin-Benson Cycle, while the other 3-C compound leaves the cycle and eventually becomes organic glucose.

Light-Dependent Stage occurs in the grana of the chloroplast organelle, while the Light-Independent Stage occurs in the stroma of the chloroplast. Grana are stacks of thylakoid-membrane bound discs that contain chlorophyll and other accessory pigments. The stroma refers to the gel-like matrix that surrounds the grana and is rich in dissolved enzymes.

[swagsxcboi]

Yeah I figured.

Carbon fixation is required to reduce carbon dioxide from its highly oxidised state as carbon dioxide and reduce it to carbon that can be used to synthesise organic glucose.

Carbon Fixation:
* CO₂ reacts with RuBP (ribulose bi-phosphate) to form a unstable 6-C compound. The reaction between carbon dioxide and ribulose bi-phosphate is catalysed by RuBisCO.
* The unstable 6-C compound splits into two 3-C compounds.
* Once of these 3-C compounds continues through the Calvin-Benson Cycle, while the other 3-C compound leaves the cycle and eventually becomes organic glucose.

Light-Dependent Stage occurs in the grana of the chloroplast organelle, while the Light-Independent Stage occurs in the stroma of the chloroplast. Grana are stacks of thylakoid-membrane bound discs that contain chlorophyll and other accessory pigments. The stroma refers to the gel-like matrix that surrounds the grana and is rich in dissolved enzymes.

I don't think you need such an extensive knowledge about carbon fixation, as long as you know the inputs/outputs of each stage (which you seem to know well), you should be fine.

[vox nihili]

I don't think you need such an extensive knowledge about carbon fixation, as long as you know the inputs/outputs of each stage (which you seem to know well), you should be fine.

I agree. Though of course it can be handy if you do know the full process to remember the other things

[wallah]

Hey guys, I have a question, : what could possibly pop up in the DNA manipulation SAC?

[Yacoubb]

Hey guys, I have a question, : what could possibly pop up in the DNA manipulation SAC?

Gene cloning, restriction enzymes, ligation, gel electrophoresis, PCR.

[Scooby]

PCR and gel electrophoresis for forensic investigations is pretty common