Yacoubb's Bio 3+4 Questions

[Yacoubb]

Why are Okazaki fragments necessary for the synthesis of a strand complementary to the lagging strand during DNA replication?

Okazaki fragments aren't used in the synthesis of lagging strand; they are actually the lagging strand constituents. During DNA replication, the lagging strand is built discontinuously 5' to 3' in okazaki fragments, because the lagging strand template is not exposed immediately by the replication fork.

So this means that because the RNA primer binds to the 5' end of the strand, and the replication fork is being formed (i.e. DNA is being unzipped), the RNA primer has to keep jumping, and that's why the lagging strand is built discontinuously.

Following DNA replication, okazaki fragments are ligated together to then form a continuous strand.

[Yacoubb]

Just some queries in regards to mutations. Could someone check my expression:

What occurs in translocation mutations:
A section of a chromosome breaks off and attaches to a non-homologous chromosome.

What occurs in inversion mutations:
A segment of a chromosome breaks off, flips around, and reattaches to the same chromosome.

What occurs in deletion mutations:
A segment of a chromosome is lost; genetic material is lost.

What occurs in a duplication mutation:
A section of a chromosome is repeated, resulting in an addition of genetic material.

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Explaining a non-sense mutation:
* As a result of the insertion/deletion/substitution of the base, a premature stop codon is present in the mRNA transcript of the gene, and a polypeptide with a shortened amino acid sequence is synthesised.

Explaining a missense mutation:
As a result of the base substitution mutation, a different amino acid is coded for at position ____. Thus, a polypeptide with an altered primary structure is produced.

Explaining a silent mutation:
Because the genetic code is redundant, and the amino acid ____ is coded for by different codons, the substitution mutation has no effect on the amino acid sequence of the polypeptide.

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Explaining the effects of a Frameshift mutation:
When a base is added or deleted, all triplets beyond the mutation are altered. As a result, a dysfunctional polypeptide with a different amino acid sequence is produced.

Explaining a frameshift mutation:
- When a base is inserted or deleted, all bases beyond this mutation point are displaced one position. The reading template is frameshifted, triplets are altered and a dysfunctional polypeptide is synthesised.


^^ Is this fine?! Thank you! (:

And can someone PLEASE explain to me translocations in regards to gamete formation? Also, how do I know whether an extra X chromosome is a result of non-disjunction occurring in the mother or the father during meiosis? Thanks

[Fingerscrossed]

I have another quick question...

Is there a formal definition for 'non-competitive inhibition'?

Thanks...

[Smiley_]

I have another quick question...

Is there a formal definition for 'non-competitive inhibition'?

Thanks...

I used a

molecule that binds to an enzyme at a site other than the active site; this changes the shape of the enzyme so that the substrate can no longer bind to
the active site

but there are no real "formal definitions" in bio

[Yacoubb]

A non-competitive inhibitor is a molecule that binds to the allosteric region of an enzyme; that is, the molecule binds to a region other than the active site of that enzyme. This inhibition induces a change in the shape of the active site of the enzyme. Consequently, the enzyme is no longer able to bind to its specific substrate molecules, and the activity rate of the enzyme decreases.

The first sentence ^^ would suffice as a definition of a non-competitive inhibitor.

[Fingerscrossed]

A non-competitive inhibitor is a molecule that binds to the allosteric region of an enzyme; that is, the molecule binds to a region other than the active site of that enzyme. This inhibition induces a change in the shape of the active site of the enzyme. Consequently, the enzyme is no longer able to bind to its specific substrate molecules, and the activity rate of the enzyme decreases.

The first sentence ^^ would suffice as a definition of a non-competitive inhibitor.

Thanks!:) That is actually amazing...