VCE Biology Question Thread

[dankfrank420]

Could someone briefly explain the insulin/blood glucose levels stimulus response model? Please make mention of the various organs and glands involved. Cheers.

[Reus]

Apparently we do

What's microarray technology?!

[RazzMeTazz]

Is DNA profiling always done with the use of STRs? Or can it be done with genes ?

[Frozone]

Does anyone have a simpler explanation of the founder effect? My book is not very clear!

[vox nihili]

Does anyone have a simpler explanation of the founder effect? My book is not very clear!

Group of people break off from the population.
Go to a new joint.
Only breed with each other.
-> lower level of genetic diversity.


Example: let's say a mutation occurs in 1 in 1 million people. If 1000 of those people break off and start a new population (isolated from the other) and it so happens that one person in that population has that mutation, you've now increased the prevalence of that mutation to 1 in 1000 in that population.

[anat0my]

What is the purpose of bacteria having plasmids for themselves?

Why is mitochondrial DNA important and what is it used for?

What is the leading/lagging strand and why are they different?

Why is RNA primer used in DNA replication instead of DNA primer? What's the difference?

[Rishi97]

What is the difference between cytotoxic T-cell and natural killer cells?

[anat0my]

What is the difference between cytotoxic T-cell and natural killer cells?

Cytotoxic T-cells are part of the cell mediated specific immune response, whereas natural killer cells are part of the non-specific immune response; T-cells recognise antigens, whereas NK cells do not.

[melons]

What is the purpose of bacteria having plasmids for themselves?

They contain extra genes... Idk what exactly but the bacteria is able to use these genes.

Why is mitochondrial DNA important and what is it used for?

Mitochondrial DNA is passed down the maternal line so can be able to used to identify people in the same maternal line. As mtDNA does not undergo recombination and has very few mutations so can be used to trace back numerous generations. In the mitochondria themselves, they code for proteins needed for cellular respiration.

What is the leading/lagging strand and why are they different?

The DNA double helix is composed of two strands. One runs from 3' to 5' when unwound and is the leading strand. When DNA replication occurs the complementary strand is synthesised continuously. The other strand is the lagging strand and as the RNA primer joins to the 3' the new strand cannot be synthesised in the same direction as the leading strand. Instead it is synthesised in fragments, called Okazaki fragments, which are joined together by the enzyme Ligase.

Why is RNA primer used in DNA replication instead of DNA primer? What's the difference?

I'm not sure why RNA primer is used instead but it is the made up of RNA (so has ribose sugar and uracil) instead of DNA (which has deoxyribose and thymine). Sorry!

Hope that helped.

Cytotoxic T-cells are part of the cell mediated specific immune response, whereas natural killer cells are part of the non-specific immune response; T-cells recognise antigens, whereas NK cells do not.

Also, NK cells target virus effected cells while cytotoxic T-cells tend to target cancers and transplanted tissues.

[Sense]

In this question on a practice SAC, it asks how many fragments of each of these DNA strands there will be after the restriction enzyme cuts them. I wrote A.7 B.5 C.5 D.3, but in the answers it says A.4 B.3 C.4 D.2. How is this the answer? I don't know how it could be that?

[melons]

In this question on a practice SAC, it asks how many fragments of each of these DNA strands there will be after the restriction enzyme cuts them. I wrote A.7 B.5 C.5 D.3, but in the answers it says A.4 B.3 C.4 D.2. How is this the answer? I don't know how it could be that? (Image removed from quote.)

When you count the number of fragments of each DNA sample, treat them as single stranded. So, ignore the bottom strand (for example) and count the number of fragments produced on the top strand. The bottom strand will have the same number of fragments. Hopefully that helped.

[Sense]

When you count the number of fragments of each DNA sample, treat them as single stranded. So, ignore the bottom strand (for example) and count the number of fragments produced on the top strand. The bottom strand will have the same number of fragments. Hopefully that helped.

Wow -_- my mind was going blank. Thanks

[anat0my]

Spoiler

They contain extra genes... Idk what exactly but the bacteria is able to use these genes.
Mitochondrial DNA is passed down the maternal line so can be able to used to identify people in the same maternal line. As mtDNA does not undergo recombination and has very few mutations so can be used to trace back numerous generations. In the mitochondria themselves, they code for proteins needed for cellular respiration.
The DNA double helix is composed of two strands. One runs from 3' to 5' when unwound and is the leading strand. When DNA replication occurs the complementary strand is synthesised continuously. The other strand is the lagging strand and as the RNA primer joins to the 3' the new strand cannot be synthesised in the same direction as the leading strand. Instead it is synthesised in fragments, called Okazaki fragments, which are joined together by the enzyme Ligase.
I'm not sure why RNA primer is used instead but it is the made up of RNA (so has ribose sugar and uracil) instead of DNA (which has deoxyribose and thymine). Sorry!

Hope that helped.
Also, NK cells target virus effected cells while cytotoxic T-cells tend to target cancers and transplanted tissues.

Thanks Gapster! 

[Jason12]

how much do we need to know about gene mutations? It's not explicitly stated in the study design.

[nerdmmb]

What is the best way to differentiate between X-linked recessive traits and X-linked dominant traits in pedigree analysis?

Thanks