Questions from the 2015 biology HSC
Q7 - why is the answer not thermoreceptors within the skin? Its them that detect changes from the norm temperature not the brain right?
Q7: You're correct in that thermoreceptors detect changes within the skin, but these thermoreceptors merely send a signal to the brain. The brain enacts on these messages and sends them back to the arterioles and muscles. So, it is a trick question because really, two things happen at or near X.
For the full picture, we'd get:
Core body temp falls below normal -> Thermoreceptors detect these changes in the skin -> Hypothalamus (brain) enacts to these changes -> Signal is sent to the muscles and arterioles -> Return to normal body temp.
So, that's why the brain is the
most correct answer.
Questions from the 2015 biology HSC
Q15 I'm at a complete loss as how to do
Q15: this is a pretty tough question, so don't feel bad!
If we read the question properly, we can see that: individual plants have either
yellow, red or orange flowers.
Right off the bat, this implies either co-dominance or incomplete dominance as three phenotypes are involved.
We can then eliminate dominant/recessive relationships (B)
Next, the sentence tells us that two plants contain
different flower colours. This allows us to eliminate (A).
We now have an even 50/50 split between (C) and (D). The question tells us that the breeding experiment was carried out like Mendel did.
If we recall how Mendel crossed his plants, the parent plants had to be pure bred or homozygous, meaning that (D) cannot be correct.
(C) will be the final answer (based on elimination).
Questions from the 2015 biology HSC
Q23 - should the process not be DNA unzipping - how can we tell its DNA replication does DNA not also unzip during transcription
Q23:
I see what you mean -- transcription or DNA unzipping is the process by which the DNA strand is copied into the mRNA. To observe why it's not transcription, consider what the end result of transcription is and what the end result of DNA replication is from a top-down perspective of the model. If we ever get a model, we should always approach the model with a top-down focus (ie from the top and reading the model going down), because that's the intended direction of how they are made.
Transcription is simply the unwinding and unzipping of the DNA strands using the enzyme helicase. It splits the two strands into its leading and lagging strands, while elongation (which is a process under DNA replication) is simply the synthesis of the complementary base pair onto the leading strand or the "template" strand.
Both of these "processes" comes under the umbrella process we call: DNA replication, which is the preferred process to name. But really, transcription and elongation are procedures that finally accumulate to the process of DNA replication.