nexttttt (4 Viewers)

[Takuto]

Next: Explain how a NAMED disease results from an imbalance of microflora in humans.

Candidiasis, or thrush results from an imbalance of the fungus 'Candida albicans' in humans. The fungus is usually kept in check by competition from other microbes in the same area. The taking of certain medications can upset the balance of microflora in the body, thus leading to thrush.

 

[midifile]

Q: Analyse and present information about the occurence, symptoms, cause, treatment/management of a named non-infectious disease

Down syndrome (trisomy 21)
Occurence - The occurence of Down syndrome increases with maternal age. 1 in 1250 babies born to a 25 year old mother will have Down syndrome; 1 in 385 babies born to a 35 year old mother will have Down syndrome; and 1 in 38 babies born to a 44 year old will have Down syndrome

Symptoms - Down syndrome is chracterised by certain facial features such as a flat apperarance of the face, slanting eyes, small mouth, large protruding tounge, as well as a single crease on the palm and only one flexion furrow on the 5th finger. People with Down syndrome also have straight pubic hair (although I might not put that one into my answer if they ask it in the HSC)

Cause - Down syndrome is caused by the fertilisation of an ovum that has undergone non disjunction of chromosome 21, resulting in that ovum having 2 copies of chromosome 21. When this undergoes fertilisation with a normal sperm, the resulting zygote will have three copies of chromosome 21. This will result in the over expression of genes on chromosome 21, resulting in increased production of certain products.

Treatment/management - There are no effective treatments for Down syndrome, however certain symtoms can be managed. Symptoms such as poor circulation can be managed with blood pressure medication and digoxin (a medication to improve the pumping ability of the heart). Surgury can be used to shorten the tounge so it does not protrude, and to repair any heart defects, intestinal blockages and spinal problems that occur as a result of Down syndrome. Physical therapy can also be used to increase muscle control, and special eduction programs can increase cognative development.

...that was a long one =]

To answer takutos qu, Im coming 1/14 (although my class isnt particularly smart)

 

[midifile]

Next qu:

Q: Explain how mutations in DNA can lead to the formation of new alleles

 

[dolbinau]

Someone already answered that a page ago:

A:Mutations generally result in the alteration of the base sequence of DNA. The mutations can result in
the removal, the replacement or destruction of certain sections of bases. The altered base sequences now
code for new information, that generally is not naturally occuring. The previous allele has been altered to create a new one.

I suppose it has to affect the gametes too for the alleles to be inherited etc..

Describe a model of polypeptide synthesis

(I seriously only have a flowchart so if anyone has anything better I'll steal it from you )

--

and my rank is 1/22 - although I can definitely see the difference between a lower ranking school and some of you guys; your answers are amazing!

 

[luucy]

Next qu:

Mutations are sources of new alleles in an organism; they are changes in the DNA information on the chromosome. Most mutations are lethal however if the mutated form survies it increases the variation within a species. If a mutation occurs in the production of egg and sperm (gametic cells) it will be passed on to the next generation.
Most mutatioons are changes in the DNA sequence smallest type is a point mutationwhere only one base changes. Other larger mutations can include
Deletion: DNA lost from the chromosome
Duplication: section of chromosome copied on same chromosome therefore the same section of DNA appears twice
Inversion: a section of chromosome breaks off and reattaches the wrong way around
Translocation: peice of DNA breaks off the chromosome and reattatches to neighbouring chromosome
Amplification: form of duplication except many more copies.
Changes in DNA sequence creates new proteins in turn creating more alleles.

 

[luucy]

Please

Outline the current understanding of gene expression.

Genetics option

 

[WantToDoBetter]

Someone already answered that a page ago:



I suppose it has to affect the gametes too for the alleles to be inherited etc..

Describe a model of polypeptide synthesis

(I seriously only have a flowchart so if anyone has anything better I'll steal it from you )

--

and my rank is 1/22 - although I can definitely see the difference between a lower ranking school and some of you guys; your answers are amazing!

Danz smashed this question a while back so ill just back hand it your way.

-An enzyme (helicase) unzips the DNA double strand, at the location where the gene coding for the protein is located.

-RNA polymerase joins complementary RNA nucleotides together, forming a messenger RNA strand.
-mRNA then travels outside of the nucleus into the cytoplasm, where it then attaches to a ribosome.
-The ribosome moves along the mRNA strand.
-tRNA molecules in the cytoplasm transport amino acids in the cytoplasm to their corresponding location as coded by the mRNA.
-the code on the mRNA ensures that amino acids are in a correct sequence.
-amino acids are then linked to each other by peptide bonds
-as the ribosome moves along the mRNA strand.. further amino acids are brought by tRNA molecules, forming a long amino acid chain (polypeptide)
-this sequence stops when the STOP codon is reached.

-Polypeptides are then released into the cytoplasm where they will link with other polypeptides to form a protein.

 

[Noobtron]

Question 29 (8 marks)
A space probe recently returned to Earth from a distant planet, with samples
containing bacteria X.

Biologists are interested in comparing the activity of an enzyme found in bacteria X
with that found in bacteria E from Earth. Both bacteria contain an enzyme that
produces a gas as a product of its activity on the same substrate.

State a hypothesis to be tested, and plan an investigation you could carry out to
compare the activity of the enzymes found in these TWO bacteria under ONE of these conditions.

What does under one of these conditions mean

Environmental conditions
where bacteria were collected
Bacteria X 50–80 6.5–8.5
Bacteria E 37–55 5.5–7.5

This question assessed skills in planning an investigation. In the better responses, candidates stated
a correct hypothesis and designed an investigation that included a logical sequence of steps, an
appropriate equipment list, correct identification of a dependent/independent variable, correct
methods for controlling other variables, awareness of the need for repetition (or a large sample size)
and risk assessment.
A significant number of candidates confused a ‘hypothesis’ with an ‘aim’, and some candidates
misunderstood the phrase ‘ONE of these conditions’ and discussed only one temperature or pH.
Very few candidates included risk assessment in their experimental design.

What does ONE OF THESE CONDITIONS mean

 

[Takuto]

temperature or ph

either keep the ph of both at optimum, or temp of both at optimum

then begin to change the other factor

 

[homijoe]

Question 29 (8 marks)
A space probe recently returned to Earth from a distant planet, with samples
containing bacteria X.

Biologists are interested in comparing the activity of an enzyme found in bacteria X
with that found in bacteria E from Earth. Both bacteria contain an enzyme that
produces a gas as a product of its activity on the same substrate.

State a hypothesis to be tested, and plan an investigation you could carry out to
compare the activity of the enzymes found in these TWO bacteria under ONE of these conditions.

What does under one of these conditions mean

Environmental conditions
where bacteria were collected
Bacteria X 50–80 6.5–8.5
Bacteria E 37–55 5.5–7.5




What does ONE OF THESE CONDITIONS mean

one of these conditions means either test enzyme activity with either a change in pH or Temperature

 

[midifile]

The confusing thing is in the examiners notes it says:

A significant number of candidates confused a ‘hypothesis’ with an ‘aim’, and some candidates misunderstood the phrase ‘ONE of these conditions’ and discussed only one temperature or pH. Very few candidates included risk assessment in their experimental design.

which makes its sound like you had to talk about both

But im guessing that that's just a typo, becasue the question speficies "one variable"

 

[homijoe]

The confusing thing is in the examiners notes it says:



which makes its sound like you had to talk about both

But im guessing that that's just a typo, becasue the question speficies "one variable"

hmmm i think wat the examiners note meant, is that students used only ONE temperture or One pH and not a range...of temp or pH

 

[Takuto]

But im guessing that that's just a typo, becasue the question speficies "one variable"

its not a typo i think

what it means is

some people only mentioned either temperature OR ph, and did not say that the other should be kept constant or at optimum


whats risk assessment btw?

 

[danz90]

The confusing thing is in the examiners notes it says:



which makes its sound like you had to talk about both

But im guessing that that's just a typo, becasue the question speficies "one variable"

what they're saying is (i think)

that candidates interpreted 'one condition' as one temperature, eg 45degrees, and thats it, disregarded other temp values. what the examiners were looking for was you using ONE of the variables, either pH or temperature. And to use it as an independent variable in an investigation.

 

[danz90]

whats risk assessment btw?

lol havent u done risk assessments before wen doing pracs?

Its basically where u identify risks, asses the risks in your practical, and then state how these risks can be controlled.

I usually do it in a table, works best.

 

[midifile]

Yeah.. that makes sense

for takuto, for the risk assesment you can say - A bunsen burner was required to heat the water baths. The open flame may be a safety risk as it can cause burns. As a result, care was taken when handelling the bunsen burner and hot water

 

[Kujah]

Risk assessment = safety issues.

 

[barry1]

Draw transverse and longitudinal sections of phloem and xylem tissue (hope this question hasn't been asked before)

 

[Takuto]

lol havent u done risk assessments before wen doing pracs?

Its basically where u identify risks, asses the risks in your practical, and then state how these risks can be controlled.

I usually do it in a table, works best.

hahaha nope. never heard of it

so basically a safety measures table ?

well seems simple enough, ta =]

 

[danz90]

Yeah.. that makes sense

for takuto, for the risk assesment you can say - A bunsen burner was required to heat the water baths. The open flame may be a safety risk as it can cause burns. As a result, care was taken when handelling the bunsen burner and hot water

exactly that it addresses IDENTIFY, ASSESS and CONTROL.