HSC Biology Question Thread

[:3]

Hey guys so i'm that confused with the difference b/w meiosis and mitosis, could someone please explain it?

Mitosis: refers to the duplication of cells; involved in the repair, growth and replacement of cells.
- Parent cell differentiates --> two genetically identical, diploid daughter cells formed.

Meisos: refers to the differentiation of cells to form sex cells, which are involved in the production of offsprings (and heredity).
- Parent cell differentiates --> 4 genetically different, haploid daughter cells formed.

[lha]

I believe it would be the flask that is open to the air and microbes.

Alright so when i write the method, do i say "have one straight necked flask as a control"?

[Daliaradosevic]

Mitosis: refers to the duplication of cells; involved in the repair, growth and replacement of cells.
- Parent cell differentiates --> two genetically identical, diploid daughter cells formed.

Meisos: refers to the differentiation of cells to form sex cells, which are involved in the production of offsprings (and heredity).
- Parent cell differentiates --> 4 genetically different, haploid daughter cells formed.

THANK YOU SO MUCH!

[:3]

Alright so when i write the method, do i say "have one straight necked flask as a control"?

Precisely; just talk about preparing two flasks followed by the insertion of a swan glass 'tube' in one flask's stopper and a straight  glass 'tube' (control) in the other.

[lha]

Precisely; just talk about preparing two flasks followed by the insertion of a swan glass 'tube' in one flask's stopper and a straight  glass 'tube' (control) in the other.

Okay but what is the reasoning behind the straight necked flask being the control?

[:3]

Okay but what is the reasoning behind the straight necked flask being the control?

To basically prove that your experiment is working; it shows that microbes ARE carried by dust particles.

[Skidous]

Mitosis: refers to the duplication of cells; involved in the repair, growth and replacement of cells.
- Parent cell differentiates --> two genetically identical, diploid daughter cells formed.

Meisos: refers to the differentiation of cells to form sex cells, which are involved in the production of offsprings (and heredity).
- Parent cell differentiates --> 4 genetically different, haploid daughter cells formed.

Just to further this point
Meiosis begins when the chromosomes of the parent cell quadruple their chromosomes (haploid (23) --> Double Diploid (46 pairs)

Meiosis is also important for genetic diversity in 3 steps
1: Chromosomes cross over with their homologous pairs at a chiasmata and trade genetic information (this creates new alleles)
2: Independent alignment: The chromosomes themselves randomly align along the equatorial plate (there is no order in which the diploid chromosomes align on one side AND they do not have to match up with their homologous pairs) when they separate into 2 DIPLOID Cells
3: Random Segregation: The Chromosomes randomly segregate into different halves of the cell when the 4 HAPLOID cells are formed.

Since these gametes are all random when they are formed, there is also the benefit of random fertilization as there no NATURAL way to ensure one gamete fertilizes another gamete to produce a specific offspring, this furthers genetic diversity
NB There are reproductive technologies such as In Vitro Fertilization (IVF) and Pre-Implantation Genetic Diagnosis (PIGD/PGD) that can ensure that one games fertilizes another and produces an offspring that is healthy or without any genetic disorders or illnesses

[vox nihili]

Just to further this point
Meiosis begins when the chromosomes of the parent cell quadruple their chromosomes (haploid (23) --> Double Diploid (46 pairs)

Meiosis is also important for genetic diversity in 3 steps
1: Chromosomes cross over with their homologous pairs at a chiasmata and trade genetic information (this creates new alleles)
2: Independent alignment: The chromosomes themselves randomly align along the equatorial plate (there is no order in which the diploid chromosomes align on one side AND they do not have to match up with their homologous pairs) when they separate into 2 DIPLOID Cells
3: Random Segregation: The Chromosomes randomly segregate into different halves of the cell when the 4 HAPLOID cells are formed.

Since these gametes are all random when they are formed, there is also the benefit of random fertilization as there no NATURAL way to ensure one gamete fertilizes another gamete to produce a specific offspring, this furthers genetic diversity
NB There are reproductive technologies such as In Vitro Fertilization (IVF) and Pre-Implantation Genetic Diagnosis (PIGD/PGD) that can ensure that one games fertilizes another and produces an offspring that is healthy or without any genetic disorders or illnesses

Just gonna jump in and clear up a couple of minor points. As normal you know your stuff well, but meiosis is a little bit tricky.


That the parent cell quadruples its chromosomes seems to imply that the parents start off with a haploid set of chromosomes. This is obviously not the case.
The parent cell starts off with 46 pairs of chromosomes. It then undergoes replication. It does not, however, double the number of chromosomes. It doubles the number of chromatids. This distinction is really critical.


3. as you've described is not a source of variation. Only the first meiotic division generates variation. You correctly identified independent assortment, during prophase I, as a means of generating variation. Independent alignment just means that the chromosomes line up in the middle randomly, from which they are segregated into the daughter cells randomly as well. After that there are no other sources of variation; so all the variation exists after the first division. The second operates just like mitosis.

[Skidous]

Just gonna jump in and clear up a couple of minor points. As normal you know your stuff well, but meiosis is a little bit tricky.


That the parent cell quadruples its chromosomes seems to imply that the parents start off with a haploid set of chromosomes. This is obviously not the case.
The parent cell starts off with 46 pairs of chromosomes. It then undergoes replication. It does not, however, double the number of chromosomes. It doubles the number of chromatids. This distinction is really critical.


3. as you've described is not a source of variation. Only the first meiotic division generates variation. You correctly identified independent assortment, during prophase I, as a means of generating variation. Independent alignment just means that the chromosomes line up in the middle randomly, from which they are segregated into the daughter cells randomly as well. After that there are no other sources of variation; so all the variation exists after the first division. The second operates just like mitosis.

Isn't the parent cell for a gamete just another gamete? Or is it another type of cell?

[vox nihili]

Isn't the parent cell for a gamete just another gamete? Or is it another type of cell?

Nope, it can't be. If you think about it, if the parent cell were a gamete, where does the variation come from? Gametes only have one copy of each chromosome, so you can't mix and match copies like you can if you start off with a diploid cell. A cell that forms gametes is called a gametocyte.

[marynguyen18]

i have three questions:
1. what's the difference between ADH and Aldosterone?
2. what is the role and function of the kidney?
3. what is the hormone replacement dot point about?
thank you in advanced

[:3]

i have three questions:
1. what's the difference between ADH and Aldosterone?
2. what is the role and function of the kidney?
3. what is the hormone replacement dot point about?
thank you in advanced

Most of the questions I'm answering can be easily found in the textbook or internet.

Anyways:
1. Both are hormones, except ADH (anti-duretic hormone) is involved in water retention, whilst aldosterone is involved in salt (e.g. sodium) retention.
2. The kidney is generally involved in homeostasis - it removes excess substances and waste (i.e. nitrogenous waste) and is involved in osmoregulation (salt/water levels).
3. Basically talk about the detrimental effects it has upon those without such hormones (due to glands not functioning properly and secreting it), followed up by why it is needed (i.e. to address the detrimental effects mentioned)

[Skidous]

Most of the questions I'm answering can be easily found in the textbook or internet.

Anyways:
1. Both are hormones, except ADH (anti-duretic hormone) is involved in water retention, whilst aldosterone is involved in salt (e.g. sodium) retention.
2. The kidney is generally involved in homeostasis - it removes excess substances and waste (i.e. nitrogenous waste) and is involved in osmoregulation (salt/water levels).
3. Basically talk about the importance of each hormone and the negative effects it has on an individual if missing (e.g. No ADH = dehydration, No aldosterone = addison's disease).

Just to add onto this for 3 you need to also talk about what the hormone replacement is for those who have Addison's disease or when they cannot produce ADH

[vox nihili]

Do you guys learn that no aldosterone=Addison's disease? Has been mentioned a few times here, so just wondering whether it's an over-simplification inherent in your course.

(VCE is full of these too unfortunately!).

[Skidous]

It's an oversimplification we are supposed to know what Addison's disease actually is but some people simplify it to mean there is no aldosterone