Edexcel AS Biology - 6B101 + 6B102 - Unit 1 and Unit 2 Exam Discussion Thread

Reply 1580

Archurus23

21

Original post by mohamedfarah55

Y'all check this out if you're wondering how to answer it the way the mark scheme want you to

It won't open

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Reply 1581

hannah_frost

polygenic inheritance please help!!

If genotypes are Bb bb bB, Why are the possible gametes Bbb BbB bbb bbB?
How do u work out the possible gametes and why isn't bBb a possible one, and Aren't Bbb and bbB the same?

Reply 1582

Amir52

13

anyone have a good understanding of what 'Xerophytes' are?
Aren't they are the plants grown in adverse conditions or more accurately in places like deserts? (just a thought)

Reply 1583

Amir52

13

Original post by hannah_frost

polygenic inheritance please help!!

If genotypes are Bb bb bB, Why are the possible gametes Bbb BbB bbb bbB?
How do u work out the possible gametes and why isn't bBb a possible one, and Aren't Bbb and bbB the same?

bB and Bb are same! let's take a disorder and mark it as 'B' for dominant allele and 'b' for recessive allele . Homozygous parent will have a 'BB' 'bb' for that condition and hetrozygous will have a 'Bb' or 'bB' for that condition. Then you just draw the gametes!

Reply 1584

PlayerBB

17

Original post by DK 96

Can anyone explain how can we use a totipotent stem cell to produce a multipotent stem cell?

The totipotent cell will divide and differentiate into a pluripotent cell by activated genes which produce mRNA which will be translated into specific proteins that will modify the cell and differentiate it then the pluripotent cell will differentiate into a multipotent cell

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Reply 1585

Tazmain

8

Yo guys, does this sound right?

Tissues
One or more different types of cells
Working towards one particular function

Organs
Many different types of tissues
Working towards one particle function

Organ system
Group of different organs
Carrying out different functions

Reply 1586

Tazmain

8

Original post by mohamedfarah55

Y'all check this out if you're wondering how to answer it the way the mark scheme want you to

"You the real MVP"

Reply 1587

AvWOW

3

Original post by Medically

Anyone explain the difference between plant cortex and parenchyma, or are they both the same?

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I think the plant cortex is the region between the vascular bundle and epidermis, and parenchyma is inside the vascular bundles. They are unspecialised cells that could specialise into cells that aid storage and photosynthesis. It also differenciates to collenchyma and sclerenchyma.

Reply 1588

annie79

9

Original post by Amir52

bB and Bb are same! let's take a disorder and mark it as 'B' for dominant allele and 'b' for recessive allele . Homozygous parent will have a 'BB' 'bb' for that condition and hetrozygous will have a 'Bb' or 'bB' for that condition. Then you just draw the gametes!

What would thr gametes be? I havent been taught this..

Reply 1589

Amir52

13

Original post by annie79

What would thr gametes be? I havent been taught this..

you deduce gametes from the genotype. Individual being homozyguos for a trait will have genotype such as , 'nn' 'NN' so will have a gamete either, 'N' or 'n', and individual being hetrozyguos for a trait will have genotype like, 'Nn' and therefore will have a gamete, 'Nn'
I used 'N' to show a normal and 'n' for default gene.

Reply 1590

PlayerBB

17

Can anyone help me with this please

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Reply 1591

Amir52

13

Original post by PlayerBB

Can anyone help me with this please

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my answers:
1. Data collected was too early
2. not all the proteins are packaged
3. all the vesicles did not arrive at the golgi when the data was taken

(hope that makes sense :s-smilie:

)

Reply 1592

annie79

9

Original post by Amir52

you deduce gametes from the genotype. Individual being homozyguos for a trait will have genotype such as , 'nn' 'NN' so will have a gamete either, 'N' or 'n', and individual being hetrozyguos for a trait will have genotype like, 'Nn' and therefore will have a gamete, 'Nn'
I used 'N' to show a normal and 'n' for default gene.

could you draw out a punnet square or something where I can see how you work out the genotype of the gametes from polygenic inheritance - so when there are 3 alleles that get inherited I think

Reply 1593

PlayerBB

17

Original post by Amir52

my answers:
1. Data collected was too early
2. not all the proteins are packaged
3. all the vesicles did not arrive at the golgi when the data was taken

(hope that makes sense :s-smilie:

)

Yeah it makes sense, thank you :yes:

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Reply 1594

lilyelisabeth

2

Original post by hannah_frost

polygenic inheritance please help!!

If genotypes are Bb bb bB, Why are the possible gametes Bbb BbB bbb bbB?
How do u work out the possible gametes and why isn't bBb a possible one, and Aren't Bbb and bbB the same?

Okay, so say all these alleles are for eye colour. Let's say the mother has the genotype Bb bb Bb and the father has the genotype Bb bb bb. We need to take an allele from each 'set' to find all the possible gamete combinations. So from the mother we could have BbB or Bbb or bbb or bbB. For the father the only combinations are Bbb or bbb. Now put the gametes into a big 'ol punnet square, I suggest the mothers gametes across the top, and the fathers up the side, then do normal punnet square business to get all the combinations for the offspring's genotype. So for example, the combination of Bbb and Bbb would make BBbbbb. In the exam they will give you some sort of information about what eye colour or whatever the feature is and which genotypes code to which eye colour.

Hope that helps, if not I'll send you a pic of the punnet square as that may make more sense 😊🌸

Reply 1595

Mr.Bretherton

1

If the exam board takes down a past paper as they have done with the January 2013 Unit 2 does that mean the real thing will be similar to that paper?

Reply 1596

Amir52

13

Original post by annie79

could you draw out a punnet square or something where I can see how you work out the genotype of the gametes from polygenic inheritance - so when there are 3 alleles that get inherited I think

currently i can't recall any, if you know one you can ask that! but in general for polygenic (or any) inheritance you can expect parental genotype being provided in the question, or at least a hint of that genotype. So you just copy\derive the gametes from there!

Reply 1597

Feraligatr

OP

20

Questions anyone?

Suggest three ways you could potentially maintain genetic diversity in a zoo
Give three differences in terms of structure between Eukaryotic and Prokaryotic cells
Define polygenic inheritance (2 marks)
Describe how natural selection occurs (4 marks)

Reply 1598

Amir52

13

Original post by Feraligatr

Questions anyone?

Suggest three ways you could potentially maintain genetic diversity in a zoo
Give three differences in terms of structure between Eukaryotic and Prokaryotic cells
Define polygenic inheritance (2 marks)
Describe how natural selection occurs (4 marks)

1. i.careful selection of mate
ii. allowing to mate with a different individual to a previous meeting
iii. allowing those with different genes to mate
2. Eukaryotic cells are larger cells with a linear DNA and has many organelles. Prokaryotic cells are smaller with circular DNA and few organelles
3. Polygenic inheritance is when more than one gene is involved in influencing the phenotype of an individual
4. A population of organisms shows genetic diversity due to having a variety of alleles often caused by mutations, when environmental condition changes nature removes some individuals with alleles that are not advantageous through selection. the remaining individuals grow and reproduce passing on the advantageous alleles. Over many generations the frequency of these alleles increases.

hope it helps :biggrin:

Reply 1599

lilyelisabeth

2

Original post by Feraligatr

Questions anyone?

Suggest three ways you could potentially maintain genetic diversity in a zoo
Give three differences in terms of structure between Eukaryotic and Prokaryotic cells
Define polygenic inheritance (2 marks)
Describe how natural selection occurs (4 marks)

The natural selection one:
A population has a range of alleles due to genetic mutation. A new selection pressure arises, the organisms with the mutated allele putting them in favour of this pressure survive and pass on their allele, the others do not survive as well and eventually die off until only those with the mutated 'helpful' allele are remaining. The frequency of this allele increases over time.

Differences between pro and euk:
Euk has strand DNA, pro has loop.
Euk has Golgi apparatus pro doesn't
Pro has a cell wall, euk does not.

Polygenetic inheritance - the phenotype expressed in the offspring depends on more than one gene from the each of the parents that may be on a different loci (my guess I'm not sure of an exact definition. It's basically just more than 1 gene is responsible for the phenotype).

Maintain genetic diversity -
1. Keep stud books to stop interbreeding and stop the loss of rare alleles.
2. Do not allow organisms to repeatedly breed with same partner.
3. Use IVF or selective breeding to control breeding partners.

This is just from what I would say and the notes I've made, hope it is helpful 😊

Edexcel AS Biology - 6B101 + 6B102 - Unit 1 and Unit 2 Exam Discussion Thread

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