OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment

ibysaiyan

My todays plan is to go over bio-tech stuff: such as batch culture/quorn synthesis/penicillin.. (boring i know) + a re-read of genome sequencing + err if i am able to squeeze in population stuff.
Btw feel free to question me on: Variation/meiosis/genome sequencing/evolution and on.Least this way we could clear each others doubts out.

Genome sequencing <3

Restriction enzymes...cut cut cut...yay! :smile:

Reply 562

ibysaiyan

=) meh anyway how is your revision going? i err don't feel in the mood to do bio. today i might spend rest of the night doing physics. :s-smilie:

Oh also congrats on your offer. ^.^

Not on faradays law yet...well in my revision anyway. I got up to electromagnetic induction today. I do OCR. Aiming for A* :smile:

I love chemistry. I find it much easier than both bio and physics. I don't have to do much for it at all. I just seem to understand everything in an instant.

We could do bio together. :smile:

Talking about topics is good.

And thanks! :smile:

Reply 563

ViolinGirl

I felt like talking about discontinous/continuous variation...

Discontinuous variation describes the qualitative differences between phenotypes. These are in clear distinguishable catergories, with no intermidate sub categories. Examples include:
-->Height in pea plants (either tall or dwarf)
-->Sex
-->Blood group

These tend to be controlled by one gene (monogenic), but if they are controlled by 2 or more genes then they interact in an epistatic way, so one gene will mask or influence the expression of another gene. This limit phenotypic variation.
Different gene loci have differenct effects on the phenotype
Different alleles at a single gene locus have large effects on the phenotype.

Continous variation describes the qualitative differences between phenotypes, the phenotypic differences have a large variety of variation. There are no distinct catergories.
-->height in humans
--->Mass in humans
----> Milk yeild in cattle.

These traits are controlled by more than one gene (polygenic)
Different alleles contribute additive amounts to phenotype.
Different alleles at each gene locus have small effects on the phenotype.

These characteristics are more affeted by the environment that discontinous ones. :smile:

Ah brilliant! also since we had variation in f212 it reminded me of continuous variation lying between two extremes with most of the population lying between the mean values.
:smile:

Reply 564

ViolinGirl

Not on faradays law yet...well in my revision anyway. I got up to electromagnetic induction today. I do OCR. Aiming for A* :smile:

I love chemistry. I find it much easier than both bio and physics. I don't have to do much for it at all. I just seem to understand everything in an instant.

We could do bio together. :smile:

Talking about topics is good.

And thanks! :smile:

Yea sure.

Reply 565

ibysaiyan

Ah brilliant! also since we had variation in f212 it reminded me of continuous variation lying between two extremes with most of the population lying between the mean values.
:smile:

Yes continous variation can be represented on a normal distibution curve. But discontinuous variaton is represented by a bar chart :biggrin:

Reply 566

Environmental factors can act as stabilising and evolutionary forces of natural selection

- Stabilising selection - maintains existing adaptations and allele frequencies.
e.g. maintaining allele frequencies of Hbs allele in malarial areas.
- Directional selection - alters allele frequencies
- Evolutionary changes:
New advantageous alleles in a population are selected.
Disadvantageous alleles are removed by stabilising selection.

Genetic drift

- Changes in allele frequencies that occur randomly by chance.
- Causes large changes in small populations.
- Small populations may have allele frequencies which are not representative of the main population from which they came.
- Founder effect - genetic drift in a small, isolated population which alters the allele frequencies further.

Isolating mechanisms

- geographical / ecological barriers - e.g. mountains, sea etc - prevent individuals from mating.
- seasonal (temporal) barriers - e.g. climate change throughout the year.
- reproductive mechanisms - e.g. individuals may not be able to mate due to genital problems, breeding times, courtship rituals.

Reply 567

What causes genetic drift? :smile:

If anyone cares to answer...

Reply 568

ViolinGirl

Yes continous variation can be represented on a normal distibution curve. But discontinuous variaton is represented by a bar chart :biggrin:

continuous can also be represented in a frequency histogram :smile:

Reply 569

*yawn* I think I will be off now...feel tired...Night guys!

Reply 570

ViolinGirl

Yes continous variation can be represented on a normal distibution curve. But discontinuous variaton is represented by a bar chart :biggrin:

Yep the way i memorize is using the words, say for example: continuous i imagine it to be a long continuous graph. LOL

Reply 571

ViolinGirl

What causes genetic drift? :smile:

If anyone cares to answer...

spontaneous mutations, separation of a smaller group from a larger population.

Reply 572

ViolinGirl

What causes genetic drift? :smile:

If anyone cares to answer...

Genetic drift is the change in the allele frequency which occurs only within isolated,small population by chance.(Note: Its not same as natural selection since no selection pressure exists).Genetic drift could also lead into diminish of allele variety.

Reply 573

smflesh

student92

Environmental factors can act as stabilising and evolutionary forces of natural selection

- Stabilising selection - maintains existing adaptations and allele frequencies.
e.g. maintaining allele frequencies of Hbs allele frequencies in malarial areas.
- Directional selection - alters allele frequencies
- Evolutionary changes:
New advantageous alleles in a population are selected.
Disadvantageous allele are removed by stabilising selection.

Genetic drift

- Changes in a allele frequencies that occur randomly by chance.
- Causes large changes in small populations.
- Small populations may have allele frequencies which are not representative of the main population from which they came.
- Founder effect - genetic drift in a small, isolated population which alters the allele frequencies further.

Isolating mechanisms

- geographical / ecological barriers - e.g. mountains, sea etc - prevent individuals from mating.
- seasonal (temporal) barriers - e.g. climate change throughout the year.
- reproductive mechanisms - e.g. individuals may not be able to mate due to genital problems, breeding times, courtship rituals.

Thank you! :biggrin:

Reply 574

smflesh

Thank you! :biggrin:

Your welcome :biggrin:

Reply 575