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WJEC Biology BY5 20th JUNE 2014

Reply 180

dogs4eva7

20

Original post by maccostello

sex linkage just refers to genes being located on chromosome X and/or Y :smile:

Isn't it just X? :redface:

Also, anyone have reaaaally old past papers for genetics questions? Love the topic, but so crap at answering Qs

Reply 181

sailorben

1

Yes basically only the X chromosome, at our level of understanding, anyway... I guess.. since it's just a little more complex in real life.

Reply 182

Aapi27

3

Any one got any predictions for the 10 markers? They all seem horrible at the moment. :confused:

Reply 183

50ShadesOfLame

Original post by Aapi27

Any one got any predictions for the 10 markers? They all seem horrible at the moment. :confused:

I was thinking about this earlier, and I really wouldn't be surprised if they did a 10 marker on plant reproduction, it wasn't in the paper AT ALL last year, so it's likely to reappear, but I can't see them making a massive question on it, so a 10 marker seems likely, maybe pollination/fertilisation?

They tend to pick something from 5.6 as well, since it's such a big topic and you can waffle about advantages/disadvantages?

My bet would be something on 5.3, and something on 5.6 (cloning/GM crops maybe?) and possibly an ecology question (5.7/5.8) since they came up loads last year, they might just put a ten marker in this year? :confused:

Reply 184

Water_fall

What exactly is the difference between non-disjunction and polyploidy? they seem the same to me :frown:

Reply 185

sailorben

1

Polyploidy is just that, having a ultiple ploidy. E.g, a triploid, a tetraploid.

So long as the ploidy is even, the organism should be fertile. As they are still able to form homologous pairs. Triploids however, cannot pair-up, thus are sterile.

Non-disjunction is different. This is the process in which faulty cell division results in one daughter cell getting two copies of the chromosome, whilst the other daughter cell gets no copies.

The daughter cell with no copies will die, however, it is possible that the cell with two copies survives, and may be fertilised, resulting in 3 copies of a chromosome.

Reply 186

bookworm246love

12

goooood luck everyone :smile:

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Reply 187

natashac0428

will someone fully explain a pregnancy test to me, all we have is a picture and im scared of it coming up as a 4 marker

Reply 188

chrismorgan7341

Original post by natashac0428

will someone fully explain a pregnancy test to me, all we have is a picture and im scared of it coming up as a 4 marker

Hey! I shall try my best! During pregnancy, the hormone hCG is released by the chorion on the blastocyst (the zygote after fertilisation as it moves to the uterus lining), anyway this hormone is excreted in the urine during pregnancy.
So urine is placed on a sample strip on the pregnancy test, where anti-bodies, which are specific to hCG bind with the hCG hormone in the urine. The anti-bodies are also attached to some coloured beads. The antibodies, which are bound to the hCG, move through the capillary after being carried by urine.
They reach the test zone, where there are a number of immobilised enzymes specific to hCG as well, the hCG binds to the immobilised enzymes. As hCG is still bound to the first antibody, there is a build up of coloured beads, signifying pregnancy!
if there is no hCG none of this happens :smile:

hope I helped in some way! good luck! :biggrin:

Reply 189

chrismorgan7341

Original post by chrismorgan7341

Hey! I shall try my best! During pregnancy, the hormone hCG is released by the chorion on the blastocyst (the zygote after fertilisation as it moves to the uterus lining), anyway this hormone is excreted in the urine during pregnancy.
So urine is placed on a sample strip on the pregnancy test, where anti-bodies, which are specific to hCG bind with the hCG hormone in the urine. The anti-bodies are also attached to some coloured beads. The antibodies, which are bound to the hCG, move through the capillary after being carried by urine.
They reach the test zone, where there are a number of immobilised enzymes specific to hCG as well, the hCG binds to the immobilised enzymes. As hCG is still bound to the first antibody, there is a build up of coloured beads, signifying pregnancy!
if there is no hCG none of this happens :smile:

hope I helped in some way! good luck! :biggrin:

******immobilised antibodies!!!! I have another unit stuck in my head!!!

Reply 190

Lilly101

Definition of gel electrophoresis as a 2 marker?! Please!

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Reply 191

Water_fall

Original post by sailorben

Polyploidy is just that, having a ultiple ploidy. E.g, a triploid, a tetraploid.

So long as the ploidy is even, the organism should be fertile. As they are still able to form homologous pairs. Triploids however, cannot pair-up, thus are sterile.

Non-disjunction is different. This is the process in which faulty cell division results in one daughter cell getting two copies of the chromosome, whilst the other daughter cell gets no copies.

The daughter cell with no copies will die, however, it is possible that the cell with two copies survives, and may be fertilised, resulting in 3 copies of a chromosome.