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Genetic Unit

Zarathrusa
Posts: 21
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7/30/2012 10:42:49 PM
Posted: 4 years ago
Dawkins writes in TSG that the smaller a genetic unit is, the less likely it is to be broken down during the meiotic process. This makes sense, but then he goes on to say that the smaller genetic units will be usually be more easily passed down from generation to generation. I'm pretty sure I'm misunderstanding this but I have a question: Doesn't meiosis randomly pick genes from each corresponding chromosomes to be fused as one and therefore even if smaller genes don't get broken up, their chances of being passed down in a single sperm cell decreases- instead of increases; a larger unit might be broken up but it would be passed down.

Dawkins states that a genetic unit with a size of 1/100 of a chromosome would have a 99% chance of getting passed down. How?

Where am I going wrong?
tarkovsky
Posts: 212
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7/31/2012 8:56:03 AM
Posted: 4 years ago
At 7/30/2012 10:42:49 PM, Zarathrusa wrote:
Dawkins writes in TSG that the smaller a genetic unit is, the less likely it is to be broken down during the meiotic process. This makes sense, but then he goes on to say that the smaller genetic units will be usually be more easily passed down from generation to generation. I'm pretty sure I'm misunderstanding this but I have a question: Doesn't meiosis randomly pick genes from each corresponding chromosomes to be fused as one and therefore even if smaller genes don't get broken up, their chances of being passed down in a single sperm cell decreases- instead of increases; a larger unit might be broken up but it would be passed down.

Dawkins states that a genetic unit with a size of 1/100 of a chromosome would have a 99% chance of getting passed down. How?

Where am I going wrong?

Perhaps I'm unsure of what exactly it is that you're saying. A 'genetic unit' will not be passed down if it is broken up inthat the genetic unit is quantized, so to speak. By breaking it up it is no longer the genetic unit, nor is it 'half' the genetic unit, it's useless. Think of the scene from One Flew Over The Cuckoo's Nest:

This is also why the smaller a genetic unit is the more likely it is to be passed on. Since the distance between the endpoints of the unit is smaller, it is less likely to be broken up. It will be passed on intact, in fact, the only way a 'genetic unit' can be passed on. If it were broken up but part of it passed on, the 'genetic unit' wouldn't have been passed but something else entirely.
Ren
Posts: 7,102
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7/31/2012 9:51:03 AM
Posted: 4 years ago
At 7/30/2012 10:42:49 PM, Zarathrusa wrote:
Dawkins writes in TSG that the smaller a genetic unit is, the less likely it is to be broken down during the meiotic process. This makes sense, but then he goes on to say that the smaller genetic units will be usually be more easily passed down from generation to generation. I'm pretty sure I'm misunderstanding this but I have a question: Doesn't meiosis randomly pick genes from each corresponding chromosomes to be fused as one and therefore even if smaller genes don't get broken up, their chances of being passed down in a single sperm cell decreases- instead of increases; a larger unit might be broken up but it would be passed down.

Dawkins states that a genetic unit with a size of 1/100 of a chromosome would have a 99% chance of getting passed down. How?

Where am I going wrong?

You're conflating chromosomes and genetic units. A chromosome is a given sequence of genes that contributes to a given characteristic of an organism. It's essentially a section of DNA. An example is the sex chromosome, which determines all manner of characteristics, from genital formation and functionality, to endocrine makeup.

A genetic unit, on the other hand, is a single fragment of information -- in other words, the most that a nucleotide can be reduced before it really isn't saying anything to the host cell.

So, let's say we're talking about someone's eye phenotype. The chromosome for this eye phenotype would contain everything that was written to manifest that eye, from the color to the shape as well as the size and functionality. A genetic unit for that phenotype, on the other hand, may be a few disparate proteins that indicate the eye color alone.

Smaller genetic units are more easily clustered with a given chromosome during transcription, making them more easily passed down. It makes logical sense that larger units comprised of several proteins would be less likely transcribed, as with each genetic unit included in the chromosome, there's less room left for further genetic units.
Zarathrusa
Posts: 21
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7/31/2012 10:01:30 AM
Posted: 4 years ago
At 7/31/2012 9:51:03 AM, Ren wrote:
At 7/30/2012 10:42:49 PM, Zarathrusa wrote:
Dawkins writes in TSG that the smaller a genetic unit is, the less likely it is to be broken down during the meiotic process. This makes sense, but then he goes on to say that the smaller genetic units will be usually be more easily passed down from generation to generation. I'm pretty sure I'm misunderstanding this but I have a question: Doesn't meiosis randomly pick genes from each corresponding chromosomes to be fused as one and therefore even if smaller genes don't get broken up, their chances of being passed down in a single sperm cell decreases- instead of increases; a larger unit might be broken up but it would be passed down.

Dawkins states that a genetic unit with a size of 1/100 of a chromosome would have a 99% chance of getting passed down. How?

Where am I going wrong?

You're conflating chromosomes and genetic units. A chromosome is a given sequence of genes that contributes to a given characteristic of an organism. It's essentially a section of DNA. An example is the sex chromosome, which determines all manner of characteristics, from genital formation and functionality, to endocrine makeup.

A genetic unit, on the other hand, is a single fragment of information -- in other words, the most that a nucleotide can be reduced before it really isn't saying anything to the host cell.

So, let's say we're talking about someone's eye phenotype. The chromosome for this eye phenotype would contain everything that was written to manifest that eye, from the color to the shape as well as the size and functionality. A genetic unit for that phenotype, on the other hand, may be a few disparate proteins that indicate the eye color alone.

Smaller genetic units are more easily clustered with a given chromosome during transcription, making them more easily passed down. It makes logical sense that larger units comprised of several proteins would be less likely transcribed, as with each genetic unit included in the chromosome, there's less room left for further genetic units.

Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell? In that case, the smaller the genetic unit, the less likely that it will be passed down.
Ren
Posts: 7,102
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7/31/2012 10:15:27 AM
Posted: 4 years ago
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.
Zarathrusa
Posts: 21
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7/31/2012 10:28:13 AM
Posted: 4 years ago
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

Isn't it 75% according to the Punnet Square, instead of 50%?
Ren
Posts: 7,102
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7/31/2012 10:29:47 AM
Posted: 4 years ago
At 7/31/2012 10:28:13 AM, Zarathrusa wrote:
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

Isn't it 75% according to the Punnet Square, instead of 50%?

Yes -- 75% for a dominant gene, 50% for each dominant gene.
TheBossToss
Posts: 154
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8/15/2012 12:00:43 PM
Posted: 4 years ago
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

I believe both types of genes have equal probabilities of being passed down.
Cats. I like cats.
-Me

Pro hasn't upheld his BOP. He forfeited last round. I did stuff.
-Wallstreetatheist

That was real intellectual property theft. They used her idea for their own profit and fame. When I pirate, I am usually downloading textbooks that I cannot afford to purchase on my own and that I do not want my parents to spend money on.
-royalpaladin
TheBossToss
Posts: 154
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8/15/2012 12:03:22 PM
Posted: 4 years ago
At 7/30/2012 10:42:49 PM, Zarathrusa wrote:
Dawkins writes in TSG that the smaller a genetic unit is, the less likely it is to be broken down during the meiotic process. This makes sense, but then he goes on to say that the smaller genetic units will be usually be more easily passed down from generation to generation. I'm pretty sure I'm misunderstanding this but I have a question: Doesn't meiosis randomly pick genes from each corresponding chromosomes to be fused as one and therefore even if smaller genes don't get broken up, their chances of being passed down in a single sperm cell decreases- instead of increases; a larger unit might be broken up but it would be passed down.

Dawkins states that a genetic unit with a size of 1/100 of a chromosome would have a 99% chance of getting passed down. How?

Where am I going wrong?

I think what Dawkins means here is that once that sperm cell has been created, the smaller genes have a 99% probability of either not breaking up or becoming defective or mutating or something along those lines. I thin he means once the sperm is created, with smaller genes there is less capacity for error. Otherwise, yes, each allele of a given gene has a 50% chance of being incorporated in a person's sperm or egg.
Cats. I like cats.
-Me

Pro hasn't upheld his BOP. He forfeited last round. I did stuff.
-Wallstreetatheist

That was real intellectual property theft. They used her idea for their own profit and fame. When I pirate, I am usually downloading textbooks that I cannot afford to purchase on my own and that I do not want my parents to spend money on.
-royalpaladin
TheBossToss
Posts: 154
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8/15/2012 12:05:28 PM
Posted: 4 years ago
At 8/15/2012 12:00:43 PM, TheBossToss wrote:
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

I believe both types of genes have equal probabilities of being passed down.

It's just the probability of expression of said allele that is different.
Cats. I like cats.
-Me

Pro hasn't upheld his BOP. He forfeited last round. I did stuff.
-Wallstreetatheist

That was real intellectual property theft. They used her idea for their own profit and fame. When I pirate, I am usually downloading textbooks that I cannot afford to purchase on my own and that I do not want my parents to spend money on.
-royalpaladin
Ren
Posts: 7,102
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8/15/2012 6:03:47 PM
Posted: 4 years ago
At 8/15/2012 12:00:43 PM, TheBossToss wrote:
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

I believe both types of genes have equal probabilities of being passed down.

You're talking about alleles.

Genes are both alleles recombined.

http://anthro.palomar.edu...
Ren
Posts: 7,102
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8/15/2012 6:04:30 PM
Posted: 4 years ago
At 8/15/2012 12:05:28 PM, TheBossToss wrote:
At 8/15/2012 12:00:43 PM, TheBossToss wrote:
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

I believe both types of genes have equal probabilities of being passed down.

It's just the probability of expression of said allele that is different.

...?

You caught it, but didn't. ^_^
TheBossToss
Posts: 154
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8/16/2012 9:38:30 AM
Posted: 4 years ago
At 8/15/2012 6:03:47 PM, Ren wrote:
At 8/15/2012 12:00:43 PM, TheBossToss wrote:
At 7/31/2012 10:15:27 AM, Ren wrote:
At 7/31/2012 10:01:30 AM, Zarathrusa wrote:
Not all parts of the double chromosome are passed into the single sex cell chromosome during meiosis, so wouldn't each gene have a 50% chance of being passed down into any given sex cell?

No.

First, chromosomes aren't neatly copied as entire packages during transcription.

Moreover, there are both dominant and recessive genes, which screw with the probability of either being passed as well as expressed. As far as I understand it, most dominant genes have a 50% chance of being passed, whereas recessive genes have only a 25%.

I believe both types of genes have equal probabilities of being passed down.

You're talking about alleles.

Genes are both alleles recombined.

http://anthro.palomar.edu...

Oh, oh, ok, I see what you're saying. Whoopsie. I thought you were referring to dominant or recessive alleles. Mah bad :)
Cats. I like cats.
-Me

Pro hasn't upheld his BOP. He forfeited last round. I did stuff.
-Wallstreetatheist

That was real intellectual property theft. They used her idea for their own profit and fame. When I pirate, I am usually downloading textbooks that I cannot afford to purchase on my own and that I do not want my parents to spend money on.
-royalpaladin