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Author | Topic: Why There Are Two Sexes | |||||||||||||||||||||||
molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Well. Genetically speaking, there are.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Sorry, RUSD! The jig is up.
(Miosm, it's RAZD ... Rebel American Zen Deist) M, I don't suppose you've had Intro Genetics. You seem to think that XX = F and XY = M. But that's not entirely true. FemaleXX normal XO Turner 1:3000 XXX Triple-X 1:1000 XXXX No name 1:??? XXXXX No name 1:??? MaleXY normal XXY Klinefelter 1:500 XXXY No name 1:??? XYY "Supermale" 1:900 XXYY "Supermale" 1:??? I would imagine there is an XXXXY too. And possibly other variations (XXXYY, XXYYY, etc.).
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Well, yes, Taz, they are abnormalities.
But some of them don't appear abnormal. The "metafemales" are only slightly below average in intelligence. Most Klinefelters are normal enough to pass unnoticed in society. As are the "metamales". In fact, most "metamales" don't even know they have the extra chromosomes.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Thanks, Arach. I didn't forget. I limited it to humans since I thought that was what his OP was referring to.
Edited by molbiogirl, : sp
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
M, please do as RAZD suggests and format your links.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
...but critics such as Stephen Jay Gould point out a number of shortcomings of this example. And Dr. Gould has been shown to be wrong in this instance. 'Bigger Is Better' View of Evolution Gains CredenceNew York Times, December 28, 2004 The notion that natural selection can create long-term trends toward large size first emerged about a century ago, but it fell out of favor in recent decades. Now researchers have taken a fresh look at the question with new methods, and some argue that these trends are real. Dr. Stephen Jay Gould, the eminent Harvard paleontologist who died in 2002, dismissed Cope's rule as a "psychological artifact." An apparent trend toward bigger sizes could appear in the fossil record, Dr. Gould and others pointed out, even if natural selection didn't favor bigger individuals. Small species, for example, might simply be more likely to survive mass extinctions. If they then gave rise to new species that were randomly bigger or smaller, they would still produce a trend toward larger sizes. That is because their descendants could not get much smaller before hitting a minimum size limit. These criticisms have prompted scientists to start putting Cope's rule to a much more rigorous test. They compare the size of ancestors to their descendants, or, at the very least, to very closely related species. They then make these measurements in many lineages in a given group to see if the trend is statistically significant. Dr. Purvis and Mr. Hone are among the co-authors of a study of Cope's rule in dinosaurs to be published in The Journal of Evolutionary Biology. The researchers compared 65 pairs of related dinosaurs separated by tens of millions of years. They found that on average, the younger dinosaurs were 25 percent larger than the older ones. The pattern spanned all the major groups of dinosaurs, from bipedal predators to long-necked grazers. "It's one of the few really thorough studies in this area, and it finds really convincing support for Cope's rule," said Dr. John Alroy, a paleontologist with the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif. Dr. Alroy's own research has revealed long-term increases in the size of North American mammals over the past 80 million years. "We got a very clear pattern," Dr. Kingsolver said. "In 80 percent of the studies, there's consistent selection favoring larger size." As Dr. Kingsolver and Dr. Pfennig reported in the July issue of Evolution, the pattern held up within both vertebrates and invertebrates, as well as in plants. Not Found, Error 404
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Much more important is the qualitative feature: in the asexual method no new quality appears, whereas in each instance of the sexual reproduction new qualities appear which are different from the parental ones. Two words. Antibiotic. Resistance.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
The double strand DNA molecule contains one DNA strand inherited from the parental DNA strand and one newly synthesized. Both strands carry genetic information, however, according to my hypothesis, only one of them - newly synthesized strand is genetically active in the double stranded DNA molecule, while another strand is blocked from transcription. This is clearly untrue. An allele that is present on one strand and not on the other is expressed.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
If an allele (a gene) is present on one strand of DNA and not on the other strand of DNA, that gene can be expressed phenotypically.
For example, if one inherits an A allele from one parent and a B allele from the other, then your blood type will be AB, because both alleles are expressed.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
... where only one DNA molecule (say a single chromosome) is shown? Each of shown genes (three total) is unique. I've taken a look and I repeat: When one inherits a copy of an A allele and a copy of a B allele, then one is AB. If your model were true, then one would be either A or B. Not AB.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
If your model were true, in the second round of replication, one would have two diploid sets with 2 nonfunctional strands (and 2 sets with 1 functional, 1 nonfunctional).
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
1. Only one allele of particular gene is expressed. (if both chromosomes are of opposite type). 2. Both alleles are expressed. (if both chromosome are of the same type and this particular allele are on the active DNA strands). 3. Both alleles are blocked. (if both chromosome are of the same type but this alleles are on the blocked DNA strands). M, I know you aren't intentionally ignoring what I've posted. Listen carefully. If one inherits an A and a B, then one is AB. If your model were true: Condition 1 = either A or B.Condition 3 = neither A or B (meaning that person would not have a blood type!) Do you understand?
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
don't worry that model allows condition 3 (person would not have a blood type!) as long as it not require this condition. I don't know what you mean. What is "it" referring to? What "condition"? Everyone has a blood type. An erythrocyte with no blood type antigens is unheard of. People with an A and a B express as AB. They do not express as A. They do not express as B.
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
One of the problems in our communication is that you are focusing on organism and I am focusing on individual cells. An erythrocyte is an individual cell. Erythrocyte: the red blood CELL that carries oxygen to body cells and carbon dioxide away from body cells.
So, for individual cell the complete blockage of A/B genes or even 50% of all genes not a problem, but mechanism by with cell differentiation occurs. Yes, it does! ABE: Hematopoietic stem cells give rise to all types of blood cells. Red, white, etc. When erythrocytes (red blood cells) differentiate, they express blood type antigens. Your model says that it is possible for an erythrocyte to have no antigens. This is impossible. Edited by molbiogirl, : addn
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molbiogirl Member (Idle past 2642 days) Posts: 1909 From: MO Joined: |
Normally blood cell receives the correct type of chromosome, so AB phenotype is properly expressed. No. I am using one of the simplest explanations I can think of and you still don't get it. A hematopoietic stem cell replicates its DNA. It divides. According to your model, during differentiation, an AB cell can have one inactive strand. If it does then it will express as either A or B. This is impossible. Let's try another example. From your paper:
The existence of two alleles of each gene, so at least one vital gene could be active. How do you explain recessive phenotypes? Just in case you don't know how dominant and recessive phenotypes work: Each strand carries either a dominant or recessive allele. Let's call dominant S and recessive s. If someone inherits SS = dominant phenotype.If someone inherits Ss = dominant phenotype. If someone inherits ss = recessive phenotype. If one strand is inactive, the recessive phenotype is impossible.
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