Lquilter: notes

2011-01-22T19:15:31Z

notes

← Older revision		Revision as of 12:15, 22 January 2011
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	; ~~Genetic~~ sex determination		; Genotypic / genetic sex determination
	* different alleles, genes, even chromosomes		* different alleles, genes, even chromosomes
	* XX/XY-sex determination -		* XX/XY-sex determination -
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	** "Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Unfertilized eggs develop into haploid individuals, which are the males. Diploid individuals are generally female but may be sterile males. Thus, if a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems."<ref name="wp-sds-122" />		** "Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Unfertilized eggs develop into haploid individuals, which are the males. Diploid individuals are generally female but may be sterile males. Thus, if a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems."<ref name="wp-sds-122" />



			; Polyphenistic sex determination
			* "A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. ... Sex-determining polyphenisms allow a species to benefit from sexual reproduction while permitting an unequal gender ratio. This can be beneficial to a species because a large female-to-male ratio maximizes reproductive capacity." <ref>[http://en.wikipedia.org/wiki/Polyphenism#Sex_determination "Polyphenism"], Wikipedia] ([http://en.wikipedia.org/w/index.php?title=Polyphenism&oldid=400653350 2011/01/22]).</ref>

Lquilter: seed

2011-01-22T19:06:57Z

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New page

; Genetic sex determination
* different alleles, genes, even chromosomes
* XX/XY-sex determination -
** "In the XY sex-determination system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY)."<ref name="wp-sds-122">[http://en.wikipedia.org/w/index.php?title=Sex-determination_system&oldid=403751469 "Sex-determination system"], Wikipedia, 2011/01/22.</ref>
** e.g., ''Homo sapiens''
* XX/XO-sex determination
** "In this variant of the XY system, females have two copies of the sex chromosome (XX) but males have only one (X0). The 0 denotes the absence of a second sex chromosome."<ref name="wp-sds-122" />
* ZW-sex determation
** "The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ)."<ref name="wp-sds-122" />
** e.g., birds, some insects
* haplodiploidy
** "Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Unfertilized eggs develop into haploid individuals, which are the males. Diploid individuals are generally female but may be sterile males. Thus, if a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems."<ref name="wp-sds-122" />

; Temperature-dependent sex determination
* e.g., crocodiles

; Social-dependent sex determination
* "In tropical clown fish, the dominant individual in a group becomes female while the other ones are male, and blue wrasse fish are the reverse."<ref name="wp-sds-122" />
* "In the marine worm Bonellia viridis, larvae become males if they make physical contact with the female, and females if they end up on the bare sea floor."<ref name="wp-sds-122" />

; Nutrition-dependent sex determination

; Infectious sex determination
* some arthropods; Wolbachia genus bacteria: "some species consist entirely of ZZ individuals, with sex determined by the presence of Wolbachia."<ref name="wp-sds-122" />

; Sex change life cycle
* e.g., snails; begin male then become female

; No sex-determination system
* hermaphroditic - common earthworm, some snails
* parthenogenetic - all female; e.g., some fish, reptiles, insects

==Further reading==
* [http://en.wikipedia.org/wiki/Sex-determination_system "Sex-determination system"], Wikipedia
* ''[[Biological Exuberance]]'' (same-sex sexuality / sociality in animals)

==References==
{{reflist}}

[[category:Biology]]

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Sex determination - Revision history

Lquilter: notes

Lquilter: seed