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In humans and many other species of animals, the father determines the sex of the child. In the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively.
A telomere (/ ˈ t ɛ l ə m ɪər, ˈ t iː l ə-/; from Ancient Greek τέλος (télos) ' end ' and μέρος (méros) ' part ') is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes (see Sequences). Telomeres are a widespread genetic feature most commonly found in eukaryotes.
The chromosome number n = 9 is the basic number in many species of Marchantiales. In some species of Marchantiales, plants with various ploidy levels (having 18 or 27 chromosomes) were reported, but this is rare in nature. [14] 11 Thale cress (Arabidopsis thaliana) 10 12 Swamp wallaby (Wallabia bicolor) 10/11: 11 for male, 10 for female [15] 13
With zero of that chromosome, the frog develops into a male. With one or more, the frog develops into a female. One female had as many as 16 of that chromosome. [48] Different populations of the Japanese frog Rana rugosa uses different systems. Two use homomorphic male heterogamety, one uses XX/XY, one uses ZZ/ZW.
The pelvis is, in general, different between the human female and male skeleton. [13] [14] Although variations exist and there may be a degree of overlap between typically male or female traits, [13] [14] the pelvis is the most dimorphic bone of the human skeleton and is therefore likely to be accurate when using it to ascertain a person's sex ...
When calculating the ratio, Y chromosomes are ignored. For example, for a diploid drosophila that has XX, the ratio is 1:1 (2 Xs to 2 sets of autosomes, since it is a diploid). For a diploid drosophila that has XY, the ratio is 1:2 (1 X to 2 sets of autosomes, since it is diploid). [ 2 ]
In the absence of a Y chromosome, the fetus will undergo female development. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. [5] Thus, male mammals typically have an X and a Y chromosome (XY), while female mammals typically have two X chromosomes (XX).
Telomerase, also called terminal transferase, [1] is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most eukaryotes. Telomeres protect the end of the chromosome from DNA damage or from fusion with neighbouring ...