Human genetics

From Wikipedia, the free encyclopedia

A karyotype of a human male, showing 46 chromosomes including XY sex chromosomes.

Humans (Homo sapiens) are a eukaryotic species. A human has 46 chromosomes (44 autosomes and 2 sex chromosomes, with an XY sex determination system). At present estimate, humans have approximately 20,000-25,000 genes . Humans share 98.5% of their DNA with their closest living evolutionary relative, the bonobos.

1 Chromosomes
2 Number of genes
3 Mitochondrial DNA
4 Genetic disorders
5 Human traits with simple inheritance patterns
6 See also
7 External links

[edit] Chromosomes

Humans have 46 chromosomes, arranged in pairs (i.e. they are diploid). 44 (22 pairs) of these are autosomes, and 2 are sex chromosomes. Humans have an XY sex determination system, so that females have the sex chromosomes XX and the males XY. The Y chromosome is shorter than the X chromosome, so that males are hemizygous over this region. X-linked recessive genes are thus expressed more often in males.

[edit] Number of genes

Estimates of the number of genes humans have has been possible since DNA sequencing was first introduced. Estimates however have varied wildly, though the present best guess is 20,000-25,000, estimates of up to 40,000 have been in the past.

[edit] Mitochondrial DNA

In addition to nuclear DNA, humans have mitochondrial DNA

[edit] Genetic disorders

Humans have several genetic diseases, often caused by recessive genes.

[edit] Human traits with simple inheritance patterns

This list is incomplete; you can help by expanding it.

Dominant	Recessive	Reference
Curled Up Nose	Roman Nose	^{[citation needed]}
Clockwise Hair Whorl	Counter-clockwise Hair Whorl	^{[citation needed]}
Can Roll Tongue	Can't Roll Tongue	^[1]
Widow's Peak	No Widow's Peak	^{[citation needed]}
Facial Dimples	No Facial Dimples	^{[citation needed]}
Able to taste PTC	Unable to taste PTC	^{[citation needed]}
Unattached earlobe	Attached earlobe	^[2]
Straight thumb	Hitchhiker's thumb	^[3]
Tip of pinkie bends in	Pinkie straight	^{[citation needed]}
Oval face	Square face	^{[citation needed]}
Cleft chin	no cleft chin	^{[citation needed]}
Broad eyebrow	Slender eyebrow	^{[citation needed]}
Separated eyebrows	Joined eyebrows	^{[citation needed]}
Long eyelashes	Short eyelashes	^{[citation needed]}
Almond eyes	Round eyes	^{[citation needed]}
Freckles	No freckles	^{[citation needed]}
Wet-type earwax	Dry-type earwax	^{[citation needed]}
Left thumb on top of interlocking fingers	Right thumb on top of interlocking fingers	^{[citation needed]}