|
Inheritance
|
Y-linked (in some families) |
|
Occurrence
|
rare |
| Description | hair grows on the pinnae of the ears-- in some cases it is quite thick; in others it is only one or two long hairs |
| Location of gene | Y chromosome |
Background:
This genetic characteristic is included because of its rare mode of inheritance in some families. There are very few genes with common variations located on the Y chromosome. One gene located on the Y chromosome is testes determining factor (TDF). There is also a "pseudo-autosomal region" of the Y chromosome that shares a few of the same genes found on the X chromosome. The suggested activity is probably best understood once students know how gender is determined by chromosomes. This could be used after X- linked traits have been discussed or as an introduction to traits on the sex chromosomes.
Activity:
Have the class hypothesize in groups how a Y-linked trait would be inherited and who would be affected. Here are some questions worth asking:
(1) Can Y-linked traits be dominant or recessive?
(2) What is the probability of an affected father passing the hairy ear trait to his oldest daughter?
(3) A son has the same trait as his father and his maternal grandfather, but not his paternal grandfather. Could this trait be Y-linked?
(4) Can a Y-linked trait skip a generation and reappear in the next generation?
For more information visit Online Mendelian Inheritance in Man
Return to Human Genetics homepage