1 / 8

Chapter 12.7

Chapter 12.7. Examples of X-Linked Inheritance Patterns . AP Biology Fall 2010. X-Linked Inheritance Characteristics . The mutated recessive gene occurs only on the X chromosome Heterozygous females are phenotypically normal

jalena
Download Presentation

Chapter 12.7

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 12.7 Examples of X-Linked Inheritance Patterns AP Biology Fall 2010

  2. X-Linked Inheritance Characteristics • The mutated recessive gene occurs only on the X chromosome • Heterozygous females are phenotypically normal • Males are more often affected because the single recessive allele (on the X chromosome) is not masked by a dominant gene on any other chromosome

  3. X-Linked Inheritance Characteristics • A normal male mated with a female heterozygote has a 50% chance of producing carrier daughters and a 50% chance of producing affected sons • In the case of a homozygous recessive female and a normal male, all daughters will be carriers and all sons affected • Can you perform these crosses?

  4. Hemophilia A • A serious X-linked recessive condition is hemophilia A (affecting 1 in 7,000 males) • Is the inability of the blood to clot because the genes do not code for the necessary clotting agent(s) • The disorder frequency was high among the royal families of Europe and Russia in the nineteenth century • Why?

  5. Red-Green Colour Blindness • Colour blindness: is the inability to distinguish some or all of the colours in the visible light spectrum • Mutated genes change the light-absorbing capacity of sensory receptors of the eyes • Red-green colour blind people can see fewer than 25 of the 150 differences in colour seen normally • It is 12 times more common in men than women

  6. Red-Green Colour Blindness • Ishihara plates: • Do you see a 7 or 29? • Do you see a 3 or 8? • 29 and 8 are normal , 7 and 3 are colour blind

  7. Duchenne Muscular Dystrophy • Duchenne Muscular Dystrophy (DMD): is characterized by rapid degeeration of muscles early in life • One in 3,500 males • Is caused by a recessive allele for a structural protein called dystrophin • When dystrophin is absent or abnormal, muscle cells progressively die (in an unstoppable manner) • Diagnosed between the ages 3 to 7, the affected boy generally dies before he reaches 25

  8. X-Linked Inheritance • More than 300 connections to known genetic disorders have been identified on the X chromosome • Does this mean women are superior? ; )

More Related