2320 Lecture 8 Modified Dihybrids NOTES (3).pptx

2320 Lecture 8 Modified Dihybrids NOTES (3).pptx -...

This preview shows page 1 - 9 out of 35 pages.

Modified Dihybrids geneticscertificate.stanford.edu
Image of page 1

Subscribe to view the full document.

Outline Lethal Alleles Modified Dihybrids Complementation Epistasis Suppression
Image of page 2
An allele that is capable of causing the death of an organism is called a lethal allele Indicates that the gene is essential to the organisms life – we call these essential genes A lethal allele can be either recessive or dominant – which can be determined by the phenotypic ratios of progeny Dominant lethal alleles are obviously quite rare Lethal Alleles
Image of page 3

Subscribe to view the full document.

Example – normal wild-type mice have coats with dark pigmentation due to the wild-type allele (A). Mutant allele called “yellow” (A Y ) is dominant, but lethal when homozygous Lethal Alleles Fig 6-7
Image of page 4
Crosses with yellow mice normal normal normal normal normal normal All normal 2/3 yellow 1/3  normal 1/2 yellow 1/2  normal
Image of page 5

Subscribe to view the full document.

The lethal gene is evidenced by the 25% death rate in progeny Allele lethality can vary significantly, from 0 to 100 percent, and depend on the gene itself, the genetic context (genome), and the environment It appears that the A Y allele might affect both coat colour and survival – this is therefore a pleiotrophic allele (A pleiotropic allele is any single allele that affects multiple properties of the organism) Lethal Alleles
Image of page 6
Other examples of homozygous lethal alleles: Lethal Alleles Achondroplasia   Sickle cell anemia Cystic fibrosis news.stanford.edu
Image of page 7

Subscribe to view the full document.

Gene interactions – as we’ve discussed, most genes code for proteins (the gene product), and one protein can influence the expression or function of other gene products Gene interactions are usually due to the fact that both proteins/enzymes are involved in different steps of a multi- step biochemical pathway If two genes interact in some way, then mutations in these genes might result in deviation from the expected 9:3:3:1 phenotypic ratio in a dihybrid cross!
Image of page 8
Image of page 9
  • Spring '12
  • TBA
  • gene interactions

{[ snackBarMessage ]}

Get FREE access by uploading your study materials

Upload your study materials now and get free access to over 25 million documents.

Upload now for FREE access Or pay now for instant access
Christopher Reinemann
"Before using Course Hero my grade was at 78%. By the end of the semester my grade was at 90%. I could not have done it without all the class material I found."
— Christopher R., University of Rhode Island '15, Course Hero Intern

Ask a question for free

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern