Genetics of Drosophila… and mice

A video on hemophilia

Determine the mode of inheritanceDominant or Recessive – do this firstAutosomal or sex linkedIf there are 2 traits:Linked or unlinked

Sex Linked inheritanceMales – XYFemales – XXY chromosome

carries genes for sex determination

X chromosome carries many other genes besides sex determination (such as colorblindness)

X – Linked recessiveThe gene is recessive and on the x

chromosomein males higher than in females

Ex. Color blindness is recessive. If a male is color blind and marries a woman who is not color blind and does not carry the color blind allele, what percent of their offspring will be color blind?

If their daughter marries a man who is not color blind, what percent of their offspring will be color blind? What percent will be carriers?

2 genes are either linked or unlinkedThey are linked if they are very close on the

chromosomeThey will be passed onto offspring more

frequently together since crossing over is less likely to occur between them.

How would we know two genes are linked by looking at offspring?

It is not in a ratio of 9:3:3:1

Complete worksheetCross of the following questions in your packet:2, 4a, 8, 9, Also, do not complete the pedigree analysis portion

Practice problemhttp://www.cgslab.com/If you want practice, type in tahoma as the

course ID and ap biology2 as the student account – I will tell you if you are right or wrong

If you are ready to begin, type in tahoma as the course ID and ap biology as the student account

Remember, for each population, you need to give me which trait(s) are dominant and which are recessive, if it is sex-linked, and if two traits are linked or unlinked (if the population gives you two traits)

statisticsIf the P value is greater than .05 then it must

match the ratio you entered (or close enough)For stats students – a P value of less than .05

means it is statistically significantly different than your expected values – in this case our expected values are the phenotypic ratios. Therefore if it is less than .05, the population must not match the expected phenotypic ratio and the mode of inheritance must be different then you predicted.