Thus far, we have discussed four major modes of inheritance in class. Alleles can be either dominant or recessive and either autosomal or sex-linked. Because you won't know when you begin the experiment which mode of inheritance occurs for each cross, you will have to deduce this from your data. Beginning with homozygous traits, what are the expected ratios in the F₁ for each of the following crosses? [Hint: In making the crosses, use 'A' to indicate a dominant trait, 'a' the recessive allele. Report the offspring phenotypes as mutant or wild type.]

Begin by crossing wild type females with mutant males. The first row is done for you.
 

If the mutant trait is	The cross would be written:	The F1 results will be:	The F2 results will be:
Autosomal Dominant	aa x AA	all mutant (AA)	3 mutant (1AA:2Aa):  1 wildtype (aa) both sexes
Autosomal Recessive
Sex-linked Dominant
Sex-linked Recessive

Now do the reciprocal crosses, using mutant females and wildtype males.
 

If the mutant trait is	The cross would be written:	The F1 results will be:	The F2 results will be:
Autosomal Dominant
Autosomal Recessive
Sex-linked Dominant
Sex-linked Recessive

Note that the information gained from crossing mutant females with wild type males differs from that from crossing wild type females with mutant males. For reasons which will become obvious during the second week of this exercise, set up your initial cross with the mutant traits on the male fly. Using the first chart above, answer the following questions.

Which two modes of inheritance can not be distinguished by looking only at the F₁?
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For each of these two crosses, what is the resulting phenotypic ratio in the F₂?
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Draw a flow chart of the cross, expected results of the F₁ and the conclusion. Use the F₂ to further distinguish your results into 4 separate classes.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Read the introductory instructions for the Virtual Fly lab. What is the one case in which homozygous flies will not be used for crosses?

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What kind of ratio would you expect to see in the F₁ if you crossed this type of mutation with a wild type fly and the inheritance is autosomal?

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What predictions can you make about the inheritance of a lethal sex-linked allele?

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While conducting research, it is imperative that you keep an accurate log of what you do and the results you obtain. One trick in conducting numerous repetitious steps with different traits is to organize your data in tables. You may find the following table format useful as you collect your data:
 

Date	Trait studied	Cross made	Results	Second cross (if needed)		Mode of inheritance
				Cross made	Results
9/14	pink eyes	pink male x WT female	all WT	F1 x F1	3:1 WT:pink  both sexes	autosomal recessive

You should complete parts 1 and 3A before coming to class next week. The data can be placed in the table provided on the following page. Any raw data should be carefully labeled and organized in an appendix in your final report.
 

Date	Trait studied	Cross made	Results	Second cross (if needed)		Mode of inheritance
				Cross made	Results
	bar eyes
	eyeless
	sepia eyes
	black body
	miniature wings
	vestigial wings
	shaven bristles
	spineless bristles
	dichaete wings
	forked bristles
	sable body
	tan body
	yellow body
	lobe eyes
	purple eyes
	star eyes
	white eyes
	dumpy wings

Recommended table format for determining linkage relationships of traits in part 2:

Results of crosses between the following traits:
 

trait	bar eyes	eyeless	sepia eyes	black body	mini wings	vestigial wings	shaven bristles
spineless bristles
shaven bristles							xxxxxxx
vestigial wings						xxxxxxx	xxxxxxx
miniature wings					xxxxxxx	xxxxxxx	xxxxxxx
black body				xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx
sepia eyes			xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx
eyeless		xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx	xxxxxxx