Question

LABORATORY 6. MENDELIAN GENETICS: GENERAL REMARKS AND Drosophila

1. Are the genes for the body color, eye color, and wing shape recessive or dominant? Explain your answer.

Yellow: _______________ White: _________________

Miniature: ____________ Sepia: _________________

Explanation:

_________________________________________

_________________________________________

_________________________________________

_________________________________________

_________________________________________

2. Where are these genes located? On an autosome(s) or sex chromosome? Explain your answer

Yellow: _______________ White: _________________

Miniature: ____________ Sepia: _________________

Explanation:

_________________________________________

_________________________________________

2. Set up a X2 to test if the yellow (y) (body color) and miniature (m) (wing size) are assorting

independently. In your answer, include a brief null hypothesis

Hint: Are you wondering about the classes with the other phenotypes? You have to omit those traits

and consider only the y and m genes. In that case, the number of flies in the class “sepia” should be

added to the class “wild” (because they are y+ m+ for these genes). Follow the same rule to the

remaining classes.

Hypothesis:

__________________________________________________________________________________________

__________________________________________________________________________________________

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Expected ratios

under Ho Phenotype Observed Expected O-E (O-E)2/E

Wild type

Grey body,

Miniature wing

Yellow body,

long wing

Yellow body,

miniature wing

Total

3. After the X2 test, what is your conclusion regarding the mode of inheritance of the y - m genes?

X2 Calculated: ______________ Degrees of freedom: _________________

X2 from table (critical value, p=0.05): ___________________

X2 Calculated higher than the critical value? ________ Reject or fail to reject Ho: __________________

4. Using the class data, construct a linkage map of the yellow (y), white (w) and miniature (m) genes.

Hint: Are you wondering about the classes with the sepia phenotype? You have to omit that trait and

consider only the y, w and m genes. In that case, the number of flies in the class “sepia” should be

added to the class “wild” (because they are y+ w+ m+ for these genes). Follow the same rule to the

remaining three classes showing the sepia trait.

Then, identify parental (PR) (larger classes) and double recombinant (DR) offspring (smaller classes).

Remember the rule of thumb: When you compare PR vs. DR, the gene that has been switched, is the

one in the middle.

Phenotype Observed # Genotype (F1 female gametes) *Type of gamete (PR, SR or DR)

Wild type

Yellow, white, miniature

Yellow

Miniature, white

Yellow, white

Mini

White

Yellow, mini

Total

Gene order: ___________________   Distance y-w: ___________________

Distance w-m: ___________________   Distance y-m: ___________________56

5. Calculate the coincidence and interference values. Show your work. Please provide a brief

explanation about each of these concepts.

C: ___________________

I: ___________________

Explanation:

_______________________________________________________

_______________________________________________________

_______________________________________________________

6. Using the pteridine and ommochrome pathways, explain why the mutation for white eyes is epistatic

over the sepia gene.

Explanation:

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

Answer 1

1.Are the genes for the body color, eye color, and wing shape recessive or dominant? Explain your answer.

yes, there genes are recessive or dominant for the body color,eye color and wing shape of drosophila.

Mendel postulated transmissible factors genes to explain the inheritance of traits. He discovered that genes exist in different forms, which we now call alleles.

Boveri and Sutton's chromosome theory of inheritance states that genes are found at specific locations on chromosomes, and that the behavior of chromosomes during meiosis can explain Mendel’s laws of inheritance.

n 1906, Thomas Hunt Morgan began work with a small fly, Drosophila melanogaster and provided the first strong confirmation of the chromosome theory.

Morgan discovered a mutation that affected fly eye color. He observed that the mutation was inherited differently by male and female flies. he observed that normal color of the eye in drosophila is red but in some flies white or brown color where observed.most of them are male.he found that genes are differently inherited in male (XY chromosome) and female(XX chromosome).

when he cross over that white eye male and red eye(normal) female he found that both offspring has red eyes these is F1generation.while in F2 generation he found that two offspring have normal red eye and one offspring has white eye.

show the below figure for more understanding.

{ red-eyed female (wild type) white-eyed male o & red-eyed females red-eyed males or & red-eyed fernales red-eyed males or white-eyed males o

he hypothesised that genotype for all three offspring are different. and genotype express in offspring is dominant but the other genes remain as recessive they never lost and that might be express in next generation. when the recessive genes are expressed in next generation called as dominant gene.

summary:

genotype of allele represent phenotype of allele. genes responsible for that present phenotype are dominant while all other genes are remain as it is and express in next generation as dominant genes,that recessive genes are shows different or variant phenotype of allele.this variation of genotype is due to genetic rearrangement in chromosome during gamate formation,and that can be for all body cells so, genes may be recessive or dominant for all phenotypic trait like body color,eye color,wing shape.