Module 6 Lesson 8 - 4

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Answer the following questions to check your understanding of the material to this point.

1. If there were 50 recombination phenotypes in 250 offspring, what is the map distance between the linked alleles?


2. A three-point test cross is performed to identify the locus of each of three alleles in relation to one another. The results were as follows:
   
   
   • AC recombinations = 225
   • BC recombinations = 165
   • AB recombinations = 60
   • Parental linkages = 550
   • Total offspring = 1000
     
     

   Show the positions and map the distances apart for each allele (A, B, and C) on a chromosome. Calculate the map units, then draw the chromosome.

Diploma Connection

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Answer the following questions from a previous Biology 30 Diploma Examination.

Use the following information to answer the next question.






1. During meiosis, which of the following pairs of genes has the greatest chance of being separated by crossing over?
   
   
   1. (m) and (d)
   2. (ne) and (p)
   3. (m) and (lc)
   4. (p) and (o)




Use the following additional information to answer the next question.

Genes	Recombinant Frequency
normal leaf (M) and tall plant (D)	12%
normal leaf (M) and normal tomato (O)	33%
normal leaf (M) and simple inflorescence (S)	64%
tall plant (D) and normal tomato (O)	21%
tall plant (D) and simple inflorescence (S)	52%




2. The cross over frequency between genes O and S is
   
   
   1. 6%
   2. 29%
   3. 31%
   4. 97%




Use the following information to answer the next two questions.

Cross over Frequencies of Some Genes on Human Chromosome 6
Genes	Approximate Recombinant Frequencies
Diabetes mellitus (1) and ovarian cancer (2)	21%
Diabetes mellitus (1) and Rhesus blood group (3)	12%
Ragweed sensitivity (4) and Rhesus blood group (3)	10.5%
Rhesus blood group (3) and ovarian cancer (2)	9%
Ragweed sensitivity (4) and ovarian cancer (2)	19.5%





Numerical Response

3. On human chromosome 6, the order of the genes numbered above is ___, ___, ___ and ___.
   
   
   
4. What is the approximate cross over frequency between the diabetes mellitus gene and the ragweed sensitivity gene?
   
   
   1. 1.5%
   2. 10.5%
   3. 15.0%
   4. 22.5%




Use the following information to answer the next question.

Gregor Mendel examined the inheritance of two traits in pea plants: seed coat texture and colour. Seed coat texture can be represented as S-smooth and s-wrinkled, and seed coat colour can be represented as Y-yellow and y-green. SSYY plants were crossed with ssyy plants to yield F1 pea seeds that were all smooth and all yellow. By crossing plants grown from these F1 seeds, Mendel obtained four different phenotypes of F2 seeds:

• smooth, green seeds

• wrinkled, green seeds

• smooth, yellow seeds

• wrinkled, yellow seeds



5. If the traits for seed coat texture and seed coat colour had been located close together on the same chromosome, Mendel might not have conceptualized
   
   
   1. gene pairs
   2. dominance
   3. the Law of Segregation
   4. the Law of Independent Assortment