Small body (nb), short spines (Is) and amoral are three recessive traits in stick the genes of which are linked on the same chromosome An heterozygous fish for all these used in a testeross and the following progeny was observed: Number 150 N 120 N 65 Progeny genotype nb ls* a/ nb ls a nb ls at / nb lsa -nb ls' a / nb ls a nb lst a / nb ls a nb ls a/ nb lsa nb ls nb is a nb sa/ nb ls a nb 19a/ nb ls a Progeny phenotype nb'ls a nb ls at nb* 1st at nb lst a Inb ls at nb ls a nb ls* a* nb ls a 200- 68 70 Total 62 578 a. Are the three genes in coupling or in repulsion? Clearly define if in coupling or repulsion for each gene in pairwise combination (e. g., is nb in coupling or repulsion with respect to Is? And with respect to a?, etc. for each gene). nb and is are in coupling nb and is are in repulsion with a?

The three genes in coupling are in repulsion.

Explanation:

Coupling happens when the dominant alleles and the recessive alleles are on the same homologous chromosome, while the repulsion happens when one chromosome has one dominant allele and one recessive allele and another homologous chromosome also has dominant and recessive alleles.

If the progeny has:

nb+ ls+ a/nb ls a ⇒ nb+ ls+ a

nb ls a+/nb ls a ⇒ nb ls a+

Where nb+ ls+ a is the dominant alleles and nb and nb+ is in middle.

ls+ nb+ are on the same chromosome (both dominant)

ls nb are on the same chromosome (both recessive)

ls nb, these two are in coupling with each other, but ls+ and a are on the chromosome and ls+ or nb+ are dominant, while nb+ and a are recessive on form a, thus, ls and nb, they are in repulsion with a.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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