Eye color in a particular strain of fly is influenced by one gene with two alleles: a dominant allele that results in red eyes and a recessive allele that results in sepia eyes. A red-eyed female from a true-breeding population is mated with a sepia-eyed male. The Fl offspring are all red-eyed. The Fl flies are allowed to interbreed, producing the following in the F2 generation. Females: 40 red eyes; 13 sepia eyes
Males: 39 red eyes; 11 sepia eyes
Which of the following best describes the likely mode of inheritance for the eye-color gene?
a. The eye-color gene is likely autosomal because males and females have similar phenotype ratios.
b. The eye-color gene is likely autosomal because more females have sepia eyes than males do.
c. The eye-color gene is likely sex-linked because the males and females have similar phenotype ratios.
d. The eye-color gene is likely sex-linked because the males and females display both phenotypes.

The correct option is a. The eye-color gene is likely autosomal because males and females have similar phenotype ratios.

Explanation:

Available data:

              Males: 39 red eyes; 11 sepia eyes

77% of the total progeny has red eyes and 23% has sepia eyes.

Among females, 75% is red-eyed, and 25% is sepia-eyed

Among males, 78% is red-eyed, and 22% is sepia-eyed.

The general phenotypic ratio is 3:1

If the eye-color gene was sex-linked, the phenotypic ratios would be different. There would be a higher proportion of red-eyed females than red-eyed males. Females would only express red eyes, while males would express red and sepia eyes. This is

Cross:         X⁺X⁻   x    X⁺Y        (Note: The symbol + represents the allele R

Phenotype: red-eyed both                    and the symbol  - the allele r)                  

Gametes) X⁺       X⁻     X⁺    Y

Punnett square)    X⁺         X⁻

                      X⁺   X⁺X⁺     X⁺X⁻

                       Y    X⁺Y       X⁻Y

F2) 3/4 of the whole progeny would be red-eyed

     1/4 of the whole progeny would be sepia-eyed

  BUT

     Females: 100% red-eyed

     Males: 50% red-eyed and 50% sepia-eyed

These proportions are not coincident with the exposed real proportions

So,

c. The eye-color gene is likely sex-linked because the males and females have similar phenotype ratios.

If this gene was sex-linked, Males and females would not have similar phenotype ratios. This is FALSE.

d. The eye-color gene is likely sex-linked because the males and females display both phenotypes.

If this gene was sex-linked, Males would display both phenotypes, but females would only be red-eyed. This is also FALSE.

According to this, we can assume that this is an autosomal gene. If this is true, then

Cross:   Rr XX    x    Rr XY

Gametes) RX, RX, rX, rX

                RX, RY, rX, rY

Punnett square:

              RX       RX       rX       rX

RX      RRXX    RRXX   RrXX   RrXX

rX       RrXX      RrXX    rrXX    rrXX

RY      RRXY     RRXY   RrXY   RrXY

rY       RrXY      RrXY    rrXY    rrXY

F2)  From the whole progeny

       Phenotypic ratio 3:1

       Among females

        Phenotypic ratio 3:1

      Among males

       Phenotypic ratio 3:1

The phenotypic ratio in all cases are 3:1.

b. The eye-color gene is likely autosomal because more females have sepia eyes than males do.

Both males and females exhibit sepia eyes in equal proportions. This is FALSE

a. The eye-color gene is likely autosomal because males and females have similar phenotype ratios.

Males and females do have similar phenotype proportions of red eyes and sepia eyes. This is TRUE

b

explanation:

transcription is a process in which information is rewritten. it is something our cells must do, in a more specialized and narrowly defined way. in biology, transcription is the process of copying out the dna sequence of a gene in the similar alphabet of rna. it needs to happen in the nucleus because that's where the dna is. dna is always inside the nucleus unless the cell is dividing.

transcription is the first step in gene expression, which involves copying a gene's dna sequence to make an rna molecule. transcription is performed by rna polymerases. it has three stages: initiation, elongation, and termination. rna molecules must be processed after transcription in eukaryotes.

explanation:

long version:

the protein synthesis consists two processes which are, transcription and translation. transcription takes place in the nucleus. it uses dna as a template to make an rna molecule. rna then leaves the nucleus and goes to a ribosome in the cytoplasm, where translation occurs. transcription is the first part of the central dogma of molecular biology: dna → rna. it is the transfer of genetic instructions in dna to messenger rna (mrna). during transcription, a strand of mrna is made that is complementary to a strand of dna.  

these three stages are:

  initiation: in which   is the beginning of transcription.occuring when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

    elongation: in which is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

    termination: in which is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.