Biology, 09.10.2019 12:00 toricarter00

Compare and contrast directional selection and disruptive
selection and provide an example of each.

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Both of these show the distribution of phenotypes. In directional selection, the distribution of phenotypes forms a "bell curve." Selection against one of the extreme phenotypes causes the distribution to "move" in one direction or the other. An example might be plants whose flower color is determined by incomplete dominance: white, pink, or red. Pink flowers may be the average phenotype, but if we start to remove red flowers from the population, the "mean" phenotype will be shifted toward white flowers.
In disruptive selection, the average phenotype is selected against. This produces a "two-humped" bell-type curve, and the greater distribution is split between the two phenotype extremes. If we have the same type of incomplete dominance as mentioned in the previous paragraph, assume that the pink flowers are selected against. This means that the two "humps" shown in the distribution will be centered around the red and white phenotypes.

Answer from: july00

Directional selection occurs when one extreme of a trait is favored. Disruptive selection is where any two extremes of a trait are favored. Ex: a flower being either red or white was beneficial over being pink

Answer from: Quest

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.

Answer from: Quest

The equator absorbs the most sunlight

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Compare and contrast directional selection and disruptive
selection and provide an example of...

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