Which is the best definition of directional selection
2 answers:
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A pedigree is a representation of a family history tracking a trait. The graph shows the inheritance pattern of the trait and its expression through several generations.
<h3>What is an autosomal dominant trait?</h3>The autosomal dominant trait is the characteristic that is coded by a gene located in an autosomal chromosome (this is, not a sexual chromosome).
This trait is dominant because it is coded by the dominant allele, meaning that the recessive allele codes for the absence of dimples. The presence of only one dominant allele in the genotype is enough for the idividual to express dimples.
<u> Genotype Phenotype </u>
DD, Homozygous dominant Dimples
Dd, Heterozygous Dimples
dd, Homozygous recessive No Dimples
<h3>What is a pedigree?</h3>The pedigree is the representation of a family history conserning a certain trait. In this case, dimples.
The pedigree shows the expression -and inheritance pattern- of the trait through several generations.
To correctly interpret a pedigree, we need to know that
- Family members
→ Individuals are represented with geometrical figures.
→ Males are squares
→ Females are circles
- Trait/Phenotype
→ Healthy/normal/not affected individuals are represented with empty figures
→ Affected/mutated individuals are represented with solid black figures
- Generations
→ Each file is represented with a roman number, indicating the Generation.
Here we will assume that
- Individuals represented with solid figures express dimples -shaded individuals-. They can be either DD or Dd. This is because dimples is not usuall.
- Individuals with no dimples are represented with empty figures and are dd.
According to the provided pedigree,
I-1 ⇒ man DD or Dd
I-2 ⇒ woman dd
II-1 ⇒ man Dd or DD
II-2 ⇒ woman dd
II - 5 ⇒ woman dd
III - 1 ⇒ man Dd
III- 2 ⇒ woman dd
III - 6 ⇒ woman dd
Since this pedigree does not specify the relationship between individuals, I can not answer the question based on it. So, I will attach another tree to specify genotypes.
I advise you study this new example, and then follow the same reasoning to choose the correct individual according to you pedigree.
Yo can learn more about pedigrees at
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