7.16–7.17: Some genes are linked together.
Most traits are passed on as independent features; however, alleles that are closely linked on the same chromosome can be passed on to offspring in one bundle.
Question 7.26
Individuals carrying two non-
- a) will develop phenylketonuria (PKU).
- b) may or may not develop PKU, because diet also plays a role in determining their phenotype.
- c) will develop both PKU and Tay-
Sachs disease, because the genes causing the traits are linked. - d) will develop both PKU and Tay-
Sachs disease, because one pleiotropic gene influences both traits. - e) do not need to worry about their phenylalanine consumption, because
Question 7.27
Because of Mendel’s law of independent assortment:
- a) individuals with red hair are more likely to have freckles.
- b) skin color and hair texture tend to be inherited together.
- c) we know that genes cannot exist as free-
floating entities within a cell but must be carried on chromosomes. - d) the alleles coding for one trait do not usually influence the inheritance pattern for another trait.
- e) Both a) and b) are correct.
Question 7.28
Thousands (or even tens of thousands) of different traits make up an individual. For this reason:
- a) in a species with 23 different chromosomes, some traits must be coded for by genes on the same chromosome.
- b) the environment must influence more than half of our traits.
- c) all genes must be pleiotropic.
- d) knowing the person’s phenotype is insufficient for determining their genotype.
- e) All of the above are correct.
