Question

Q5. You also want to determine the genotype of your parental pea plants based on the color of the plant (green is dominant to albino). One of your pea plants is green and the other is albino. What could you do to determine the genotype for color of each of your pea plants? 13 Q6. Based on the information you added to Table 8.2, explain why autosomal recessive traits can skip generations but autosomal dominant traits generally do not. /2

Answer 1

Genotype refers to the genetic constitution for a trait in an organism, represented by the form of alleles present in that organism.

Homozygous individuals are those with the same copy of the allele for a gene and heterozygous individuals have different copies of alleles for the same gene.

Dominant alleles are expressed in both homozygous and heterozygous forms in an organism and they do not skip generations.

Recessive alleles are only expressed when they are present in homozygous form in the absence of the dominant allele.

5. The parent plants are green and albino in color. The albino trait is recessive to the green trait, hence the albino plant has to be homozygous, whereas the green plant having the dominant trait can be homozygous or recessive.

Let the color trait be controlled by alleles G and g, where G is the dominant form of allele expressing green phenotype whereas g be the recessive form expressing albino phenotype

Therefore the albino plant has genotype "gg"

The green plant can be GG or Gg. To test the genotype of the green plant, we need to perform a test cross, where the plant is crossed with a homozygous recessive plant. in this case a "gg" albino plant. If the test plant is homozygous dominant, all the progenies would be green and if the plant is heterozygous dominant, the progenies would be green and albino in the ratio of 1:1.

GG x gg	G	G
g	Gg (green)	Gg (green)
g	Gg (green)	Gg (green)

Gg x gg	G	g
g	Gg (Green)	gg (Albino)
g	Gg (green)	gg (Albino)

6. Autosomal traits are the traits that get inherited through the autosomes or autosomal chromosomes, that are inherited equally unlike sex chromosome which varies in male and female.

Autosomal recessive traits can skip generations in their heterozygous form when they are not expressed due to the presence of the dominant alleles and may reappear in future generations when two recessive alleles are brought together in an individual. Autosomal dominant traits do not skip generations because they are expressed whenever they appear in an individual, whether in homozygous or heterozygous form.

Table 8.2

1. If a child has an autosomal dominant trait, then at least one of the parents has a dominant form of the allele present in their genotype, that gets transmitted to the child and expressed for the phenotype.

2. If the parents have an autosomal dominant trait, the child would also have the trait expressed in his/her phenotype.

3. If the parents have an autosomal recessive trait, the child too would have the trait expressed, since there is an absence of the dominant form of allele

4. In the absence of an autosomal recessive trait, the children would exhibit the homozygous form of the dominant allele.

5. Yes, an autosomal recessive trait can skip generations. They are not expressed in the heterozygous form with the dominant allele and may be expressed in future generations when the recessive alleles are in homozygous form.

6. Sons inherit the X chromosome from their mothers, hence an X linked recessive allele from a mother would be inherited by all the sons, whereas the daughters receive X chromosomes equally from both father and mother and thus would receive recessive allele from mother but the expression of the trait would depend on the paternal contribution.

7. Sons inherit the Y chromosome from their fathers and thus X linked traits from father are not inherited by the sons

8.

For parents with x linked recessive traits, both sons and daughter would inherit the traits since mother contribute X chromosomes to both son and daughter

For parents without x linked recessive trait and with dominant x linked trait would transmit the trait to both sons and daughters because of the equal contribution of the X chromosome from mother to both sons and daughters

X linked recessive traits can skip generations when present in the heterozygous form with dominant allele and will be expressed in further generations when present in homozygous form in females (XX) and in males (XY) where the X chromosome is contributed by the female, the trait will be expressed based on the allele present on the X chromosome.

9. The number of male or female individuals with X linked recessive trait depends on the number of progeny generated and not on the expression of trait alone.