Carnation plants show co-dominance for the anthocyanin gene. FA – allele for anthocyanin pigment (red flowers) FN – allele for no anthocyanin pigment (white flowers). State the genotype of a carnation

Here's the breakdown of the genetics problems:

c) Carnation plants show co-dominance for the anthocyanin gene.
$F^A$ – allele for anthocyanin pigment (red flowers)
$F^N$ – allele for no anthocyanin pigment (white flowers)

i) State the genotype of a carnation plant that is heterozygous for this gene.
A heterozygous plant has two different alleles.
The genotype is $\boxed{F^A F^N}$.

ii) Describe the phenotype of a heterozygous carnation plant for this gene.
Since the alleles show co-dominance, both pigments are expressed.
The phenotype is $\boxed{\text{Red and white flowers}}$.

iii) The breeder crossed a $F^A F^N$ carnation plant with a $F^A F^A$ carnation plant. Predict, using a genetic diagram, the proportion of pure breeding carnation plants in the offspring.

Parental genotypes: $F^A F^N \times F^A F^A$

Gametes:
For $F^A F^N$: $F^A$, $F^N$
For $F^A F^A$: $F^A$, $F^A$

Punnett square:

$$\begin{array}{|c|c|c|} \hline & F^A & F^N \\ \hline F^A & F^A F^A & F^A F^N \\ \hline F^A & F^A F^A & F^A F^N \\ \hline \end{array}$$

Offspring genotypes:
$F^A F^A$, $F^A F^N$

Offspring phenotypes:
Red flowers ($F^A F^A$), Red and white flowers ($F^A F^N$)

Proportion of pure breeding carnation plants:
Pure breeding plants are homozygous. In this cross, the homozygous genotype is $F^A F^A$.
There are 2 $F^A F^A$ offspring out of 4 total offspring.
The proportion is $\boxed{\frac{2}{4} \text{ or } \frac{1}{2}}$.

3) a) Sex in cats is determined in the same way as in humans. Complete the diagram below to show how sex is determined in cats.

Parental genotypes: Male cat ($XY$) $\times$ Female cat ($XX$)

Gametes:
Male cat: $X$, $Y$
Female cat: $X$, $X$

Punnett square:

$$\begin{array}{|c|c|c|} \hline & X & Y \\ \hline X & XX & XY \\ \hline X & XX & XY \\ \hline \end{array}$$

Offspring genotypes:
$XX$, $XY$

Offspring phenotypes:
Female, Male