you asked a really important question here, and the whole concept of linked genes comes up A LOT in the actual test

so let me try to explain this as clearly as I can because it's very important you understand this concept before you move on.

1. Linked genes refers to 2 different genes that seem to be inherited together.

For this question, we are looking at two different genes here : one that determines flower color, the other that determines height.

The question further states that one of the parental genotypes is GGDD, the other ggdd.

In this case, if a parent has a genotype of GGDD, 

the only gametes that this organism will be able to produce through meiosis is GD and GD, right?

The same for the other parent organism with the genotype of ggdd.

This parent will only be able to produce gd and gd gametes.

2. These parent organisms have been crossed to produce the F1 generation.

The F1 genotype is GgDd.

Think carefully about what's going on here.

Once again, the term "linked genes" means that the genes "g" and "d" are likely inherited together.

(think of a chain link that holds the "g" section of the chromosome and "d" section of the chromosome together)

The F1 organism received genes from both parents

One of the parents gave it GD. The other gave it gd.

The big G is linked with big D. The small g is linked with small d.

Why? Because they are inherited from different parents and they like to stick together.

This part is really important. Make sure you get this!

3. The F1 generation is now crossed with a homozygous recessive individual : ggdd.

The F1 individual can theoretically produce 4 different types of gametes, like we saw on question 7 a).

But question c) asks us to assume that these genes are linked.

Now let's imagine creating gametes by the F1 individual.

I want to start off with the big G.

But big G is linked with big D, so it's likely to produce gametes that look like GD, not Gd.

If I started off with small g, then that is linked with small d,

so it's much more likely for me to produce gd gametes, instead of gD.

4. Let's look at what gametes the F1 individual has produced.

GD : Gd : gD : gd

There's going to be a lot of GD gametes, and a lot of gd gametes because once again, they are linked.

The Gd and gD gametes will be much less numerous for the same reason.

Now let's go back to how the F2 generation is created.

The F1 gametes are crossed with a homozygous recessive individual : ggdd.

This recessive individual can only create one type of gamete : gd.

5. If we were to combine the F1 gametes to create F2 generations, how would the ratios look like?

There's a lot of GD gametes produced by the F1,

this will be crossed with a "gd" gamete from the homozygous recessive individiual.

The resulting offspring will be GgDd. and the phenotype will be "GD" just like the F1 individual.

This is why this offspring is called the "parental phenotype".

There's also going to be a lot of gd gametes produced by the F1.

cross this with the "gd" gamete from the recessive individual

and the genotype is ggdd, phenotype "gd" just like the other parent (homozygous recessive).

This is also the "parental phenotype"

6. Because GD and gd are linked, there's very low probability that crossing over occurs between the two genes,

so Gd gametes and gD gametes are very few in numbers.

Gd crossed with gd gamete produces Ggdd offspring, who's phenotype looks like "Gd"

There is no parent that looks like that, so this is referred to as a "recombinant phenotype"

Likewise, gD and gd cross results in ggDd offspring, phenotype "gD" another recombinant phenotype.

This is why when two genes are supposedly linked,

there is higher chance of parental phenotypes being produced, compared to recombinant phenotypes.

The 25% (1/4) number comes from equal probability for the 4 different phenotypes possible.

Try going through the steps carefully in your mind and reviewing the lecture about linked genes.

Ask me more questions if this still seems weird.

Hope this helps! :D