If a purebred white flower is crossed with a purebred red flower, what percentage of the offspring flowers will be red? Red is completely dominant to white.
Complete Dominance: If two alleles have a complete dominance relationship, the phenotype of the heterozygote will be indistinguishable from the phenotype of the homozygous dominant. For example, for one of the gerbil fur color genes, that wild type agouti/brown allele (B) is completely dominant to the black (b) allele of the same gene. BB gerbils are brown; bb gerbils are black; Bb gerbils are brown. And you can't tell by looking at a brown gerbil whether it is BB or Bb, no matter how closely or carefully you look.
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47 Comments
Alain Vercammen-Grandjean
On the first generation (as the question is asked) you will get all red flowers.
On the second if you breed the resulting Bb (red) with bb (white) you will get 25% bb (white) 25% BB (red) and 50% Bb (red)...
c judith
No, Travis. That would happen if the red parent was not purebred. Example: The Red flower Rr and White flower rr. But the question said the red flower was a purebred so the genotype would be RR. So when you cross RR with rr, all flowers for the first generation would show up as Rr, which is red.
Debbie Dunton
Travis read Alain's explanation. The difference is in first generation etc. In the second and succeeding generations you might have two recessive white genes contributed and then your numbers fall into line.
jhndwrdlws
I guess you didn't pay attention in 8th grade. When two purebred are crossed, the dominant trait is expressed in 100% of the offsprings.
Kath Thomson
Koos Gouws, doesn't only apply to horriculture but to every living thing, including humans. But I agree that the explanation was not a good one. It could have been explained much more clearly.
australianworsfold
Alain Vercammen-Grandjean, gee thanks for the added information, but I really like the last sentence in the original question. I wonder how many people missed that and it's importance to the correct answer (?)
earlepg
Doesn't the "completely dominant" comment dictate the answer?
robert karel
Trixie Pettman-South, Not!
robert karel
Terry Evans, 🤣 Did you watch South Park last night?
robert karel
Why bother crossing the two?
Lynne Zeman
😴💤 snoozer of an answer. But, either it will, or it won't be red.
Vicky Rosenberg
when I read that red is completely dominant to white, the answer wasn't difficult
sdyson
That is the worst explanation ever
Cari G.
Like the q, but found the answer a bit complex for the average reader.
Suraya Choudhury
I knew !
ninakamwene
I studied genetics so I know this. A great biology trivia. Thank you.
Koos Gouws
I was lost as I started reading the explanation. Not a horticulturist!
Julie Rinehart
I was going to say 25 %, but I missed and got the right answer 😊
Sandy Roberts-Anderson
Stephen Weekly, the second generation can now carry BB Bb and bb genes, so the resulting third generation can produce either red or white flowers. If I remember my biology correctly (not a sure thing), they could also produce red and white flowers.