Genetics Question....

[squints02]

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red flowers (R) are dominant to white (r)
broad leaves (B) are dominant to narrow (b)

What are the genotypes of the parents given the phenotypes of the parents and their progeny?

1. Red flowers with broad leaves crossed with white flowers and narrow leaves gives 1/2 red, broad plants and 1/2 white narrow plants?

2. White flowers with broad leaves crossed with red flowers and narrow leaves gives all red, narrow plants.

Anyone know how to work this out?

 

[mindblowing]

thats very simples
lets consider an example for this

if you have red plant with broad leave there can be two posiibilities
#1 its homozygous mean(RRBB)
OR #2 hetrozygous means(RrBb)


where as for white plant it can only (rrbb) caz its recessive.
correct.......makes sense.


now if u cross RRBB with rrbb(as in questuin #2)
you should get all red with broad

and when u cross RrBb with rrbb(as in question 1)
u can get 1/2 and 1/2


hope this helps🙂

 

[Streetwolf]

red flowers (R) are dominant to white (r)
broad leaves (B) are dominant to narrow (b)

What are the genotypes of the parents given the phenotypes of the parents and their progeny?

1. Red flowers with broad leaves crossed with white flowers and narrow leaves gives 1/2 red, broad plants and 1/2 white narrow plants?

2. White flowers with broad leaves crossed with red flowers and narrow leaves gives all red, narrow plants.

Anyone know how to work this out?

Okay when I write an asterisk (*) that means either dominant homozygous or dominant heterozygous - so R* means either RR or Rr.

1. Red/Broad x White/Narrow = 1/2 Red/Broad + 1/2 White/Narrow

So you have one of:

(RRBB, RrBB, RRBb, or RrBb) x rrbb

Since you want to have 1/2 R*B* and 1/2 rrbb you NEED both recessives in both parents. If one parent has RR or BB then the offspring will all have an R or a B. The only one that works this way is RrBb.

2. White/Broad x Red/Narrow = Red/Narrow

So you have one of:

(rrBB or rrBb) x (RRbb or Rrbb)

You want all red/narrow which is R*bb.

Given the parents, this isn't possible (theoretically). Since both of the white/broad parental genotype possibilities have a dominant gene for broadness, there is a chance they will pass on a B allele to their offspring, resulting in broad leaves.

I will assume you meant red/broad leaves since that could work.

R*B* would be the genotype.

So you need to ensure both an R and a B from either parent. That means if both parents have an r or a b, it won't be good.

If you chose rrBb x Rrbb, both parents have an r and a b. So in some cross, you could end up with rr or bb (or both). That would give you either white or narrow which we don't want.

The only two genotypes which do not share recessive alleles for a gene is rrBB x RRbb. This will always result in RrBb = red/broad.

 

[squints02]

Thanks to both of you for taking the time to explain all that...and in such detail too. I truly do appreciate it and yes it does make much more sense to me now!
Again thank you very much to you both and all the best to you!