Biology/genetic, Help?

Question

I might have the right answer to this already, but just what you have to say.

1. A spotted rabbit when crossed with a solid-colored rabbit produced all spotted offspring. When the F1 rabbits were crossed among themselves, the produced 32 spotted rabbits and 10 solid colored rabbits. Which of these chracteristics is dependent upon a dominant gene?



I'll post the problems as they are set up on the page, combining the ones that are grouped.

In poultry, rose comb is dependent upon gene (R); single comb upon its recessive allele (r). Birds of the Wyandotte breed are required to have rose combs. In certain strains of Wyandottes, however, single combed birds occasionally appear. Why is this?


A rose combed male is mated with two rose combed females, Female A produces 14 chicks, and all rose combed. Female B produces 9 chicks, 7 of which are rose combed adn 2 single combed. What are the genotypes of the three parent birds?



Those questions are grouped together. I would much appreciate on how to do any of the work for the problems also.

When oats with normal green leaves were crossed with a variety of golden leaves, the F1 were all normal, while the F2 included 130 green plants, and 40 golden ones. Diagram the genotypes of the parents and the progeny of these crosses.


You use a punnett square I'm assuming, but how do you set it up?

Two black female mice were crossed with a brown male. In several litters, female A produced 9 black and 7 brown; female B produced 57 black. What deductions can you make concerning the inheritance of black and brown coats in mice? What are the genotypes of the parents?

A breeder of Short-horn cattle has cows which are white and a bull which is roan. What proportions of the calved produced in this herd will be white? roan? and red?


Which of the calves in the preceding problem with be homozygous? Which would be heterozygous?


Starting with a roan bull and white cows could you eventually establis ha true-breeding red herd? How?

If you want to produce four o'clock seed, ALL of which would yield pink flowered plants when sown, how would you do it?

Note: In four o'clock flowers, red flower color (R) is incompletely dominant over white (r). The heterozygous plants (Rr) being pink flowered.

Thank you for all the help, it means a lot. I just started this stuff in honors biology and it totally freaked me out. The way you explain it makes so much sense.

Answer 1

Spotted is dominant (S)

Solid is recessive (s)

In the 1st generation
Spotted SS X Solid (ss) Yields all (Ss) heterozygotes (who are spotted).

___S__S
s_Ss__Ss
s_ss___ss


Then in the F1
Ss X Ss yields SS, Ss, sS and ss
ie SS, Ss, ss in a 1:2:1 ratio (25%, 50%, 25%) rabbits
but who's phenotypes are Spotted in 75% and Solid in 25% (ss)

___S___s
S_SS__Ss
s__Ss__ss


This explains why 23.8% of the F1 offspring are Solid (10/42)

and 76.2% of the F1 offspring are Spotted (32/42)

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In the poultry, Rosed comb is dominant (R) and single comb is recessive (r) as you state.

For the population of Wyandotte fowl to produce single comb chickens intermittently, there must be a small population of the rose combed chickens who are heterozygous (Rr) and when they mate their offspring are 75% rose combed (RR and Rr) and 25% single combed (rr). These single combed chickens are presumably excluded from mating which will select against the r allele and reduce its frequency in the population (but not entirely eliminate it).

Rose combed male mates with female A and female B ;-)

Because of the single combed chicks that it produces with female B, both the male and female B must have Rr genotype and so produce RrXRr = RR, Rr, rr in a 1:2:1 ratio (75% rose combed, 25% single combed) - they produce 7 rose combed chicks and 2 single combed chicks.

___R___r
R_RR__Rr
r__Rr___rr

1 RR : 2 Rr : 1 rr
3 Rose Combed : 1 Single Combed

The offspring of the male and female A are all rose combed. It is still possible that female A is Rr and that they (just by luck) have not produced any single combed chicks. The chances of this happening in RrXRr is P = 0.75^14 (a shade under 2% probability).

It is FAR more likely that female A has a homozygous RR genotype and hence their offspring will be RRxRr with genotypes RR (50%) and Rr (50%) all of whom will have a rose combed phenotype.

___R___r
R_RR__Rr
R_RR__Rr

---------------------

Oats
Green (G) dominant
Golden (g) recessive

Set up your punnett square
__G__G
g
g

in the initial GGxgg

Then with the GgxGg F1 cross you get
__G__g
G
g

--------------------

Mice
Black B
Brown b

This is similar (but not identical) to the Rose combed/single combed chickens

-------------------------

cattle
I guess if you have RR (Red), Rr (Roan) and rr (White) your Roan bull and white cows will produce

Rr x rr

offspring (50% Rr and 50% rr)

It would be possible to establish a Red herd by breeding the Rr offspring and when enough RR (Red) cattle are produced you could breed them together and not breed the Rr (Roan) or rr (White) cattle thus producing a true breeding Red herd.

------------------

4 o'clock seed

To produce ALL Rr you would need RR x rr parents (Red homozygotes x White homozygotes)