2. In four-o’clocks, the allele for red flowers is incompletely dominant over th

Question

2. In four-o’clocks, the allele for red flowers is incompletely dominant over the allele for white flowers, so heterozygotes have pink flowers. What ratios of flower colors would you expect among the offspring of the following crosses: (a) pink X pink, (b) white X pink, (c) redX red, (d) redX pink, (e) white X white, and (f) red X white? If you specifically wanted to produce pink flowers, which of these crosses would be most efficient?


3. A cross between two plants that both have yellow flowers produces 80 offspring plants, of which 38 have yellow flowers, 22 have red flower, and 20 have white flowers. If one assumes that this variation in color is due to inheritance at a single locus, what is the genotype associated with each flower color, and how can you describe the inheritance of flower color?

Explanation / Answer

Red-----------------R allele

Red flowers-genotype -------RR

WHITE-----------------r allele

WHITE flowers-genotype -------rr

heterozygotes have pink flowers-----------Rr

(a) pink X pink,

Rr           x     Rr

R

r

R

RR red

Rr pink

r

Rr pink

Rr white

====================================================

(b) white X pink                      rr x Rr

R

r

r

rR pink

rr white

r

rR pink

rr white

(c) redX red

RR XRR

R

R

R

RR red

RR red

R

RR red

RR red

(d) redX pink

                   RR XRr

R

r

R

RR red

Rr pink

R

RRred

Rr pink

e) white X white rr x rr

all oofspring are white

(f) red X white

RR x rr

all oofspring are pink Rr

(f) red X white-----------------efficent for pink ----production

RR x rr

================================================

A cross between two plants that both have yellow flowers produces 80 offspring plants, of which 38 have yellow flowers, 22 have red flower, and 20 have white flowers. If one assumes that this variation in color is due to inheritance at a single locus, what is the genotype associated with each flower color, and how can you describe the inheritance of flower color?

Answer ----------expected Ratio --------------- 1:2:1

80--------------22(red); 38 ( yellow ): 20 (white )

As three colors assumed , there may due segration of genes of hetrozygote

Consider red------------R, genotype---------RR

white--------r------------- genotype---------rr

heterozygote----------Rr------yellow

Rr------yellow x Rr------yellow

R

r

R

RR red

Rr-yellow

r

Rr-yellow

rr white

R

r

R

RR red

Rr pink

r

Rr pink

Rr white

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