1. In a plant, we note the following traits: Blue (Sl) flower is dominant over s

Question

1. In a plant, we note the following traits:
Blue (Sl) flower is dominant over slate (sl) flower
Green stigma (R) is dominant over red (r) stigma
Short style (Lg) is dominant over long (lg) style
All three genes are located on the same chromosome.
After a mating between two homozygotes, you obtain a plant that is heterozygous for all three traits. This heterozygote is test crossed and the following progeny are obtained:
Phenotype # of progeny
slate flower, green stigma, short style 27
slate flower, red stigma, short style 285
blue flower, red stigma, short style 202
slate flower, red stigma, long style 977
slate flower, green stigma, long style 227
blue flower, green stigma, long style 295
blue flower, green stigma, short style 960
blue flower, red stigma, long style 27
TOTAL 3000

A. (4 points) Make a map of these genes showing gene order and distances between genes. SHOW ALL WORK to get credit!! Use addition paper if needed.







B. (1 point) Determine Coefficient of coincidence and interference (SHOW WORK!)




please help me i'm so lost! does this involve a 3-point cross? thanks so much!!

Explanation / Answer

According to the given data,

Blue (Sl) flower is dominant over slate (sl) flower

Green stigma (R) is dominant over red (r) stigma

Short style (Lg) is dominant over long (lg) style

All 3 genes are located on the same chromosome.

The progeny are

sl   R   Lg   = 27

sl   r    Lg   = 285

SL r    Lg   = 202 (double recombinants)

sl   r    lg    = 977

sl   R   lg    = 227 (double recombinants)

SL R   lg    = 295

SL R   Lg   =960

SL r   lg     = 27

Total progeny = 3000

Recombinant frequency between SL and R = 27+ 202+ 227+ 27 = 483 / 3000 = 0.161

Recombinant frequency between R and Lg = 285+ 202+ 227+ 295 = 1009 / 3000 = 0.336

Recombinant frequency between SL and Lg = 27+ 285+ 295+ 27 = 634 / 3000 = 0.211

a). So, the map distance of the genes is

--r-------SL----------Lg

--R------sl------------lg

Actual double recombinant frequency = 202 + 227 = 429

expected double recombinant frequency = recombinants between SL , R and R , Lg

                                                              = 483 /3000 * 1009 / 3000 = 0.0541

                                                              = 162.3 per 3000

Therefore coefficient of coincidence = 429 / 162.3 = 2.64

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