Download Mendelian genetics_makeup test

1
Genetics 3500 Fall 2014:
In the tomato three genes are linked to the same chromosome. Tall is dominant to
dwarf, skin that is smooth, is dominant to skin that is peachy, and fruit with a
normal tomato shape is dominant to oblate. A plant that is true breeding for the
dominant traits was crossed to a dwarf plant with peachy skin and oblate fruit. The
F1 plants were then test-crossed to dwarf plants with peachy skin and oblate fruit.
The following results were obtained.
155, tall smooth normal
+
+
+
160 dwarf, peach ,oblate
D
P
O
36
+
+
O
11 tall , peach oblate
+
P
O
37 dwarf peach, normal
D
P
+
12 dwarf, smooth normal
d
+
+
1 dwarf smooth oblate
D
+
O
2 tall peach normal
+
P
+
(a)
(b)
(c)
(d)
(e)
(f)
(g)
tall smooth, oblate
What indicates that the genes are linked?
What was the genotype of the original heterozygous females?
What is the order of the genes?
What is the map distance between tall and smooth
Between smooth and normal
What is the coefficient of coincidence?
Diagram the crosses in this experiment.
2
6 marks
In cats , yellow coat color is determined by the b allele and black coat color is
determined by the B allele. The heterozygous condition results in a condition known
as tortoise shell. These genes are X linked. What kinds of offspring would be
expected from a cross of a black male and a tortoise shell female. What are the
chances of getting a tortoise shell male.
4 marks
In mice, a series of five alleles determines fur color. In order of dominance, these alleles
are: yellow fur but homozygous lethal; agouti with light belly; agouti (wild-type);
black and tan; and a, black. For each of the following crosses, give the genotypes of the
parents that generate these phenotypic ratios
Parents
A:light belly x yellow
B; agouti x black and tan
Offspring
1 yellow: 1 light belly
1 agouti: 1 black and tan
3
6 marks
Summer squash plants with the dominant allele C bear white fruit, whereas plants
homozygous for the recessive allele c bear colored fruit. When the fruit is colored, the
dominant allele G causes it to be yellow; in the absence of this allele (that is, with
genotype gg), the fruit color is green. What are the phenotypes and proportions expected
from intercrossing the progeny of CC GG and cc gg plants (in otherword the F2
generation) ? Assume that the C and G genes assort independently.
6 marks
ina puppy mill, multiple crosses were made between true-breeding lines of black and
yellow Labrador retrievers. All the progeny were black. When these progeny were
intercrossed, they produced puppies consisting of 91 black, 39 yellow, and 30 chocolate.
(a) Propose an explanation for the inheritance of coat color in Labrador retrievers. (b)
Propose a biochemical pathway for coat color determination and indicate how the
relevant genes control coat coloration.
4
4 marks
In fruitflies the genes b and r are separated by 16 map units. A fruitfly of genotype B R/b
r is test crossed with b r/b r. What proportion of the progeny will be br/br?
4 marks
A true breeding pea plant with round and green seeds was crossed to a true breeding plant
with wrinkled and yellow seeds. The F1 were allowed to self fertilize. What percentage
of the seeds are expect to be round and green?
5 marks
A cross was made between a true breeding plant with blue flowers and purple seeds to a
true breeding plant with white flowers and green seeds. The following data were
obtained.
F1 all progeny had blue flowers and purple seeds. Assume that there are two genes
involved and that blue flowers and purple seed traits are dominant. What is the genetic
explanation for this result?
F2 generation :
103 blue flowers, purple seeds
40 blue flowers, green seeds
41white flowers. Purple seed
104 white flowers, green seeds.