Download Homework p. 148 q. 2 - Ms. Pasic

Homework p. 148 q. 2
Guinea pigs with a yellow coat colour have
the genotype CYCY. Guinea pigs with cream
coat colour (cream-coloured hair) have the
genotype CYCW, and those with white coat
colour have the genotype CWCW. Is the
condition for coat colour one of complete
dominance, incomplete dominance or
codominance? Explain.
Homework p. 148 q. 2
The condition for guinea pig coat colour
is one of incomplete dominance. The
heterozygous coat colour is a blend of
yellow and white.
Complete dominance would result in either a yellow coat or a white coat.
Codominance would result in individual hairs that are either yellow or white.
Homework p. 148 q. 3
Phenylketonuria is a genetic disorder caused by a
dominant allele. People with PKU are unable to
metabolize an .. amino acid, phenylalanine. If [it]
accumulates, it inhibits the development of the
nervous system, leading to mental retardation. The
symptoms of PKU are not usually evident at birth but
can develop quickly if the child is not put on a special
diet. Figure 5 is a pedigree chart that shows the
inheritance of the defective PKU allele in one family.
Homework p. 148 q. 3
I
II
III
a.
How many generations are shown on the pedigree chart?
b.
There are three generations shown on the pedigree chart.
How many children were born to the parents of the 1st generation?
There were five children born.
Homework p. 148 q. 3
I
II
III
c.
d.
What are the genotypes of individuals 1 and 2 in generation I?
The female is heterozygous. The male is homozygous recessive
How is it possible that in generation II, some of the children showed
symptoms of PKU while others did not?
The mother has a heterozygous genotype. Homozygous recessive
children can be produced when she mates with a homozygous
recessive male.
Homework p. 149 q. 4
Multiple alleles control the intensity of pigment in mice. The
gene D1 designates full colour, D2 designates dilute colour,
and D3 is deadly when homozygous. When a full coloured
male is mated to a dilute-coloured female, the offspring are
produced in the following ratio: two full colour to one dilute to
one dead. Indicate the genotypes of the parents.
Homework p. 149 q. 4
D2
D1
D3
Phenotypic Ratios
Full(2):Dilute(1):Dead(1)
50% Full Colour
D 1D2
D1D 3
25% Dilute Colour
25% Dead
D3
D 2D3
D3D 3
Homework p. 149 q. 5
Multiple alleles control the coat colour of rabbits. A grey
colour is produced by the dominant allele C. The Cch allele
produces a silver-grey condition, called chinchilla, when
present in the homozygous condition. When Cch is present
with a recessive allele, a light silver-grey colour is produced.
The allele Ch is recessive to both the full-colour allele and the
chinchilla allele. The Ch allele produces a white colour with
black extremities. This colour is called Himalayan. An allele
Ca is recessive to all alleles. The Ca allele results in a lack of
pigment, called albino.
Homework p. 149 q. 5
Table 4
Phenotypes
Genotypes
full colour
CC, CCch, CCh, CCa
chinchilla
CchCch
light grey
CchCh, CchCa
Himalayan
ChCh, ChCa
albino
CaCa
Homework p. 149 q. 5a
Indicate the genotypes and phenotypes of the F1 generation from the mating
of a heterozygous Himalayan rabbit with an albino rabbit.
Ch
Ca
Phenotypic Ratios
Himalayan(2):Albino(2)
50% Himalayan
Ca
ChCa
CaCa
Ca
ChCa
CaCa
50% White
Homework p. 149 q. 5b
The mating of a full-colour rabbit with a light-grey rabbit produces two fullcoloured offspring, one light-grey offspring and one albino offspring.
Indicate the genotypes of the parents.
C
Cch
Ca
Phenotypic Ratios
FC (2) : LG (1) : Albino(1)
50% Full Colour
CCch
CchCa
25% Light Grey
25% Albino
Ca
CCa
CaCa
Homework p. 149 q. 5c
A chinchilla rabbit is mated with a light-grey rabbit. The breeder knows that
the light-grey rabbit had an albino mother. Indicate the genotypes and
phenotypes of the F1 generation from this mating.
Cch
Ca
Phenotypic Ratios
Chinchilla (2) : Light Grey (2)
50% Chinchilla
Cch
CchCch
CchCa
Cch
CchCch
CchCa
50% Light Grey
The Sum of the Parts
Independent Assortment
The Law of Independent Assortment
• If genes are located on separate chromosomes they
are inherited independently from one another.
• Mendel`s studies included investigations into the
inheritance of two separate characteristics during
crossbreeding. He cross-pollinated plants with
yellow, round seeds with plants with green,
wrinkled seeds.
Mendel`s Cross
The genotype for green colour is yy. The genotype
for wrinkled seeds is rr. This pea`s genotype is yyrr.
The genotype for yellow colour is YY. The genotype
for round seeds is RR. This pea`s genotype is YYRR.
The gametes of the yellow pea will have YR genotypes; the
gametes of the green pea will have yr genotypes. The
genotype of the entire F1 generation is YyRr.
What will the F1 generation look like?
Crossing Heterozygous
Round Yellow Peas
YR
Yr
yR
yr
YR
YYRR
YYRr
YyRR
YyRr
Yr
YYRr
YYrr
YyRr
Yyrr
yR
YyRR
YyRr
yyRR
yyRr
yr
YyRr
Yyrr
yyRr
yyrr
Phenotypic Ratios
Round Yellow (9) : Wrinkled Yellow (3) : Round Green (3) : Wrinkled Green (1)
The probability of producing a round, yellow pea is 9
out of 16. What are the probabilities of producing
peas that have wrinkled yellow peas, round green
peas and wrinkled green peas?
Wrinkled Yellow
3 out of 16
Round Green
Wrinkled Green
3 out of 16
1 out of 16
One Trait; Multiple Genes
The colour of human eyes is determined by two genes
[gey2 located on c15 and gey located on c19]. These
genes are located on separate chromosomes and
thus sort independently.
The gey gene is epistatic over the gey2 gene. This
means that the gey gene influences the expression of
alleles by the gey2 gene.
One Trait; Multiple Genes
If the gey2 genotype is BB or Bb the offspring will
have brown eyes regardless of the gey genotype.
If the gey2 genotype is bb the offspring will have
green eyes if the gey genotype is GG or Gg.
If the gey2 genotype is bb the offspring will have
blue eyes if the gey genotype is gg.
One Trait; Multiple Genes
Identify the phenotypic ratios for a cross between two parents
who are heterozygous for the gey2 and gey gene.
The genotype for both parents is BbGg!
0:00
0:01
0:02
0:03
0:04
0:05
0:15
0:30
0:45
1:00
1:15
1:30
1:45
2:00
2:15
2:30
2:45
3:00
3:15
3:30
3:45
4:00
4:15
4:30
4:45
5:00
Crossing Heterozygous
Brown Eyed Parents
BG
Bg
bG
bg
BG
BBGG
BBGg
BbGG
BbGg
Bg
BBGg
BBgg
BbGg
Bbgg
bG
BbGG
BbGg
bbGG
bbGg
bg
BbGg
Bbgg
bbGg
bbgg
Phenotypic Ratios
Brown (12) : Green (3) : Blue (1)
12 in 16 chance of Brown Eyes
3 in 16 chance of Green Eyes
1 in 16 chance of Blue Eyes