Download How are traits inherited

Variant - Purple
Gene
Chromosome
TRAIT
FlowerColor
Color
Trait ––Flower
Chromosome
Gene
Variant -white
Genetics based on
Law of Segregation &
Law of Independent Assortment
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Dominant [R]
Recessive [r]
Genotype
Phenotype
Gene
Allele
Homozygous [RR or rr]
Heterozygous [Rr]
Variant
Trait
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This Trait is recessive
This gene codes so that the individual does
not produce any melanin (protein which gives
pigment to hair, eyes, skin)
1. What are the Variants for this trait?
2. What is the Genotype for an albino? (use A a)
3. What is the Phenotype for an albino? (use the
physical characteristic…)
Mark on white board!
Pea Plants –
Trait of
Flower Color
Variants:
Purple (gene/allele) P
White (gene/allele) p
Cross a purple flower (homozygous) with a white
flower and determine the Genotypic ratio &
Phenotypic ratio of the offspring.
1.
Identify the genotypes of the parents
◦ Homozygous Purple - ______
◦ White
- ______
2.
Determine the possible gamete
combinations for each parent
◦ Purple parent ___
◦ White parent ___
3.
4.
___
___
Use punnett square to place the parents’
possible gene/alleles for each gamete AND
Cross the two gamete alleles to determine
the genotype of all the offspring
One parent’s
genotype along the
top, one parent ‘s
genotype along the
side.
p
p
P
?
?
P
?
?
5.
Determine the Genotypic ratio
All four boxes have a genotype of Pp
So…. 1/1 or 100% or all are
100% Pp
6.
Pp
Determine the Phenotypic ratio
What color will the offspring show?
So…1/1 or 100% or ALL are Purple Flowers
100% Purple Flowers
Round Pea
Dominant
R
Wrinkled Pea
Recessive
r
Problem: Cross a Wrinkled pea with a heterozygous
round pea. Determine the genotypic & phenotypic
Ratio of the offspring.
Wrinkled pea crossed with Heterozygous
round
1. pp crossed with a Pp
2. Possible gametes “p” and “P” & “p”
p
p
3. Place in Punnett square
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P
p
4. Determine genotype of offspring
5. Record % of genotype of offspring
6. Record % of phenotype of offspring
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Using the information regarding Albinism,
determine the Genotypic & Phenotypic Ratios
for a couple who are both heterozygous for
albinism. (Both parents have normal skin
color)
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Just because the Dominant Trait only needs 1
allele/gene to express itself phenotypically, it
DOES NOT mean that it is always the most
popular (largest number of individuals with
that phenotype)
Examples:
◦ Poly-dactylyism
◦ Dwarfism
Answer last questions in notebook for WS 1
Dr. Ain
Achondroplasia
Dwarfism
Dominant Trait
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Begin work using your textbook (pages 8889), notes and/or the ORCA book to assist
you with the genetic problems
REMEMBER:
1. Determine the parents’ genotypes
2. Use punnett square to list the alleles / genes in
the parents gametes
3. Cross the gamete alleles to determine the
offspring’s genotypes
4. Record the ratio, fraction or % of the Genotypes
5. Record the ratio, fraction or % of the Phenotypes
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Note the following Modes of Inheritance
1. Complete dominance; ex: Tongue Rolling (T, t)
2. Incomplete dominance; ex: flower color (R, R’)
3. Sex-Linked Trait; ex: Red-Green Colorblindness
(XC, XC, Y)
4. Multiple Alleles; ex: Blood Type (A, B, O)
5. Codominance; ex: Blood Type (ABO)
6. Dihybrid Cross; ex: Pea Pods color and shape
(R, r, and Y, y)
RR
Red
RR’
Pink
R’R’
white
White Board Problem: Cross a White with a Pink flower.
Determine Genotypic & Phenotypic Ratio of offspring.
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White flower genotype R’R’
Pink Flower genotype
R R’
Determine the gamete combination & place in
Punnett square
R
R’
R’
RR’
R’R’
R’
RR’
R’R
Genotypic and Phenotypic Ratios
½ RR’
½ R’R’
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½ Pink
½ white
White Board new problem:
Cross a red flower with a white flower
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Genes located on Sex Chromosomes (X &/or Y)
Which sex (in humans) will express a phenotype of
a trait with only 1 gene/allele for the trait?
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How will a punnett square be arranged?
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Example: Red/Green Colorblindness
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White Board Problem: Cross a Heterozygous female
for normal color vision with a normal male for
color vision. What are the GR and PR for their
offspring.
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Parents Genotype
◦ Mom - XC Xc
x
◦ Dad - XC y
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Place in Punnett square
XC
Xc
X C XCXC XCXc
y
XC y
Xc y
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Genotypic Ratio
◦
◦
◦
◦
¼
¼
¼
¼
XCXC
XCXc
XC y
Xc y
Phenotypic Ratio
½ Female normal color vision
¼ Male normal color vision
¼ male colorblind
White board problem:
Cross a colorblind dad with Homozygous mom for
normal color vision. Determine the GR and PR of
the offspring.
3 Alleles for ABO Blood Type Trait
A B O - Alleles (genes)
[Multiple Alleles]
Variants (phenotypes) Possible are:
Blood Type AB [Codominance]
Blood Type A
Blood Type B
Blood Type 0
Phenotype
AB
A
B
O
Genotype(s)
AB
AA or AO
BB or BO
OO
White Board Problem: Cross AB blood type
With 0 blood type. Give the GR & PR.
AA
AO
BB
BO
AB
OO
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Cross with 2 traits!
Remember that both letters for the possible
allele combinations within a gamete, need to
be determined
Example: A homozygous round and
heterozygous yellow pea is crossed with a
wrinkled and green pea. Determine the
gamete combinations using Rr and Yy letters.
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Parent Genotype:
◦ RRYy
◦ rryy
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Parents gamete combinations are:
RY and Ry crossed with ry
ry
RY
Ry
RrYy
Rryy
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Cross a Heterozygous Round and
Heterozygous Yellow pea with a wrinkled and
green pea.
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Show your work completely
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White board – ABO problem…
◦ Cross a Heterozygous B with a O person
◦ Determine the genotypic and phenotypic ratio of
their offspring
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White board – Sex-linked problem…
◦ Cross a Colorblind man with a Homozygous normal
color vision woman.
◦ Determine the genotypic and phenotypic ratio of
their offspring
Note the
2 traits
Below – R & Y
green
POD
color
yellow
Constricted
POD
Shape
smooth
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Cross a Heterozygous Tongue roller with no
widow’s peak with a non-tongue roller that is
Heterozygous for a widow’s peak.
[You may use T & t for tongue rolling and W &
w for widow’s peak; Tongue rolling and
widow’s peak are both dominant alleles.]
Determine the Genotypic and Phenotypic ratio
for the above cross.
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1. Determine the genotype of the parents
2. Determine the gamete combinations with 2
traits
3. Place the gamete combinations into a
punnett square (2 different letters per
gamete)
4. Using the punnett square, figure each
offspring combination (4 letters)
5. Determine the genotypic ratio (%, fraction
or ratio
6. Determine the phenotypic ratio (%, fraction
or ratio
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Ttww X ttWw
Tw; tw X tW; tw
Tw
tw
tW
TtWw
ttWw
tw
Ttww
ttww
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Final Genotypic ratio:
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Final Phenotypic ratio:
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Cross a Heterozygous Tongue roller;
Heterozyous Widow’s Peak with a person who
has the same Genotype for these 2 traits.
Determine the Genotypic and Phenotypic ratio
of this cross.
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A heterozygous Tongue roller with no
widow’s peak is crossed with a heterozygous
Tongue roller & heterozygous for widow’s
peak.
Determine the genotypic and phenotypic ratio
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Answer key available AFTER you have
completed the worksheet…
More practice problems available…
If completely finished… extra practice
problems - challenge ws is available.