Transcript Plant Genetics

Plant Genetics
Genetics can be defined as
A. the study of genes.
B. the inheritance of physical traits.
C. the study and inheritance of DNA.
D. the study and inheritance of
chromosomes
E. all of the above.
Genetics can be defined as
A. the study of genes.
B. the inheritance of physical traits.
C. the study and inheritance of DNA.
D. the study and inheritance of
chromosomes
E. all of the above.
How are traits inherited from one
generation to another?
How are traits inherited from one
generation to another?
The genetic mechanism that controls
the trait is transferred through
gametes from parents to their
offspring.
How are gametes formed in the
parents?
How are gametes formed in the
parents?
Meiosis
Do the gametes have the same
number of chromosomes as regular
somatic cells?
Do the gametes have the same
number of chromosomes as regular
somatic cells?
Gametes have half the chromosome
number as regular somatic cells.
Meiosis
Reduction of
chromosome
number by half
Production of
gametes - egg
(ovary), pollen
(anthers)
Two divisions each
with phases
If a root tip cell nucleus of onion has 16
chromosomes, how many chromosomes are in
a pollen cell nucleus of onion?
A. 0
B. 4
C. 8
D. 16
E. 32
If a root tip cell nucleus of onion has 16
chromosomes, how many chromosomes are in
a pollen cell nucleus of onion?
A. 0
B. 4
C. 8
D. 16
E. 32
Where are the genetic information
stored?
Where are the genetic information
stored?
Chromosomes
Character vs. Trait
Seed color
Plant height
Alleles: codes for each trait
Dominant traits

traits that always appear and that we see
Recessive traits

traits that disappear or recede into the
background and only show up in a few
generations.
These type of traits are
controlled by two
alleles.

P (dominant)
p (recessive)
Homozygous
PP or pp
Heterozygous

Pp or pP
This combination is
called the genotype
Phenotype
The physical appearance of the plant is
called the phenotype.


One dominant allele is needed to show the
dominant phenotype.
Two recessive alleles is needed to show
the dominant phenotype.
Flower color example
Pink
White
Punnett Square
Monohybrid Cross
Dihybrid Cross
Dihybrid Cross
9:3:3:1 ratio
Testcross
Review
We know that P (purple flower) is dominant
over p (white flower). We wanted to test the
genotype of a plant with purple flowers. After
a testcross experiment we counted 46 purple
flowers and 48 white flowers. What is the
genotype of interest?



PP
Pp
pp
Review
We know that P (purple flower) is dominant
over p (white flower). We wanted to test the
genotype of a plant with purple flowers. After
a testcross experiment we counted 46 purple
flowers and 48 white flowers. What is the
genotype of interest?



PP
Pp
pp
Review
Monohybrid Cross

3:1
Dihybrid cross

9:3:3:1
Test Cross


Homozygous dominant
Heterozygous
No dominance, incomplete
dominance
Important for
phenotype, phenotype
ratios change
No dominance, incomplete
dominance
Important for
phenotype, phenotype
ratios change
Genotypic ratios stay
the same
No dominance, incomplete
dominance
Important for
phenotype, phenotype
ratios change
Genotypic ratios stay
the same
F1 phenotype is
intermediate of both
parents
No dominance, incomplete
dominance
Important for
phenotype, phenotype
ratios change
Genotypic ratios stay
the same
F1 phenotype is
intermediate of both
parents
F2 phenotypic ratios
same as genotypic
ratios 1Red:2Pink:1White
Incomplete Dominance
F1: all intermediate
F2: 1R:2P:1W ratio
In a cross between a red flowered plant and a white flowered plant,
what would be the color of the flowers in the progeny if red flower
color was incompletely dominant to white color, flower color is
controlled by a single locus, and both parents were completely
homozygous for flower color?

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
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A. Red
B. Pink
C. White
D. Red and white
E. None of the above
In a cross between a red flowered plant and a white flowered plant,
what would be the color of the flowers in the progeny if red flower
color was incompletely dominant to white color, flower color is
controlled by a single locus, and both parents were completely
homozygous for flower color?




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A. Red
B. Pink
C. White
D. Red and white
E. None of the above
If I were to cross a sweet pea plant that had red flowers and round pollen
grains with a plant that white flowers and long pollen grains, what would be
the phenotype of the offspring? Assume that red flowers are dominant to
white flowers and long pollen grains are recessive to round pollen grains.
Also assume that both traits exhibit complete dominance and both parents are
homozygous for both traits.





A.
B.
C.
D.
E.
Red flowers, long pollen grains
Red flowers, round pollen grains
White flowers, long pollen grains
White flowers, round pollen grains
Pink flowers, round pollen grains
If I were to cross a sweet pea plant that had red flowers and round pollen
grains with a plant that white flowers and long pollen grains, what would be
the phenotype of the offspring? Assume that red flowers are dominant to
white flowers and long pollen grains are recessive to round pollen grains.
Also assume that both traits exhibit complete dominance and both parents are
homozygous for both traits.





A.
B.
C.
D.
E.
Red flowers, long pollen grains
Red flowers, round pollen grains
White flowers, long pollen grains
White flowers, round pollen grains
Pink flowers, round pollen grains
Law of Segregation
Alleles segregate
during meiosis and
then come together
randomly during
fertilization.
Law of Independent Assortment
Each pair of alleles
segregate
independently
during meiosis.
Practice
YYRr x YyRr
yyRr x Yyrr
Dominant Recessive
Yellow (Y) Green (y)
Round (R) Wrinkled (r)