Transcript F1 generation - Haiku Learning

Chapter 9: Fundamentals of
Genetics
Essential Question: How do we
inherit characteristics from our
parents?
I. Mendel’s Legacy
A. Genetics: field of biology that studies how
characteristics are transmitted from parents to
offspring
B. Gregor Mendel: monk that studied science and
math and tended to the monastery gardens
1. Heredity: transmission of
characteristics from parents to offspring
2. Mendel’s Garden peas: observed 7
characteristics of pea plant
3. Traits: characteristics
a) contrasting characteristics
b) plant height: long or short
c) pod color: green or yellow
4. Mendel wanted to understand why characteristics
varied
Mendel
C. Mendel’s Methods
1. Pollination: pollen grains produced
in the male reproductive parts (anthers)
are transferred to the female reproductive
part (stigma)
2. Self-pollination: pollen is transferred to the stigma
of a flower on the same plant Self
3. Cross-pollination: pollen is transferred to
the stigma of a flower on a different plant Cross
4. Peas plants usually self pollinated but Mendel
removed the anthers and with a brush pollinated
different flowers
5. Mendel controlled the breeding of certain plants
to see what traits would be produced
D. Mendel’s Experiments
1. He studied each characteristic and its contrasting
traits individually
a) True-breeding or Pure: trait was always
produced in offspring
b) Strain: plants that are pure for a specific trait
2. Parental generation (P1): 14 strains for each trait
3. He crossed pollinated these strains of a plant pure for
one trait of another plant pure for the contrasting
trait
a) Crossed a pure plant with green pods with a
pure plant with yellow pods
b) The seeds developed and
were allowed to mature into plants
4. F1 generation (first filial(son) generation):
offspring of the P1 plants
F1
5. He allowed the flower from the F1 generation
to self-pollinate
6. F2 generation: offspring from F1
generation
F2
7. He recorded the number of each type of
offspring and he performed hundreds of
crosses
Mendel’s Seven F1 Crosses on Pea
Plants
Seed Coat
Color
Pod
Shape
Pod
Color
Smooth
Green
Seed
Shape
Seed
Color
Round
Yellow
Gray
Wrinkled
Green
White
Constricted
Round
Yellow
Gray
Smooth
Flower
Position
Plant
Height
Axial
Tall
Yellow
Terminal
Short
Green
Axial
Tall
• Mendel Video
E. Mendel’s Results and Conclusions
1. Crossed green pod plant with yellow pod
plant and got only green pod plants in F1
a) Allowed F1 to self-pollinate and
F2 was ¾ green and ¼ yellow
2. Factors: controlled the characteristics
a) each trait was inherited by means of a separate
factor
b) must be a pair of factors controlling each trait
3. When crossed, one of the P1 traits did not appear in
F1 but reappeared in F2
4. Dominant: trait that appeared in F1 and seems to
dominate the other factor
5. Recessive: trait that appears in F2- Need two
recessive factors for recessive trait to appear
6. If a dominant factor is present only the
dominant trait will appear.
7. Law of segregation: a pair of factors is
separated during the formation of gametes
8. Law of independent assortment: factors
for different characteristics are distributed to
gametes independently (factors for different
characteristics are not connected)
Principles of Dominance
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
F. Chromosomes and Genes
1. Molecular genetics: study of structure and
function of chromosomes and genes
a) agrees with Mendel’s findings
2. Gene: segment of DNA on a chromosome that
controls a particular hereditary trait
3. Chromosomes occur in pairs so genes also occur
in pairs
4. Allele: alternative form of a gene
a) Mendel called alleles factors
allele
5. Capital letters refer to dominant alleles and lower
case letters refer to recessive alleles
a) G for green pod color and g for yellow pod
color
b) only chose one letter (g)
6. One allele for a given trait comes from
each parent
7. Law of independent assortment is
observed for genes located on separate
chromosomes or located far apart on the
same chromosomes and crossing over can
occur
II. Genetic Crosses
A. Genotype: genetic makeup of an organism
1. Consists of the alleles that the organism
inherits from its parent
2. Genotype for a white flower color is pp and
genotype for a purple flower color is PP or Pp
B. Phenotype: physical appearance of an organism as a
result of its genotype
1. Purple flower is the phenotype for Pp or PP
2. White flower is the phenotype for pp
3. Homozygous: both alleles of a pair are alike (PP
or pp)
4. Heterozygous: two alleles
in the pair are different (Pp)
C. Probability: likelihood that a specific event will
occur
1. Probability = number of times expected
number of opportunities
2. Mendel’s experiment: yellow seeds appeared
6,022 times and green appeared 2,001 times (8,023
total)
a) Probability of yellow: 6022/8023 = .75 or
75% or ¾ or 3:4
b) Probability of green 2001/8023 = .25 or 25%
or ¼ or 1:4
D. Predicting results of monohybrid crosses
1. Monohybrid cross: cross between individuals
that involves one pair of contrasting traits
2. Punnett square: diagram used to predict the
probability that certain traits will be inherited by
offspring
3. Example 1: Homozygous X Homozygous
a) Purple flower (PP) with white flower (pp)
b) Diagram
p
p
P
P
Pp
Pp
Pp
Pp
c) 100% that genotype will be Pp
d) 100% that phenotype will be purple
4. Example 2:Homozygous X Heterozygous
a) Black coat (BB) and heterozygous (Bb)
b) Diagram
B
b
B
B
BB
BB
Bb
Bb
c) Genotype: 50% BB and 50% Bb
d) Phenotype: 100% black coat
5. Example 3:Heterozygous X Heterozygous
a) Both Bb for black coat
b) Diagram
B
B
BB
b
Bb
b
Bb
bb
c) Genotype: 25% BB, 50% Bb, 25%bb
d) Phenotype: 75% black, 25% brown
6. Example 4: Testcross: individual of unknown
genotype is crossed with a homozygous recessive
a) Can determine the genotype of any individual
whose phenotype is dominant
b) If unknown is homozygous black then all
offspring will be black
c) If unknown is heterozygous black then half
will be black
7. Example 5: Incomplete Dominance
a) Complete dominance: one allele is
completely dominant over another allele
b) Incomplete dominance: phenotype that is in
between that of the parents
c) Two or more alleles influence the phenotype
d) Flower that has allele for red (R) and allele for
white (r) neither is dominant so the flower is
pink
Incomplete Dominance in Four
O’Clock Flowers
rr can also
be used
8. Example 6: Codominance: both alleles for a
gene are expressed in heterozygous offspring
a) both alleles will be expressed
b) horse with red coat and white coat mix is
called roan
Roan Horse
Roan Cow
Codominant Chicken
E. Predicting Results of Dihybrid Crosses
1. Dihybrid cross: cross between
individuals that involves two pairs of
contrasting traits
2. Homozygous X Homozygous
a) Homozygous for round, yellow seeds and
homozygous for wrinkled, green seeds
b) Round is dominant (R) over wrinkled (r) and
Yellow is dominant (Y) over green (y)
c) RRYY with rryy and it will have 16 boxes in the
Punnett square
d) all offspring will be heterozygous for both traits
RrYy
3. Heterozygous x Heterozygous
a) RrYy X RrYy
b) 9 of 16 are round, yellow (RRYY, RRYy,
RrYY, and RrYy)
c) 3 of 16 are round, green (RRyy, Rryy)
d) 3 of 16 are wrinkled and yellow (rrYY, rrYy)
e) 1 of 16 are wrinkled, green (rryy)
f) Ratio of heterozygous cross is 9:3:3:1
Independent Assortment in Peas
In a Dihybrid Cross
Section 11-3
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