Download Biological Applications in Agriculture

Biology
Principles of Heredity
Part I
Learning Objectives
1. Define genetics and explain why it is
important.
2. Explain what factors govern genetics.
3. Explain how organisms reproduce.
4. Explain what Gregor Mendel learned
about genetics.
5. Explain the outcome of a monohybrid
cross for complete dominance.
Terms
Allele
Cell
Chromosome
Complete dominance
Cross-pollination
Dominant
Gametes
Gene
Genetics
Genotype
Gregor Mendel
Heredity
Heterozygous
Homozygous
Inheritance
Meiosis
Mitosis
Monohybrid cross
Terms
Phenotype
Pollination
Principle of
Independent
Assortment
Principle of Segregation
Probability
Punnett square
Recessive
Self-pollination
Species
Zygote
I. What is genetics and why is it
important to understand genetics?
A. Genetics is the study of how traits
are passed from parents to offspring
1.The passing of traits from one
generation to another is heredity
2. traits are governed by genetics as
well as the environment
3. The amount of environmental
influence can vary greatly
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B. Each living thing
produces
offspring like
itself
C. Traits
1. common
characteristics that
distinguish one
organism from
other kinds of
organisms
2. i.e. cats, dogs,
humans, and corn
plants have
different defining
traits
http://www.acc.umu.se/~zqad/cats/index.html;
http://www.fotosearch.com/NGF002/71952708/;
http://puppydogweb.com/gallery/labradorretrievers/labradorretriever_tink.
D. Organisms within a
species have traits
that vary and
distinguish them as
different from each
other
1. white leaves vs.
green leaves
2. purple seeds vs.
white seeds
E. Understanding genetics is important
because:
1. Gain disease resistance
2. Gain insect resistance
3. Improve environmental adaptation
4. Improve productivity
5. Make a species more suited to
cultural practices
6. Obtain a more desirable product
II. What governs genetics and how are
genes passed from offspring to
parents?
A. cell - the basic unit of life
1. made up of the cell
membrane, cytoplasm, and
nucleus
2. cell membrane protects the cell
and regulates what can go in and
out of the cell
3. cytoplasm contains the organelles
which are like small organs that
perform a variety of functions that
are vital to the cell
4. organelles include the mitochondria,
microtubules, ribosomes, endoplasmic
reticulum, golgi complex, vacuoles,
plastids
5. nucleus is the “brain” of the cell and
contains the genetic information that
directs the activities of the cell
B. Chromosomes
1. found in the nucleus
2. carry the genes which
govern specific traits
3. Chromosomes are found
in pairs in all cells except in
the reproductive cells
4. corn has 20
chromosomes or 10 pairs
C. Gene
1. a sequence of DNA that codes for
a protein and thus determines a trait
2. Both members of the
chromosome pair contain the same
genes in the exact same location on
the chromosome
3. for any one trait there exists a pair
of genes responsible for its
expression
D. chromosomes numbers
corn—20
barley—14
alfalfa—32
potato—48
cotton—52
carrot—18
garden pea—20
lettuce—18
wheat—42
Need animals,
etc.
Comparative Scale of a Gene Map
Mapping of Earth’s
Mapping of Cells,
Features
Chromosomes, and Genes
Earth
Country
State
Cell
Chromosome
Chromosome
fragment
City
Gene
People
Nucleotide
base pairs
III. How do organisms reproduce?
Cells can reproduce by two main methods in
multicellular organisms—mitosis & meiosis
A. Mitosis - type of asexual reproduction
where two new cells are created from the
original cell
1. Each new cell is genetically identical to
the parent
2. continues throughout an organism’s life
3. steps of cell cycle
Interphase
Mitosis
prophase
metaphase
anaphase
telophase
Cytokinesis
a. Interphase - the cell grows in
size and replication of the
chromosomes occurs
b. Mitosis – division of the nucleus
c. Cytokinesis - division of the
cytoplasm
4. Mitosis is important to the growth of
many organisms
5. For example, human cells contain 46
chromosomes
a. During the cell cycle, the number of
chromosomes is doubled
b. the cell divides into two new cells
each containing 46 identical
chromosomes
B. Meiosis - cell division
that creates four sex
cells
1. occurs in the flower (in
angiosperms) to form
the sex cells - pollen
grains and the embryo
sac (contains the egg)
2. Animals - sperm
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3. The four new cells or daughter cells are
not genetically identical nor are they
identical to the parent cell
4. The chromosomes in the daughter cells
do not contain chromosomes in pairs
(haploid)
5. Steps of Meiosis: Interphase, Prophase
I, Metaphase I, Anaphase I, Telophase I,
Interphase, Prophase II, Metaphase II,
Anaphase II, Telophase II, and
Cytokinesis
6. Meiosis allows for the random
assortment of parental genes
a. Crossing over
1) homologous chromosomes
exchange portions of their
chromatids
2) results in new
combinations of alleles
3) occurs during meiosis I
7. For example, human cells - 46
chromosomes
a. The chromosomes replicate —
divide once forming two cells
containing 46 chromosomes—and
then divide again forming four
daughter cells of 23 chromosomes
b. The egg and sperm cells are
examples of cells created through
meiosis
C. When the gametes which
are created by meiosis
unite or fertilize sexual
reproduction has occurred
1. Offspring produced by
sexual reproduction
receive half of their
genetic information from
their female parent and
the other half from their
male parent
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D. zygote
1. protoplast
resulting from the
fusion of gametes
2. the beginning of
a new individual in
sexual
reproduction
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E. species
1. a group of related organisms that
produce fertile offspring
Bulldog - http://puppydogweb.com/gallery/bulldogs/bulldog_shallow.jpg; cocker spaniel http://puppydogweb.com/gallery/cockerspaniels/cockerspaniel_wade1.jpg; yorkshire terrier http://puppydogweb.com/gallery/yorkshireterriers/yorkshireterrier_diaz.jpg
F. breed, cultivar or variety
1. an international term denoting certain
cultivated plants or other organisms that
are clearly distinguishable from others by
any characteristic
2. when reproduced they retain their
distinguishing characters
2. different cultivars can be crossed to
obtain organisms with unique
characteristics
IV. What did Mendel learn about how traits
are passed form parents to offspring?
A. Gregor Mendel an Austrian monk
that conducted
experiments on pea
plants
http://www.accessexcellence.org/RC
/AB/BC/Gregor_Mendel.html
Figure 11-3 Mendel’s Seven F1 Crosses
on Pea Plants
Section 11-1
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
1. Inheritance
a. the acquisition of traits by
offspring
2. Heredity
a. the passing of traits from parents
to offspring
3. The passing of pure traits always
results in offspring with the same
trait
B. Plants pass their traits to their
offspring through the process of
pollination
1. Pollination - the transfer of pollen
from one flower to another flower of
the same species
2. Self-pollination - the transfer of
pollen from the anther (male) of one
flower to the stigma (female) of
another flower on the same plant
3. Cross-pollination - the transfer of
pollen from an anther on one flower
to the stigma on another plant
C. Mendel’s Conclusions
1. Principle of Independent
Assortment
a. there are two factors
which govern a particular
trait and they are
distributed
independently
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b. dominant factor is one that hides the
other factor for a particular
characteristic
1) Green pea pods and purple
flowers
2) In humans, tongue rolling and free
ear lobes
3) Represented by capital letters
c. recessive factor - one that is hidden
by the dominant factor
1) Yellow pea pods and white
flowers
2) In humans, dwarfism, straight
hairline, short eyelashes, and
straight thumbs
3) Represented by lowercase letters
2. Principle of Segregation
a. each pair of factors is separated
during the formation of the
gametes (egg and sperm)
b. happens through the process of
meiosis
D. allele
1. a contrasting form of a gene
2. green pea pods vs. yellow pea
pods (G = green, g = yellow)
3. short vs. tall pea plants
(T = tall, t = short)
E. Generations
1. P generation = parental
2. F1 generation = offspring of P
cross
3. F2 generation = offspring of
self- pollinated F1 generation
V. How is the outcome of a monohybrid
cross for complete dominance
determined?
A. monohybrid cross - a cross between
two individuals involving one pair
of alleles or traits
B. Complete dominance
1. a condition where one allele
completely masks or hides the
other allele
2. it is completely dominant over
the other
C. punnett square used to determine
the genotype,
phenotype, and
probability of a
genetic cross
D. Phenotype - the physical makeup or
outward appearance of an organism
1. For example, green pea pods or
yellow pea pods
E. Genotype - the genetic makeup of an
organism - alleles are represented by
letters
1. “G” may represent green pea pods while
“g” represents yellow pea pods
2. Because green pea pods are dominant to
yellow pea pods, the green allele is
dominant and the yellow allele is
recessive
3. a pea plant with the genotype “GG” or
“Gg” is green while one with the
genotype “gg” is yellow
F. Homozygous
1. the same alleles are present
2. “GG” and “gg”
G. Heterozygous
1. different alleles are present
2. “Gg”
H. Probability - the chance that a
specific event will occur
1. calculated by dividing the number
of one kind of event by the total
number of events
2. four pea pods and one is yellow probability is ¼ or 25%
Summary/Review
Plants are an important part of our life.
A cell is the basic unit of life.
The cell is made up of the cell membrane,
cytoplasm, and the nucleus.
Cells can reproduce by two main methods in
multicellular organisms—mitosis and meiosis.
One of the keys to understanding genetics is
to understand how to determine the outcome of
various genetic crosses.
The End
I. What is genetics and why is it
important to understand genetics?
Plants are an important
part of our life.


They not only supply us
with food for nutrition, but
they also provide us with
medicine, latex, oils, latex,
and resins.
Because plants are so
valuable,humans have tried
to manipulate plants for our
benefit for thousands of
years.
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What is genetics and why is it
important to understand genetics?
Early man realized that some plants tasted
better than others and that seeds could be
harvested and planted to increase the
availability of certain plants.

Modern methods of plant breeding have
dramatically improved crop yield and nutritional
quality in modern cultivars, (i.e. the development
of hybrid corn in the 1930’s is one of the most
important developments in agriculture in the 20th
Century).
What is genetics and why is it
important to understand genetics?
The planting of hybrid
cultivars and good
farming practices
have resulted in corn
yields of 400 bushels
per acre.
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What is genetics and why is it
important to understand genetics?
The founding of the International Rice
Research Institute (IRRI) in 1962 is another
example of how man has manipulated plant
genetic information for our benefit.



This was one of the cornerstones of the green
revolution of the 1960’s.
The IRRI developed cultivars which dramatically
increased yields.
By 1974, modern dwarf rice accounted for more
than 99% of irrigated rice averaging 45–80
bushels per acre.
What is genetics and why is it
important to understand genetics?
During the 19th century we learned that
genetics governs the traits that are expressed
in plants.
 Today scientists are experimenting with
genetic engineering to change the genetic
make-up of plants.