Transcript Chapter 3

Chapter 3
Heredity and Reproduction
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Heredity and Reproduction
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A plant or animal is only
as developed as its
genetic components.
An animal or plant
receives its
characteristics from its
parents.
Scientists are
continously searching
for improved crop and
animal varieties through
Selective Breeding.
Read pages 43-45
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Heredity and Reproduction
page 43
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The first major breakthrough in plant
breeding occurred in the 1930’s with the
development of hybrid seed.
Hybrid seed produce 25% to 50%
greater yields than traditional corn
varities.
Why would hybrids produce more seed?
What is drawback to hybrids and how
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do researchers control this?
Heredity and Reproduction
page 43
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Plant breeders use knowledge of
genetics and heredity to design plant
breeding programs.
A combination of traditional and
molecular techniques are used.
Scientists believe that there are about
50 controllable traits in plants that can
be produced through plant breeding.
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Heredity and Reproduction
page 45
Controllable traits include:
Palatability
Heat and drought tolerance
Shape and color
Oil
Starch, sugar, protein
Fiber content, height, salt tolerance, flavor
Texture, and time to maturity
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Chapter 3 Objectives
page 45
1. How is inheritance of traits in plants regulated?
2. How do dominant and recessive genes affect plant
characteristics?
3. How does pollination in plants occur?
4. Why are some plants unable to self pollinate?
5. How do scientists use principles of plant genetics to
guide their plant breeding programs?
6. How is biotechnolgy being used to supplement
traditional plant breeding programs?
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Answer these questions
1. What is selective breeding?
2. Identify five controllable traits that
scientists can control.
3. Which types of combinations are used
in plant breeding.
4. What percent does hybridization
increase yield by.
5. When and what was the first major
breakthrough in plant breeding?
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Flowering and Pollination
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Two major plant
classifications are
the Gymnosperms
and the
Angiosperms.
These include
flowering plants,
grasses, and
cereals.
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Flowering and Pollination
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All angiosperms develop flowers which
contain one or more ovules that are
enclosed in an ovary or carpel.
The flower is the reproductive structure
for the angiosperms.
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Flowering and Pollination
A flower is complete
if it has all four of
the the following
structures:
Sepals, Petals,
Stamens, and a
Carpel (pistil)
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Flowering and Pollination
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An incomplete
flower lacks one or
more of the before
mentioned
structures.
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Flowering and Pollination
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A flower that has both stamens (male
reproductive tissues) and a carpel
(female reproductive tissues) is a
perfect flower.
Imperfect flowers have either stamens
or a carpel, but not both.
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Answer These Questions
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1. Identify the two major classifications
of plants.
2. The flower is the ____________ of
the angiosperms.
3. A complete flower has four structures,
identify them.
4. A flower which has both male and
female is tissues is which type of flower?
5. If a flower has either stamen or a
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carpel, which type of flower is this?
Flowering and Pollination
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The sepals and petals help to attract
insects to the plant by producing a
sugary solution called nectar.
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Flowering and Pollination
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An incomplete flower is one which has
no sepals or petals.
Most cereal and grass plants have
incomplete flowers, which makes the
flowers less visible.
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Flowering and Pollination
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Flowering is initiated by:
Length of uninterrupted darkness
(photoperiodism)
Exposure to low temperatures
(vernalization)
Morphological maturity (able to produce
seed)
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Flowering and Pollination
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The majority of food-producing plants
induce flowering without external
stimulation.
As long as they are actively growing,
they initiate flowers at almost any
temperature or day length.
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Flowering and Pollination
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The Stamen,
consists of the
Anthers and their
supporting their
supporting filament.
The development of
pollen grains
(microspores)
occurs in the
Anthers.
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Flowering and Pollination
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As the Anther
matures, they
break open
and pollen
grains are
spread by the
wind and
insects.
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Flowering and Pollination
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The Carpel, includes
the Stigma, Style, and
Ovary.
The Stigma is the
swollen end of the
Style, is colorful and
allows for the pollen
to stick.
Pollen grain must
land on the Stigma in
order for pollination to
occur.
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Answer these questions
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1. What does the Carpel include?
2. Where does the development of the
pollen grain occur.
3. What is the photoperiodism?
4. What is meant by morphological
maturity?
5. A flower which has no sepals or
petals is which type of flower.
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Flowering and Pollination
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Self-pollination occurs when the anther
and the stigma are from the same
flower.
From different flowers on the same
plant.
From different plants of the same
cultivar or variety.
Cross-pollination involves different
flowers on plants or different cultivars. 22
Flowering and Pollination
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Some plants are self-fertile and produce
fruit and seed without the transfer of
pollen form another cultivar.
Most monocot plants.
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Flowering and Pollination
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A plant is considered self-sterile if it
requires pollen from another plant in
order to set fruit.
Sterility is due to the protien
composition of the cell of wall of pollen
grains.
The protein sends a signal to the stigma
indicating whether the pollen is from its
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own species or the same plant.
Flowering and Pollination
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Each pollen grain contains a tube cell
and a generative cell.
When the pollen lands on the stigma,
germination occurs.
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Flowering and Pollination
•The tube cell
forms a pollen
tube that grows
through the
stigma and style.
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The pollen tube
enters the
nucleus of the
ovule by passing
through the
Micropyle
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Flowering and Pollination
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The generative cell has produced two
male gametes through the process of
Mitosis.
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Flowering and Pollination
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One gamete unites
with the egg cell to
form the Zygote,
which form the
embryo.
The other male
gamete unites with
the polar nucleus in
the ovule to form
the endosperm.
The endosperm the
seeds food reserve
for germination.
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Flowering and Pollination
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The time between
pollination and
fertilization in most
angiosperms is 24
to 48 hours.
Once fertilization
has occurred, the
ovule becomes the
seed and the ovary
becomes the fruit.
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Answer These Questions
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1. What is the time between pollination
and fertilization.
2. How many male gametes are
produced through mitosis?
3. What is the function of the gametes?
4. Pollen enters the nucleus by passing
through what opening?
5. What causes sterility.
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Genetics and Heredity page 54
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The nucleus of a living cell contains
Chromosomes.
Chromosomes contain information
about the genetic makeup of the plant.
They transmit the information to
offspring.
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Genetics and Heredity page 54
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Each plant species
has the same
number of
chromosomes in all
vegetative cells.
Sex cells have half
the number of
chromosomes as
vegetative cells.
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Genetics and Heredity page 54
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Chromosomes are
long, thread-like
structures consisting
of DNA
(deoxyriboneucleic
acid), RNA
(ribonucleic acid),
and consisting of
proteins.
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Genetics and Heredity page 54
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Genes: organic
bases located along
DNA molecules.
The gene is the
heredity unit of a
plant.
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Answer these questions
1. Why do vegetative and reproductive
cells have varying numbers of
chromosomes?
2. Which type of material do
chromosomes contain?
3. What does DNA stand for?
4. What does RNA stand for?
5. What is a gene?
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Genetics and Heredity page 55
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Chromosomes are usually found in
pairs in each vegetative cell.
These are called Homologous
Chromosomes.
They have the same genes affecting the
same traits and are located at the same
position along the chromosomes.
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Genetics and Heredity page 55
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Matching genes on Homologous
Chromosomes are called Alleles.
Gene alleles always occur on the same
Locus (location) along the pair of
chromosomes.
Allelic genes can be dominant or
recessive.
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Genetics and Heredity page 55
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A dominant gene causes a certain
characteristic to be expressed.
A recessive gene causes the character
to be expressed only if the alleles from
both parents are recessive.
Dominant genes are represented by
capital letters.
Recessive genes are represented by
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small letters.
Genetics and Heredity page 56
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Meiosis controls the formation of egg
and sperm cells.
As gametes are formed, the two alleles
for a particular trait separate
(segregate).
They segregate randomly so that each
gamete receives one allele or the other.
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Genetics and Heredity page 56
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The allele composition of a plant is the
Genotype.
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Genetics and Heredity page 56
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A common method of predicting the
genotypes and phenotypes of offspring
is the Punnett Square.
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Answer these questions
1. A common method for determining
phenotypes and genotypes is the?
2. The allele composition of a plant is
known as the?
3. What is a homologous chromosome?
4. Meiosis controls formation of which
two sex cells?
5. Allelic chromosomes can be of two
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types, identify them.
Plant Breeding page 57
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Read pages 57-60
Plant Breeding: the process of
selectively mating plants.
A basic type of plant breeding is
Selection.
Selection is when two plants with
desirable traits are chosen from a
population and then reproduced.
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Plant Breeding page 58
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Hybridization: the crossing of two plants
that have different genotypes.
Crossbreeding usually produces a plant
that is more vigorous in growth that
either of its two parents.
Hybrids do not pass many of their traits
to their offspring, so parent stocks must
be crossed each year to produce new
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seed.
Plant Breeding page 58
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The production of hybrid seed is
managed by production organizations.
Growers are under contract to grow the
parent lines and make the hybrids.
Seed production fields must be isolated
from other fields to prevent unwanted
cross-pollination.
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Plant Breeding page 58
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When tassels begin to emerge, the
female plants are detassled to prevent
selt-pollination.
The wind then cross-pollinates the male
parent with the female to produce hybrid
seed.
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Plant Breeding page 59
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Single Cross
Inbreeding: the
Inbred parent A x Inbred Parent B
process of
Single cross AxB
crossing two
similar parents.
After inbreeding
Three Way Cross
five to seven
Inbred parent A x Inbred Parent B
generations,
Single Cross AxB x Unrelated Inbred C
certain
Three-way cross (AxB) x C
phenotypes will
be expressed.
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Plant Breeding page 59
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Backcrossing: offspring are continously
crossed with one of the parents.
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Biotechnology Techniques
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Biotechnology: the management of
biological systems for the benefit of
humanity.
Biotech uses molecular biology and
molecular genetics for developing plant
breeding methods.
These include: tissue culture, protoplast
fusion, embryo manipulation,
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recombinant DNA.
Biotechnology Techniques
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Micropropagation: the propagation
(asexual) of plant cells or tissues in a
closed container.
Cell culture: modifying the genetic
makeup of the cell and then
regenerating plants with desired traits.
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Biotechnology Techniques
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Microinjection: the mechanical insertion
of genetic material into a single, living
cell.
Cell walls can be dissolved using
enzymes.
This exposes the cells protoplast.
This allows the genetic makeup of
different plants to be fused together.
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Biotechnology Techniques
Recombinant DNA or genetic
engineering involve;
1. Gene splicing
2. Replication
3. Transfer of genes to other organisms
Transgenic organisms would carry in their
cells a foreign gene.
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Biotechnology Techniques
1. Starts with
cutting gene with
an enzyme.
2. The sliced gene
is then removed
and inserted into
a circular DNA
molecules called
plasmids found in
bacteria.
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Biotechnology Techniques
3. An enzyme is
used to seal the
spliced ends.
4. The DNA
plasmid is
inserted into a
cell selected for
alteration.
5. The result is a
new sequence
of DNA.
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Answer these Questions
1. What three items does genetic
engineering include?
2. What is micro-injection?
3. What is cell culture?
4. What is biotechnology?
5. Describe the process of gene splicing?
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