1 chapter 3 heredity and reproduction. 2 n a plant or animal is only as developed as its genetic...

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Chapter 3

Heredity and Reproduction

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Heredity and Reproduction

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 Reproductionpage 43

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 do

researchers control this?

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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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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 Objectivespage 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

Two major plant classifications are the Gymnosperms and the Angiosperms.

These include flowering plants, grasses, and cereals.

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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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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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An incomplete flower lacks one or more of the before mentioned structures.

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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 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 carpel,

which type of flower is this?

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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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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 is initiated by: Length of uninterrupted darkness

(photoperiodism) Exposure to low temperatures

(vernalization) Morphological maturity (able to produce

seed)

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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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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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As the Anther matures, they break open and pollen grains are spread by the wind and insects.

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Flowering and Pollination 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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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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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.

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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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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 own species or the same plant.

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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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The pollen tube enters the nucleus of the ovule by passing through the Micropyle

•The tube cell forms a pollen tube that grows through the stigma and style.

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The generative cell has produced two male gametes through the process of Mitosis.

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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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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

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

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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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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Chromosomes are long, thread-like structures consisting of DNA (deoxyriboneucleic acid), RNA (ribonucleic acid), and consisting of proteins.

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Genes: organic bases located along DNA molecules.

The gene is the heredity unit of a plant.

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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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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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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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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 small letters.

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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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The allele composition of a plant is the Genotype.

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A common method of predicting the genotypes and phenotypes of offspring is the Punnett Square.

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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 types, identify them.

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Plant Breeding page 57

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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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 seed.

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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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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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Inbreeding: the process of crossing two similar parents.

After inbreeding five to seven generations, certain phenotypes will be expressed.

Single CrossInbred parent A x Inbred Parent B

Single cross AxB

Three Way CrossInbred parent A x Inbred Parent B

Single Cross AxB x Unrelated Inbred CThree-way cross (AxB) x C

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Backcrossing: offspring are continously crossed with one of the parents.

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Biotechnology Techniques

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, recombinant DNA.

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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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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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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 Techniques1. 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 Techniques3. 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?

1 chapter 3 heredity and reproduction. 2 n a plant or animal is only as developed as its genetic...

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