Principles of Genetics
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Questions and Answers

What is the primary focus of plant genetics?

  • Studying animal inheritance
  • Examining genetic variation in plants (correct)
  • Understanding soil composition
  • Analyzing climate impact on crops

What did Gregor Mendel discover in his research?

  • Traits are inherited independently in discrete units (correct)
  • Chromosomes do not play a role in inheritance
  • Plants exhibit no genetic variation
  • Genes are located on chromosomes

What are chromosomes primarily responsible for during cell division?

  • Suppressing genetic variation
  • Duplicating and distributing genes (correct)
  • Storing RNA molecules
  • Creating environmental adaptations

What is a locus in the context of genetics?

<p>A specific location on a chromosome (B)</p> Signup and view all the answers

Which of the following is NOT a role of biodiversity in crop improvement?

<p>Decreasing the variety of crops available (B)</p> Signup and view all the answers

What defines an organism as diploid?

<p>It has two sets of chromosomes from each parent. (A)</p> Signup and view all the answers

What is the role of meiosis in sexual reproduction?

<p>It produces haploid reproductive cells. (A)</p> Signup and view all the answers

How does climate change impact plant genetic diversity?

<p>It may lead to the extinction of some species (A)</p> Signup and view all the answers

What term describes the complete set of chromosomes in a given species?

<p>Karyotype (B)</p> Signup and view all the answers

What does the term 'allele' specifically refer to?

<p>The different forms of a gene at a specific locus. (A)</p> Signup and view all the answers

How is genetic variation primarily achieved?

<p>By mutations and random assortment during meiosis. (C)</p> Signup and view all the answers

Which of the following correctly defines a gene?

<p>A unit of inheritance controlling specific characteristics (A)</p> Signup and view all the answers

If an individual is heterozygous at a locus, what does that mean?

<p>It has different alleles for that gene. (A)</p> Signup and view all the answers

What is the composition of a genotype?

<p>The total alleles possessed at specific loci. (A)</p> Signup and view all the answers

What distinguishes a haploid cell from a diploid cell?

<p>Haploid cells have half the number of chromosomes. (C)</p> Signup and view all the answers

What is meant by the 'phenotype' of an individual?

<p>The physical appearance or observable traits. (A)</p> Signup and view all the answers

What defines a locus as homozygous?

<p>The alleles at a locus are the same. (B)</p> Signup and view all the answers

Which method is described as the simplest for genotype assessment?

<p>Morphological markers (A)</p> Signup and view all the answers

What are molecular markers used for?

<p>Identifying differences in genetic code among individuals (D)</p> Signup and view all the answers

What process is used to visualize DNA fragments after gel electrophoresis?

<p>Staining with a reactive solution (A)</p> Signup and view all the answers

Which statement correctly reflects the limitations of morphological markers?

<p>They are often insufficient in number for unique identification. (A)</p> Signup and view all the answers

How do restriction endonucleases function in molecular marking?

<p>They cut DNA at specific code segments. (B)</p> Signup and view all the answers

What impact does a plant species' mating system have on its genetic variation?

<p>It reduces heterozygosity in individuals. (B)</p> Signup and view all the answers

Which of the following traits is NOT commonly associated with morphological markers in plants?

<p>Root length from DNA analysis (B)</p> Signup and view all the answers

What defines self-pollination in plants?

<p>Seeds are derived solely from the same plant's pollen. (D)</p> Signup and view all the answers

Which process leads to genetically equal offspring to the parental plant?

<p>Apomixis. (D)</p> Signup and view all the answers

What is the consequence of inbreeding in cross-pollinated species?

<p>Inbreeding depression. (B)</p> Signup and view all the answers

What is heterosis more commonly referred to as?

<p>Hybrid vigor. (B)</p> Signup and view all the answers

How does self-pollination affect heterozygosity in plants?

<p>It tends to reduce heterozygosity over time. (D)</p> Signup and view all the answers

Which statement best characterizes apomictic species?

<p>They can produce seeds without fertilization. (D)</p> Signup and view all the answers

What role does heterozygosity play in plant reproduction?

<p>It promotes diversity in predominantly cross-pollinated species. (C)</p> Signup and view all the answers

What is the primary impact of inbreeding on plant performance in self-pollinated species?

<p>It leads to little to no inbreeding depression. (C)</p> Signup and view all the answers

What primarily drives evolution leading to local adaptation in plant populations?

<p>Natural selection (B)</p> Signup and view all the answers

Which trait associated with fitness may affect plant survival?

<p>Longevity and fertility (A)</p> Signup and view all the answers

What is genetic drift likely to occur?

<p>When population size becomes very small (B)</p> Signup and view all the answers

What effect does artificial selection have on plant populations?

<p>It increases frequencies of desired phenotypes (C)</p> Signup and view all the answers

What does it mean when a trait is described as 'heritable'?

<p>It is genetically based with a heritability greater than 0 (A)</p> Signup and view all the answers

What is the relationship between fitness and allele frequencies in a population?

<p>Higher fitness individuals leave more offspring, increasing their allele frequencies (C)</p> Signup and view all the answers

Which process can lead to the complete exclusion of alleles in a small sample during genetic drift?

<p>Random sampling of rare alleles (C)</p> Signup and view all the answers

How does natural selection relate to alleles and fitness in a population?

<p>It favors alleles that contribute to higher fitness (D)</p> Signup and view all the answers

What is genetic erosion primarily associated with?

<p>The loss of genetic diversity in crops and their wild relatives (D)</p> Signup and view all the answers

What is one major cause of crop diversity erosion?

<p>Increasing monoculture practices (B)</p> Signup and view all the answers

Which of the following is an example of a factor contributing to the disappearance of crop diversity?

<p>Emergence of new pests and diseases (B)</p> Signup and view all the answers

How has the seed market been affected in recent years according to the information provided?

<p>A few multinational companies dominate the supply of commercial seeds (C)</p> Signup and view all the answers

What was the fate of many cabbage varieties over the years as highlighted in the study?

<p>A significant reduction to just 28 varieties occurred (C)</p> Signup and view all the answers

In the context of crop diversity, what does the term 'resilience' refer to?

<p>The capability of food systems to withstand challenges (D)</p> Signup and view all the answers

What can be implied about the relationship between extreme weather events and crop diversity?

<p>They can contribute to the erosion of crop diversity (C)</p> Signup and view all the answers

What is a likely consequence of losing crop varieties according to the provided information?

<p>Greater reliance on a few high-yield crops (A)</p> Signup and view all the answers

Flashcards

Plant Genetics

The study of genes, genetic variation, and heredity in plants.

Gene

A segment of DNA that carries instructions for traits.

Chromosome

Threadlike structure of DNA and protein carrying genes.

Locus

Specific location of a gene on a chromosome.

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Genetic Variation

Differences in genes or genetic makeup among individuals.

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Mendel's Work

Research revealing how traits are inherited in organisms (like pea plants).

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Chromosome Complement

The complete set of chromosomes in a cell.

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Karyotype

Visual representation of chromosomes in a cell.

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Diploid organism

An organism with two sets of chromosomes, one set inherited from each parent.

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Haploid cell

A cell containing half the number of chromosomes as a diploid cell.

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Allele

A specific composition of DNA at a gene.

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Genotype

The set of alleles an individual possesses at a specific location(s) on a chromosome.

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Heterozygous

A locus with different alleles in an individual.

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Phenotype

An individual's observable characteristics, resulting from its genes.

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Homozygous

A locus with identical alleles, meaning the organism has two copies of the same gene variant.

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Morphological Marker

An easily observable physical trait determined by genetics, used to identify genotypes.

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Molecular Marker

A difference in DNA sequence used to identify genotypes, like DNA fingerprinting.

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Restriction Endonuclease

Enzymes that cut DNA at specific sequences, used in DNA fingerprinting.

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Gel Electrophoresis

Technique that separates DNA fragments based on size using an electric current through a gel.

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What affects genetic variation?

The mating system, especially in plants, can influence genetic variation within a population.

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Heterozygosity

The proportion of heterozygous loci within an individual or population.

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Self-pollination

A reproductive process where a plant's pollen fertilizes its own ovules, leading to offspring with a high degree of homozygosity.

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Cross-pollination

A reproductive process where pollen from one plant fertilizes the ovules of a different plant, resulting in greater genetic diversity in offspring.

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Apomixis

An asexual reproductive process in plants where seeds develop without fertilization, producing clones of the parent plant.

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Inbreeding

Mating between closely related individuals, leading to increased homozygosity and reduced genetic diversity.

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Inbreeding Depression

A decrease in plant performance and fitness due to inbreeding, often resulting from increased homozygosity for harmful recessive alleles.

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Heterosis (Hybrid Vigor)

Increased vigor and performance in offspring resulting from crosses between genetically different individuals.

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Homozygosity

Having two identical alleles (versions) of a gene.

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Natural Selection

The process where organisms with traits better suited to their environment are more likely to survive and reproduce, passing those traits to future generations.

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Fitness in Evolution

The ability of an organism to survive and reproduce successfully in its environment, measured by its contribution to the next generation.

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Heritable Trait

A trait that is passed down from parent to offspring, often based on the genetic makeup (genotype) of the parent.

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Genetic Drift

A change in the frequency of alleles in a population due to random chance, especially significant in small populations.

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Allele Frequency

The proportion of a specific allele (version of a gene) in a population.

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Artificial Selection

The process where humans intentionally breed organisms with desired traits to create specific populations.

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Local Adaptation

The process where a population evolves to become better suited to a particular environment.

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How does genetic variation matter?

Genetic variation provides the raw material for natural selection to act upon. This variation is essential for populations to adapt to changing environments.

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Crop Diversity

The variety of different crops grown, including their genetic variations and wild relatives.

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Threats to Crop Diversity

Factors that reduce the variety of crops, such as extreme weather, changes in farming practices, and the spread of pests and diseases.

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Genetic Erosion

The loss of genetic diversity within crops, leading to fewer varieties and species. Often caused by replacing traditional crops with modern ones.

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What is a landrace?

A variety of a crop that has been developed and adapted over time by farmers in a specific region.

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Why Are Landraces Important?

Landraces have unique traits and genetic diversity, valuable for adapting to changing environments and diseases.

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Seed Monopoly

A situation where a few large companies control the majority of seeds sold across the world, limiting the variety available.

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Impact of Seed Monopoly

It reduces the genetic diversity of crops, making them more vulnerable to diseases and pests, and impacting farmers' choices.

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Consequences of Losing Crop Diversity

Loss of food security, reduced resilience to climate change, and reliance on a limited number of crops.

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Study Notes

Principles of Genetics

  • The study of genes, genetic variation, and heredity in plants is known as plant genetics.
  • Understanding plant genetics is crucial for crop breeding and conservation of plant genetic diversity.
  • Plant genetic resources include genotypes of particular species collected from different sources and geographical origins for use in plant breeding.
  • Germplasm is the sum total of hereditary material (alleles of various genes) in a crop species and its wild relatives.
  • Different types of plant genetic resources exist including landraces, farmers' varieties, parental lines of hybrids, released varieties, primitive cultivars and wild/weedy relatives.
  • Biodiversity is crucial for crop improvement, influencing the resilience of ecosystems and the stability of societies.
  • Destroying biodiversity is akin to setting fire to the planet's lifeboat.
  • Each species has a characteristic number of chromosomes in its somatic (non-reproductive) cells.
  • There are different methods of assessing genotypes, both morphological and molecular.
  • Morphological markers are easily observed genetically-determined traits.
  • Molecular markers identify differences in the genetic code and are used for DNA fingerprinting.
  • Plant DNA is segmented by enzymes called restriction endonucleases.
  • DNA fragments are separated by gel electrophoresis.
  • Alleles are variations of genes that may differ between chromosomes in a diploid species or among chromosomes in a polyploid species.
  • Multiple alleles of a gene develop through mutations, which are structural or chemical changes in DNA.
  • Reproductive cells (like sperm and egg) are haploid, with half the number of chromosomes as a diploid cell.

Genetic Variation in Plants

  • Genetic variation is the result of differences between individuals in a population.
  • It's influenced by allelic differences due to mutations and random assortment of alleles during meiosis (a special type of cell division that creates sperm and egg cells).
  • A diploid organisms has two genomes, one from each parent.
  • The total chromosomal DNA of an organism is called its genome.
  • Genotype refers to the set of alleles an organism possesses at a given locus or over many loci.
  • Phenotype refers to the observable characteristics of an organism.
  • If different alleles exist at a given locus, that locus is called heterozygous.
  • If alleles at a locus are the same, that locus is homozygous.
  • Different methodologies exist that can help in the assessment of genotypes (morphological and molecular).
  • Although morphological markers are simple to use, their availability is limited, mostly focusing on intensively studied cultivated varieties.
  • Molecular markers use the genetic code(DNA) for identification, through the process called DNA fingerprinting.

Reproduction, Mating Systems, and Genetic Variation

  • Reproduction in plants can range from complete self-pollination to complete cross-pollination.
  • Individuals in self-pollinated species tend to be highly homozygous.
  • In cross-pollinated species, heterozygosity is more common and preserved across generations.
  • Apomixis is an asexual reproductive process where seeds develop from body cells rather than the combination of sperm and egg.
  • Inbreeding may lead to a decline in plant performance known as inbreeding depression.
  • A single genotype can occupy large areas in apomictic species, leading to less genetic diversity.
  • Heterosis, or hybrid vigor is observed when the offspring of a mating have superior performance compared to the parent plants.

Crop Diversity

  • Crop diversity is essential for sustainable food production and ensuring food security in the face of climate change and other challenges.
  • Conserving and utilizing crop diversity is important as it enables species to adjust to a range of circumstances and various environmental conditions.
  • Plant species exhibit great variability in sexual reproduction significantly affecting genetic constitution of species.
  • Current practices are limited to using a small sample of limited crop diversity.
  • The loss of plant varieties and wild relatives is irreversible, making their conservation vital.
  • The global loss of varieties is problematic as it is now fewer than 200 of the 20,000 edible plants which make up the majority of our food crops globally.
  • Many crop varieties are now endangered or have become extint.
  • The reduction in crop biodiversity makes crop species susceptible to pests and disease, and reducing resilience to environmental changes affecting agricultural production.
  • Genetic uniformity makes crop species vulnerable to epidemics, whereas diversity makes them more resilient.
  • A handful of multinational companies currently supply most commercial seeds, which contributes to the decline of crop diversity.
  • Artificial selection is comparable to natural selection as plant breeders choose (retain) plants with desirable traits.

Genetic Erosion

  • The loss of genetic diversity in crops and wild relatives is referred to as genetic erosion.
  • The modernization of agriculture, including the replacement of traditional varieties with high-yield cultivars; natural disasters; and large-scale habitat loss contribute to genetic erosion.
  • Genetic uniformity contributes to a species being susceptible to epidemics.

Evolution and Natural Selection

  • Evolution is a collection of processes that results in allele frequency changes over time.
  • Natural selection is based on fitness—the tendency of an individual and its offspring to survive—and may be connected to a plant's longevity, fertility, ability to produce viable offspring.
  • Genetic variation influencing a trait is heritable (heritability > 0), higher fitness individuals have more offspring on average, and genetic composition in the population becomes more similar to that of the more fit individuals.

Other Processes that Can Lead to Genetic Changes

  • Random genetic drift is a process driven by chance.
  • The founder effect is a type of genetic drift that occurs when a new population is established from a very small number of individuals from an original population.

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Description

This quiz explores the fundamental concepts of plant genetics, including gene variation, heredity, and the importance of biodiversity in crop breeding. Additionally, it covers the types of plant genetic resources and the significance of preserving genetic diversity for sustainable agriculture. Test your knowledge and understanding of these critical topics.

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