Mendel's Experiments and Inheritance Principles
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Questions and Answers

Which of the following best describes the function of a codon?

  • It is a three-base sequence that codes for a specific amino acid. (correct)
  • It is a regulatory gene that controls gene expression.
  • It is part of the DNA backbone composed of phosphate and sugar.
  • It is a non-coding sequence within a gene.

What are the primary components of the DNA backbone?

  • Phosphate and deoxyribose sugar (correct)
  • Exons and introns
  • Cytosine and guanine
  • Adenine and thymine

What is the ultimate source of all new genetic variation?

  • Changes in the sequence of DNA bases (correct)
  • Natural selection
  • Neutral mutations
  • Gene flow

What is the primary function of regulatory genes, such as enhancers and silencers?

<p>To control when and how other genes are turned on or off. (A)</p> Signup and view all the answers

What was the primary conclusion of Mendel's pea breeding experiments regarding inheritance?

<p>There are physical units of inheritance (genes) that retain their identity when passed from parents to offspring. (A)</p> Signup and view all the answers

What does the term 'polymorphic' refer to, in the context of genetics?

<p>When a gene has multiple versions or alleles. (D)</p> Signup and view all the answers

Which of the following best describes a 'locus' in the context of genetics?

<p>The physical location of a gene on a chromosome. (B)</p> Signup and view all the answers

What is the difference between a monogenic and a polygenic trait?

<p>Monogenic traits are determined by one gene, while polygenic traits are influenced by multiple genes. (B)</p> Signup and view all the answers

Which of the following is true about neutral mutations?

<p>They neither benefit nor harm an organism. (C)</p> Signup and view all the answers

What is the term for the existence of two or more alleles at a locus?

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

What is the role of gel electrophoresis in genetic studies?

<p>To detect differences between individuals in the amino acid sequence of proteins. (D)</p> Signup and view all the answers

According to the evolutionary model discussed, what is the significance of neutral mutations?

<p>They increase the importance of genetic drift and can be a source of future adaptive variation. (B)</p> Signup and view all the answers

How many total chromosomes are typically found in a human cell?

<p>46 (A)</p> Signup and view all the answers

What is the primary function of the 2-3% of DNA that is directly and consistently involved in protein production?

<p>Gene expression. (C)</p> Signup and view all the answers

Which agricultural practice is NOT explicitly mentioned in the context?

<p>Irrigation techniques (A)</p> Signup and view all the answers

What genotype results in the production of normal hemoglobin?

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

What are epigenetic changes, in genetic terms?

<p>Changes in DNA structure that do not involve changes in base sequence. (D)</p> Signup and view all the answers

Which of the following processes produces gametes through cell division?

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

In the life cycle of Plasmodium falciparum, what is the immediate stage following the parasite entering the bloodstream of a human?

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

What is the primary geographical region where sickle cell anemia is most commonly found?

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

What effect does low oxygen pressure have on hemoglobin and red blood cells, as detailed in the content?

<p>Decreased ability to load oxygen at the lungs (C)</p> Signup and view all the answers

How does the genetic mutation causing sickle cell anemia affect the hemoglobin protein?

<p>Change in 1 out of 146 amino acids in the beta chain (A)</p> Signup and view all the answers

What genetic inheritance pattern is exhibited by the sickle cell trait (AS), according to the text?

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

What is a characteristic of a disruptive selection?

<p>Both homozygotes are fitter than the heterozygotes (A)</p> Signup and view all the answers

What is the primary effect of gene flow on genetic variation within a breeding population?

<p>It increases genetic diversity. (A)</p> Signup and view all the answers

What is a critical requirement for natural selection to occur?

<p>Differential mortality due to some stress. (B)</p> Signup and view all the answers

In the context of the medium ground finches studied by the Grants, what environmental change led to an increase in average beak size?

<p>Decreased rainfall leading to fewer small seeds and more tough seeds. (C)</p> Signup and view all the answers

What characteristic of the peppered moth makes it a classic example of directional selection?

<p>Its monogenic trait for coloration, which showed a shift in frequency due to industrial pollution. (B)</p> Signup and view all the answers

What does 'balanced polymorphism' mean with regard to genetics, specifically referring to stabilizing selection?

<p>It signifies a state where multiple alleles are maintained in a population because heterozygotes have a survival advantage. (A)</p> Signup and view all the answers

Why is the S allele for sickle cell anemia maintained at higher levels in some African populations?

<p>Because AS individuals are better adapted in environments with falciparum malaria, despite SS having a reduced survival rate. (C)</p> Signup and view all the answers

How does the change from hunter-gatherer lifestyle to Bantu horticulture influence the frequency of malaria and thus the S allele?

<p>It increased malaria rates due to sedentary lifestyles and increased population size. (D)</p> Signup and view all the answers

What is a direct result of directional selection on a polygenic trait?

<p>A shift in the population towards one extreme phenotype. (B)</p> Signup and view all the answers

In the example of the rabbits and the virus, what was a critical factor in the rabbit’s survival and the virus's decreased virulence?

<p>Rabbits that possessed neutral mutations and were more likely to survive while the virus became less harmful. (B)</p> Signup and view all the answers

Which of the following scenarios best exemplifies stabilizing selection on a polygenic trait?

<p>A population of birds where those with medium-sized wings have a higher survival rate than those with very small or very large wings. (A)</p> Signup and view all the answers

What is the relationship between seed size and plant location within the Galapagos environment mentioned in the content?

<p>Plants that produce large seeds tend to occupy low-lying areas where there’s greater access to groundwater. (A)</p> Signup and view all the answers

How did the return to normal rainfall levels following the 1977 drought affect the average body size of the medium ground finches?

<p>The average body size gradually decreased as food resources changed. (A)</p> Signup and view all the answers

What immediate impact did the El Nino event have on the finch population?

<p>It resulted in a greater proportion of small seeds, giving small birds a higher chance of survival. (C)</p> Signup and view all the answers

What observation about the change of the peppered moth population after the Clean Air Act was implemented best demonstrates the effects of natural selection?

<p>The pattern reversed, and there was a decrease in the population of black moths. (A)</p> Signup and view all the answers

In the context of stabilizing selection, if heterozygotes are better adapted, what happens to the prevalence of different alleles in a population?

<p>Both alleles are maintained at some stable rate within the population. (A)</p> Signup and view all the answers

Flashcards

Evolution

A change in the frequency of alleles in a population over generations.

Mutation

The ultimate source of new genetic variation; changes the sequence of DNA bases.

Codon

Three consecutive DNA bases that code for a specific amino acid, forming the smallest unit of genetic information.

Introns

Non-coding regions of DNA within genes, often removed from the final mRNA transcript.

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Exons

Coding regions of DNA within genes, translated into protein.

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Regulatory Genes

DNA sections that regulate gene expression, often located far from the gene they control. They can act as enhancers or silencers.

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Homeobox Genes (Hox Genes)

A type of regulatory gene involved in development, controlling the body plan during embryonic stages.

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Neutral Mutation

Changes in the codon sequence that are neither advantageous nor disadvantageous to the organism.

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Blending Theory of Inheritance

A theory that states that offspring inherit distinct units of inheritance from their parents, which do not blend together.

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Genes

Physical units of inheritance that hold information and are passed from parents to offspring. They are responsible for traits like eye color, hair color, etc.

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Monogenic Trait

A trait determined by a single gene, resulting in distinct categories of phenotypes. For example, pea color is determined by a single gene, resulting in either yellow or green peas.

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Polygenic Trait

A trait influenced by multiple genes, resulting in a continuous range of phenotypes. For example, human height is influenced by many genes, leading to a wide range of heights.

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Polymorphism

The existence of two or more alleles for a particular gene within a population. This leads to variations in the genotype and phenotype.

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Locus

The physical location of a gene on a chromosome.

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Alleles

Different versions of the same gene.

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Meiosis

A cell division process that occurs in germ cells, producing gametes (sperm and egg cells), leading to the creation of offspring with a unique combination of genetic material.

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Slash and burn agriculture

A type of farming where land is cleared by burning vegetation, often used for crops like cassava and yams.

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Genotype

The genetic makeup of an organism, specifically how it relates to a particular trait.

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Sickle cell anemia (SCA)

A condition caused by a faulty gene leading to abnormal hemoglobin, resulting in red blood cells that are sickle-shaped instead of round.

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Codominance

A type of inheritance where both alleles are expressed equally, creating a mixed phenotype. In sickle cell anemia, this means that individuals with one normal and one sickle cell allele (AS) will have some sickle cells, but not as many as those with two sickle cell alleles (SS).

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Plasmodium falciparum

The parasite that causes malaria, transmitted by infected mosquitos.

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Disruptive selection

A type of natural selection where individuals with extreme traits are more likely to survive and reproduce than individuals with average traits. This leads to a population where the extremes are favored and the average decreases.

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Adaptation

The ability to withstand environmental challenges due to favorable genetic traits. This increases the likelihood of survival and reproduction.

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Natural selection

The process by which organisms with advantageous traits are more likely to survive, reproduce, and pass on those traits to their offspring. This leads to a gradual change in the frequency of traits within a population over generations.

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Virgin Population

A population that has never been exposed to a particular virus or pathogen.

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Gene Flow

The movement of individuals from one breeding population to another. This can involve the exchange of mates.

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Directional Selection

A type of natural selection where there is a shift towards one extreme of a trait distribution. This is often driven by changing environmental conditions.

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Stabilizing Selection

A type of natural selection where the intermediate phenotype has the highest probability of survival. The extreme phenotypes are selected against.

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Balanced Polymorphism

The maintenance of two or more alleles at a locus, even when one allele is less advantageous. This happens when the heterozygous genotype has a higher fitness than either homozygous genotype.

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Sickle Cell Anemia

A genetic condition characterized by an abnormality in the shape of red blood cells. Individuals with sickle cell anemia experience various health complications.

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Malaria

Malaria is a mosquito-borne infectious disease caused by a parasite. It is a significant health concern in many tropical regions.

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Sickle Cell Allele Frequency

The frequency of the sickle cell allele is higher in populations exposed to malaria. This is because the heterozygous genotype (AS) provides resistance to malaria.

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Balanced Polymorphism: Sickle Cell & Malaria

The sickle cell allele is maintained at a higher frequency in populations exposed to malaria because it provides resistance to malaria.

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Hunter-Gatherer Lifestyle

Prior to the agricultural revolution, humans lived in small, nomadic groups. This lifestyle limited the exposure to malaria and influenced the frequency of the sickle cell allele.

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Bantu Horticulturists

The adoption of agriculture led to a more sedentary lifestyle, increased population density, and greater exposure to malaria. This shift drastically affected the frequency of the sickle cell allele.

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Evolutionary Change

Changes in the frequency of traits within a population over time, as a result of natural selection and other evolutionary forces, can lead to significant evolutionary change.

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Study Notes

Mendel's Experiments

  • Gregor Mendel (1822-1884) conducted breeding experiments on pea plants.
  • He studied 7 different discreet combinations of traits.
  • Mendel used 28,000 plants and 400,000 seeds.
  • He found that traits were not blended, but instead inherited as discrete units (genes).

Inheritance Principles

  • There's no blending of traits during inheritance.
  • Physical units of inheritance (genes) maintain their identity when passed from parents to offspring.
  • Dominance, recessiveness, and codominance are important concepts in understanding trait inheritance.
  • Locus: physical location of a gene.
  • Allele: different forms of a gene at a specific locus.
  • Homozygote: A pair of the same allele.
  • Heterozygote: A pair of different alleles.
  • Genotype: Specific combination of alleles.
  • Phenotype: Morphological (appearance) result of the genotype.
  • Monogenic traits are determined by one gene.
  • Polygenic traits are influenced by multiple genes.
  • Polymorphism—the existence of two or more alleles at a locus, leading to two or more genotypes at that locus.

Chromosomes and DNA

  • Chromosomes are containers of DNA.
  • Humans have 23 pairs of chromosomes (46 total) in each cell.
  • Each chromosome has one strand from each parent.

DNA Structure and Function

  • DNA produces at least 100,000 proteins. -2-3% of DNA is directly involved in protein production; the rest is involved in regulating gene expression.
  • Noncoding RNA plays an important role in regulating genes.
  • Epigenetics: Changes in DNA structure without changing the DNA sequence itself; this may be significant in response to environmental stressors.
  • Exons (coding) vs introns (non-coding), with some introns being regulatory genes playing a significant function in controlling complex traits.
    • Homeoboxes—Hox genes—are involved in developmental processes.

Evolution

  • Evolution refers to changes in allele frequencies in a population over multiple generations.
  • Mutation is the ultimate source of new genetic variation.
  • Spontaneous mutations and mutagens can lead to new genetic variations.
  • Natural selection is a force of evolution.
  • Gene flow: the exchange of individuals between populations can increase genetic variation within populations, but decrease the genetic differences between them.

Natural Selection and Adaptation

  • Individuals with traits better suited for their environment are more likely to survive and reproduce.
  • Environmental pressures (e.g., changes in rainfall, food availability) influence the selective pressures that drive adaptation.
  • Polygenic traits (continous)—like body size—may show a pattern of adaptations over many generations, with larger or smaller forms being more useful in different environmental scenarios.

Monogenic vs. Polygenic Traits

  • Monogenic: Traits controlled by one gene.
  • Polygenic: Traits controlled by multiple genes (e.g., body size). -Stabilizing selection: favours average traits; -Directional selection: favours extreme traits; such as in response to environmental changes.

Sickle Cell Anemia

  • Sickle cell anemia is a genetic disease.
  • It has a high frequency in some populations due to a balanced polymorphism— an allele that is maintained in a population because it confers a survival advantage in certain environments, even if it might be harmful in other environments.

Microevolution and Population Genetics

  • Microevolution describes changes in allele frequencies within populations over relatively short timeframes.
  • Population genetics studies the genetic makeup of populations, including the concepts of allele frequency, gene pool, and Hardy-Weinberg equilibrium.
  • Macroevolution describes changes over long timeframes; changes that are too large or gradual to be readily observed.

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Description

Explore the revolutionary work of Gregor Mendel and his experiments with pea plants. This quiz covers Mendel's findings on genetic inheritance, including key concepts such as genes, alleles, and the principles of dominance and recessiveness. Test your knowledge of how traits are passed from parents to offspring and the terminology associated with genetics.

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