Mendel's Experiments and Inheritance Patterns
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Questions and Answers

In Mendel's experiments with pea plants, what was the phenotypic ratio observed in the F2 generation when crossing purebred round and wrinkled seeds?

  • 1:1
  • 1:2:1
  • 3:1 (correct)
  • 9:3:3:1

What is the term for different forms of the same gene?

  • Genotype
  • Alleles (correct)
  • Locus
  • Phenotype

Which term describes an individual with two different alleles for a particular gene?

  • Homozygote
  • Polygenic
  • Monogenic
  • Heterozygote (correct)

Which of the following best describes a polygenic trait?

<p>A trait influenced by multiple genes, often showing continuous variation (C)</p> Signup and view all the answers

What is the process of cell division that produces gametes?

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

Approximately what percentage of human DNA is directly involved in protein production?

<p>2-3% (A)</p> Signup and view all the answers

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

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

What term describes changes in DNA structure that do NOT involve changes in base sequence, but can alter gene expression?

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

Which farming practice is NOT associated with traditional cassava and yam cultivation?

<p>Rotating field use. (D)</p> Signup and view all the answers

An individual with the genotype 'AS' for hemoglobin will:

<p>Carry the sickle cell trait. (A)</p> Signup and view all the answers

The parasite Plasmodium falciparum requires which two organisms to complete its life cycle?

<p>Humans and anopheles mosquitos. (D)</p> Signup and view all the answers

In the etiology of sickle cell anemia (SCA), which of these is the primary site of uncontrolled parasite reproduction?

<p>Red blood cells. (B)</p> Signup and view all the answers

What is the primary effect of low oxygen pressure on hemoglobin and red blood cells in individuals with sickle cell disease?

<p>Reduced lifespan of red blood cells and decreased oxygen loading. (C)</p> Signup and view all the answers

Sickle cell anemia results from a change in one of the amino acids in the beta chain of hemoglobin. How many amino acids are there in each beta chain of hemoglobin?

<p>146 (C)</p> Signup and view all the answers

If a trait exhibits a codominant pattern of inheritance, and two alleles A and s exist at a locus, what is true of the heterozygote?

<p>The heterozygote will express both the phenotypes coded by A and s independently. (B)</p> Signup and view all the answers

In disruptive selection, which phenotypes are favored over others?

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

What is the primary function of codons?

<p>To provide the sequence information that determines the amino acid order in protein synthesis. (A)</p> Signup and view all the answers

Which of the following describes the structure of the DNA backbone?

<p>A chain of phosphate groups and deoxyribose sugars. (A)</p> Signup and view all the answers

What is a 'neutral mutation'?

<p>A mutation that changes a codon sequence without changing the functionality of the protein. (D)</p> Signup and view all the answers

What is the ultimate source of all new genetic variation?

<p>Mutation (C)</p> Signup and view all the answers

What is the role of regulatory genes?

<p>To control the timing and location of gene expression through elements like enhancers and silencers. (D)</p> Signup and view all the answers

Which statement best describes the relationship between codons and amino acids?

<p>Each codon codes for a specific amino acid, which then forms the building blocks of proteins. (B)</p> Signup and view all the answers

What is gel electrophoresis used to determine?

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

Initially, a large majority of mutations were thought to be deleterious. Why is this not necessarily true?

<p>Because it has since been shown that many mutations have a neutral aspect. (B)</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 by introducing new alleles. (A)</p> Signup and view all the answers

In directional selection, what is a key outcome when environmental conditions favor one extreme phenotype in a polygenic trait?

<p>The average phenotype shifts away from the ancestral mean. (C)</p> Signup and view all the answers

What was the key observation that led to the understanding of directional selection of the medium ground finches on the Galapagos Islands?

<p>Increased survival of larger finches with larger beaks when seed availability shifted. (B)</p> Signup and view all the answers

What primary change occurred in the peppered moth population during the industrial revolution?

<p>The percentage of black moths increased due to higher survival rates. (B)</p> Signup and view all the answers

What is the defining characteristic of stabilizing selection?

<p>It maintains multiple alleles at a stable frequency because heterozygotes have higher fitness. (D)</p> Signup and view all the answers

In the context of sickle cell anemia, why does the S allele persist at high frequencies in some populations?

<p>The AS heterozygote exhibits a survival advantage in malaria-prone areas. (A)</p> Signup and view all the answers

What is the effect of a change in the environment from normal to drought conditions on the medium ground finches?

<p>Plants producing larger seeds have a higher chance of survival, impacting finches with larger beaks. (B)</p> Signup and view all the answers

What condition must be present for natural selection to occur?

<p>A stress resulting in differential mortality between individuals. (B)</p> Signup and view all the answers

What effect does the movement of individuals from one breeding population to another have on genetic differences between those populations?

<p>It decreases genetic differences by facilitating a mixing of gene pools. (D)</p> Signup and view all the answers

What is a critical factor influencing the shift from a light moth-dominated population to a dark one during the industrial revolution?

<p>Increased survival among the dark moths due to better camouflage. (A)</p> Signup and view all the answers

In stabilizing selection of a polygenic trait, which individuals are most likely to experience increased probability of survival?

<p>Individuals with average phenotypic traits. (B)</p> Signup and view all the answers

How can environmental fluctuations over short time periods affect genetic change in a population?

<p>They can result in substantial genetic change despite long term stability. (A)</p> Signup and view all the answers

What is the primary difference between directional selection and stabilizing selection?

<p>Directional selection results in a shift in the frequency of an allele for a trait whereas stabilizing maintains current frequencies. (B)</p> Signup and view all the answers

How does the change from hunter-gatherer to horticulturist lifestyles impact the frequency of malaria and the S allele?

<p>Malaria became more frequent along with an increase in the S allele frequency due to sedentary lifestyles. (A)</p> Signup and view all the answers

What is an evolutionary consequence of the cleaner air act related to peppered moths?

<p>A shift back towards a higher percentage of mottled gray moths. (C)</p> Signup and view all the answers

Flashcards

Evolution

The process of changes in the frequency of alleles within a breeding population over generations.

Mutation

The ultimate source of all new genetic variation; a change in the sequence of DNA bases.

Neutral Mutation

A change in the sequence of DNA bases that is neither beneficial nor harmful to the organism.

Codon

Three consecutive DNA bases that code for a specific amino acid, the building block of proteins.

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Exons

Segments of DNA that code for proteins.

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Introns

Segments of DNA that do not code for proteins and are removed during RNA processing.

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Regulatory Genes

Genes that control the expression of other genes, often functioning in different combinations.

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Meiosis

A process of cell division that produces four genetically unique daughter cells from one parent cell, contributing to genetic diversity.

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Blending Theory of Inheritance

The theory that inheritance is based on discrete units, not blending, which maintain their identity during inheritance. Mendel's experiments with peas demonstrated this concept, leading to the discovery of genes.

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Locus

The physical location on a chromosome where a gene resides.

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Alleles

Different forms of the same gene.

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Homozygote

An organism with two identical alleles for a specific gene.

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Heterozygote

An organism with two different alleles for a specific gene.

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Genotype

The specific combination of alleles an organism possesses.

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Phenotype

The observable physical or biochemical characteristic of an organism, resulting from its genotype.

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Polymorphism

The existence of two or more alleles at a single locus, resulting in multiple possible genotypes for that gene.

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Slash and burn farming

A type of farming where trees are cut down, burned, and the ashes are used as fertilizer. This method is often used in areas with fertile soil and warm climates.

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Codominance

A genetic trait where both alleles are expressed equally in the phenotype, leading to a blend of characteristics from both parents.

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Sickle cell anemia (SCA)

A condition where the homozygous recessive genotype (SS) leads to a sickle-shaped red blood cell, causing various health complications.

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Disruptive selection

A form of natural selection where extreme phenotypes have a higher fitness than the intermediate phenotype, leading to diversification.

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Plasmodium falciparium

The parasite responsible for causing malaria, a life-threatening disease transmitted through mosquito bites.

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Using iron tools in farming

The process of using iron tools for farming purposes. It involves tools like hoes, axes, and plows.

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Abandoned field

An abandoned field is a piece of land that was previously used for agriculture but is no longer cultivated.

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Genotype involved in hemoglobin production

The genetic makeup or composition of an organism, specifically referring to the alleles responsible for hemoglobin production.

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Gene Flow

The movement of individuals from one breeding population to another, leading to mate exchange and shifts in genetic diversity.

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Natural Selection

A change in the genetic makeup of a population over time, driven by differences in survival and reproduction based on traits.

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Directional Selection

A type of natural selection where individuals with extreme traits at one end of a range are favored, shifting the overall population towards that extreme.

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Stabilizing Selection

A polygenic trait where individuals with average traits have a higher survival rate, leading to a narrowing of the trait distribution.

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Balancing Selection

A type of selection where individuals with intermediate traits have a survival advantage over those with extreme traits, leading to a balanced distribution of traits.

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Monogenic Trait

A single gene determines a trait with distinct phenotypes. For example, the peppered moth's color is determined by a single gene, resulting in either a light or dark phenotype.

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Polygenic Trait

A trait influenced by multiple genes, resulting in a continuous range of phenotypes. For example, beak size in finches is influenced by multiple genes, leading to a range of beak sizes.

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Adaptation

A type of natural selection where individuals with a particular genotype have a higher survival rate in a specific environment, leading to an increase in the frequency of that genotype.

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Study Notes

Mendel's Experiments

  • Gregor Mendel (1822-1884) conducted breeding experiments on pea plants
  • He used 28,000 plants and 400,000 seeds
  • Mendel's experiments demonstrated that inheritance is not a blending process.
  • Traits are maintained in their original form when passed to offspring - physical units of inheritance that maintain their identity (genes).

Inheritance Patterns

  • Dominance/Recessiveness (Codominance):
    • Dominant alleles mask the expression of recessive alleles
    • Recessive alleles are expressed only when the dominant allele is not present
    • Codominance involves the expression of both alleles in a heterozygous genotype.
  • Locus: the physical location of a gene on a chromosome
  • Alleles: alternate forms of a gene
  • Homozygote: having two identical alleles for a gene(e.g., AA, aa)
  • Heterozygote: having two different alleles for a gene (e.g., Aa)
  • Genotype: genetic makeup of an organism
  • Phenotype: observable characteristics of an organism arising from the genotype

Other Genetic Concepts

  • Monogenic traits: traits determined by one gene (discrete)
  • Polygenic traits: traits determined by multiple genes (continuous)
  • Polymorphism: the existence of two or more alleles at a locus.
  • Chromosomes:
    • Contain DNA
    • Humans have 23 pairs of chromosomes (46 total) per cell

DNA and Genes

  • DNA:
    • Main component of chromosomes
    • Contains genes.
  • Genes:
    • Units of inheritance
    • Direct the production of proteins involved in various traits.
    • Humans produce at least 100,000 proteins and 21,000 genes.
    • Composed of exons (coding) and introns (non-coding sequences).
  • Noncoding RNA:
    • Portion of DNA once thought "junk"
    • Role in regulating gene expression and other cellular processes.

Evolution

  • Mutation:
    • The ultimate source of new genetic variation
    • A change in the DNA sequence.
  • Natural Selection:
    • Process where traits that enhance survival and reproduction become more common in a population over time.
    • Individuals with traits best suited to the environmental pressures are more likely to reproduce.
    • Environmental factors play a crucial role in selecting alleles
  • Gene Flow:
    • Transfer of genetic material between populations through migration
    • Results in increased genetic diversity in recipient populations and decreased diversity among donating populations.
  • Drift:
    • Random processes influencing allele frequency.
    • Can affect small populations more drastically.

Polygenic Traits and Selection

  • Directional selection:
    • Favors individuals at one extreme of the range of phenotypes.

Monogenic Traits

  • Stabilizing selection:
    • Favors the intermediate phenotypes and selects against extreme values
    • Phenotypic traits are tightly regulated to maintain balance
  • Balanced polymorphism:
    • Heterozygotes (e.g., AS for sickle cell anemia) have a survival advantage over homozygotes.

Sickle Cell Anemia

  • Heterozygotes (AS):
    • Have resistance to malaria
    • Alleles are equally maintained over time.
  • Homozygotes(SS):
    • Affected by sickle cell anemia

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Description

Explore Gregor Mendel's groundbreaking experiments with pea plants that laid the foundation for modern genetics. Understand key concepts such as dominance, recessiveness, genotypes, and phenotypes while learning how traits are inherited. This quiz will help reinforce your knowledge of classical inheritance patterns.

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