Genetic Concepts: Bottleneck vs. Founder Effect

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Questions and Answers

How is a genetic bottleneck different from the founder effect?

A genetic bottleneck occurs when a population experiences a sudden decrease in size, resulting in a loss of genetic diversity and altered allele frequencies. The founder effect involves a small group of individuals establishing a new population, leading to a different allele frequency composition compared to the original population.

How does gene flow change allele frequencies in neighboring populations?

Gene flow, the movement of alleles between populations, can cause allele frequencies to become more similar. Individuals migrating from one population to another introduce new alleles or alter the existing proportions of alleles in the recipient population.

What is the only source of new genetic variation in a species?

Mutations are the sole source of new genetic variation. They introduce changes in the DNA sequence, leading to new alleles that can be passed down through generations.

What are the possible consequences of a mutation, with regard to its effect on an organism? Are mutations always bad? Always good?

<p>Non-viable zygote (A), Protein has new function (B), Protein non-functional (C), Protein has improved function (D), Reduced protein function (E), Neutral effect (most common) (F)</p> Signup and view all the answers

What does gene flow refer to?

<p>Gene flow is the movement of alleles between populations through interbreeding.</p> Signup and view all the answers

What is Microevolution?

<p>Microevolution refers to changes in the frequencies of alleles within a population over time.</p> Signup and view all the answers

What is the source of new alleles?

<p>Mutations are the primary source of new alleles.</p> Signup and view all the answers

What is a population?

<p>A population is a group of individuals of the same species that can interbreed and reproduce within a particular geographic area.</p> Signup and view all the answers

Describe the founder effect

<p>The founder effect occurs when a small group of individuals from a larger population establishes a new population in a new location, leading to a different allele frequency composition compared to the original population.</p> Signup and view all the answers

Describe the genetic bottleneck effect?

<p>A genetic bottleneck occurs when a population experiences a sudden and dramatic decrease in size, often due to environmental factors or natural disasters. This leads to a loss of genetic diversity and altered allele frequencies.</p> Signup and view all the answers

What are the main differences between mitosis and meiosis?

<p>Mitosis is a process of cell division that results in two identical daughter cells, each containing the same number of chromosomes as the parent cell. Meiosis, on the other hand, is a specialized type of cell division that produces gametes (sex cells), containing half the number of chromosomes as the parent cell.</p> Signup and view all the answers

What happens during the first stage of mitosis?

<p>The first stage of mitosis involves the replication of each chromosome, resulting in two identical sister chromatids attached at the centromere.</p> Signup and view all the answers

What happens during the second stage of mitosis?

<p>During the second stage of mitosis, the sister chromatids separate and move towards opposite poles of the cell.</p> Signup and view all the answers

How many pairs of chromosomes do humans have?

<p>Humans have 23 pairs of chromosomes, totaling 46 chromosomes in each cell.</p> Signup and view all the answers

Why are chromosomes found in pairs in somatic cells?

<p>Chromosomes are found in pairs in somatic cells because one chromosome of each pair is inherited from the mother and the other from the father.</p> Signup and view all the answers

What is the difference between a homologous chromosome and a sister chromatid?

<p>Homologous chromosomes are pairs of chromosomes that carry the same genes but may have different alleles. Sister chromatids are identical copies of a chromosome, created during DNA replication, and are attached at the centromere.</p> Signup and view all the answers

What is a nucleotide?

<p>A nucleotide is the basic building block of nucleic acids, such as DNA and RNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base.</p> Signup and view all the answers

What is a somatic cell?

<p>A somatic cell is any cell in the body that is not a sperm or egg cell.</p> Signup and view all the answers

What is a ribosome?

<p>A ribosome is an intracellular structure responsible for protein synthesis, made up of both RNA and protein.</p> Signup and view all the answers

What are the main functions of proteins, and what are they made of?

<p>Proteins have diverse functions, including structural support (e.g., muscle and bone), defense (e.g., antibodies), enzymatic catalysis, and transport of molecules. Proteins are made up of chains of amino acids linked together.</p> Signup and view all the answers

What is the function of an antibody?

<p>Antibodies bind to foreign elements, such as pathogens, to neutralize them and protect the body from infection.</p> Signup and view all the answers

What is the function of an enzyme?

<p>Enzymes are biological catalysts that speed up chemical reactions within cells and organs.</p> Signup and view all the answers

What is the function of a messenger molecule?

<p>Messenger molecules, such as hormones, coordinate biological processes between cells and organs.</p> Signup and view all the answers

What is the function of a transport protein?

<p>Transport proteins bind and carry molecules throughout the body, such as hemoglobin, which binds and transports oxygen.</p> Signup and view all the answers

Describe the process of translation and transcription in protein synthesis.

<p>Transcription is the process of copying the genetic code from DNA to RNA, specifically messenger RNA (mRNA). Translation is the process where the mRNA sequence is read by a ribosome, and based on the codons, a specific amino acid is added to the growing polypeptide chain, ultimately forming a protein.</p> Signup and view all the answers

How does DNA replicate itself?

<p>DNA replication begins with the unwinding of the double helix, separating the two strands. Each strand then serves as a template for the synthesis of a new complementary strand through the action of enzymes. The process results in two identical DNA molecules, ensuring that each daughter cell receives a complete copy of the genetic information.</p> Signup and view all the answers

Describe the independent assortment principle mentioned by Mendel.

<p>The independent assortment principle states that during gamete formation, alleles for different traits are sorted independently of each other. This means that the inheritance of one trait does not affect the inheritance of another trait.</p> Signup and view all the answers

What is allele frequency?

<p>Allele frequency refers to the proportion of a specific allele compared to the total number of alleles for that gene in a population.</p> Signup and view all the answers

What is a hypothesis?

<p>A hypothesis is an educated guess or prediction about the relationship between two variables.</p> Signup and view all the answers

What is a theory?

<p>A theory is a well-substantiated explanation of some aspect of the natural world that is supported by a large body of evidence from many different sources and has been repeatedly tested and confirmed through experimentation.</p> Signup and view all the answers

What are the main steps in the scientific method?

<p>The scientific method involves a systematic approach to investigation, including observation, hypothesis formulation, prediction, experimentation, and analysis.</p> Signup and view all the answers

Why does selection on individuals usually outweighs selection on a group?

<p>Natural selection typically acts on individuals, favoring those with traits that enhance survival and reproduction in a particular environment. Selection on a group level can occur but is less common, as it is more difficult to measure the effects of a trait on the overall fitness of a group.</p> Signup and view all the answers

What does heterozygous mean?

<p>Heterozygous refers to an individual that has two different alleles for a particular gene at a locus. This means that the individual inherits one allele from each parent.</p> Signup and view all the answers

What is pleiotropy?

<p>Pleiotropy is a phenomenon where a single gene can affect multiple different phenotypic traits.</p> Signup and view all the answers

What does recessive trait mean?

<p>A recessive trait is only expressed if the individual inherits two copies of the recessive allele, one from each parent.</p> Signup and view all the answers

Give an example of why blending inheritance is not the mechanism by which traits are passed from parents to offspring?

<p>Blending inheritance suggests that traits would be blended together in offspring, resulting in a gradual loss of variation across generations. However, this is not what we observe in nature. If blending inheritance were true, then populations would eventually converge to a uniform appearance, with no distinct traits. Instead, we see that traits are passed down in discrete units, and variation can be maintained, even re-emerging across generations.</p> Signup and view all the answers

What properties of pea plants made them perfect for Gregor Mendel’s experiments?

<p>Pea plants were an excellent model organism for Mendel's experiments due to their short generation time, ease of cultivation, readily observable traits, and ability to self-pollinate. This allowed for controlled crosses and accurate recording of inheritance patterns.</p> Signup and view all the answers

What is a haploid cell?

<p>A haploid cell contains a single set of chromosomes, rather than the two sets found in diploid cells.</p> Signup and view all the answers

What is the role of mRNA?

<p>mRNA functions as a messenger molecule, carrying the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis takes place.</p> Signup and view all the answers

What are sister chromatids?

<p>Sister chromatids are identical copies of a chromosome, created during DNA replication, and are joined at the centromere.</p> Signup and view all the answers

Describe the structure of DNA?

<p>DNA has a double helix structure, resembling a twisted ladder with two strands of nucleotides wound around each other. The strands are held together by hydrogen bonds between complementary base pairs: adenine (A) with thymine (T) and guanine (G) with cytosine (C).</p> Signup and view all the answers

Which bases pair with each other in DNA?

<p>In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).</p> Signup and view all the answers

What is genotype frequency?

<p>Genotype frequency is the proportion of individuals within a population that possess a specific genotype. It is calculated by dividing the number of individuals with that genotype by the total number of individuals in the population.</p> Signup and view all the answers

What are the different types of mutation, how do they happen, and which cause a 'frameshift'?

<p>Mutations are changes in the DNA sequence. Point mutations involve a single base change. Insertion mutations add one or more bases, while deletion mutations remove one or more bases. Inversion mutations flip a segment of DNA. Frameshift mutations, caused by insertions or deletions that are not in multiples of three, alter the reading frame of the genetic code, leading to potentially significant changes in the amino acid sequence and protein function.</p> Signup and view all the answers

What limits gene flow?

<p>Gene flow is limited by factors such as physical barriers (e.g., mountains or oceans) that prevent individuals from moving between populations. Social rules or preferences can also restrict gene flow, such as mating preferences within specific groups.</p> Signup and view all the answers

What is the main difference between gene flow and natural selection?

<p>Gene flow is the movement of alleles between populations, driven by random factors such as migration. Natural selection, on the other hand, is a non-random process where individuals with traits that enhance their chances of survival and reproduction are more likely to pass on their genes, leading to a gradual shift in allele frequencies within a population.</p> Signup and view all the answers

How can Mendelian traits produce continuous variation?

<p>When multiple genes contribute to a trait, known as polygenic inheritance, a wide range of phenotypes can be observed, even if each contributing gene has only a few alleles. The combined effects of multiple genes create a continuous distribution of phenotypes, rather than discrete categories. This is often seen in traits like height or skin color, where we see a gradual variation rather than distinct groups.</p> Signup and view all the answers

Describe Occam's Razor?

<p>Occam's Razor is a principle that suggests the simplest explanation for a phenomenon is usually the correct one, when faced with multiple competing explanations.</p> Signup and view all the answers

What observations did Darwin make that sparked his ideas about natural selection?

<p>Darwin observed that fossils of extinct organisms resembled the living species in the same region, suggesting a connection between past and present life forms. He also noted that plants and animals on different islands of the Galapagos archipelago had distinct variations, with different beak shapes in finches being a striking example. This variation suggested that species were not fixed and might adapt to their environments.</p> Signup and view all the answers

What are Darwin's 3 postulates (required for natural selection to act)?

<p>Darwin's three postulates are the struggle for existence, variation, and inheritance of variation. He proposed that organisms compete for resources, that individuals within a population have variations, and that these variations can be passed on to their offspring.</p> Signup and view all the answers

How did the Grants' study of the Galapagos finches support each of the three postulates?

<p>The Grants' long-term study of Galapagos finches provided compelling evidence for Darwin's postulates. They observed variations in beak size among finches, with some having adaptations better suited for specific food sources. During droughts, finches with larger beaks that could crack open seeds were more likely to survive and reproduce, demonstrating the struggle for existence and the advantage of certain variations. Additionally, they documented the inheritance of beak size from parents to offspring, confirming that variation is heritable.</p> Signup and view all the answers

Why are there still finches with small beaks, if during droughts, small-beaked finches are less likely to survive?

<p>Even though small-beaked finches face challenges during droughts, they are not entirely eliminated. Natural selection favors the most well-adapted individuals in a given environment, but it does not eliminate all other variations. In times of plenty, smaller beaks might present advantages, such as better efficiency in consuming smaller seeds. This variation allows for a greater diversity within the population, providing resilience and flexibility to adapt to changing environmental conditions.</p> Signup and view all the answers

What is wrong with the argument that an eye is far too complex to have arisen by chance?

<p>The argument that an eye is too complex to have evolved by chance ignores the principles of gradual evolution. Evolution is a slow, step-by-step process. Each step can be advantageous, even if it is a small improvement over the previous state. For example, even a simple light-sensitive patch of cells can be beneficial, providing a slight advantage in detecting predators or resources. Over time, through selection of advantageous variations, these simple structures become more intricate and complex, forming the intricately designed eyes we see today. The intermediate forms are not useless; they provide adaptive advantages in their respective environments, demonstrating the gradual progression of evolution.</p> Signup and view all the answers

Why is “evolution a tinkerer, not an engineer”?

<p>Evolution is a process of small modifications of existing structures, not a process of designing entirely new systems. It works by repurposing existing components and features, building complexity over time through gradual changes. This is analogous to a tinkerer who modifies and reassembles existing components, rather than an engineer who designs and builds new structures from scratch.</p> Signup and view all the answers

What is an allele?

<p>An allele is a specific variant of a gene, responsible for determining a specific trait. Each individual carries two alleles for each gene, one inherited from each parent.</p> Signup and view all the answers

What is a dominant trait?

<p>A dominant trait is a trait that is expressed even when only one copy of the dominant allele is present. In other words, the dominant allele masks the expression of the recessive allele.</p> Signup and view all the answers

What is a genotype?

<p>A genotype is the genetic makeup of an individual for a specific trait. It refers to the combination of alleles that an individual possesses for a given gene.</p> Signup and view all the answers

What is a locus?

<p>A locus is the specific physical location of a gene or allele on a chromosome.</p> Signup and view all the answers

What is a monohybrid cross?

<p>A monohybrid cross is a type of genetic cross that involves examining the inheritance of a single trait by crossing two individuals that differ in that trait.</p> Signup and view all the answers

What are polygenic traits?

<p>Polygenic traits are traits that are influenced by multiple genes working together.</p> Signup and view all the answers

What is the principle of segregation?

<p>The principle of segregation states that during gamete formation, alleles for a trait separate, so that each gamete receives only one allele from each pair. During fertilization, the pairs reunite to determine the expression of the trait in the offspring.</p> Signup and view all the answers

What does TT, Tt, and tt represent?

<p>TT represents a homozygous dominant genotype for a trait, Tt represents a heterozygous genotype, and tt represents a homozygous recessive genotype. The capital letter indicates the dominant allele, while the lowercase letter indicates the recessive allele.</p> Signup and view all the answers

Are dominant alleles always the most common in a population?

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

What are amino acids and their importance?

<p>Amino acids are the building blocks of proteins, essential for various functions in the body. They are linked together in chains to form proteins.</p> Signup and view all the answers

What is an anticodon?

<p>An anticodon is a sequence of three nucleotides located on a transfer RNA (tRNA) molecule. It is complementary to a specific codon on messenger RNA (mRNA), enabling the tRNA to transport the appropriate amino acid to the ribosome during protein synthesis.</p> Signup and view all the answers

What is base pairing in DNA, and what are the names of the bases?

<p>Base pairing in DNA involves the formation of hydrogen bonds between complementary nitrogenous bases. Adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).</p> Signup and view all the answers

What is crossing over?

<p>Crossing over is an exchange of genetic material between homologous chromosomes during meiosis (the process of cell division that produces sex cells). It involves the swapping of segments of DNA, resulting in new combinations of alleles and increased genetic diversity in offspring.</p> Signup and view all the answers

What does diploid refer to?

<p>Diploid refers to a cell or organism that has two sets of chromosomes, one set inherited from each parent.</p> Signup and view all the answers

What does DNA stand for, and what is its role?

<p>DNA stands for deoxyribonucleic acid. It is the molecule that carries the genetic instructions for the development, function, and growth of all living organisms.</p> Signup and view all the answers

Flashcards

Genetic Bottleneck

A sharp reduction in population size leading to different allele frequencies in survivors.

Founder Effect

When a small group moves to a new area, changing allele composition.

Gene Flow

The movement of alleles between populations through interbreeding.

Mutation

The only source of new genetic variation within a species.

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Effects of Mutation

Mutations can lead to non-viable zygotes, neutral effects, improved functions, or new functions.

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Microevolution

Changes in allele frequencies within a population over time.

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Mitosis

Cell division resulting in two identical diploid cells.

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Meiosis

Production of four haploid gametes from one diploid cell.

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Homologous Chromosomes

Pairs of chromosomes containing the same sets of genes but not identical.

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Sister Chromatids

Identically copied chromosomes from DNA replication.

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Ribosome

An intracellular structure where protein synthesis occurs.

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Translation

The process that synthesizes proteins based on mRNA sequences.

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Transcription

The process of making mRNA from a DNA template.

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Allele Frequency

The ratio of a specific allele compared to the total number of alleles in a population.

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Heterozygous

Having two different alleles at a locus.

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Homozygous

Having two of the same alleles at a locus.

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Phenotype

The observable characteristics or traits of an organism.

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Genotype

The genetic constitution of an organism.

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Diploid

Cells containing two complete sets of chromosomes, one from each parent.

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Haploid

Cells containing a single set of chromosomes (n).

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Crossing Over

Exchange of genetic material between homologous chromosomes during meiosis.

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Codon

A sequence of three nucleotides coding for an amino acid.

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Anticodon

A trinucleotide sequence that pairs with a codon during protein synthesis.

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Occam's Razor

The principle suggesting the simplest explanation is usually the correct one.

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Natural Selection

The process where traits that improve survival and reproduction become more common.

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Theory

A scientific explanation that has been extensively tested and supported by data.

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Pleiotropy

A single genetic locus affecting multiple phenotypic traits.

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Dominant Trait

A trait that is expressed even when only one copy of the allele is present.

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Recessive Trait

A trait that is expressed only when two copies of the allele are present.

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Independent Assortment

Mendel's principle that alleles for different traits are distributed independently during gamete formation.

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Study Notes

Genetic Bottleneck vs. Founder Effect

  • Founder effect: Movement of alleles from one location to another altering allele frequencies, distinct from bottleneck.
  • Bottleneck: Changes in allele frequencies due to survivors of events like natural disasters, population growth.

Gene Flow

  • Gene flow: The movement of alleles between neighboring populations through interbreeding, increasing similarities in allele frequencies among populations.

Mutation

  • Mutation: The only source of new genetic variation in a species.
  • Mutations' Consequences:
    • Non-viable zygote (unsuccessful reproduction)
    • Protein non-functional
    • Reduced protein function
    • Neutral effect (most common)
    • Improved protein function
    • New protein function
  • Mutations are not always bad or beneficial.

Gene Pool

  • Gene pool: All alleles within a population.

Microevolution

  • Microevolution: Changes in allele frequencies within a population.

Population

  • Population: A community of individuals of the same species capable of interbreeding.

Mitosis & Meiosis

  • Mitosis:
  • Diploid cell starts with 46 chromosomes.
  • Replicates chromosomes forming sister chromatids.
  • Sister chromatids separate.
  • Cell divides, resulting in two identical diploid cells (46 chromosomes).
  • Meiosis:
  • Diploid cell with 46 chromosomes begins.
  • Chromosomes replicate and become sister chromatids.
  • Sister chromatids separate.
  • Cell divides twice to produce four haploid cells (23 chromosomes each), involved in sexual reproduction.

Chromosomes in Humans

  • Humans have 23 pairs of chromosomes.
  • Somatic cells have chromosomes in pairs (one inherited from each parent).

Homologous Chromosomes vs. Sister Chromatids

  • Homologous Chromosomes: Two different chromosomes carrying the same genes, but not necessarily identical.
  • Sister Chromatids: Genetically identical copies of a single chromosome formed during DNA replication.

Nucleotide

  • Nucleotide: Basic building block of nucleic acids (DNA and RNA).

Protein Functions & Structure

  • Protein functions: Structural, antibody production, enzymatic activity, signaling.
  • Protein composition: Made of amino acids linked together.

Protein Synthesis (Translation & Transcription)

  • Transcription: DNA sequence copied into mRNA.
  • Translation: mRNA sequence translated into a protein sequence.

DNA Replication

  • DNA replication: Unzipping of the double helix and separation of DNA strands to create identical copies.

Independent Assortment

  • Independent assortment: Alleles for different traits segregate independently during gamete formation.

Allele Frequency

  • Allele frequency: The proportion of a specific allele compared to the total number of alleles in a population.

Hypothesis & Theory

  • Hypothesis: An educated guess or prediction about a relationship between variables.
  • Theory: A hypothesis supported by a significant amount of data.

Scientific Method

  • Observation: Generating a question based on observations.
  • Hypothesis: Proposed explanation for the observation.
  • Testable Predictions: Expected outcomes if the hypothesis is correct.
  • Experiments: Testing and validating predictions.

Natural Selection

  • Individual selection is often more impactful than group selection.
  • Natural selection acts on individuals but results in changes to populations.

Heterozygous & Homozygous

  • Heterozygous: Having two different alleles for a trait.
  • Homozygous: Having two identical alleles for a trait. Dominant or recessive.

Trait Inheritance (Recessive Traits)

Recessive trait: An individual expressing a recessive trait must have two copies of the recessive allele.

Gene Flow vs. Natural Selection

  • Mutations, gene flow, and genetic drift are random processes.
  • Natural selection favors alleles that increase survival and reproduction.

Continuous Variation

  • Multiple genes can determine traits resulting in continuous variation rather than distinct phenotypes.

Occam's Razor

  • Simplest explanation is most likely correct.

Predictions

  • Predictions: Statements of what will happen next in a process or event.

Darwin's Observations

  • Fossils: Species change over time.
  • Flora/Fauna: Similar/different species exist in different locations.

Darwin's Postulates for Natural Selection

  • Struggle for existence (more individuals produced than can survive).
  • Variation among individuals (some are more suited for their environment).
  • Inheritance (variation in characteristics can be inherited).

Other Important Terms

  • Allele: Variant form of a gene
  • Dominant trait: Trait expressed even if only one copy of the allele is present.
  • Recessive trait: Trait expressed only if both the alleles are present.
  • Gene: A sequence of DNA that codes for a specific protein.
  • Genotype: The genetic makeup of an organism for a particular trait.
  • Phenotype: The observable characteristics of an organism for a particular trait.
  • mRNA: Messenger RNA
  • rRNA: Ribosomal RNA
  • tRNA Transfer RNA
  • Amino Acids- building blocks of proteins
  • DNA: Deoxyribonucleic Acid
  • Gametes (sex cells): Haploid cells (reproductive cells)

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