Genetics Unit 1
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Questions and Answers

What is the phenotypic ratio for a monohybrid cross between two heterozygous parents?

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

Down syndrome is caused by a missing chromosome.

False (B)

What is the Mendelian ratio for a dihybrid cross between two heterozygous parents?

9:3:3:1

A female with Turner syndrome has a _____ of the sex chromosomes.

<p>monosomy</p> Signup and view all the answers

Match the condition with its corresponding chromosome abnormality:

<p>Down syndrome = Trisomy 21 Turner syndrome = Monosomy of X Klinefelter syndrome = XXY Edwards syndrome = Trisomy 18</p> Signup and view all the answers

What is the main cause of allopatric speciation?

<p>Physical separation of populations (C)</p> Signup and view all the answers

Analogous structures share a common ancestor but serve similar functions.

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

What type of evidence of evolution involves studying the distribution of organisms in different geographical locations?

<p>Biogeography</p> Signup and view all the answers

The evolutionary links between species are illustrated through ________ fossils.

<p>transitional</p> Signup and view all the answers

Match the type of structure with its description:

<p>Homologous structures = Similar structures from a common ancestor with different functions Analogous structures = Different structures from different ancestors performing similar functions Vestigial structures = Remnants of structures that had important use in ancestors but are now functionless</p> Signup and view all the answers

Which of the following is NOT a factor that contributes to allopatric speciation?

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

Mules are an example of a hybrid that is typically fertile.

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

What defines sympatric speciation?

<p>Genetic or reproductive isolation within the same population</p> Signup and view all the answers

Species that have similar adaptations due to environmental factors, yet are not closely related, exhibit ________ similarity.

<p>convergent</p> Signup and view all the answers

Which mechanism prevents different species of frogs from mating successfully?

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

Hybrid sterility prevents different species from mating successfully.

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

What is the term for when male gametes do not recognize the eggs of a different species?

<p>Gametic isolation</p> Signup and view all the answers

The mating of sheep and goats may result in a zygote that is unable to develop properly, which is an example of __________.

<p>hybrid inviability</p> Signup and view all the answers

Match the reproductive isolation mechanism with its description:

<p>Temporal isolation = Different species breed at different times Habitat isolation = Species live in different habitats Mechanical isolation = Differences in reproductive structures Gametic isolation = Sperm and eggs do not recognize each other</p> Signup and view all the answers

Which of the following is an example of hybrid sterility?

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

Temporal isolation allows different species to mate successfully during the same time period.

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

Which reproductive isolation mechanism involves structural differences that prevent fertilization?

<p>Mechanical isolation</p> Signup and view all the answers

Some marine animals rely on __________ to ensure that their sperm fertilizes the eggs of their own species.

<p>chemical markers</p> Signup and view all the answers

What does natural selection primarily refer to?

<p>The environment selecting desirable traits (B)</p> Signup and view all the answers

Mimicry involves a harmful creature imitating a harmless one.

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

What is the primary difference between the bottleneck effect and the founder effect?

<p>The bottleneck effect involves a severe reduction in population size due to environmental stress, while the founder effect involves a small group establishing a new population.</p> Signup and view all the answers

The _______ adaptation of an organism includes its migration patterns and hibernation.

<p>behavioral</p> Signup and view all the answers

Match the adaptation types with their definitions:

<p>Behavioral adaptations = Responses to environmental cues Physiological adaptations = Internal processes within organisms Structural adaptations = Physical features for survival Mimicry = Harmless imitation of harmful species</p> Signup and view all the answers

Which of the following is an example of structural adaptation?

<p>Camouflage of a chameleon (D)</p> Signup and view all the answers

The founder effect occurs when a large group of individuals from a population establish a new population.

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

Flashcards

What is a gene?

A unit of heredity that is responsible for a particular trait. It is a segment of DNA that contains the instructions for building a protein or RNA molecule.

What is an allele?

A version of a gene. Different alleles for the same gene can lead to variations in a trait. For example, one allele for eye color could be for brown eyes, while another allele could be for blue eyes.

What is a Punnett square?

A diagram that helps predict the possible genotypes and phenotypes of offspring from a cross between two parents.

What is trisomy?

A condition where an individual has three copies of a specific chromosome instead of the usual two. Down syndrome, for example, is caused by trisomy 21.

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What is monosomy?

A condition where an individual has only one copy of a specific chromosome instead of the usual two. Turner syndrome is an example, caused by monosomy of the X chromosome.

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Adaptations

Traits that help an organism survive and reproduce in its environment.

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Structural Adaptation

A type of adaptation involving an organism's physical features. Examples include camouflage, sharp claws, or a beak suited for a specific food source.

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Physiological Adaptation

A type of adaptation that involves an organism's internal processes. Examples include venom production, temperature regulation, or poison resistance.

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Behavioral Adaptation

A type of adaptation involving how an organism behaves in response to its environment. Examples include migration, hibernation, and social behaviors.

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Bottleneck Effect

A situation where a dramatic reduction in population size leads to a loss of genetic diversity. This can occur due to events like diseases, natural disasters, or habitat destruction.

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Founder Effect

A situation where a small group of individuals from a larger population establish a new population, leading to a reduced genetic diversity compared to the original population.

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Mimicry

A harmless species mimicking the appearance of a harmful species to deter predators. This increases the harmless species' chances of survival.

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Behavioral Isolation

Different species have unique mating calls that attract only their own species. Example: male frogs.

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Temporal Isolation

Species breed at different times of the year (seasons, day/night). Example: Orchids bloom on different days.

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Habitat Isolation

Species occupy different habitats within a region despite being very similar. Example: mountain vs. eastern bluebirds.

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Mechanical Isolation

Structural differences in reproductive organs prevent successful fertilization. Example: snails with different shell orientations.

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Gametic Isolation

Sperm and eggs of different species are unable to recognize or fertilize each other. Example: marine animals releasing sperm and eggs into the water.

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Hybrid Inviability

Hybrid offspring (from different species) are unable to develop properly. Example: sheep and goat mating.

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Hybrid Sterility

Hybrid offspring are fertile but cannot reproduce. Example: mules (horse-donkey cross).

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Hybrid Breakdown

First generation hybrids are fertile but their offspring (second generation) can be sterile or weak. Example: cotton plants.

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Postzygotic Mechanisms

A hybrid offspring is sterile or has reduced survival rates due to genetic incompatibility. Example: a liger.

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Allopatric speciation

The formation of new species due to physical separation of populations, preventing gene flow and leading to gradual divergence over generations.

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Sympatric speciation

The formation of new species within the same geographic area, often due to genetic or reproductive isolation.

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Transitional fossil

A fossil that exhibits intermediate features between two groups of organisms, providing evidence of evolutionary transitions.

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Biogeography

The study of the geographic distribution of organisms, both past and present.

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Homologous structures

Structures in different species that share a common ancestor but have evolved different functions.

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Analogous structures

Structures in different species that have similar functions but evolved independently from different ancestors.

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Vestigial structures

Structures present in an organism that have lost their original function and are reduced or nonfunctional.

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Evidence of evolution

The accumulation of evidence from fossils, biogeography, anatomy, molecular biology, and embryology that supports the theory of evolution.

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Evolution

The concept that all living organisms are related through a shared common ancestor and have diversified over vast spans of time.

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Study Notes

Unit 1 Genetics

  • Allele: An alternate form of a gene, caused by differences in DNA sequences at a specific position within a gene. Examples include genes coding for eye color.
  • Chromosome: A physical structure storing genetic information, composed of long DNA strands coiled around proteins.
  • Sister Chromatid: Identical copies of chromatids formed by DNA replication of a chromosome, joined by a centromere.
  • Daughter Chromosome: Sister chromatids that have separated, becoming independent chromosomes.
  • Chromatin: The mixture of DNA and histone proteins, the uncoiled form of chromosomes.
  • Genotype: The combination of alleles (e.g., Cc or CC).
  • Phenotype: The physical appearance of an organism's traits (e.g., black fur).
  • F1 generation: The offspring of the parental (P) generation.
  • F2 generation: Offspring of the F1 generation.
  • Homozygous: Both alleles are identical (e.g., CC or cc).
  • Heterozygous: Alleles are different (e.g., Cc). The dominant allele is usually expressed.
  • Recessive: An allele or trait only expressed when both alleles are present (e.g., cc).
  • Dominant: Alleles that are represented regardless of the other allele (e.g. Cc or CC).
  • Nucleotide: The basic unit of DNA, consisting of a sugar group, phosphate group, and a nitrogenous base.
  • Nitrogenous base: A molecule containing nitrogen that's a component of DNA and RNA. These bases include adenine, thymine, cytosine, and guanine.

Cell Cycle/Mitosis

  • Mitosis: The process of asexual reproduction in body cells.
  • Interphase: (Not part of mitosis) The majority of a cell's life cycle, including growth and synthesizing molecules for the next phase. -G1: Major phase of growth. -S: DNA synthesis. -G2: More molecule synthesis.
  • Prophase: Chromatin condenses into chromosomes; centrioles move to poles, forming spindle fibers. Nuclear membrane begins to dissolve.
  • Metaphase: Spindle fibers attach to centromeres, moving chromosomes to the cell's center (equatorial plate).
  • Anaphase: Sister chromatids separate and move to opposite cell sides.
  • Telophase: Chromosomes decondense into chromatin; spindle fibers break down; nuclear membranes reform around each set of chromosomes. Cytokinesis takes place.

Meiosis

  • Meiosis: A type of cell division for sexual reproduction in testes and ovaries, producing gametes (sperm and eggs).
  • Two Goals:
    • Genetic reduction: Daughter cells (haploid) receive half the genetic material of the parent cell (diploid).
    • Genetic recombination: The shuffling of alleles in haploids results in genetic variation in the offspring.
  • Prophase I: Starts as a diploid cell (e.g., 46 ds chromosomes), where the nuclear membrane dissolves, centrioles move to poles to form spindle fibers, homologous chromosomes align (synapse), and the homologous chromosomes exchange DNA segments (crossing over).
  • Metaphase I: Homologous pairs align at the cell's equator.
  • Independent Assortment: Homologous chromosomes have multiple ways of being sorted and assorted into daughter cells.
  • Anaphase I: Homologous chromosomes separate and move to opposite poles.
  • Telophase I: Chromosomes uncoil into chromatin, spindle fibers break down, nuclear membranes reform, and cytokinesis occurs.
  • Meiosis II: The cells now haploid (e.g., 23 ds chromosomes), then duplicate, align at the cell's equator, separate chromosomes to opposite poles, re-form the nuclear membrane, and undergo cytokinesis to produce 4 haploid cells.

Inheritance Patterns

  • Mendelian Inheritance: Traits determined by a single gene with two alleles.
  • Sex-linked Inheritance: Traits linked to genes on sex chromosomes (e.g., colorblindness).
  • Codominance Inheritance: Both alleles fully expressed in heterozygous individuals.
  • Incomplete Dominance: Heterozygous phenotype is intermediate between two homozygous phenotypes.
  • Multiple Alleles: A gene with more than two alleles (e.g., ABO blood types).

Other Relevant Concepts

  • Karyotype: Arrangement of an organism's chromosomes.
  • Monosomy: Missing a chromosome.
  • Trisomy: Extra chromosome.
  • Nondisjunction: Error in meiosis where chromosomes fail to separate properly.
  • Crossing Over: Exchange of genetic material during prophase I of meiosis
  • Independent Assortment: Random arrangement of chromosomes during metaphase I of meiosis.
  • Nucleotides: Basic building blocks of DNA and RNA.

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