Principles of Genetics: Chapter One Quiz
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Questions and Answers

What ratio did Mendel observe for the violet to white flowers in the F2 generation?

  • 1:1
  • 3:1 (correct)
  • 4:1
  • 2:1

Which statement best describes Mendel's conclusion regarding traits from parents?

  • Traits are always expressed by both parent alleles.
  • Only dominant traits are passed on to the offspring.
  • Parents pass traits unchanged through heritable factors. (correct)
  • Parents pass on traits that can be altered in the offspring.

What does the dominant allele do in a heterozygous genotype according to Mendel's principles?

  • It fully expresses itself while masking the recessive allele. (correct)
  • It co-expresses with the recessive allele.
  • It has no effect on the recessive allele.
  • It can be masked by the recessive allele.

What characteristic did Mendel notice about one of the two traits during his experiments?

<p>One trait could completely disappear from the F1 generation. (A)</p> Signup and view all the answers

How did Mendel’s approach contribute to our understanding of genetics?

<p>He established that traits are inherited through heritable factors. (D)</p> Signup and view all the answers

What does the basic structural unit of chromatin consist of?

<p>Nucleosome made of histone proteins (A)</p> Signup and view all the answers

How many pairs of chromosomes do humans typically have?

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

What characterizes heterochromatin regions in chromosomes?

<p>Gene-poor areas (D)</p> Signup and view all the answers

What is the term for the complete set of chromosomes in an organism?

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

During which phase of the cell cycle does a eukaryotic cell grow and prepares for division?

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

What is the ploidy of gametes in humans?

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

Which histone protein is involved in binding the core particle to linker DNA?

<p>H1 (A)</p> Signup and view all the answers

In the karyotype of an organism, which feature is likely to vary significantly among different species?

<p>The number of chromosomes (C)</p> Signup and view all the answers

What does the law of segregation state about gamete production?

<p>One gene copy is randomly allocated to each gamete. (A)</p> Signup and view all the answers

What conclusion was drawn by Sutton and Boveri regarding Mendel's work?

<p>Behavior of chromosomes can explain Mendel's laws. (A)</p> Signup and view all the answers

Which observation supports the chromosome theory of inheritance?

<p>Homologous chromosomes come from both parents. (C)</p> Signup and view all the answers

How does the chromosome theory explain Mendel’s law of independent assortment?

<p>Different chromosomes segregate independently during meiosis. (D)</p> Signup and view all the answers

In the context of the chromosome theory, where are individual genes located?

<p>At specific positions on chromosomes. (C)</p> Signup and view all the answers

What happens to homologous chromosomes during meiosis?

<p>They separate, leading to genetic diversity. (B)</p> Signup and view all the answers

What is a key feature of Mendel's genes that is reflected in chromosome behavior?

<p>Genes are inherited in pairs, similar to chromosomes. (C)</p> Signup and view all the answers

Which statement is true about gene allocation during gamete formation?

<p>Gametes receive only one gene copy randomly. (B)</p> Signup and view all the answers

What occurs during anaphase I?

<p>Chromosomes in tetrads separate. (A)</p> Signup and view all the answers

What characterizes telophase I in meiosis?

<p>A nuclear envelope may develop around the chromosome bundle. (A)</p> Signup and view all the answers

How does prophase II differ from prophase I?

<p>Centromeres still hold sister chromatids together in prophase II. (A)</p> Signup and view all the answers

In metaphase II, what is the state of the chromosomes?

<p>Sister chromatids are aligned at the center of the cell. (D)</p> Signup and view all the answers

What happens to the germline cells in some organisms, such as human females, prior to birth?

<p>They pause at telophase I for an extended period. (B)</p> Signup and view all the answers

What is a common feature of the anaphase I stage?

<p>Homologous pairs move toward opposite poles. (B)</p> Signup and view all the answers

What distinguishes metaphase II from the metaphase of mitosis?

<p>There are no homologous chromosomes present in metaphase II. (C)</p> Signup and view all the answers

Which statement about the sister chromatids during anaphase I is accurate?

<p>They remain connected at the centromere. (C)</p> Signup and view all the answers

During which phase does the cell synthesize a complete copy of its DNA?

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

What occurs during the G1 phase of interphase?

<p>The cell grows and copies organelles (C)</p> Signup and view all the answers

What is the correct order of mitosis stages?

<p>Prophase, Metaphase, Anaphase, Telophase (A)</p> Signup and view all the answers

What is the primary function of the centrosome during the S phase?

<p>To separate DNA during mitosis (D)</p> Signup and view all the answers

In which phase do the daughter cells begin a new round of the cell cycle?

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

What is karyokinesis primarily concerned with?

<p>Separation of the nuclear DNA (C)</p> Signup and view all the answers

Which phase transitions the cell from G2 phase to M phase?

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

What distinguishes cytokinesis in animal cells from plant cells?

<p>The way cytoplasm is split between daughter cells (A)</p> Signup and view all the answers

What does Mendel's law of segregation state?

<p>Paired unit factors segregate randomly during gamete formation. (D)</p> Signup and view all the answers

What was the purpose of Mendel's dihybrid crosses?

<p>To study the inheritance patterns of two different genes. (A)</p> Signup and view all the answers

What does the law of independent assortment imply about hereditary factors?

<p>They assort independently of one another. (A)</p> Signup and view all the answers

Which ratio was observed by Mendel that led to the formulation of the law of independent assortment?

<p>9:3:3:1 (D)</p> Signup and view all the answers

What is a test cross used for?

<p>To determine if an organism is heterozygous or homozygous. (D)</p> Signup and view all the answers

In the context of Mendelian genetics, what does gamete formation involve?

<p>Random assortment and segregation of alleles. (D)</p> Signup and view all the answers

Which statement best describes the relationship between genes during independent assortment?

<p>Genes can be inherited separately from other genes. (C)</p> Signup and view all the answers

What conclusion can be drawn from Mendel's experiments regarding traits?

<p>Traits follow predictable patterns of inheritance. (D)</p> Signup and view all the answers

Flashcards

Alleles

A pair of genes that control a single trait, such as flower color.

F1 Generation

The offspring of a cross between two genetically different parents.

F2 Generation

The offspring produced from self-fertilization of the F1 generation.

Dominant Allele

The allele that masks the expression of the other allele in a heterozygous state.

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Recessive Allele

The allele whose expression is masked by the dominant allele in a heterozygous state.

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Law of Segregation

During gamete (sperm or egg) formation, each cell receives only one copy of each gene from the pair.

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Law of Independent Assortment

Genes for different traits are inherited independently of each other. For example, the inheritance of eye color doesn't influence the inheritance of hair color.

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Chromosomal Theory of Inheritance

Genes are located at specific positions on chromosomes. The behavior of chromosomes during meiosis explains the patterns of inheritance observed by Mendel.

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Homologous Chromosomes

Chromosomes, like Mendel's genes, come in pairs. One member of the pair comes from the mother, and one from the father.

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Segregation of Homologous Chromosomes

During meiosis, homologous chromosomes separate, ensuring each sperm or egg cell receives only one copy of each chromosome.

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Mendel's Law of Segregation (First Law of Inheritance)

During gamete formation, paired alleles separate randomly, meaning each gamete receives only one allele from each pair.

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Mendel's Law of Independent Assortment (Second Law of Inheritance)

This law states that alleles for different traits assort independently of each other during gamete formation. They are not inherited as a unit.

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Dihybrid Cross

A cross between two individuals who are heterozygous for two different traits.

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9:3:3:1 Phenotypic Ratio

A 9:3:3:1 phenotypic ratio is observed in the offspring of a dihybrid cross. This ratio is expected when the alleles for each trait assort independently of each other.

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Test Cross

A cross between an individual with an unknown genotype for a particular trait and a homozygous recessive individual.

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Unknown Genotype

An organism with an unknown genotype. In a test cross, this is the organism with the dominant phenotype.

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Homozygous

An organism with two copies of the same allele for a specific trait.

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Heterozygous

An organism with two different alleles for a specific trait.

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What is a nucleosome?

The basic unit of chromatin, composed of an octameric histone core (H2A, H2B, H3, H4) wrapped by DNA in segments of approximately 200 base pairs.

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What is a karyotype?

The complete set of chromosomes in an organism, characterized by the number and structure of chromosomes.

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What is ploidy?

The number of sets of chromosomes in the nucleus of an organism.

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What are diploid cells?

Cells with two sets of chromosomes, one from each parent.

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What are haploid cells?

Cells with one set of chromosomes, found in germ cells (sperm and egg).

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What is heterochromatin?

Densely packed regions of DNA in the nucleus, often containing fewer genes and staining more intensely.

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What is euchromatin?

Loosely packed regions of DNA in the nucleus, often containing more genes and staining less intensely.

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What is the cell cycle?

A series of events that occur in a cell as it grows and divides, including interphase and mitosis (M phase).

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Interphase

The period in the cell cycle where the cell grows, duplicates its DNA, and prepares for division.

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M Phase (Mitotic Phase)

The phase where the cell divides its DNA and cytoplasm into two new cells.

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G1 Phase

The first gap phase of interphase where the cell grows, copies organelles, and prepares for DNA replication.

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S Phase

The phase of interphase where the cell replicates its DNA, ensuring each new cell receives a complete copy.

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G2 Phase

The second gap phase of interphase where the cell prepares for mitosis by growing further and making proteins.

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Karyokinesis

The process during M phase where the nucleus divides, separating the replicated chromosomes into two daughter nuclei.

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Cytokinesis

The process during M phase where the cytoplasm divides, forming two new daughter cells.

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Mitosis

The process of cell division where the replicated chromosomes are separated and two genetically identical daughter cells are formed.

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Anaphase I

The phase of meiosis I where homologous chromosome pairs move towards opposite poles of the cell. Each tetrad separates, but sister chromatids remain connected.

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Telophase I

The phase of meiosis I where the chromosomes partially decondense and the cell divides into two daughter cells. The bundle of chromosomes may develop a nuclear envelope.

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Meiosis I in Germline Cells

The first four stages of meiosis (Prophase I, Metaphase I, Anaphase I, and Telophase I) that occur in germline cells before birth in some organisms, such as human females. These cells are arrested at Telophase I until needed for reproduction.

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Continuous Meiosis II

In some organisms, the second round of meiosis starts immediately after Telophase I, without a significant pause.

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Prophase II

The phase of meiosis II where chromosomes condense, the spindle apparatus moves them to the middle of the cell, and the sister chromatids stay connected.

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Metaphase II

The phase of meiosis II where chromosomes align at the center of the cell. This is similar to mitosis metaphase, but without homologous pairs aligned together.

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Difference between Metaphase II and Mitosis Metaphase

The main difference between Metaphase II and mitosis metaphase is the absence of homologous pairs lined up together in Metaphase II.

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Anaphase II

The final stage of meiosis II, where the centromeres separate, sister chromatids move to opposite poles, and the cell divides into two daughter cells. Each daughter cell contains one chromatid from each original chromosome.

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Study Notes

Principles of Genetics (BIOL 4041)

  • Course offered by the Department of Biology, College of Science, Bahir Dar University
  • Instructor: Sileshi A., Ph.D.
  • Date: December 20, 2024

Chapter One: Introduction

  • What is Genetics?: The study of trait inheritance across generations, variations at molecular, individual, and population levels, and species evolution.
  • Genetics Definition: The science of coming into being. Coined by William Bateson (1905).
  • Genes as Hereditary Vehicles: Units of biological information serving as hereditary vehicles.

Branches of Genetics

  • Transmission Genetics: Mechanisms of gene transmission and recombination across generations.
  • Molecular Genetics: Structure, function, replication, transcription, translation, and regulation of genes on a molecular level.
  • Population Genetics: Behavior and distribution of genes in natural populations.

Applications of Genetics

  • Agriculture: Crop and animal improvement (breeding).
  • Medicine: Molecular basis of diseases, diagnostics (rapid, cheap, and sensitive), and pharmaceuticals.
  • Forensics: DNA fingerprinting for criminal and court cases.
  • Eugenics: Misuse of genetic knowledge on human species (e.g., segregation).
  • Euphenics: Medical/genetic interventions to mitigate the impact of defective genotypes on individuals.

Historical Milestones

  • Modern Genetics as Young Field: Relatively a young field, only around a century old.Established as distinct science in 1900.
  • Mendel's Contribution: Gregor Mendel's work on garden peas, rediscovered in 1900. Mendel is the father of genetics.
  • Pre-Mendelian Ideas: Hippocrates (500-400 BC), Aristotle (384-322 BC), and theories of inheritance.
  • Pre-Mendelian Theories: Epigenesis, Pre-formation, and Pangenesis.

Mendelian Experiments & Principles

  • Experimental Methodology: Selecting and analyzing traits in garden peas.
  • Mendelian Traits: Plant height, seed coat color, flower position, pod shape, seed color, and seed shape.
  • Mendel's Success: Choosing a model system (garden pea), careful experimentation, thorough record-keeping, and employing mathematical models for data analysis.
  • Concepts: Alternative versions of genes (alleles), dominance/recessive alleles, and the law of segregation and independent assortment.

The Law of Segregation

  • Genes as Pairs: Each parent contributes one copy of each gene.
  • Particulate Nature of Genes: Hereditary material is particulate.
  • Gamete Formation: Paired factors (genes) are segregated randomly during gamete formation.
  • Predicting traits from Parents: The law underlies the prediction of traits in offspring.

The Law of Independent Assortment

  • Inheritance of different traits: Genes on different pairs of homologous chromosmes assort independently of each other.
  • Dihybrid crosses: Experiments that determine if traits are transmitted independently or are linked.
  • Gamete Combination Ratios: Observing ratios in dihybrid crosses confirms independent assortment of genes.

Test Crosses

  • Determining Genotype: Establishing whether an organism is homozygous or heterozygous for a dominant trait.
  • Phenotype/Genotype Ratio: A key confirmation of Mendel's laws of inheritance from test cross experiments.

Monohybrid Crosses

  • Understanding Inheritance: Observing ratios of traits in the F1 and F2 offspring to deduce parental genotype.
  • Ratio in F1/F2: Key to understanding the principles of inheritance as observed in offspring from parent genotypes.

Exceptions to Mendel's Laws/ Rules

  • Incomplete Dominance: An intermediate phenotype is produced when both alleles for a gene are present
  • Multiple Alleles: Genes can have multiple possible alleles (versions).
  • Codominance: Both alleles for a gene are fully expressed in the heterozygote.
  • Pleiotropy: A single gene affects multiple traits.
  • Lethal Alleles: Alleles that cause death when present and/or the resulting combination.
  • Sex Linkage: Inheritance patterns differ for genes located on sex chromosomes.

The Cytological Basis of Inheritance

  • Location of genes: Chromosomes are the location of genes
  • Meiosis: A special type of cell division responsible for germ cell production
  • Mendel's work: The chromosome, through the behavior of chromosomes during meiosis.
  • Chromosome theory of inheritance: Putting Mendel's ideas in the context of chromosomes' function.

The Cell Cycle

  • Interphase: Period of cell growth and preparation for division: G1, S, G2 phases.
  • M phase (Mitosis): Active cell division.
  • Mitosis stages: Prophase, metaphase, anaphase, telophase
  • Significance of Mitosis: Cell division for growth, repair, and asexual reproduction
  • Cytokinesis: Division of the cytoplasm and organelles, following mitosis, in animal and plant cells.
  • G0 phase: A non-dividing state for some cells.

Meiosis

  • Sexual Reproduction: Cell division in sexual reproduction; halving the chromosome number
  • Meiosis process stages: Prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, and telophase II.
  • Significance: Formation of gametes (sperm and egg) with half the chromosome of somatic cells.

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Principles of Genetics (Biol 4041) PDF

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Test your understanding of the fundamental concepts in genetics. This quiz covers topics such as the definition of genetics, heredity, and various branches including transmission, molecular, and population genetics. Explore how these concepts apply to real-world scenarios in agriculture and beyond.

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