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?

One trait could completely disappear from the F1 generation. Signup and view all the answers

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

He established that traits are inherited through heritable factors. Signup and view all the answers

What does the basic structural unit of chromatin consist of?

Nucleosome made of histone proteins Signup and view all the answers

How many pairs of chromosomes do humans typically have?

46 Signup and view all the answers

What characterizes heterochromatin regions in chromosomes?

Gene-poor areas Signup and view all the answers

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

Karyotype Signup and view all the answers

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

Interphase Signup and view all the answers

What is the ploidy of gametes in humans?

Haploid Signup and view all the answers

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

H1 Signup and view all the answers

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

The number of chromosomes Signup and view all the answers

What does the law of segregation state about gamete production?

One gene copy is randomly allocated to each gamete. Signup and view all the answers

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

Behavior of chromosomes can explain Mendel's laws. Signup and view all the answers

Which observation supports the chromosome theory of inheritance?

Homologous chromosomes come from both parents. Signup and view all the answers

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

Different chromosomes segregate independently during meiosis. Signup and view all the answers

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

At specific positions on chromosomes. Signup and view all the answers

What happens to homologous chromosomes during meiosis?

They separate, leading to genetic diversity. Signup and view all the answers

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

Genes are inherited in pairs, similar to chromosomes. Signup and view all the answers

Which statement is true about gene allocation during gamete formation?

Gametes receive only one gene copy randomly. Signup and view all the answers

What occurs during anaphase I?

Chromosomes in tetrads separate. Signup and view all the answers

What characterizes telophase I in meiosis?

A nuclear envelope may develop around the chromosome bundle. Signup and view all the answers

How does prophase II differ from prophase I?

Centromeres still hold sister chromatids together in prophase II. Signup and view all the answers

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

Sister chromatids are aligned at the center of the cell. Signup and view all the answers

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

They pause at telophase I for an extended period. Signup and view all the answers

What is a common feature of the anaphase I stage?

Homologous pairs move toward opposite poles. Signup and view all the answers

What distinguishes metaphase II from the metaphase of mitosis?

There are no homologous chromosomes present in metaphase II. Signup and view all the answers

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

They remain connected at the centromere. Signup and view all the answers

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

S phase Signup and view all the answers

What occurs during the G1 phase of interphase?

The cell grows and copies organelles Signup and view all the answers

What is the correct order of mitosis stages?

Prophase, Metaphase, Anaphase, Telophase Signup and view all the answers

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

To separate DNA during mitosis Signup and view all the answers

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

Interphase Signup and view all the answers

What is karyokinesis primarily concerned with?

Separation of the nuclear DNA Signup and view all the answers

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

Mitosis initiation Signup and view all the answers

What distinguishes cytokinesis in animal cells from plant cells?

The way cytoplasm is split between daughter cells Signup and view all the answers

What does Mendel's law of segregation state?

Paired unit factors segregate randomly during gamete formation. Signup and view all the answers

What was the purpose of Mendel's dihybrid crosses?

To study the inheritance patterns of two different genes. Signup and view all the answers

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

They assort independently of one another. Signup and view all the answers

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

9:3:3:1 Signup and view all the answers

What is a test cross used for?

To determine if an organism is heterozygous or homozygous. Signup and view all the answers

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

Random assortment and segregation of alleles. Signup and view all the answers

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

Genes can be inherited separately from other genes. Signup and view all the answers

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

Traits follow predictable patterns of inheritance. Signup and view all the answers

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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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.