Cell Biology Quiz

Chromosome Transmission During Cell Division and Sexual Reproduction

• Learning changes everything.
• Chapter 2 covers chromosome transmission during cell division and sexual reproduction.
• Topics include features of chromosomes, karyotypes, cell division (prokaryotes and eukaryotes), mitosis, meiosis, and mechanisms of sex determination.

General Features of Chromosomes

• Chromosomes are structures within living cells that contain genetic material (genes).
• They are composed of DNA, the genetic material, and proteins that provide an organized structure.
• In eukaryotes, the DNA-protein complex is called chromatin.
• Eukaryotic chromosomes may also contain non-coding RNA.

Two Types of Cells

• Two main types of cells are prokaryotes and eukaryotes.
• Prokaryotes include bacteria and archaea.
• Eukaryotes include protists, fungi, plants, and animals.
• Prokaryotic cells lack a nucleus and membrane-bound organelles.
• Eukaryotic cells contain a nucleus and membrane-bound organelles.

Features of a Prokaryotic Cell

• A typical prokaryotic cell, like Escherichia coli, displays an outer membrane and flagellum.
• The nucleoid contains the bacterial chromosome.
• Ribosomes are present within the cytoplasm

Features of a Eukaryotic Cell

• Eukaryotic cells contain structures like microfilaments, the Golgi body, a nuclear envelope, nucleolus, chromosomal DNA, and the nucleus.
• Other structures include mitochondria, mitochondria DNA, centrioles, microtubules, polyribosomes, ribosomes, the rough endoplasmic reticulum, cytoplasm, membrane proteins, the plasma membrane, smooth endoplasmic reticulum, and lysosomes.

Two Types of Animal Cells

• Animal cells are categorized into somatic and germ cells.
• Somatic cells include body cells and blood cells, excluding gametes.
• Germ cells include gametes (sperm and egg cells).

Cytogenetics

• Cytogenetics involves the microscopic examination of chromosomes.
• It aids in identifying individuals with abnormal chromosome numbers or structures.
• It helps distinguish closely related species.
• Karyotypes are created for a diploid human cell, displaying two sets of chromosomes.

Most Eukaryotic Species are Diploid

• Diploid species possess two sets of chromosomes.
• Humans have 46 total chromosomes (23 per set).
• Dogs have 78 total chromosomes (39 per set).
• Fruit flies have 8 total chromosomes (4 per set).

Eukaryotic Chromosomes are Inherited in Sets

• Homologous chromosomes (pairs) have nearly identical size and banding patterns/centromere locations.
• Homologous chromosomes share the same genes, but not necessarily the same alleles.
• DNA sequences are remarkably similar (usually less than 1% difference).

Sex Chromosomes

• Sex chromosomes (X and Y) are not homologous.
• They differ in size and genetic composition.
• They have short regions of homology (shared genes).
• The physical location of a gene on a chromosome is called its locus.

Homologous Chromosomes Have the Same Loci

• Gene loci are locations on homologous chromosomes.
• Genotypes AA/Bb/cc describe the alleles at corresponding loci.

Cell Division

• Cell division serves two primary functions: asexual reproduction in single-celled organisms like bacteria, amoeba, and yeast; and enabling multicellularity in more complex organisms such as humans.

Binary Fission

• Binary fission is a process of asexual reproduction in bacteria.
• The bacterial cell replicates its chromosome before dividing into two daughter cells.
• FtsZ protein is crucial in creating the new cell wall.

The Eukaryotic Cell Cycle

• Cell division in eukaryotes involves complex replication and sorting processes, more intricate than binary fission.
• These processes involve distinct stages, such as G1, S, G2, and M (mitosis) phases.

Chromosomes Following DNA Replication

• Replicated chromosomes are composed of two identical sister chromatids joined by a centromere.

Chromatids and Chromosomes During Mitosis

• A human cell with 46 chromosomes in G1 phase would result in 46 pairs of sister chromatids after S phase.
• The terms "chromosome" and "chromatid" are context-dependent.

Mitosis

• Mitosis has the primary purpose of distributing replicated chromosomes to the two daughter cells.
• It comprises five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

Structure of the Mitotic Spindle

• The mitotic spindle comprises structures like the spindle pole (centrosome with centrioles), astral microtubules, polar microtubules, and kinetochore microtubules.

Entire Process of Mitosis

• Visualized images depict the phases of mitosis, showcasing progression from Interphase to Prophase, Prometaphase, Metaphase, Anaphase, and Telophase/Cytokinesis.

Cytokinesis

• Cytokinesis typically follows mitosis in most cells
• In animal cells, a cleavage furrow forms.
• In plant cells, a cell plate forms.

Meiosis

• Meiosis enables sexual reproduction in eukaryotes.
• Diploid parents make haploid gametes with half the genetic material.
• These gametes fuse during fertilization.

Meiosis Produces Haploid Gametes

• Gametes are haploid with one set of chromosomes (1n).
• Diploid cells (2n), like human cells with 46 chromosomes, have two sets.
• Human gametes, sperm and eggs, have 23 chromosomes each.
• Haploid cells are produced from diploid cells during meiosis.

Meiosis 2

• After meiosis 1, followed frequently by cytokinesis, meiosis 2 proceeds,
• The chromosome content is reduced by meiosis.
• A diploid organism with 6 chromosomes starts with 12 chromatids (joined as 6 pairs of sister chromatids) in mitosis.
• Meiosis 2 begins with 6 chromatids (joined as three pairs of sister chromatids).

Entire Process of Meiosis

• Depicted figures demonstrate the stepwise stages of meiosis during which the chromosome number is reduced from diploid to haploid.

Mitosis versus Meiosis

• Mitosis produces two genetically identical diploid daughter cells.
• Meiosis produces four genetically unique haploid daughter cells.

Sexual Reproduction

• Sexual reproduction is a common method of reproduction in eukaryotes, involving gametogenesis.
• Parents produce haploid gametes through gametogenesis (a process reducing the genetic material to half).
• Gametes fuse during fertilization to create a new diploid organism.

Types of Gametes

• Simple eukaryotic species are isogamous, producing morphologically similar gametes.
• Most eukaryotic species are heterogamous, with morphologically different gametes: sperm (relatively small and mobile) and egg/ovum (usually large and non-motile).

Spermatogenesis

• Spermatogenesis is the process of sperm production.
• A diagram illustrates the steps from a primary spermatocyte (diploid) to spermatids and eventually sperm cells (haploid) through two divisions (Meiosis I and Meiosis II).

Oogenesis

• Oogenesis is the process of egg cell production.
• Oogenesis differs from spermatogenesis in being asymmetrical, producing polar bodies with limited cytoplasm and one functional egg (haploid).

The Chromosome Theory of Inheritance

• The chromosome theory describes how chromosome transmission reflects Mendelian inheritance patterns.
• It establishes chromosomes as carriers and transmitters of genetic traits.

Basis for the Chromosome Theory of Inheritance

• The theory arose from three lines of inquiry: analysis of trait transmission across generations, investigation of inheritance's material basis, and microscopic observation of mitosis, meiosis, and fertilization.

Sex Determination

• Chromosomes influence sex determination in many animal species.
• Other factors, such as temperature, can determine sex for some reptiles and fish.

Human Sex Determination

• Humans have 46 chromosomes (44 autosomes and 2 sex chromosomes).
• Males have one X and one Y chromosome (heterogametic); females have two X chromosomes (homogametic).
• The Y chromosome is crucial to male determination.

X-O Sex Determination in Some Insects

• In some insects, the ratio of X chromosomes (X) to autosomes (A) determines sex. An X/A ratio of 0.5 results in a male; 1.0, a female.

Z-W Sex Determination in Birds and Some Fish

• In birds and some fish, males are homogametic (ZZ) and females are heterogametic (ZW).

Haplodiploid Sex Determination in Bees

• In bees, males (drones) are haploid, originating from unfertilized eggs.
• Females (worker bees and queen bees) are diploid, developing from fertilized eggs.

Ch 2 Study Guide

• The study guide encompasses differentiating prokaryotic and eukaryotic cells, defining chromosomes, describing cytogenetics and karyotypes, summarizing cell division (binary fission and the eukaryotic cell cycle), differentiating mitosis and meiosis, distinguishing sexual and asexual reproduction, differentiating somatic and germ cells, describing gamete formation, contrasting isogamous and heterogamous species, and explaining various mechanisms of sex determination.