Chromosome Transmission, Cell Division, and Mendelian Inheritance: Key Concepts and Examples

What are the main differences between prokaryotes and eukaryotes?

Prokaryotes are small, lack a nucleus and membrane-bound organelles, have circular DNA, and divide by binary fission. Eukaryotes have a nucleus, membrane-bound organelles, linear chromosomes, and undergo mitosis and meiosis.

What is a chromosome composed of?

A chromosome is composed of DNA and proteins (not lipids).

What are sister chromatids?

Sister chromatids are identical copies of a replicated chromosome joined at the centromere.

What are homologous chromosomes?

Homologous chromosomes are chromosomes that have the same genes but different alleles, one inherited from each parent.

Describe the process of binary fission in prokaryotes.

Binary fission involves replicating DNA, elongating the cell, forming a septum, and resulting in two identical daughter cells.

What are the phases of the eukaryotic cell cycle?

The eukaryotic cell cycle consists of G1 (growth), S (DNA replication), G2 (preparation), and M phase (mitosis + cytokinesis).

What happens during prophase of mitosis?

During prophase, chromosomes condense and become visible.

What is the significance of crossing over during meiosis?

Crossing over occurs in Prophase I and creates recombinant chromosomes, contributing to genetic variation.

What is independent assortment?

Independent assortment occurs in Metaphase I when homologous pairs align randomly, leading to variation in gametes.

What is the M checkpoint in the cell cycle?

The M checkpoint ensures that all chromosomes are attached to spindle fibers before separation to prevent nondisjunction.

What roles do cohesin, separase, securin, and shugoshin play in cell division?

Cohesin holds chromatids together, separase cuts cohesin, securin inhibits separase until the correct timing, and shugoshin protects centromeric cohesin during Meiosis I.

What are the main differences between spermatogenesis and oogenesis?

Spermatogenesis is continuous and produces 4 equal sperm, while oogenesis involves unequal cytokinesis, producing 1 ovum and polar bodies.

What are somatic cells and germ cells?

Somatic cells are body cells that undergo mitosis, while germ cells are gamete-producing cells that undergo meiosis.

Why were pea plants ideal for Mendel's experiments?

Pea plants had many varieties, allowed controlled mating, had a short generation time, produced large numbers of offspring, and exhibited clear traits.

What is the Law of Segregation?

The Law of Segregation states that two alleles for a trait separate during gamete formation, with each gamete receiving one allele.

What does the Law of Independent Assortment state?

The Law of Independent Assortment states that alleles of different genes assort independently due to random alignment of homologs in Metaphase I.

What is a Punnett square used for?

A Punnett square is used to predict the genotypes and phenotypes of offspring from genetic crosses.

What is the null hypothesis in a chi-square test?

The null hypothesis states that there is no significant difference between observed and expected data.

Who discovered sex-linked inheritance?

Thomas Hunt Morgan discovered sex-linked inheritance through his work with Drosophila (fruit flies).

What are wild-type and mutant alleles?

Wild-type alleles are common and functional, while mutant alleles are altered and may reduce function.

What is incomplete dominance?

Incomplete dominance occurs when a heterozygote displays an intermediate phenotype, such as red and white flowers producing pink flowers.

What is codominance?

Codominance occurs when both alleles are fully expressed, such as red and white flowers producing red flowers with white spots.

What is penetrance and expressivity?

Penetrance is the percentage of individuals showing a phenotype, while expressivity is the degree or intensity of that phenotype.

What are the symbols used in pedigrees?

In pedigrees, a square represents a male, a circle represents a female, shaded indicates affected individuals, and half-shaded indicates carriers.

What is the difference between autosomal dominant and autosomal recessive inheritance?

Autosomal dominant traits appear in every generation with affected individuals having affected parents, while autosomal recessive traits can skip generations with affected individuals often having carrier parents.

What is the primary difference between prokaryotes and eukaryotes?

Prokaryotes lack a nucleus and membrane-bound organelles, while eukaryotes have both.

What are chromosomes composed of?

Chromosomes are composed of DNA and proteins.

What is the function of the centromere?

The centromere serves as the attachment point for spindle fibers during cell division.

What is the role of cohesin in cell division?

Cohesin holds sister chromatids together until they are separated during anaphase.

What occurs during binary fission?

In binary fission, a prokaryotic cell replicates its chromosome, elongates, and divides into two identical daughter cells.

What is the outcome of meiosis I?

Meiosis I results in two haploid cells with duplicated chromosomes.

What is crossing over and when does it occur?

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis.

What is the purpose of a Punnett square?

A Punnett square is used to predict the genetic outcomes of a cross between two organisms.

What is pleiotropy?

Pleiotropy occurs when one gene affects multiple traits.

What are the symbols used in a pedigree chart?

A square represents a male, a circle represents a female, shaded shapes indicate affected individuals, and half-shaded shapes indicate carriers.

What is the difference between autosomal recessive and autosomal dominant inheritance?

In autosomal recessive inheritance, affected individuals can have unaffected parents, while in autosomal dominant inheritance, affected individuals must have an affected parent.

What is the significance of the spindle fiber checkpoint?

The spindle fiber checkpoint ensures that all chromosomes are properly attached to spindle fibers before sister chromatids separate.

What is the role of separase in cell division?

Separase is an enzyme that cleaves cohesin, allowing sister chromatids to separate during anaphase.

What is the outcome of meiosis II?

Meiosis II results in four haploid gametes with single chromatids.

What is the significance of environmental effects on genetics?

Environmental factors can influence the expression of certain alleles, such as temperature-sensitive alleles.

What is the difference between spermatogenesis and oogenesis?

Spermatogenesis produces four equal sperm, while oogenesis produces one ovum and polar bodies due to unequal cytokinesis.

What is the concept of genetic variation?

Genetic variation arises from processes such as crossing over, independent assortment, and random fertilization.

What is the role of shugoshin in meiosis?

Shugoshin protects centromeric cohesin during meiosis I, preventing premature separation of sister chromatids.