Biology Unit 2

Cell Theory

The foundational scientific principle stating that all living organisms are composed of one or more cells, cells are the basic unit of life, and all cells arise from pre-existing cells.

Genome

The complete set of genetic information encoded in the DNA of an organism, encompassing all of its genes.

Types of Cells based on Chromosome Structure

Prokaryotes typically have a single circular DNA molecule, while eukaryotes possess multiple linear DNA molecules organized into chromosomes.

Unicellular Organism Process

Unicellular organisms primarily undergo a process of reproduction, which can be asexual through methods like binary fission.

DNA in Chromosomes

DNA is tightly coiled around histone proteins to form chromatins that condense into chromosomes during cell division, ensuring organized genetic material distribution.

Haploid vs. Diploid Cells

Haploid cells contain one complete set of chromosomes (n), while diploid cells contain two complete sets of homologous chromosomes (2n), one inherited from each parent.

S Phase of Cell Cycle

The specific phase in the cell cycle dedicated to DNA replication, wherein each chromosome is duplicated to ensure proper genetic content for daughter cells.

Mitosis

A cellular process wherein the nucleus divides to produce two genetically identical daughter cells, maintaining the original cell's chromosome number.

Prophase of Mitosis

The initial stage of mitosis where chromosomes condense and become visible, the mitotic spindle begins to form, and the nuclear envelope disintegrates.

Mitotic Spindle

A dynamic structure composed of microtubules that facilitates the separation of chromosomes during cell division.

Stages of Meiosis

Meiosis occurs in two consecutive stages: Meiosis I (includes prophase I, metaphase I, anaphase I, telophase I) followed by Meiosis II (including prophase II, metaphase II, anaphase II, and telophase II).

Sexual Reproduction and Genetic Variation

The process of sexual reproduction introduces genetic variation by combining genes from two parents, leading to offspring with diverse genetic traits.

Mendel’s Law of Segregation

The genetic principle that during the formation of gametes, the alleles for a gene segregate from each other so that each gamete carries only one allele for each gene.

Monohybrid Cross

A genetic breeding experiment involving two parents that differ in a single trait, used to study inheritance patterns.

RNA Polymerase in Transcription

An enzyme that synthesizes RNA from a DNA template, initiating transcription by binding to the promoter and unwinding the DNA strands.

tRNA in Translation

Transfer RNA (tRNA) is responsible for bringing the correct amino acids to the ribosome during protein synthesis, matching specific codons on the mRNA strand.

Purpose of PCR

Polymerase Chain Reaction (PCR) is a technique used to amplify a specific segment of DNA, generating numerous copies for analysis or experimentation.

Eukaryotic vs. Prokaryotic Gene Regulation

Eukaryotic gene regulation is more complex than that of prokaryotes, involving multiple regulatory mechanisms including chromatin structure changes and various post-transcriptional modifications.

Significance of Gel Electrophoresis

A laboratory technique employed to separate DNA fragments by size, allowing researchers to analyze genetic material and confirm results from PCR.

Griffith’s Experiment

An influential experiment demonstrating that DNA serves as the genetic material through the process of transformation in bacteria.

Common Method for DNA Sequencing

Dideoxyribonucleotide chain termination sequencing, commonly used to determine the exact sequence of nucleotides in a DNA molecule.

Cytokinesis

The final stage of cell division where the cytoplasm divides, resulting in two separate daughter cells following mitosis or meiosis.

Mitosis vs. Meiosis in Daughter Cells

Mitosis results in two genetically identical diploid daughter cells, while meiosis generates four genetically diverse haploid daughter cells.

Sister Chromatids

Identical copies created by the replication of a chromosome, connected together at a region called the centromere, and separated during mitosis.

Crossing Over

The process of genetic exchange between homologous chromosomes during prophase I of meiosis, leading to genetic variation in gametes.

Anaphase in Mitosis

The mitotic phase where sister chromatids are pulled apart to opposite ends of the cell by the mitotic spindle, ensuring each daughter cell receives an identical set of chromosomes.

Result of Synapsis in Meiosis

The pairing of homologous chromosomes during prophase I of meiosis results in the formation of tetrads, facilitating genetic recombination.

Phases of Mitosis

The process of mitosis includes four main phases: prophase, metaphase, anaphase, and telophase, each vital for accurate cell division.

Telophase in Mitosis

The concluding phase of mitosis where chromatids arrive at the cell poles, the nuclear envelope reforms around each set of chromosomes, and the chromosomes de-condense.

Purpose of Meiosis

To produce haploid gametes needed for sexual reproduction, promoting genetic diversity through mechanisms such as crossing over and independent assortment.

Homologous Chromosomes

Pairs of chromosomes containing the same genes at the same loci, one inherited from each parent, crucial for genetic independence and variation.