General Biology Reviewer

• Eukaryotes are capable of two types of cell division: mitosis and meiosis.
• DNA encodes heritable information; different types of RNAs interact with DNA in protein synthesis.
• Mitosis allows for cells to produce identical copies of themselves, which means the genetic material is duplicated from parent to daughter cells.
• Mitosis produces two daughter cells from one parent cell.
• Single-celled eukaryotes, such as amoeba and yeast, use mitosis to reproduce asexually and increase their population.
• Multicellular eukaryotes, like humans, use mitosis to grow or heal injured tissues.
• Meiosis is a specialized form of cell division that occurs in organisms that reproduce sexually.
• Meiosis produces reproductive cells, such as sperm cells, egg cells, and spores in plants and fungi.
• In humans, special cells called germ cells undergo meiosis and ultimately give rise to sperm or eggs.
• Germ cells contain a complete set of 46 chromosomes (23 maternal chromosomes and 23 paternal chromosomes).
• By the end of meiosis, the resulting reproductive cells, or gametes, each have 23 genetically unique chromosomes.
• The overall process of meiosis produces four daughter cells from one single parent cell.
• Each daughter cell is haploid because it has half the number of chromosomes as the original parent cell.
• Meiosis is reductional, meaning the daughter cells produced during meiosis are genetically diverse.
• Homologous chromosomes exchange bits of DNA to create genetically unique, hybrid chromosomes destined for each daughter cell.
• A diploid human body cell has a chromosome number of 46; when it divides by mitosis, both cellular offspring also have a chromosome number of 46.
• If only the total number of chromosomes mattered, then one cell might inherit, say, two pairs of chromosome 22 and no chromosome 9.
• A cell cannot function normally unless it has a proper complement of chromosomes.
• During G1, each of a cell's chromosomes consists of one double-stranded DNA molecule.
• DNA replication occurs during S, so by G2 each chromosome consists of two double-stranded DNA molecules attached as sister chromatids.
• The sister chromatids stay attached until mitosis is almost over, and then they are pulled apart and packaged into two separate nuclei.
• When sister chromatids are pulled apart, each becomes an individual chromosome with one double-stranded DNA molecule.
• The two new nuclei that form by mitosis contain the same number and types of chromosomes as the parent cell.
• When the cytoplasm divides, these nuclei are packaged into separate cells, each with the chromosome number of the parent.
• New alleles arise by mutation and may encode slightly different forms of a gene’s product, influencing the details of shared, inherited traits.
• Different forms of the same gene are called alleles.
• Sexual reproduction produces offspring that differ from one another and from parents, giving it an evolutionary edge in a changing environment.
• Variation in the DNA sequence is the basis of variation in traits among species, and it is also the basis of variation in forms of traits among individuals of sexually reproducing species.
• In sexual reproduction, about half of a sexual reproducer’s genes are passed to each offspring.
• Alleles of the shared genes are the basis of variation in traits.
• Meiosis in diploid germ cells gives rise to eggs (female gametes) or sperm (male gametes).
• Mitosis and cytoplasmic division are part of asexual reproduction in eukaryotes, but not all species can use this reproductive mode.
• When a diploid cell undergoes meiosis, it produces haploid cells.
• Mitosis maintains the chromosome number, while meiosis halves the chromosome number.
• In asexual reproduction, all of its genes are passed to every one of its offspring.
• Many eukaryotes reproduce sexually, either exclusively or most of the time.
• Offspring arise from two parents and inherit genes from both in sexual reproduction.
• In plants and animals, germ cells form in organs set aside for reproduction, but the two groups make gametes differently.
• In plants, haploid germ cells (spores) form by meiosis and divide by mitosis to form structures that produce or contain gametes.
• Genes are the basis of an organism’s traits — its form and function.