Lecture 2 Flashcards
Evolution
Change in genetic frequency in a population over time
Characteristics of Prokaryotic Cells
Unicellular, no nucleus, relatively small, usually one circular DNA molecule not complexed with histones in bacteria (some histones in archaea), relatively small amount of DNA, and no membrane bound organelles
Characteristics of Eukaryotic Cells
uni and multi cellular, nucleus, relatively large, multiple linear DNA molecules complexed with histones, relatively large amount of DNA, has membrane bound organelles
Viruses
Neither prokaryotic or eukaryotic; has an outer protein coat surrounding nucleic acid; needs host cell reproduce
Homologous Chromosomes
Similar but not identical; each homolog carries the same genes in the same order, but the alleles for each trait may not be the same
Diploid Cells
Carry two sets of genetic information
Haploid Cells
Carry one set of genetic information
Centromere
Attachment point for spindle microtubules
Telomeres
Tips of a linear chromosome
Origins of Replication
Where DNA synthesis begins
Submetacentric Chromosomes
Centromere situated so that one chromosome arm is somewhat shorter than the other
Metacentric Chromosomes
Centromere in the middle
Telocentric Chromosomes
Centromere at the end with no short arm visible in a light microscope
Acrocentric Chromosomes
Centromere near the end producing a short arm
Interphase
Extended period between cell divisions, DNA synthesis, and chromosome replication phase
M Phase
Mitotic phase
G1 of Interphase
Growth; proteins necessary for cell division synthesized
S of Interphase
DNA synthesis
G2 of Interphase
Biochemical preparation for cell division
G2/M Checkpoint
Only passed if DNA completely replicated and undamaged
Mitosis
Separation of sister chromatids
Cytokinesis
Separation of cytoplasm; cell wall forms in plant cells
G0 Phase
Stable, nondividing period of variable length
Prophase
Chromosomes condense and mitotic spindle forms
Prometaphase
Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores
Metaphase
Chromosomes align on the metaphase plate; spindle-assembly checkpoint
Anaphase
Sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles
Telophase
Chromosomes arrive at spindle poles, the nuclear envelope re-forms, and the condensed chromosomes relax
Meiosis
Production of haploid gametes
Fertilization
Fusion of haploid gametes
Genetic Variation
Consequence of meiosis
Meiosis 1
Separation of homologous chromosome pairs, and reduction of the chromosome number by half
Meiosis 2
Separation of sister chromatids, also known as equational division
Chromatid
Either of 2 daughter strands of a duplicated chromosome that are joined by a single centromere and separate during cell division to become individual chromosomes
Synapsis
Close pairing of homologous chromosomes in prophase 1
Tetrad
Closely associated four-sister chromatids of 2 homologous chromosomes
Crossing Over
Crossing over of chromosome segments from the sister chromatid of one chromosome to the sister chromatid of the other synapsed chromosome; exchange of genetic information, the first mechanism that generates genetic variation in newly formed gametes
Metaphase 1
Random alignment of homologous pairs of chromosomes along the metaphase plate
Anaphase 1
Separation of homologous chromosome pairs, and the random distribution of chromosomes into 2 newly divided cells; second mechanism of generating genetic variation in the newly formed gametes; chromosomes move toward opposite poles
Telophase 1
Chromosomes arrive at the spindle poles and the cytoplasm divides
Prophase 1
Chromosomes begin to condense and the spindle forms; homologous chromosomes pair; crossing over takes place and the nuclear membrane breaks down
