POL sections 7.1 - 7.3 Flashcards
Cell division
A process by which a parent cell duplicates its genetic material and then divides into two similar cells
Two Strategies of Reproduction
Asexual reproduction and sexual reproduction
Asexual reproduction is __________; offspring are _____
a rapid and effective means of making new individuals common in nature; clones of the parent organism: genetically identical to each other and parent
Mutations
Alterations in DNA sequence caused by environmental factors or errors in DNA replication
Single-celled prokaryotes reproduce by ___________
binary fission
Sexual reproduction
Involves fusion of two specialized cells called gametes
Meiosis
Process of cell division resulting in daughter cells with only half the genetic material of the original cell; usually occurs in diploid cells; increases genetic diversity
Chromosome
Consists of a double-stranded molecule of DNA and associated proteins
Somatic cells
Body cells that are not specialized for reproduction; contain two sets of chromosomes and occur in homologous pairs (one from female parent and the other from male parent)
Homologous pair
Homologs bear corresponding, though not identical, genetic information
Gametes
Contain only a single set of chromosomes; n chromosomes; haploid cell
Zygotes
Contain two sets of chromosomes; 2n chromosomes; diploid cell
Fertilization
Two haploid gametes fuse to form a zygote
Essence of sexual reproduction
Random selection of half of the diploid chromosome set to make a haploid gamete, followed by fusion of two haploid gametes from separate parents to produce a diploid cell
Events that must occur for any cell to divide
Reproductive signals, DNA replication, DNA segregation, Cytokinesis
Reproductive signals
Initiate cell division and may originate from inside or outside the cell
DNA replication
Replication of the genetic material; Each of the new cells will have a full complement of genes to complete cell functions
DNA segregation
Process of distributing the replicated DNA to each of the two new cells
Cytokinesis
Process in which cytoplasm divides to form two cells, each surrounded by a cell membrane and sometimes a cell wall
Binary fission
Occurs in single-celled prokaryotes; process by which cell grows in size, replicates its DNA, and separates the DNA and cytoplasm to two cells
Binary fission: reproductive signals
Environmental conditions and nutrient concentrations
Binary fission: DNA replication
Single chromosome is circular; DNA is threaded through a “replication complex” of proteins near the center of the cell; Begins at ori and ends at ter; Two daughter DNA molecules separate and segregate to opposite ends of the cell
Ori
The site where replication of the circular chromosome starts (the origin of replication)
Ter
The site where replication of the circular chromosome ends (the terminus of replication)
Binary fission: DNA segregation
As replication proceeds, ori move toward opposite ends; DNA sequences adjacent to ori region bind proteins necessary for segregation; active process (ATP is hydrolyzed);it makes use of prokaryotic cytoskeleton to move ori regions and associated proteins (structurally actin, functionally tubin)
Binary fission: cytokinesis
Pinching in of cell caused by contraction of ring of fibers on inside surface of membrane (major component: structurally tubulin, functionally actin); As membrane pinches in, new cell wall materials are deposited, which finally separate the two new cells
Eukaryotic cells: reproductive signals
Unlike prokaryotes, signals are related to the function of the entire organism