Zoo-Lab (Sem-1) - Exercise 6: Cell Reproduction

reproduction

basic characteristic of production of new life

cell division

underlying all forms of reproduction; reproduction of cells

single cell

has a double function: maintain itself and participate in the entire life of the organism

cell division in single-celled animals

results in the reproductiom of the whole organism

cell division in multicellular organisms

results in the development of the organism by the formation of additional cells

perpetuate one’s kind

primary purpose of reproduction

cellular reproduction

for repair of worn-out tissues; for growth and development of the body of an organism

amitosis

nucleus divides into two halves without the formation of spindle fibers; two daughter cells do not have the same number of chromosomes; occurs in some protozoans, especially the ciliates and suctorians

mitosis

typical cell division; consists of an equal division of nuclear materials (karyokinesis) followed by division of the cell body (cytokinesis) in such a fashion that each of the two daughter cells receive exactly the same number of chromosomes that the parent cell

karyokinesis

equal division of nuclear materials; chromosomes segregate to separate poles of the cell

cytokinesis

division of the cell body; division of the cytoplasm to form two separate daughter cells due to the formation of a new cell membrane

interphase; prophase; metaphase; anaphase; telophase

different stages in mitosis

early; middle; late stages

3 stages of transverse/binary fission

binary fission

type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells

early stage - binary fission

macro-nuclei/micro-nuclei elongate;

middle stage - binary fission

deepening of indentation and constriction around the middle of the individual plane at right angles to the animal’s longitudinal axis

late stage - binary fission

the constructions deepen resulting in the pinching off of the animal into two daughter paramecia, each is half the size of the parent animal

interphase

aka resting cell stage; period between mitotic divisions; nucleus enlarges due to the synthesis of proteins and nucleic acids, large molecules found in every nucleus, and duplication of each chromosome

prophase

chromosomes are coiling, shortening, and thickening; chromosomes are irregular threads and each is composed of two chromatids; nucleus disappears and nuclear membrane disintegrates

metaphase

chromosomes are aligned in the middle; spindle fibers extending from one centriolee (centrosomes) to the other; chromosomes are attached to some fibers by their centromeres

anaphase

sister chromatids of chromosomes separate and start moving towards opposite poles of the cell

telophase

chromosomes reach the poles of the cells and begin to uncoil; new nuclear region formation; cleavage furrow deepens and divides cytoplasm into 2 cells

nucleolus

a spherical structure found in the cell's nucleus whose primary function is to produce and assemble the cell's ribosomes

chromosome

threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell

spindle fibers

responsible for organizing packages of DNA (chromosomes) on opposite ends of a cell to ensure that duplicated nuclei can divide into subsequent cells

centrosome

primary microtubule-organizing centre (MTOC) in animal cells; regulates cell motility, adhesion and polarity in interphase, and facilitates the organization of the spindle poles during mitosis

centriole

paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope; organizing microtubules that serve as the cell's skeletal system