Lecture 19 Flashcards
How do viruses store genetic information? What about prokaryotes and eukaryotes?
Viruses store genetic information in the form of double stranded or single stranded DNA or RNA, Prokaryotes store it in the form of a circular single copy naked double strand of DNA, eukaryotes store it in a linear form with one or more copies, DNA is histone bound and a sexual cycle is used.
What processes do multicellular organisms depend on cell division for?
Development from a fertilised cell, growth to adulthood and repair.
What are the two phases in the cell cycle?
The mitotic phase (the actual cell division) and interphase (preparing materials for the cell division).
What steps occur in mitosis?
The mitotic phase begins with mitosis (karyokinesis). This consists of 5 stages, in order of occurence these are prophase, prometaphase, metaphase, anaphase and telophase.
Prophase: Chromosomes condense and become visible, the spindle fibers begin to emerge from centrosomes as the nuclear envelope breaks down and the nucleolus disappears.
Prometaphase: Chromosomes condense more and kinetochores appear at the centromeres which mitotic spindle microtubules attach to. Centrosomes move to opposite poles.
Metaphase: fully developed mitotic spindle with centrosome at opposite poles of the cell, chromosomes lined up at metaphase plate.
Each sister chromatid is attached to a spindle fiber from opposite poles.
Anaphase: The sister chromatids (now chromosomes) are seperated and pulled to opposite poles, meanwhile the non kinetochore spindle fibers lengthen, causing the cell to elongate.
Telophase: chromosomes arrive at opposite poles and begin to decondense as nuclear material surrounds each set and the mitotic spindle breaks down.
What stages occur in the mitotic phase? What occurs in the final mitotic phase step?
karyokinesis (mitosis) and cytokinesis. Cytokinesis is the final stage and occurs through the formation of a cleavage furrow which seperates the daughter cells in animal cells, in plant cells a cell plate seperates the daughter cells.
What steps occur during interphase? What do they do?
Interphase consists of the G1 (gap 1), S and G2 (gap 2) phases.
In the G1 phase the cell makes many proteins ecessary for DNA replication. In the S phase the cell synthesises a second set of DNA and in the G2 phase the cell synthesises a variety of proteins necessary for the daughter cells as well as microtubules for the mitosis stage.
What is a kinetochore?
A kinetochore is a protein structure that forms on a chromatid during cell division and allows it to attach to a spindle fiber on a chromosome.
