Chapter 8 Flashcards
chromosomes
made of strands of DNA (info containing molecules) and protiens (histones)
tightly coiled during cell divisions
most living things contain
a single copy of genetic info in each cell
in prokaryotes
a single choromsome attached to the plasma membrane
some prokayotes also have a plasmids
plasmids
small circular strands of DNA
eukaryotes contain
a number of chormosomes with the nucleus
every species has specified number of
chorosomes (humans 46)
each chromosome contains different genetic info, so each has to be passed on to new cells
cell division
all cells are created from the division of other cells
for genetic info to be passed to each new cell
1. chromosomes need to be copied and
2. the copies divided
prokaryotic cell division
chromosome is copied
plasma membrane grows, forcing the chromosomes apart
plasma membrane divides cell into two
eukaryotic cells have defined periods when division is possible
the cell cycle: two main phases
- interphase
- mitotic phase
interphase
period of metabolic activity and growth in size
period when DNA is copied
cells spend most of their time in interphase
mitotic phase
period when chromosome pairs (the copies) seperate (mitosis) and when cells divide (cytokinesis)
sister chromatids
identical copies of the same chromosome
stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
prophase
chromosomes become tightly packed
long stands of protiens (mitotic spindles) at microtuble organising centers
nuclear membrane breaks down
stands of mitiotic spindle from either end of the cell attach to each sister chromatid pair
mitotic spindles get longer until they reach a chromosome
once the spindle fibers attach from both sides of the sister chromatid, they start to contract
metaphase
chromosomes line up in the middle of the cell
