cell division Flashcards
(30 cards)
where are the chromosomes found in a eukaryotic cell?
in the nucleus
describe the chromosomes found in a human
23 pairs
each pair consists of one paternal and one maternal
what is the diploid number of chromosomes?
the total number of chromosomes in a normal body cell
what is the diploid number in humans ?
46
give the definition of a chromosome
long, linear structures consisting of DNA and histone proteins. they are made of units called genes
give the definition of chromatid
one of the two threads of a chromosome, formed after DNA replication. Each chromatid in a chromosome is and exact replica of the other (known as sister chromatids )
give the description of a homologous chromosome
a pair of chromosomes containing the same genes in the same position (loci), each derived originally from a different parents gamete at fertilisation
what are chromatids held together by ?
centromere
name the two types of cell division
meiosis and mitosis
what are produced from mitosis?
two new daughter cells
what is the DNA like in the daughter cells after mitosos?
an exact replica of the parent cells, genetically identical
what is the only way that variation can arise when a cell divides by mitosis?
mutation
give the main uses of mitosis
- increase the number of cells during growth
- replaces tissue during repair, replacing the gut
- it allows asexual production which produces offspring that are gentically identical to the parent
why is asexual reproduction useful?
ideal for when organisms are rapidly establishing a population and variation would be a disadvantage
what happens to the chromosomes during prophase?
condense/shorten due to the coiling up of DNA and become visible
what is the function of the centromere?
holds 2 chromatids together
what happens to the nuclear membrane at the end of prophase?
breaks down
what happens to DNA during inerphase?
replicates
what other events occur during interphase?
- protein syntheisis
- increase number of organelles
- ATP production (repiration)
- cell increases in size
are the chromosomes visible during interphase?
no
describe interphase
cell is actively synthesising proteins. the chromosomes are no visible prior to mitosis. the DNA has replicated
describe prophase
the nuclear membrane breaks down . the nucleolus disappears. The DNA is free in the cytoplasm. chromosomes condense and become shorter. chromosomes become visible. Centrioles divide and move to the poles of the cell. spindle fibres form across the cell
describe metaphase
chromosomes move to the equator of the cell. chromosomes attach to the spindle at their centromere
what happens to the chromosomes during metaphase?
line up along the equator of the cell and attach to spindle fibres by their centromeres
