Cell Division Flashcards
What are spindle fibres?(1)
Protein microtubules
What is the significance of mitosis? (3)
-asexual reproduction
-growth of multicellular organisms
-repair of tissues
What occurs in prophase? (5)
-chromosomes condense
-sister chromatids are joined by the centromere
-the two centrosomes move to opposite poles
-the spindle fibres begin to emerge from centrosomes
-the nuclear envelope breaks down into small vesicles
What occurs in telophase? (3)
-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelopes begin to reform around both sets of chromosomes
-the spindle fibres break down
What occurs in anaphase? (3)
-the sister chromatids separate at the centromere (divides in two)
-spindle fibres begin to shorten
-the separate sister chromatids are pulled to opposite poles of the cell by the spindle fibres
What occurs in metaphase? (5)
-centrosomes reach opposite poles
-spindle fibres continue to emerge from the centrosomes
-the chromosomes line up along the spindle equator (or metaphase plate) so they are equidistant to the two centrosome poles
-spindle fibres reach the chromosomes and attach to the centromeres
-each sister chromatid is attached to a spindle fibre that originates at opposite poles.
What features of chromosomes are important for cell division? (5)
-the shape of a chromosome is characteristic
-chromosomes occur in homologous pairs
-not all homologous chromosomes have the same alleles
-different species have a fixed number of chromosomes
-chromosomes are copied prior to division so appear double
How are karograms used? (1)
Are used by genetic counsellors to check for abnormalities in an individual’s chromosomes (such as Down’s syndrome)
What is a karogram? (1)
Arranging an individuals chromosomes in descending order of size and numbering them.
What is a heterozygous? (1)
A diploid organism that does not have two of the same alleles for a particular gene.
What is an autosome? (1)
Any chromosome in a cell that is not a sex chromosome.
What is a karyotype? (1)
The number and shape of a chromosome in a somatic cell.
What is a locus? (1)
The position of a particular gene of a specific chromosome.
What is a homozygous? (1)
A diploid cell that have the same alleles for a particular gene.
What is a diploid? (1)
A cell that contains 2 copies of each chromosome.
What is an allele? (1)
One of two or more different forms of the same gene.
What is a centromere? (1)
A narrow region occupying a specific position on each chromosome this is the only site at which spindle fibres can attach during mitosis.
What is asexual reproduction? (1)
The formation of an organism without the fusion of gametes.
What is a somatic cell? (1)
A cell in an organisms that is not a germ cell or undifferentiated cell.
What are homologous chromosomes? (2)
A pair of chromosomes in a diploid cell that have the same size and shape and carry the same genes in the same order.
What are the main stages of cell division? (3)
Interphase
Mitosis
Cytokinesis
In the G2 phase; what is checked for? (2)
Cell size
DNA replication
What is the mitotic index? (1)
How many cells going through a specific phase divided by the number of cells in total.
What is the difference between plant cells and animal cells in terms of cell division? (1)
Plant cells do not have spindle fibres.
How do cells divide in prokaryotes? (1)
Via binary fission
How do cells divide in eukaryotes? (1)
Via the cell cycle
What are the divisions in mitosis called? (1)
Mitotic divisions
What is meiosis? (1)
The production of 4 genetically different haploid gametes.
What is s-phase? (1)
When the cell gets big enough the DNA replicates.
In the G1 phase; what is checked for? (4)
Cell size
Cell growth
Nutrients
DNA damage
What are the phases of mitosis? (4)
-prophase
-metaphase
-anaphase
-telophase
What is mitosis? (1)
The production of 2 diploid genetically identical cells
What are the chromosomes of a human divided into? (2)
Autosomes
Sex chromosomes
How are chromosomes divided in humans? (2)
22 autosomes
1 sex chromosomes
What sex chromosomes do females have? (1)
XX
What sex chromosomes do males have? (1)
XY
What are stem cells? (1)
Are unspecialised/undifferentiated cells that can divide.
What are histones? (1)
Proteins that DNA wraps around (protects genetic information)
How many chromosomes do humans have? (1)
23 pairs of chromosomes.
