Cell Division Flashcards
What does DNA exist as
when a cell is not dividing?
-When a cell is not dividing the DNA exists as chromatin within the nucleus
What does chromatin consist of and where are they found?
consists of DNA and histone proteins and is found in the nucleus of eukaryotic cells
When cell division begins, what does chromatin do?
condenses to form chromosomes
What do chromosomes consist of?
Chromosomes consist of DNA, protein and a little RNA- The DNA is made up of many small sections called genes.
In diploid cells, what are are chromosomes found in?
in matching pairs called homologous chromosomes
What happens to chromosomes at the start of cell division?
the DNA replicates (during interphase) and the chromosomes are visible as two identical sister chromatids joined at the centromere.
What does a centromere do?
links two sister chromatids together
How many pairs of homologous chromosomes do humans have?
23
What does each homologous pair consist of?
one chromosome inherited from the mother (maternal) and one inherited from the father (paternal)
What is the diploid number?
The total number of chromosomes in a somatic (body) cell (2n)
What do gametes (sex cells) have?
one of each type of chromosome (i.e. half the diploid)
What is the diploid number of chromosomes for humans?
46
What is the haploid number of chromosomes for humans?
23
Where is the majority of time spent in a cell’s cell cycle?
interphase
What happens during interphase?
-a newly formed cell increases in size and performs several activities:
•DNA replicates
•Organelles are produced
•Protein synthesis occurs
•ATP synthesis occurs
What happens during G2?
-protein synthesis
-centrioles replicate
What happens during G1?
-cell gets bigger
-organelles replicated
-protein synthesis
-ATP synthesised
What happens during S phase?
DNA is replicated inside the nucleus (DNA helicase/DNA polymerase) so DNA content doubles
What are 3 process processes take place during interphase?
G1 and S and G2- cell is getting ready for entering mitosis (including replication of DNA)
What is the process of interphase?
-DNA replicates- occurs during S phase of interphase
-Organelles are produced = so daughter cells have the same number
-Protein synthesis occurs = including enzymes for cell division
-ATP synthesis occurs
what is mitosis and what are the four phases?
the division of the nucleus-
-Prophase
-Metaphase
-Anaphase
-Telophase
What happens in prophase?
•Chromatin condenses into visible sister chromatids joined at the centromere.
•Centrioles move to opposite poles, forming protein microtubules and developing the spindle.
•The nuclear envelope disintegrates, the nucleolus disappears, and chromosomes move towards the cell equator.
•Prophase is the longest stage of mitosis.
What happens during anaphase?
-A rapid stage (fastest) in which spindle fibres contract and shorten, the centromere splits, and sister chromatids are pulled apart.
-Chromatids are drawn towards opposite poles with the centromere leading.
What happens during metaphase?
Chromosomes align along the cell equator and attach to spindle fibres at the centromere