Cell Division Flashcards
What is it called when cells develop a specialised structure to carry out a specific function
Differentiation
Diploid
Cells that contain two sets of matching chromosomes
What type of cell divides by mitosis
A diploid cell divides to produce two more diploid cells
Why are cells produced through mitosis
For growth
Repair damage tissues
Replace old cells
Asexual reproduction
What has to happen before mitosis
DNA replicates itself to double the chromosomes
This produces two cells that are genetically identical
How does a cell make an exact copy of its DNA
Before mitosis
Double helix ‘unzips’
New bases pair up with exposed bases on each strand
An enzyme bonds the new bases together forming complementary strands
Two identical strands of DNA are formed
What cells are produced through meiosis
Gametes
How many copies of chromosomes do gametes have
What is the name for this
One copy
Haploid cells
What is the process of meiosis
(diploid cell divides twice to produce four haploid cells)
Each chromosome replicates itself
One chromosome from each pair separates to opposite pole of the cell
Cell divides for first time
Chromosomes divide again and move to opposite pole
Four haploid cells formed, genetically different
When fertilisation occurs what is formed
How many sets of chromosomes has it
A zygote (fertilised egg)
Two sets, a diploid
Half chromosomes from egg, half from sperm
What are adaptations of the sperm
Mobility from tail
Contains many mitochondria in neck to supply energy for swimming. Small size is an adaption for swimming
Sperm produced in vast numbers to increase chance of fertilisation
Explain how sperm enters egg
The Sperm’s acrosome, a structure on its head, bursts
Releases enzymes that digest egg cell membrane
Allowing sperm nucleus (containing one set of genes) to enter
How does sexual reproduction promote variation
Gametes are produced by meiosis, genes are ‘shuffled’
Gametes fuse randomly, with one of each pair of alleles for gene coming from each parent
Alleles in a pair may be same or different producing different characteristics
What do single celled organisms eg. Amoeba rely on to obtain glucose and oxygen and to remove waste products
Diffusion
