Cell Division Flashcards
What is cell continuity and chromosomes?
“Cell continuity is the way in which cells give rise to new cells as a result of cell division”
Chromosomes:
- found in the nucleus
- made of 60 % protein and 40% DNA
- when cells not dividing, chromosomes are elongated into chromatin
- At cell division chromatin contracts to form rod shaped structures called chromosomes
- genes are located along the length of each chromosome
- A gene is a section of DNA that controls production of a particular protein
Human cells have 46 chromosomes
What does haploid and diploid mean?
“A haploid cell has one of each type of chromosome”
Haploid represented as ‘n’
Total number of chromosomes may be given as n=2
Human sperm cells are haploid n=23
“A diploid cell has two of each type of chromosome”
Diploid represented as 2n normal human cells have a diploid nu,be rod 46, 2n= 46
What is the cell cycle?
“The cell cycle describes the events in the life of a cell”
Interphase refers to the time when a cell is not dividing
Interphase is a very active phase
During early interphase new cell organelles are being formed
In late interphase each chromosome makes a copy of itself ie. DNA replication
What is mitosis?
” Mitosis is a form of nuclear division in which a nucleus forms 2 nuclei containing identical sets of chromosomes”
Divided into 4 parts, prophecy, metaphase,anaphase and telophase
What is prophase ?
Chromatin contracts
Chromosomes appear as double stranded structures
Nuclear membrane breaks down
Spindle fibres form later in prophase
What is metaphase?
Chromosome line up along the equator of the cell
2 spindle fibres attach to each centromere
What is anaphase?
Spindle fibres contract
Centromere break, each chromosome is pulled apart, opaossite strands pulled to each pole
What is telophase?
Chromosomes elongate and revert back to chromatin
Spindle fibres break down
Nuclear membrane forms around each group of four chromosomes
Cell divides to form two daughter cells when a groove called the cleavage furrow forms
Mitosis in plant cells
A cell wall is present around each plant cell
At division there is no cleavage furrow. Instead many small vesicles collect at the equator of the cell.
These vesicles contain the materials needed to form new cell membranes
The vesicles join to form a cell plate
What are the functions of mitosis?
In single called organisms mitosis increases the number of organisms, it’s a method of multiplication or reproduction
In multi cellular organisms it is for growth and repair
