Cell Division Flashcards
Define cell continuity
All cells develop from pre-existing cells
What are chromosomes made up of?
40% DNA and 60% protein
How many chromosomes do human cell in each body cell (except for gametes)?
46
How many chromosomes are in a gamete?
23
Define chromatin
Long, thin strands when chromosomes are not dividing
Draw a labelled diagram of the nucleus
See notes
Define gene
Short strand of DNA that codes for a protein/unit of inheritance
What do all the genes make up?
Genome
Give some examples of what genes control
- Hair colour
- Shape of face
- Skin pigment
What kind of proteins are produced in cell division?
Enzymes
What is the metabolic role of a protein?
Enzymes
Define haploid
One set of chromosomes - 23. n=23
Define diploid
Two sets of chromosomes - 46. 2n=46. Chromosomes are in pairs
Give an example of a diploid
Somatic cells (non-sex cells)
Define triploid
Three sets of chromosomes
Define homologous pair
A pair of chromosomes that each have genes for the same features at the same positions.
In diploids, where does each chromosome come from
One from the mother and one from the father
Define mitosis
Cell division. One nucleus divides to form two nuclei each containing the same number of chromosomes with identical genes. Produces identical cells
Define daughter cell
New cell formed by mitosis
What are the four stages of mitosis in order?
Prophase, metaphase, anaphase and telophase
Describe what happens in prophase
- Before nucleus divides
- Chromatin starts to condense/contract and become visible as double stranded (identical), held together at the centromere
- Nucleolus disappears
- Spindle fibres appear
- Nucleus membrane starts to break down
- 2n=4
Draw a diagram to show prophase
See notes
Describe what happens during metaphase
- Nuclear membrane breaks down
- Spindle fibres attached to each centromere from the pole
- Chromosomes line up at equator of the cell
Draw a diagram to show metaphase
See notes
Describe what happens during anaphase
- Spindle fibres contract causing the centromeres to split
- Chromosomes are pulled to opposite poles
Draw a diagram to show anaphase
See notes
Describe what happens during telophase
- Chromosomes at each pole begin to lengthen and become hard to distinguish -> chromatin
- Spindle fibers break down
- Nucleolus begins to reform
- A nuclear membrane forms around each clump of chromatin
Draw a diagram to show telophase
See notes
Describe cell division in plant cells
- Vesicles gather in area between nuclei
- Cell plate forms as vesicles fuse together made of cellulose
- Area between two plant cells called middle lamella
- Cell wall prevents cleavage furrow from forming
Show diagram to show cell division in plant cells
See notes
Describe cell division in animal cells
- Small grove called a cleavage furrow appears in cell near the equator
- This becomes deeper until it divides the cytoplasm into two identical cells
Draw a diagram to show cell division in animal cells
See notes
Define interphase
When the cell is not dividing
How often does interphase occur?
80% of the time
What happens to chromosomes during interphase?
- They are in chromatin form - elongated, only visible as a mass
- In later stages chromosomes duplicate in preparation for mitosis
What organelles does the cell produce during interphase?
- Mitochondria
- Chloroplasts
- Ribosomes
- Centrioles
What does the cell produce during interphase?
- Organelles: Mitochondria, chloroplasts, ribosomes, centrioles
- Enzymes needed for growth - protein synthesis.
- Biomolecules: Nucleic acid, protein, fat, carbohydrates
What biomolecules does the cell produce during interphase?
- Nucleic acid
- Protein
- Fat
- Carbohydrates
What cellular reactions take place during interphase?
- Protein synthesis
- Respiration
- Photosynthesis
- Growth
- Replication
Define meiosis
Cell division. One cell divides into four daughter cells each with half the number of chromosomes as the parent
Where does meiosis occur in humans?
- In ovaries to make eggs
- In testes to make sperm
What are the functions of meiosis?
- Allows for sexual reproduction - two cells (gametes) join to form diploid zygotes
- Allows for variation - cells that divide by meiosis are not identical
What are the functions of mitosis in multicelluar organisms?
- Growth
- Repair/replace tissues/cells
What are the functions of mitosis in unicellular organisms?
Asexual reproduction - increases number of individuals
What are some examples of unicellular organisms where mitosis is use as a form of asexual reproduction?
- Amoeba
- Yeast
Define cancer
When a group of cells lose the ability to control the rate of mitosis
Define benign tumors
Not life threatening tumors
Give an example of a benign tumor
Warts
Define malignant tumors
May be life threatening tumors - can invade other cells
What are some causes of cancer?
Carcinogens:
* Cigarette smoke
* Asbestos fibres
* UV rays
