cell and nuclear division Flashcards
Outline the steps of cytokinesis in animal cells
- actin and myosin proteins form a contractile ring that pinches the membrane together forming a cleavage furrow.
- Furrow deepens and splits cytoplasm into two daughter cells
Outline the steps of cytokinesis in plant cells
- vesicles containg cell wall materials fuse together forming a cell plate
- cell plate splitds parent cell into two daughter cells
What are two examples of unequal division of cytoplasm?
- oogenesis
- yeast budding
explain why oogenesis is an unequal division of cytoplasm
produces one large egg cell + three smaller polar bodies
explain why yeast budding is an unequal division of cytoplasm
small bud grows from parent cell
Products of mitosis
Two identical daughter cells
Products of meiosis
forms 4 haploid cells with unique genetic material which develop into gametes.
Describe the shared features of mitosis and meiosis.
- DNA replication happens before both
- similar stages PMAT
- spindle formation
Explain why meiosis is a reduction division.
goes from 46 chromosomes to only 23
How many chromosomes + chromatids does meiosis start with?
46 chromosomes
92 chromatids
How many chromosomes + chromatids does meiosis end with?
23 chromosomes
23 chromatids
Describe the causes of non-disjunction.
an error in meiosis where homologous chromosomes or sister chromatids fail to separate properly
At what stages in meiosis does genetic variation occur?
- M1:P1
- M1:M1
- M2: M2
What are the consequences of non-disjunction?
Produces gametes with too many or too few chromosomes
Leads to disorders like Down syndrome (trisomy 21)
Can cause miscarriage or developmental issues
Outline the need for cell proliferation.
- growth
- repair
- reproduction
Outline the phases of the cell cycle.
- interphase
- mitosis
- cytokinesis
Describe the changes that occur in a cell during interphase.
G1 phase: Cell growth, protein + organelle synthesis
S phase: DNA replication
G2 phase: Further growth and preparation for mitosis
G0 (after the entire cell cycle): cell moves out of cell cycle permanently or temporarily.
Describe how cyclins control the cell cycle.
- Bind to CDKs to activate events like DNA replication.
- regulate checkpoints to make sure everything is correct before moving onto the next stage
Explain the possible consequences of mutations in genes that control the cell cycle.
uncontrolled cell division - malignant tumour and benign tumor
describe malignant tumours
- cancerous
- can spread
describe benign tumours
- localised
- non-cancerous
definition of mutagens
agents that cause gene mutations
State examples of mutagens
- carcinogens (present in tobacco)
- X-rays
- UV light
- some viruses
definition of oncogene
A mutated gene that will lead to tumor growth.
