2.1.6 Cell Divison, Cell Diversity and Cellular Organisation Flashcards
What are the phrases of the cell cycle?
Growth 1 Synthesis Growth 2 Mitosis Cytokinesis
What are the 2 phases of the cell cycle? CC
- Interphase
2. Miotic
What happens during Growth 1? CC
- Organelles replicate
- Cell size increases
- Protein synthesis
- Respiration
- G1 Checkpoint
What happens during Growth 2? CC
- Duplicated DNA checked for errors
- Cell size increases
- Energy store increases
- G2 checkpoint: DNA replication error, everything in G1
What happens during Synthesis? CC
- Splitting cytoplasm into 2 daughter cells which will start the cell cycle
What happens if a checkpoint detects an error in the cell cycle?
Enters G0/ resting phase
What are reasons for entering G0 phase? (3) CC
- Differentiation- specialised cells don’t replicate
- DNA Damage- no longer divides
- Senescent cells- max. no. of division
What regulates the cell cycle?
Checkpoints
Why do cells need mitosis?
- Growth
- Repair
- Sexual reproduction
Abbreviation for the Mitosis phases?
PMAT
Prophase, metaphase, anaphase and telophase
What happens during Interphase? Way to remember?
- DNA = chromatin
- DNA replicates
I = Invisible chromosomes
What happens during Prophase? Way to remember? (Mitosis)
- Chromatin condenses = Chromosomes visible
- Nucleolus disappears
- Centrioles move to poles
- Nuclear envelope breaks down
P = centrioles to Poles
What happens during Metaphase? Way to remember? (Mitosis)
- Spindle fibres attach to centrosomes
- Chromosomes line up on equator
M = middle (equator)
What happens during Anaphase? Way to remember? (Mitosis)
- Spindle fibres shorten
- Chromosomes divided into Chromatids
- Chromatids are separated to either pole
A = away to poles
What happens during Telophase? Way to remember? (Mitosis)
- Nuclear envelopes form around daughter chromosomes/ chromatids
- Chromosomes invisible
- Cytokinesis
T = Two indentical daughter chromosomes/ chromatids
What is Cytokinesis? Differences in plants/ animals? Way to remember? (Mitosis)
- Cells separate producing two identical daughter cells
- Animals: cleavage furrow
- Plants: cell wall production
C = Cleavage
What is Chromatin?
DNA wrapped around histone proteins
What are centrioles? Function?
- Part of centrosome in cell: 2 centrioles per centrosome
- Produce spindle fibres
What are spindle fibres? Function?
- Microtubules produced from centrioles
- Attach to centrosomes + shorten to poles
What is a Centromere?
Where chromatids are joined in a chromosome
What is a Chromatid?
Single- stranded chromosome
What are the 3 differences in Mitosis between animals and plants?
- (A) Centrioles (P) none
- (A) cells rounded before (P) no shape change
- (A) spindle fibres go before split (P) some spindle fibres present
Abbreviation for the Meiosis phases?
PMAT & PMAT2
How many chromosomes do gametes have?
23
What is meiosis?
Nuclear division, haploid cells produced
What happens in Prophase I? Way to remember? (Meiosis)
- Nuclear envelope & nucleolus disappears
- Spindle fibres formed
- Homologous pairs line up
- Bivalents do crossing over
What happens in Metaphase I? Way to remember? (Meiosis)
- Homologous chromosomes line up on equator
Independent assortment
What happens in Anaphase I? Way to remember? (Meiosis)
- Homologous chromosomes pairs are separated
Random segregation
What happens in Telophase I? Way to remember? (Meiosis)
- Chromosomes at either pole
- Cytokinesis- cleavage
- 2 haploid cells formed
What happens in Prophase II? Way to remember? (Meiosis)
- Chromosomes condense
- Nuclear envelope & nucleolus disappears
- Spindle fibres formed
What happens in Metaphase II? Way to remember? (Meiosis)
- Chromosomes line up on equator
Independent assortment
What happens in Anaphase II? Way to remember? (Meiosis)
- Random segregation of Chromatids
What happens in Telophase II? Way to remember? (Meiosis)
- Chromatids at either poles
- Cytokinesis
- 4 haploid daughter cells formed
What is a homologous chromosome?
A chromosome with 2 chromatids; same size and DNA in same order
What is a bivalent?
Two chromosomes with 4 chromatids; two homologous chromosomes crossing over and temporarily joined
What is crossing over?
Homologous chromosomes exchanging codes for specific genes
What is independent assortment?
Chromosomes align on equator in random orientation
What is random segregation?
Chromosomes align on equator in random orientation and are separated
What is a haploid cell?
Half number of chromosomes in nucleus
Why are cells haploid after Meiosis I?
46 chromatids -> 92 chromatids -> 46 chromatids
.. technically 46 chromosomes -> 92 chromosomes -> 46 chromosomes bc centromeres are counted
How does crossing over cause genetic variation?
New combination of alleles
How does independent assortment cause genetic variation?
Different combination of chromosomes in haploid cell
How does random segregation cause genetic variation?
Different combination of chromatids in haploid cell/ gamete
What is a tissue?
Group of differentiated cells that work together; specific function
What are the examples of tissue you need to know? (6)
- Squamous epithelium
- Ciliated epithelium
- Cartilage
- Skeletal muscle
- Xylem
- Phloem
What is an organ?
Collection of several tissues that work together for specific function(s)
What is an organ system?
Group of organs that work together to perform a function
Smallest to largest organisation of cells?
Specialised -> tissue -> organ -> organ system
What is a specialised cell?
Differentiated cell from stem cell; structure -> specific function
What are the examples of specialised cells you need to know? (6)
- Erythrocytes
- Neutrophils
- Sperm cells
- Palisade cells
- Root hair cells
- Guard cells
What is a stem cell?
Undifferentiated cells; haven;t specialised for specific function
Why are stem cells important in an organism?
- Growth
- Development
- Tissue repair
Stem cells are a source of what and why?
- Undifferentiated cells
- Can do cellular division many times
Where do blood cells in animals come from?
Stem cells; bone marrow
Where do xylem vessels and phloem sieve tubes come from in plants?
Stem cells; meristem
Examples of stem cells being used as medicine?
- Repair damaged tissue
- Treat neurological conditions
Why is using stem cells in medicine sometimes seen to be unethical?
Embryonic cells; potential life
What is totipotent? Way to remember?
- Stem cells that can specialise as any specialised cell
- Potential to be whole organism
What is Pluripotent?
- Stem cells that can specialise as any specialised cell
- No potential to be whole organism
What is Multipotent?
Stem cells that can only specialise within a LIMITED range of specialised cell
How are guard cells specialised?
Can increase/ decrease size determining if stoma is open
How are root hair cells specialised?
- Long, narrow -> large SA
- Large vacuole, high conc. of solute -> increase osmosis
How are palisade cells specialised?
- Lots of chloroplasts- more light = photosynthesis
- Thin walls -> more CO2 diffusion
- Large vacuole -> turgor pressure
How are sperm cells specialised?
- Flagella -> movement
- Lots mitochondria -> energy for movement
- Acrosome -> digest exterior of egg, penetration
How are neutrophils specialised?
- Multi-lobed -> fit through capillary wall gaps
- Many lysosomes -> hydrolytic enzymes (destroy pathogens)
How are erythrocytes specialised?
- Flattened bioconcave shape with no organelles -> increase SA = more oxygen carried
2 Animal and plant examples of organ system?
A: digestive; respiratory
P: shoot; root
