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Cell division/diversity/differentiation flashcards
Flashcards do conjunto (48)
- 1What is the cell cycle?The sequence of events that take place as a parent cell duplicates its contents and divides, to produce two new daughter cells
- 2What are the stages of the cell cycle?- INTERPHASE (G1, S and G2 and G0 phases)
- M PHASE (prophase, metaphase, anaphase, telophase)
- CYTOKINESIS - 3What happens at each stage of interphase?G1 = cell growth, transcription of genes to make RNA, biosynthesis, organelles duplicate, enzymes for DNA replication are made, controlled by p53 gene
G0 = when cells undergo apoptosis/differentiation/senescence and can no longer divide (neurones = always in G0) and if DNA errors. Lymphocytes = special case as can be brought OUT of G0
S phase = where DNA replication occurs - is a specific sequence to the replication of DNA (housekeeping genes - active in ALL cells - are duplicated first and genes that are inactive in specific types of cells are replicated last) Chance of spontaneous mutations happening increase as nucleotide bases exposed
G2 = cell growth, energy stores are increased (anaphase), special chemicals made that stimulate chromatin condensation + spindle formation - 4Why are there checkpoints in the cell cycle?They ensure that chromosomes are in the right place, DNA is error-free and the formation of a tumour is prevented as much as possible
- 5What can cause the formation of a tumour?- Tumour supressor gene p53 controls the cell cycle and prevents tumour formation. If this gene is INACTIVATED, tumours are more likely to form
- Proto-oncogenes encourage normal cell growth. If these MUTATE to form oncogenes, cell growth could spiral out of control - 6What are the cell cycle checkpoints?- G1/S checkpoint = checks the chemicals needed for DNA replication are present + DNA is error-free
- G2/M checkpoint = checks DNA has been replicated with no errors
M checkpoint = checks that all chromosomes are attached to the spindle by their centromeres - 7Why is mitosis needed?- Growth
- Repair
- Asexual reproduction (leads to less genetic variation + reduced gene pool eg. budding in yeast and binary fission in bacteria)
Mitotic Index = (no. of cells with visible chromosomes/total number of cells) x100 - 8What happens in prophase?- Replicated chromsomes from interphase CONDENSE/SUPERCOIL (shorten + thicken)
- Nuclear envelope breaks down
- Daughter CENTROSOMES, containing centrioles, move to opposite poles of the cell
- Tubulin threads form a spindle between the centrioles - 9What happens in metaphase?- Replicated chromosomes line up along the cell equator
- Each chromosome becomes attached to the spindle by their centromere (via the kinetochore
- Chromatids face opposite poles - 10What happens in anaphase?- Replicas of each chromosome are pulled to opposite cell poles. The centromere DIVIDES, which separates the sister chromatids
- Motor proteins 'walk' along the cytoskeletal TUBULIN THREADS, pulling the chromatids. This is lead by the centromere, forming a 'V' shape
- Spindle fibres shorten as chromatids move
- Sister chromatids now become individual chromosomes - 11What happens in telophase?- Two new nuclei form as nuclear envelopes form around each new set of chromosomes
- The spindle fibres break down
- The chromosomes now UNCOIL meaning they are no longer visible - 12How is cytokinesis different in animal and plant cells?Cytokinesis = the whole cell splits into 2, forming 2 new daughter cells
Animals = the plasma membrane folds inwards and 'nips' in the cytoplasm (forms 2 distinct cells)
Plants = an end plate forms where the cell equator was. Vesicles holding cell wall material line up along this point and FUSE - 13What is meiosis?This is SEXUAL REPRODUCTION, forming genetically unidentical GAMETES with a HAPLOID number of chromosomes (23 = n)
Normal body (germ) cells contain a diploid number of chromosomes (46 = 2n). A diploid cell is produced when an egg and sperm fuse, forming a ZYGOTE
Meiosis occurs in the gonads (ovaries + testes). The 23 chromosomes from the egg and sperm will form MATCHING PAIRS - 14What are homologous chromosomes?These are chromosomes that form MATCHING PAIRS (1 from egg and 1 from sperm). Homologous chromosomes contain the same genes, at the same places, on the same chromosome, but have different ALLELES (versions) of these genes
- 15Interphase (meiosis)Same as for mitosis. G1, S, G2 and G0 phases
- 16Prophase I- The DNA supercoils
- Nuclear envelope breaks down
- Spindle starts to form
- Chromosomes come together in their homologous pairs (bivalents), and CROSSING OVER occurs - 17Metaphase I- The homologous chromosomes attach along the cell equator by spindle fibres attaching to their centromeres
- Random, independent assortment of homologous chromosomes occurs - 18Anaphase I- Members of each pair of homologous chromosomes are pulled apart by motor proteins (independent segregation of CHROMOSOMES - the centromeres WON'T divide as individual chromosomes are NOT split)
- Most PLANTS will go straight from anaphase I to prophase II - 19Telophase I (mainly animal cells)- Nuclear envelopes will form
- Cytokinesis occurs
- There is a brief interphase where the chromosomes uncoil - 20Prophase II- Nuclear envelopes will disintegrate if they were formed
- Chromosomes (which are no longer indential) will condense
- The spindle forms - 21Metaphase II- Chromosomes attach by their centromeres to the spindle at the equator (independent/random assortment of CHROMATIDS)
- 22Anaphase II- The centromeres will DIVIDE and sister chromatids are pulled apart to opposite cell poles (independent segregation of chromatids)
- 23Telophase II + cytokinesis- Nuclear envelopes will form around the now HAPLOID nuclei
- Animals and plants undergo cytokinesis differently (animals = 4 distinct haploid cells, plants = a tetrad of haploid cells is formed) - 24How does meiosis produce genetic variation?- Crossing over between homologous chromosomes, forming chiasmata (allele shuffling)
- Independant assortment/segregation of chromosomes/chromatids
- Random fertilisation
- Mutations - 25Animals - epithelial cells- Make up the epithelium tissue
- Found in: alveoli walls, skin, capillaries (so in AND out the body)
- SQUAMOUS EPITHELIAL CELLS = have flattened shapes (thin for the diffusion of gases)
- CILIATED EPITHELIAL CELLS (SIMPLE COLUMNAR) = have cilia that moves the mucus along in a synchronised manner - 26Animals - erythrocytes- Carry oxygen from the lungs, to respiring cells
- Very SMALL, so a large surface area to volume ratio for the FAST diffusion of oxygen
- Biconcave disc shape increases SA
- Flexible (a good cytoskeleton allows it to change shape as it moves through the capillaries)
- Most ORGANELLES ARE LOST at differentiation to give more space for haemoglobin - 27Animals - neutrophils- Ingest invading pathogens by PHAGOCYTOSIS
- Twice the size of erythrocytes (gives them lots of room to carry out phagocytosis)
- Contains a MULTILOBED NUCLEUS (DNA packaged in spheres - further helps to kill pathogens)
- Neutrophils are attracted to infection sites by CHEMOTAXIS - 28Animals - sperm cells- Many MITOCHONDRIA for respiration (so the undulipodium can move)
- SMALL, LONG and THIN + streamlined shape
- Contains HYDROLYTIC ENZYMES in the head (are released from the acrosome - a special lysosome) that can digest the outer ovum covering
- Very little cytoplasm in the head (more room for nucleus) - 29Animals - epithelial tissue- Covers internal/external body surfaces
- Roles = protection/absorption/secretion/excretion/ filtration
- Made of cells close together (bound by lateral contacts), forming continuous sheets
- No blood vessels (nutrients obtained from tissue fluid)
- Short cell cycles (divide often) - 30Animals - muscular tissue- Allows movement by CONTRACTION
- Has many blood vessels
- Muscle cells = FIBRES (elongated + contain myofilaments made of actin + myosin, allowing muscle tissue to contract - need to SHORTEN in length to move bones)
- SKELETAL (packaged by connective tissue sheets, joined to bones by tendons so they can MOVE)
- CARDIAC (walls of heart)
- SMOOTH (blood vessels - propels stuff) - 31Animals - connective tissue- Supports and holds tissues together eg. ligaments, tendons
- Consists of a NON - LIVING extracellular matrix containing proteins + polysaccharides eg. elastin, hyaluronic acid
- The matrix separates the living cells in tissue + enables them to withstand forces
- CARTILAGE = immature CHONDROBLASTS secrete the extracellular matrix. After this, they become mature CHONDROCYTES + maintain the matrix
Types = hyaline (embryonic skeleton), fibrous (knee, compression) + elastic (support + distortion eg. outer ear) - 32Plants - palisade cells- Photosynthesis occurs here
- LONG and CYLINDRIC (pack closely but still space for air)
- LARGE VACUOLE (so chloroplasts on outside - smaller diffusion distance for CO2)
- Many CHLOROPLASTS
- Have cytoskeletal threads + motor proteins that move the chloroplasts according to height - 33Plants - root hair cells- Hair-like projections increase the surface area for absorption
- Mineral ions are ACTIVELY TRANSPORTED in so water will follow (down the water potential gradient)
- Are carrier proteins in the membrane for the active transport of mineral ions
- Produce ATP - 34Plants - xylem tissue- Carries water + mineral ions
- DEAD cells, aligned end to end
- LIGNIN waterproofs them
- Narrow tubes (so the water column doesn't break + for capillary action)
- BORDERED PITS in the dignified walls allows water to move sideways, between adjacent vessels
- Lignin deposited in annular/reticular/spiral patterns -> flexibility - 35Plants - phloem tissue- Transports assimilates
- Consists of sieve tubes, made of sieve tube elements + companion cells (elongates the sieve tubes)
- NO NUCLEUS and LITTLE CYTOPLASM (space for the mass flow of sap)
- Sieve plates (assists sap movement) - 36Plants - guard cells- Open and close the stomata
- Light energy is used for ATP to actively transport K+ ions in - water enters then by osmosis and the cell swells (cell wall flexible at the tip and a rigid inner wall) - causes turgidity so stomata opens for gas exchange - 37Other tissues- Parenchyma = packing tissue
- Collenchyma = strengthens vascular bundles with cellulose
- Schlerenchyma = lignified - 38Other (plant cells/tissues)- Plant organs = stem, leaves, root
- CAMBIUM CELLS in the vascular bundle differentiate into XYLEM and PHLOEM
- MERISTEM CELLS = thin walls with little cellulose, no chloroplasts, small vacuole - 39Plants - epidermal tissue- Flattened, closely packed cells that LACK CHLOROPLASTA (except guard cells)
- Form a protective covering over leaves, stems and roots
- Some walls have a WAXY CUTICLE to prevent water loss - 40Plants - meristematic tissue- Contains stem cells, so is where all other plant cells are derived from
- Found at the TIPS OF SHOOTS AND ROOTS and in the CAMBIUM of the vascular bundle - 41Plants - vascular tissue- Transport
- Consists of the xylem and phloem - 42What is a stem cell?This is an unspecialised cell that is able to express ALL of its genes and divide by mitosis
Once stem cells have become SPECIALISED, they enter the G0 stage of the cell cycle (have become differentiated so can no longer divide) - 43What are the 3 different levels of stem cell potency (a stem cell's ability to differentiate into different cell types)?- TOTIPOTENT = can differentiate into ANY type of cell (zygote + first 8-16 cells from mitosis)
- PLURIPOTENT = can form ALL TISSUES in the body (human early embryos) - ethical issues
- MULTIPOTENT = can only form a range of cells in CERTAIN TISSUE TYPES (bone marrow, umbilical cord) - 44Abilities of some stem cells- Meristematic stem cells can CLONE PLANTS (eg. for disease resistance)
- Embryonic stem cells = found in the inner cell mass of the BLASTOCYST (the embryo 5-6 days after fertilisation) - 45What are induced pluripotent stem cells (iPSC's)?They are made in labs. They are generated from adult cells that have REGAINED the capacity to be pluripotent.
- 46What are the main uses of stem cells?- Bone marrow transplants
- Drug trials/research
- Developmental biology (study of process of how animal and plant cells grow +
develop)
- Repair/replacement of damaged tissues
- Medical uses (eg. type 1 diabetes, Parkinson's, Alzheimer's (neurological conditions), spine injuries, growing organs for transplantation) - 47What is therapeutic cloning and its process?In therapeutic cloning, the stem cell is made to have the SAME GENES as the patient, to reduce the risk of rejection
PROCESS:
- Nucleus taken out of a human egg cell
- Nucleus from patient put into egg cell
- Egg cell stimulated to develop into an embryo
- Stem cells grown
- Stem cells treated - 48How are erythrocytes and neutrophils produced?The production of erythrocytes and neutrophils are derived from the stem cells in bone marrow
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- A level Biology FlashCards sobre Cell division/diversity/differentiation flashcards, criado por Rhea Sekhon em 04-12-2021.
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- Rhea Sekhon
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