2.6 cell division, diversity and differentiation Flashcards
What events happen within the cell during M phase?
- cell growth stops
- mitosis
- cytokinesis
What are the processes in mitosis?
- prophase
- metaphase
- anaphase
- telophase
How do cells reproduce?
By duplicating their contents then splitting into two identical daughter cells.
What is cytokinesis?
Cytoplasmic division following nuclear division, resulting in two new daughter cells.
What is interphase?
The phase of the cell Cycle, where the cell is not dividing, it is subdivided into growth and synthesis phases.
What is mitosis?
Type of nuclear division that produces daughter cells, genetically identical to each other and to the parent cell.
What are the two main checkpoints?
- G1/S
- G2/M
What is the purpose of checkpoints
- prevent uncontrolled division, which leads to tumours.
- to detect and repair damaged DNA.
Why do molecular events that control the cell cycle happen in a specific sequence?
- the cycle can’t be reversed
- DNA is only duplicated once in each cell cycle.
What is the hayflick constant?
The number of subdivisions cell can undergo. It is usually 50.
What is the P53 gene do?
Triggers the two main checkpoints in the regulation of the cell cycle.
What are the components of interphase.
- Growth 1
- synthesis
- growth 2
What other components of m phase?
- Mitosis
- cytokinesis.
What is for G0 phase?
My cells undergo differentiation or apoptosis.
What is apoptosis?
The cell death
What events happen in the G0 phase?
- apoptosis
- differentiation
- senescence
some cells remain in this phase for a very long time or indefinitely.
What events happen in the G1 phase?
- cells grow and increase in size.
- Protein synthesis
- organelles duplicate
What events happen in the synthesis phase?
- DNA replicates
- chromosomes have been duplicated, each pair has identical sister chromatids.
What happens during the G2 phase?
The cells grow
How is mitosis used?
FOR:
- growth—-> clonal expansion of B cells
- tissue repair
- asexual reproduction —>strawberries
What are chromatids?
Replicates of chromosomes.
What is tubulin?
cytoskeleton protein.
What is a centrosome?
A cellular structure made from two microtubule rings known as centrioles.
What is a chromosome?
Structures in a cell that contain genetic material.
What is a centriole?
A component of the cytoskeleton that is located near the nuclear envelope.
What is a centromere?
The structure in a chromosome that holds together the two chromatids.
What is a simplified explanation of what happens during prophase?
Preparation for nuclear division.
What is a simplified explanation of what happens during metaphase?
Middle. The chromosomes are at the equator.
Why is it simplified explanation of what happened during anaphase?
Away- the chromosomes are at the poles.
What is a simplified explanation of what happens during telophase?
Two nuclei - the membranes are forming.
What are the 5 steps in prophase?
- Two identical cystic chromatids shorten and thick and into DNA supercoils.
- Nuclear envelope breaks down.
- centrioles divided into 2
- The two new centrioles moved to opposite poles of the cell
- tubulin threads form a spindle between the centrioles
What happens during metaphase?
- Two sister chromatids
line up around the middle of the cell - Spindle threads attach to the centromere of each chromatid.
What happens during Anaphase?
- the centromere of each pair of cystochromatids splits
- the spindles contract by motor proteins walking along the tubulin threads, which pull each of the sister chromatids towards opposite poles
- the centromeres go first, making chromatids into V shapes.
What happens during telophase?
- the separated chromosomes reach opposite poles
- a new nuclear envelope forms around each set of chromosomes
- the cell now contains two nuclei, each genetically identical to each other and the parent cell.
What happens after mitosis?
Cytokinesis.
What happens during cytokinesis in animal cells?
Plasma membranes fold inwards and into the cytoplasm
What happens during cytokinesis in plant cells?
An end plate forms where the spindle equator was, a new plasma membrane and cellular cell wall form either side of the plate.
How do eukaryotic cells divide?
mitosis and meiosis
How do prokaryotic cells divide?
binary fission
how do viruses replicate?
by injecting their nucleic acid into the host cell to replicate virus particles.
what is the longest stage of the cell cycle?
interphase (95%)
what are the stages of the cell cycle?
- interphase
- nuclear division—-> mitosis, meiosis
- cytokinesis
what are diploid cells?
cells with 2 copies of each chromosome
What does haploid mean?
Having only one set of chromosomes, it is represented by the symbol n.
What homologous chromosomes?
Matching chromosomes contain the same genes at the same place.
What are alleles
Alternative forms of a gene.
What is meiosis?
a type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
What is the significance of meiosis in life cycles?
It increases genetic variation within a species allowing an increased chance of survival in the environment changes.
Where is the diploid cell?
a cell with two sets of chromosomes represented by the symbol 2N.
How many chromosomes do human cells have?
46 chromosomes
—> 23pairs.
Why do the chromosomes only become visible in prophase?
Because they begin to condense.
What are the 5 stages in meiosis?
- interphase
- meiosis 1
- short interphase
- meiosis 2
- cytokinesis.
What happens during prophase one of meiosis?
- chromatin condenses, become visible
- nuclear envelope breaks down and Spindle fibres form the centriole
- the chromosomes come together in their homologous pairs, each consisting of two chromatids
- crossing over
What happens during metaphase one with meiosis?
- pairs of homologous chromosomes attach along the equator of the spindle by their centromere.
- Homologous pairs are arranged randomly with the members of each pair facing opposite poles of the cell.
What happens during anaphase one of meiosis?
- The members of each pair of homologous chromosomes are pulled apart.
- The centromeres do not divide
- each chromosome consists of two chromatids - The crossover area separate from each other, resulting in swapped areas of chromosome and allele shuffling.
What happens during telephase one of meiosis?
- Two nuclear envelopes form around each set of the chromosomes in a cell divides by cytokinesis.
- Each new nucleus contains half the original number of chromosomes, but each chromosomes consist of two chromatids.
What happens during prophase two of meiosis?
- Nuclear envelope breaks down.
- Chromosomes coil and condense
- the chromatids of each chromosome are no longer identical
- Spindles form.
What happens during metaphase two of meiosis?
- Chromosomes attached by their centromere to the equator of the Spindle.
- The chromatids are randomly arranged.
What happens during anaphase Two of meiosis.
- Centromeres divide
- Chromatids of each chromosomes are pulled apart towards opposite poles.
What happens during telephase two of meiosis?
- nuclear envelope forms around each other for haploid nuclei.
- The two cells now divide to give four haploid cells.
How many haploid cells are produced in meiosis?
4.
How can meiosis produce genetic variation?
- The crossing over during prophase one shuffles the alleles
- Independent assortment of chromosomes leads to further random distribution
What are epithelial cells?
Cells that constitute tissue lining
What are stem cells?
Unspecialised cells are able to express all of their genes and divide by mitosis
What is differentiation?
Process by which stem cells become specialised into different types of cell
What is differentiation?
Process by which stem cells become specialised into different types of cell
What are examples of specialised plant cells?
- palisade cells
- guard cells
- root hair cells
What are examples of specialised plant cells?
- palisade cells
- guard cells
- root hair cells
Where are palisade cells found, and what are they adapted for?
- in the leaves
- photosynthesis
How are palisade cells adapted?
- long and cylindrical
- large vacuole
- many chloroplasts
- cytoskeleton threads and motor proteins
Where are guard cells found, and what are they adapted for?
- lower epidermis
- gas exchange
How are guard cells adapted?
- inner and outer walls can bend
- large vacuole so can become turgid
What are examples of plant organs?
- leaf
- root
- stem
- flower
Where are root hair cells found, and what are they adapted for?
- epidermal cells
- absorption of water + mineral ions
How are root hair cells adapted?
- long projections
- thin permeable cell wall
- large vacuole
- lots of mitochondria
What are the main functions of the leaf?
Photosynthesis
What are the main functions of the root?
- anchorage in soil
- absorption of mineral ions+water
- storage
What are the main functions of the stem?
- support
- holds the leaf up
- storage
- transport water+minerals
- transport products of photosynthesis
What is the kain function of the flower?
Sexual reproduction
What are the 4 main types of body tissue?
- epithelial
- muscle
- connective
- nervous
What is a tissue?
Group of cells that work together to perform a specific function
What is an organ?
A collection of tissues working together to perform a function
What is an organ system?
A number of organs working together to carry out an overall life function
What are examples of human organs?
- brain
- lungs
- heart
- skin
What are examples of organ systems?
- endocrine
- nervous
- digestive
Why do multicellular organisms need specialised cells?
Because they have a smaller surface area to volume ratio, so most of their cells are not in direct contact with the external environment.
What is a zygote?
An egg cell that has been fertilised by a sperm cell.
What are examples of specialised animal cells?
- erythrocytes
- neutrophils
- spermatozoa.
How will erythrocytes adapted to carry out their function?
- very small
- biconcave
- well developed cytoskeleton so that they are flexible
- no nucleus, mitochondria, endoplasmic reticulum and very little cytoplasm.
How are neutrophils adapted to occur at their function?
They have a lobed nucleus.
How are sperm cells adapted to carry out their function?
- Many mitochondria
- long, thin and small
- acrosome
- Very little cytoplasm
- Haploid male gametes.
How are epithelial cells adapted to carry out the function?
Squamous epithelial cells are flattened in shape. They have cilia
What are the characteristics of epithelial tissue?
- cells are very close together, forming continuous sheets
- no blood vessels
- Smooth surfaces
- Some have cilia or microvilli
- Short cell cycles.
Were the functions of epiphelial tissue?
To cover a line free surfaces of the body.
Where can epithelial tissue be found?
Digestive and respiratory system
- skin
- blood vessels
- heart chambers
- walls of organs.
What does connective tissue consist of?
Non-living extracellular proteins (collagen and elastin) and polysaccharides.
What are examples of connective tissues
- Blood
- bone
- cartilage
- tendons
- ligaments.
What are immature cells in cartilage called?
chondroblasts
What are the three types of cartilage?
- Hyaline
- Fibrous
- elastic.
What does hyaline cartilage form?
- EMBRYONIC SKELETON
- it covers the end of long bones in adults
- joins ribs to the sternum found in the nose, trachea and Larynx.
Where is fibrous cartilage found?
In between the vertebrae in the spine.
Where is elastic cartilage found?
In the epiglottis.
What are the three types of muscle tissue?
- Skeletal
- cardiac
- smooth.
What is skeletal muscle used for?
When is skeletal muscles contract bones move
Where is cardiac muscle found and what does it do?
It is found in the walls of the heart and allows the heart to beat and pump blood.
Where is smooth muscle found?
The walls of the intestine, blood vessels, uterus, and urinary tracts.
What does smooth muscle do?
propels substances along the respiratory tracks.
What is epidermal tissue?
Flattened cells in plants that form protective covering over leaves stems and roots.
What is meristematic tissue contains?
Stem cells.
Where is meristematic tissue found?
Root and shoot tips and in the cambium of vascular bundles.
What other characteristics of meristem tissue?
- can divide by mitosis and differentiate into other cells.
- thin walls with very little cellulose
- no large vacuole.
- no chloroplasts
How do cambium cells differentiate into xylem vessels?
Lignin is deposited into the cell walls to reinforce and waterproof them, which kills the cell. The ends of the cell breaks down to form a wide continuous column
How do cambium cells differentiate into phloem sieve tubes?
sieve tubes lose most of their organelles and sieve plates develop between them.
How do cambium cells differentiate into phloem companion cells?
Companion cells retain their organelles and continue metabolic functions to provide ATP for active loading of sugars into the sieve tubes.
