Chapter 6- Cell Division Flashcards
Interphase
Long periods of growth and normal working separate divisions. These periods are called interphase and a cell spends the majority of its time in this phase
DNA is replicated
Protein synthesis occurs in cytoplasm
Mitochondria grow and divide, increasing in number in the cytoplasm
Chloroplasts grow and divide
The normal metabolic processes occur
Three stages of interphase
G1- the first growth phase: proteins from which organelles are synthesised are produced and organelles replicate. The cell
increases in size
G2- the second growth phase: the cell continues to increase in size, stores are increased and duplicated DNA is checked for errors
Miotic phase
Mitosis-the nucleus divides
Cytokinesis-the cytoplasm divides
What is G0
The phase in which the cell leaves the cycle temporality or permanently
Reasons to go into G0
Differentiation-A cell that becomes specialised to carry out a particular function. It will carry out this function indefinitely
The DNA of a cell may be damaged, in which case it is no longer viable. A damaged cell can no longer divide and enters a period of permanent cell arrest. As you get older the number of these cells in your body increases
Checkpoints at various stages
G1-if satisfies these requirements it is triggered to begin DNA replication. If not it enters G0
G2- this checkpoint is at the end of G2 phase, before the start of the mitotic phase , DNA has to of been replicated without error
Spindle assembly checkpoint- at point where all spindles should be attached and aligned
Importance of mitosis
For growth,tissue repair and asexual reproduction
Prophase
Coil and condense to form chromosomes, the nucleoulus disappears, and nuclear envelope is broken down.
Micrtubles form spindle shaped structures linking the poles of the cell. Necessary to move the chromosomes into position. Centrioles migrate to poles of the cell. By end of prophase nuclear envelope has also disappeared
Metaphase
The chromosomes are moved by the spindle fibres to form a plane in the centre of the cell, and then held into position
Anaphase
The centromeres holding together the pairs of chromatids are separated and are pulled to opposite poles of the cells and form v shaped chromatids.
Telophase
Chromatids have reached the poles and are now capped chromosomes, the two new sets of chromosomes and nuclear envelope reforms around them. Chromosomes start to uncoil smd nucleolus is formed
Meiosis
Nucleus divides twice to produce four daughter cells
Homoglogus chromosome
Each organisms cell contains two full sets of genes one from each parent
Prophase 1
Chromosomes condense, the nuclear envelope disintegrates, the nucleoulus disappears and spindle formation begins.
Metaphase 1
Chromosomes lie across the metaphase plate , but not as individual chromosomes
Anaphase 1
Pulled to opposite poles of the cells but chromatids are held together. Can form recombinant chromatids. Genetic variation arises
Telephase 1
Chromosomes assemble at each pole and nuclear membrane reforms. Chrmomsomss uncoil. Cells undergo cytokinesis
Prophase 2
Still consist of two chromatids, condense and become visible, nuclear membrane breaks down
Metaphase 2
More independent assortment more genetic variation as they lie across the middle
Anaphase 2
V shaped chromosomes are formed same as in anaphase of mitosis
Telephase 2
Chromatids assemble at the poles, form chromatin again nuclear envelope reforms and the nucleus becomes visible. Cytokinesis occurs forming four daughter cells in total.
How are erythrocytes specialised?
Have a flattened bioconcave shape
No nuclei
Flexible so can squeeze through gaps
How are neutrophils specialised
Multi lobed nucleus makes it easier for them to squeeze through gaps
Cytoplasm contains many lysosomes
How are sperm cells specialised
Have a tail so are capable of moving and contain many mitochondria to help create energy to swim
Head contains enzymes which help penetrate the ovum
How are palisade cells specialised
Contain chloroplasts which absorb lots of light
Thin cell walls to allow diffusion
Large vacuole to help maintain pressure
How are root hair cells specialised
Large SA
maximises uptake of water
How are guard cells specialised?
Thicker on one side so doesn’t change shape
Changes shape depending on water
Types of tissues
Nervous tissue
Epethial tissue
Muscle tissue
Connective tissue
Squamous epethielium
Forms lining of lungs
Flat layer of squamous cells
Ciliated epethieulum cells
Hair like structures called cilia that move in a rhythmitic manner. Globlet cells are also present releasing mucus to trap any unwanted particles present in the air.
What is cartilidge
A connective tissue found on the ear contains elastin and collagen
What does epidermis cover
The surfaces of plants
What are stem cells differentiated into in bone marrow
Erythrocytes and neutrophils
What are produced in the meristems
Xylem vessels
Phloem siege tubes
