biology unit 2
has most things that are covered in biology as level topic 3
- Created by: rima
- Created on: 01-06-13 22:44
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- unit 2 biology
- prokaryotic cells
- infolding of cell surface membrane
- the site of respiration, as it has a large surface area for production of energy
- plasmid
- circle of DNA
- capsule
- slimy layer on the surface for protection and prevention of dehydration
- pili
- thin protein tubes which allows bacteria to adhere to the surfaces
- flagellum
- hollow cylidricle structures to move and rotate the cell
- cell wall
- containing peptidoglycan
- circular DNA
- ribosomes
- cytoplasm
- infolding of cell surface membrane
- eukaryotic cells
- protein transport
- meiosis
- a type of cell division where gametes with half the number of chromosomes are formed
- genetic variation
- independent assortment
- happens during meiosis 1 where chromosomes pairs as they line up
- there are many combinations which creates genetic variation
- happens during meiosis 1 where chromosomes pairs as they line up
- crossing over
- chromosomes come together as pairs
- all four chromatids come into contact
- at the contact points the chromatids break and rejoin their sections of DNA
- independent assortment
- chromosomes replicate before division
- chromosomes pair up then seperate
- chromatids seperate forming gametes
- chromosomes pair up then seperate
- cell cycle
- mitosis
- prophase
- chromosomes are more visible
- nuclear envelope breaks down
- chromosomes becomes shorter and thicker
- spindle forms
- centrioles position themselves at opposite sides of cell
- metaphase
- centromeres attach to spindle fibres
- chromosomes move to the equator of cell
- anaphase
- spindle fibres shorten
- spindle fibres pull cromatids towards the poles and are seperated
- spindle breaks down
- telophase
- nuclear envelope reforms
- chromosomes unravel
- prophase
- interphase
- gap 1
- gap 2
- synthesis
- cytoplasmic division
- cell surface membrane constricts around the cell , till it is divided into two
- mitosis
- stem cells
- these are unspecialised cells which keep on dividing and can give rise to other cells
- totipotent stem cells can give rise to all the cell types including embryonic cells
- these can be found in the early embryo
- pluripotent stem cells can give rise to most types of cells but not embryonic cells
- these can be found in the older embryos
- when a blastocyst is formed the outer layer forms the placenta while the inner cell mass forms the tissues for the developing embryo
- these can be found in the older embryos
- when cells become increasingly differentiated (specialised) they lose there capacity to develop into a wide range of cells
- multipotent stem cells retain a certain capacity to still give rise to a varity of cell types
- differential gene expression
- this is where different genes are expressed
- first a correct stimulus is given to unspecialised cells
- secondly some genes are either switched off or on
- thirdly mRNA is only made from the active switched on genes
- fourthly the mRNA moves to the ribosomes and protein is made
- this protein can alter the function and the strcture of the cells
- as the embryo develops , cells differentiate and become specialised for one function
- Igor and Thomas demonstrate that different genes are expressed in different cells
- firstly they extracted mRNA from both differentiated and undifferentiated cells
- secondly they used reverse transription to produce cDNA strands for the differentiated mRNA
- thirdly they mixed the cDNA strands with the mRNA from undifferentiated cell , which produced double strand hybrid
- these hybrids were then seperated finding that two cells were expressing some of the same genes and also different genes
- this is where different genes are expressed
- cell organisation
- cells
- cells are specialised for a particular function
- tissue
- a group of specialised cells working together to carry out a particular function
- organ
- a group of tissues working together to carry out one function
- organ systems
- a group of organs working together to carry out a particular function
- cells
- genes and environment
- genes interact with the environment to produce the organisms phenotype
- phenotype is an organisms characteristics
- discontinuous variation is when characteristics are controlled by genes at a single locus
- continuous variation is usually affected by both genes and the environment
- eg human height meaning that there is a bigger range
- a person may have the genes for being tall but not achieve their full potential height because of thier poor diet
- eg human height meaning that there is a bigger range
- polygenetic inheritance is when a number of genes are involved in the inheritance of a characteristic
- prokaryotic cells
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