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About the Science Teacher - Mark

25 years experience teaching students aged 11-18, fully qualified teacher status, BSc (Hons) Natural Science with Chemistry (Open), Diploma in Chemistry (Open), PGCE Secondary Science (University of East London), Experience in both State and Private schools, Experience as an examiner marking exam papers, Experience working for a home learning school, including the role of lead tutor for Chemistry.

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Organism	How growth and development occur
Animal	Mitosis increases cell number. Daughter cells grow and differentiate to form tissues such as muscle or nervous tissue.
Plant	Mitosis produces new cells in meristems near root and shoot tips. Many new cells then take in water, elongate and differentiate.

Feature	Asexual reproduction	Sexual reproduction
Parents and gametes	One parent; no fusion of gametes.	Gametes fuse at fertilisation; usually two parents.
Advantages	No need to find a mate. A rapid reproductive cycle can produce many offspring in favourable conditions.	Genetically varied offspring increase the chance that some survive a change in conditions.
Disadvantages	Clones have little or no genetic variation, apart from mutations. The same disease or environmental change may affect many of them.	Finding a mate takes time and energy in many species; reproduction is often slower.

Feature	Mitosis	Meiosis
Daughter cells	Two.	Four.
Chromosome sets	The same number as the parent cell.	Half the number in the original diploid cell.
Genetic information	Genetically identical, unless mutation occurs.	Genetically different.
Main role	Growth, repair and asexual reproduction.	Production of haploid gametes.

Term	Meaning
Chromosome	A long DNA molecule associated with proteins. It carries many genes.
Gene	A section of DNA that codes for a specific protein.
Genome	The entire DNA of an organism, including coding and non-coding regions.

Base on one strand	Complementary base
Adenine (A)	Thymine (T)
Thymine (T)	Adenine (A)
Cytosine (C)	Guanine (G)
Guanine (G)	Cytosine (C)

Step or material	Purpose
Crushing fruit	Breaks up tissue and helps release cells and their contents.
Detergent	Disrupts the cell and nuclear membranes, releasing DNA.
Salt	Helps DNA molecules come together when alcohol is added.
Filtering	Removes larger pieces of cell debris; dissolved DNA passes into the filtrate.
Cold ethanol	DNA is poorly soluble in ethanol and precipitates as visible strands.

DNA template base	RNA base added
A	U
T	A
C	G
G	C

mRNA codon	Amino acid
AUG	Methionine
CCU	Proline
GAA	Glutamic acid

Location of variant	Possible effect	Link to phenotype
Protein-coding DNA	An altered base sequence can change the amino acid sequence and protein activity.	For example, an enzyme may make less pigment because its active site changes.
Non-coding regulatory DNA	Altered RNA polymerase binding can change how much mRNA and protein are made.	The amount of pigment may change even if the protein sequence stays the same.

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