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What are the 4 things that an animal cell has?

Cell membrane


What are the 7 things that a plant cell has?

Cell membrane
Cell wall


What are the main feature of a bacterial cell?

Plasmid DNA
Chromosomal DNA
Cell wall


What do light telescopes do?
Electron telescopes?
What is the magnification formula?

Let us see nuclei, chloroplasts and mitochondria

Smaller things like plasmids in more detail

Length of image / length of specimen


What does DNA stand for and what is it made up of?

Deoxyribonucleic acid
Has two strands coiled together and is made up of four bases: adenine, guanine, cytosine and guanine
Which pair together A-D and C-G with a weak hydrogen bond
Has a sugar phosphate backbone in the shape of a double helix


What is DNA and what does it do?
What is a gene?

The code for you characteristics and determines which genes are turned on or off so which proteins a cell produces
A small section of the DNA strand that carry the instructions to make a specific protein


What did Watson, Crick, Franklin and Wilkins do?

1) Rosalind Franklin and Maurice Wilkins worked out that genes had a helical structure by directing beams of X-rays onto crystallised DNA and looking at patterns the X-rays then formed when the bounced off
2) James Watson and Francis Crick then used this research and their knowledge that the amount of adenine + thymine = cytosine and guanine to make a model and fit the pieces together


What is protein synthesis and the two steps involved?

The making of proteins which join together eventually to make enzymes/other proteins
Transcription and Translation


How to cells make proteins?
How many amino acids are there?

By stringing a number of amino acids together in a particular order
20 which make thousands of different proteins


What does the order of bases in a gene do?
What codes for an amino acid?

Tell the cells which order to put the amino acids together
A set of 3 bases (codons)


What do proteins do?

Help to make all the other things which aren't made of proteins (cell membrane) from substances that come from the diet like fats and minerals


How are proteins made?

By organelles called ribosomes and protein synthesis


Describe why transcription happens

DNA is found in the nucleus and is so big that it can't be moved out of it, but the ribosomes in the cytoplasm need to get the information from the DNA in order to make the proteins


Describe the mRNA

Similar to DNA but is shorter and only a single strand with the base thymine replace by Uracil
mRNA is effectively the messenger between the nucleus and the ribosome


Describe transcription

The DNA unzips itself with the use of an enzyme and the DNA strand is them used as a template for the mRNA the base pairing ensures its complementary (exact match)
The DNA then is zipped backed up by another enzyme


Describe translation

The mRNA then moves out of the nucleus and joins to a ribosome, the ribosome reads the mRNA in codons and a tRNA is then used to bring the specific amino acid to those codons
The ribosome sticks the amino acids together to make a polypeptide (protein) which follow the order of the codons on the mRNA


What is the result of protein synthesis

Proteins are made with their own specific sequence and number of amino acids, the DNA sequence is what tells the proteins what sequels feel it needs to be in
It then folds up into the right shape to do a specific job e.g. Be a protein


What is a mutation?

Change in a organisms DNA base sequence, affecting the sequence of amino acids in the protein the shape of the protein and so the function. Eventually it could affect the characteristics of the organism


What can mutations be?

Harmful- e.g. Causing a genetic disorder
Beneficial- child produce a new characteristic that benefits them e.g. A bacterial plasmid can have a mutation making them resistant to antibiotics
Neutral- neither harmful or beneficial and don't affect a proteins function


What are enzymes?
What are they made out of?
What is a catalyst?

Catalysts produced by living things
A substance which increases the speed of reaction without being changed or used up in it


Why does the body produce enzymes?

Speed up reactions
Enzymes reduce the need for high temperatures and reduces the unwanted reactions speeding up so, it only increases the useful chemical reactions in the body


What can enzymes be used for?

DNA replication – enzymes helps copy a cells DNA before it divides by mitosis on meiosis
Protein synthesis – enzymes hold amino acids in place and form bonds between them and it also unzips and re-zips the DNA strand
Digestion - various enzymes are secreted into the gut to digest different food molecules


What does a chemical reaction usually do?
What is the substrate?
What is the active site?
Why does only one substrate fit?

Chemical reactions involve things either being split apart or joined together
The molecule changed in the reaction
The place where the substrate joins on to catalyse the reaction
Enzymes have a high specificity for their substrate meaning that only one specific substrate will fit and cause the reaction to happen


What is the 'lock and key' mechanism?
What are the three factors which affect the rate of reaction of an enzyme?

The idea that the substrate has to fit perfectly onto the active site or the reaction won't be catalysed
Substrate concentration pH and temperature


What is the key temperature for enzymes in the body?
What happens if an enzyme gets too hot?

The enzyme bonds that hold the enzyme together start to break this means that they lose their shape of the active site it doesn't fit the shape of the substrate anymore, so can't catalyse the reaction stops. The enzyme is now denatured and will not return to its usual shape if it cools down


What happens if the pH is incorrect for that enzyme?
What pH does pepsin work best at? (the optimum pH)

The pH interferes with the bonds holding the enzyme together so means that if it is incorrect it will denature the enzyme


How does the substrate concentration affect the reaction speed?

It will make the reaction faster up to a point
(When all the active sites are full and adding more doesn't make a difference)


What is the human genome project?

Thousands of scientists from all over the world collaborated to map out the 25,000 genes that there are in 23 chromosomes
The collaboration from worldwide scientists meant that the genes were found quicker and the data could be made public


What are the good things about the human genome project?

Predict and prevent diseases – if doctors knew about what genes caused what diseases then we could all have unique advice on the best lifestyle and diet, doctors could regularly check us to find diseases early on and cures can be found for genetic disorders
Develop new and better medicines – medicines the design specifically for us on how the our bodies will react to the disease and any possible treatments (treatment will be more effective)
Accurate diagnosis – some diseases are hard to test for, if we know the genetic causes of them accurate testing will be a lot easier e.g. Testing for Alzheimer's
Improved forensics science- forensic scientists can produce a DNA fingerprint from material found at a crime scene and can match it to the suspects DNA. In the future it might be possible to find out what the suspect looks like for the DNA found at the scene.


What are the bad things about the human genome project?

Increased stress – if someone knew from an early age that they're susceptible to a nasty break disease make a panic every time we get headache.
Geneism – people with genetic problem problems could come under pressure to not have children and pass the genes on
Discrimination by employers and insurers – life insurance could become impossible to get if you have a genetic likelihood e.g. A serious disease also employees may discriminate against people who are genetically likely to get a disease.


What is genetic engineering?

Scientists can now cut and paste useful Genes using enzymes from one organisms chromosomes into the cells of another
E.g. The useful gene is cut from one organisms chromosomes using enzymes, that gene is then inserted into another organism producing a genetically modified organism


How can genetic engineering benefit humans?

Vitamin A

Reducing vitamin a deficiency – beta-carotene is used by our bodies to make vitamin A, Vitamin A deficiency is a big problem in south Asia and Africa up to 500,000 children go blind to due to the lack of vitamin A. Golden rice is a variety of GM rice and it contains two genes from other organisms who together enable the rice to produce vitamin A. So growing golden rice in these places will reduce the number of people who suffer from vitamin a deficiency


Benefiting humans: Producing human insulin

Human insulin gene can be inserted into bacteria to produce human insulin rapidly
Lots of human insulin can be produced rapidly and cheaply for people with diabetes


Benefiting humans: Increasing crop yield

GM crops have their genes modified e.g. to make them resistant to herbicides
Fields of these crops can be sprayed with herbicide and all the plants except the GM crops are killed, this increases the yield of the crops and makes more food


What are the concerns that people have about GM crops?

Many people worry about the number of weeds and flowers and therefore the wildlife that usually live in and around the crops - reducing farmland biodiversity
Not everybody is convinced that GM crops are safe people are worried that they might develop allergies to the food
A big concern is that transplanted genes could make it out to the natural environment eg the herbicide resistance Gene could be picked up by weeds making a superweed variety that are resistant to herbicide


What is mitosis and what does it do?
How many cells does mitosis result in?

The division of diploid cells to produce new cells for growth and repair
2 genetically identical diploid cells


What does diploid mean?

All 46 chromosomes (23 pairs)


Explain mitosis

When the cell gets the signal to divide it will duplicate all the DNA for a Cody for each cell, the DNA will form an. Shaped chromosome with each 'arm' an exact replica of the other
The chromosomes will then line up in the centre of the cell and the cell fibres will pull each area of the chromosome to the opposite poles
Membranes then begin to form around each set of chromosomes and these become the nuclei of the two new cells
Lastly the cytoplasm divides you know have to diploid cells containing the exact same DNA (they are genetically identical)


What can mitosis also be used for?

Asexual reproduction
Organisms such as strawberry plants form runners and reproduce this way
The runners from into new plants and the offspring has exactly the same genes as the parent (there is no genetic variation)


What is meiosis and when does it happen?
What is a gamete?
What is a haploid cell?

Meiosis is the process which create sex cells in order for the organism to reproduce it occurs before a female is born to form the eggs and throughout a males life
Gametes are sex cells
Haploid is half the amount of chromosomes (23)


What is a zygote?
How many gametes are produced in meiosis?

When two haploid cells combine to form a gamete
4 genetically different haploid cells


Describe meiosis

You start off with one diploid cell and it duplicates the DNA with one arm being exactly the same copy as the other
The first division is when the 2 lines of chromosome are pulled to the end of each pole with some of the mothers DNA and some the fathers DNA going into the different two cells
Each cell will have a mixture of the mothers and the fathers chromosomes, mixing up the alleles in this way great variation in the offspring is a huge advantage of sexual reproduction over a sexual
The next division is when the chromosomes lineup again in the centre of the cell and the arms of the crime is chromosomes are pulled apart
As a result of the cell membrane forming round the cell and nuclei you get four haploid gametes each with only a single set of chromosomes in it


What is cloning?

A type of asexual reproduction producing cells and organisms directly identical to the original organism
E.g. Dolly the sheep


Describe the process of cloning

1. a normal skin cell is taken from the organism that you want to clone and has its nucleus with the genetic material needed removed
2. An unfertilised egg cell is taken from a female and then using enzymes has the nucleus removed making it to an enucleated egg
3. The diploid nucleus of the skin cell is then inserted into the unfertilised empty egg and the eggs nucleus is thrown out
4. The now filled egg is then stimulated using an electric shock making it divide like a normal embryo would
5. The embryo is then placed into the surrogate mother for it to divide and produce a genetically identical copy of the original body cell/organism


What are the uses of cloning?

•Help with the shortage of organs for transplants- genetically modified pigs are being bred to provide suitable organs for humans- helping to meet the demand of organ transplants
•The study of animal clones could lead to greater understanding of the development of the embryo and of ageing and age related disorders
•cloning could also help protect endangered species


What are the issues surrounding cloning?

— cloning mammals leads to a reduced gene pool, this means that there are fewer alleles in the population meaning if the population are closely related and a disease appears they could all be wiped out because there might be no allele in the population giving resistance
— cloned mammals might not live as long – Dolly only lived for six years, she's put down because of lung disease and arthritis (usually found in older sheep) he was cloned from older sheep so some suggest her true age maybe older but it is possible she was just unlucky
— there are risks and problems associated with cloning, the cloning process often fails, clones are often born with genetic defects and their immune systems are sometimes unhealthy so they suffer from more diseases


What is a stem cell?

And undifferentiated cell which has the ability to turn into any cell perform any job
They are able to divide to produce even more stem cells or different types of specialised cell
To start with, all the cells in an embryo are the same (undifferentiated) and these are called embryonic stem cells
It is by the process of being specialised (differentiation) that an embryo starts to develop a recognisable human body with organs and systems
Many animal cells lose the ability to differentiate an early stage but lots of plant cells don't ever lose this ability


Where can stem cells be found?

Adult stem cells can be found in certain places like bone marrow these cells aren't as versatile as the stem cells in embryos they can only differentiate into certain types of cell


What can stem cells be used for?

Cure diseases e.g. sickle-cell anaemia can sometimes be cured with bone marrow transplant containing adult stem cells which produce new blood cells
Scientists have experimented with extracting stem cells from very early human embryos and growing them under certain conditions they will differentiate into specialised cells
It might be possible to use themselves to create specialised cells to replace those which have been damaged by diseases or injury e.g. new cardiac muscle cells to help someone with heart disease


What are the ethical concerns of stem cells?

Some people are strongly against embryonic stem cell research they argue that human embryo should be used for experiments because each one is a potential human life, they say scientists should find other sources of stem cells
Other people think that caring place in who are suffering to be more important than potential life of the embryo they point out the embryos used are often unwanted
In some countries and stem cell research is banned, it's allowed in the UK under strict guidelines