Studied by 0 peopleMitosis
This is the replication of a nucleus into two new nucleus which is typically accompanied by cytokinesis.
Epistasis
is a form of inheritance in which a characteristic is controlled by 2 different genes at different loci, each gene having 2 alleles.
Dominant epistasis
the dominant allele of one gene (the epistatic gene) masks the effect of the other (hypostatic) gene. The ratio obtained from two double heterozygotes is 12 : 3 :1.
Recessive epistasis
the recessive allele does the masking, so the dominant allele of the epistatic gene needs to be present in order for the hypostatic gene to be expressed, the ratio obtained from two double heterozygotes is 9 :3 :4
Variation
refers to the difference that occur in the phenotype and genotype of organisms.
Intraspecific variation
occurs in members of the same species due to sexual reproduction
Sources of variation
Crossing over or exchange in genetic material in meiosis
Independent assortment of alleles due to random alignment on the spindle of the chromosomes in meiosis.
Random fertilizations for any male gametes can fertilize any female gametes.
Gene
is the length of DNA that codes for a specific polypeptide
Double stranded Chromosome
has 2 sister chromatids, that are identical to each other having the same allele at the same loci
Karyogamy
this is a map of all chromosomes, obtained by karyotyping.
Phases of interphase
G1
S
G2
G1- Phase
This is the first growth phase, cellular contents double and materials for DNA synthesis accumulate.
S-Phase
This is the synthesis phase, DNA replicated and chromosomes become double stranded.
G2-Phase
This is the second growth stage proteins which are needed for cell division are synthesized including microtubules.
Stages of Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Not seen as an actual stage of mitosis.
Nucleus is still intact
Replicates in a semiconservative manner to avoid errors.
Is 95% of the cell cycle
Nuclear materials seen like thread like structures chromatids.
Prophase
Chromatids start to condense into chromosomes
chromosomes become visible
nucleus membrane disassociates
centrioles move apart
microtubules become spindle
Mutation
this is the change in DNA structure or the amount of DNA in a an organism
Metaphase
Nuclear membrane has broken down allowing chromosomes to move.
Chromosomes randomly align at the equator of the spindle. Spindle fiber attach to the centromeres at the kinetochore.
Anaphase
The centromeres split.
Spindle fibers contract pulling chromatids apart which move to opposite poles.
Telophase
Opposite of prophase
Spindle fibers breakdown
Chromosomes unwinds and become chromatids once again
Nuclear membrane reforms around each set of chromosomes.
Cytokinesis in Animal Cells
This is when invagination takes creating a cleavage furrow moves inward forming 2 cells
Cytokinesis in plant cells
Since the cell wall has to be formed the Golgi vesicles export materials to form new cell walls which separates the cell into teo parts
Genetic Engineering
involves the manipulation of genes by removing DNA from one organism and placing it into the genome of another.
Purposes of Genetic Engineering
Using another organism e.g. bacteria to produce a product such as human insulin
Altering the phenotype of an organism in some way by inserting foreign genes into its genome, creating GMOs (genetically modified organisms) in order to improve some aspects of the organism
Gene therapy, which involves delivering genes into cells to treat a genetic disorder e.g. cystic fibrosis. (this area has not been very successful and now a gene editing tool –CRISPR , shows more promise)
Use of Bacteria in Genetic engineering
Have tiny rings of DNA called plasmids, in addition to DNA in the nucleoid, which have antibiotic resistant genes – these are used as vectors to deliver the gene of interest into a cell
Can be used to express a gene and make a product, as they are very small and multiply rapidly
Have enzymes called restriction endonucleases which are used to cut the DNA of invading viruses (bacteriophages). They recognize and cut a particular base sequence and are used as “molecular scissors” in GE
Enzymes used in GE
Restriction Enzyme
DNA Ligase
Reverse transcriptase
DNA Polymerase
Restriction Enzyme
These cut DNA at a particular sequence in a palindromic way. The same enzyme is used to cut out the gene of interest from a cell as well as cutting the bacterial plasmid, so that the exposed bases in each are are complementary to each other. Staggered cuts create “sticky ends” which give a more secure join when they are put together.
DNA Ligase
molecular glue, joins sections of DNA covalently
DNA Polymerase
used to make multiple copies of DNA from free nucleotides in the polymerase chain reaction
Reverse Transcriptase
found in retroviruses (viruses which have RNA and not DNA). They are able to convert RNA to DNA, which is the reverse of transcription.
Stages in GE
Gene isolation – finding the gene of interest i.e. the one which is going to be expressed
Copying the Gene – many copies of the gene of interest have to be made
Inserting the gene into a vector – plasmids need to be cut open and the gene of interest inserted and joined up
Inserting the vector into a cell – the recombinant gene is now carrying the gene of interested and needs to be placed in the cell, where it will be expressed
Screening – the cells that have the vector with the foreign gene need to be identified ( as the process is only about 1% will be successful)
Cloning – bacteria that have successfully taken up the genes will be allowed to multiply and make the product
Gene Isolation
Can be cut out of the genome of the cell using restriction enzymes (the same one that will cut the plasmid)
Can be made by reverse transcription by extracting RNA from the cells that are expressing the gene and using reverse transcriptase to make cDNA
Can be assembled in a lab from free nucleotides if the sequence is known. This is called gene synthesis cloning.
Gene synthesis cloning
the assembling of free nucleotides when the sequence is known
Processes involved in Polymerase Chain Reaction
DNA polymerase and short lengths of DNA called primers are loaded into the machine
A series of heating and cooling take place
Heating opens the DNA and complementary nucleotides are added
Multiple copies of the gene are made in a short time.
Methods of inserting a vector
Micro-injection
Micro-projectiles
Electroporation
Liposomes
Micro-injection
a very fine pipette is used to inject the DNA into the cell
Micro-projectiles
minute pellets of a heavy metal coated with DNA are shot into a cell at very high speed
Electroporation
rapid brief electrical pulses create temporary gaps in the cell membrane of the host cell, allowing the DNA to enter.
Liposomes
tiny spheres formed from plasma membrane with DNA in them – these pass easily through the cell membrane
Biochemistry
This is the study of chemicals of living organisms
4 most common elements in living things
hydrogen
Carbon
oxygen
nitrogen
4 most common earth elements
oxygen
silicon
aluminum
sodium
What is responsible for the acidic nature of fatty and amino acids?
The carboxylic group (COOH)
Unsaturated bonds
Compounds containing double or triple carbon-carbon bonds eg ethene C2H4
Polarity
This is the uneven charge distribution within a molecule
Dipole
This is when in a molecule one part/pole is slightly negative and the other is slightly positive
Transpiration
The loss of water from plants to the atmosphere outside mainly through the stomata of the leaves
Phloem
Transport solutes and photosynthesis products specialized for the movement of organic and inorganic materials
Xylem
Conducts water and minerals upwards from the roots to the other parts of the plant
How much percentage of blood is water?
Approximately 90%
What is the H-O-H angle?
105 °
Liquid water has what kind of shape?
A tethadral shape
What kind of bonds does water have?
Polar covalent bonds
What kind of molecule is water
A polar molecule
What are hydrogen bonds?
Hydrogen bonds are the forces of attraction formed when slightly positive regions of a water molecule come close to the slightly negative regions of another water molecule.
What causes the high cohesive strength of water?
It is caused by the presence of hydrogen bonds
Surface tension in water is......
High
What is cohesion?
This is the force whereby individual molecules stick together
What is maximum density of water?
Maximum density is achieved at 4°C
Water has a ______ heat of vaporization and fusion
High
What is vaporization?
This is the amount of heat required to convert liquid water into gaseous water.
Liquid water has a ______ specific heat capacity.
High
What is specific heat capacity?
Specific heat capacity is the amount of energy required to raise the temperature of 1 kg by 1°C.
What is Zooxanthellae?
These are microscopic algae that live in a symbiotic relationships with coral polyps.
What is hydrophobic interaction?
This is the action of the non polar molecules clustering together.
What happens in the ionisation of water?
One of the hydrogen atoms leaves the oxygen atom to which it is covalently bonded and jumps to the oxygen atom of another water molecule where it becomes hydrogen bonded.
In ionization of water
what is produced?
What is concentration?
This is the number of solute particles per unit volume.
What is a alkaline solution?
This is one in which the concentration of OH- exceeds the concentration of H+
What is an acid?
This is a substance that causes the concentration of hydrogen ions to rise above its equilibrium value of 1 x 10 -7 molL-
Acids are considered as _______________
These are proton donors
What is a base?
This is a substance that causes a decrease in the relative numbers of H+
Bases are considered as _____________
Proton acceptors
What is alkali?
This is a soluble base.
What are strong acids and bases?
These are substances that ionize almost completely in solution resulting in large increases of H+ and OH-
What is pH value?
This is defined as the negative logarithm of the H+concentration in molL- which is the same as the reciprocal of H+ concentration.
What is the equation to calculate pH?
This is -Log[H+]=log[1\H+]
What are buffers?
These are chemical systems that maintain a relatively constant pH when small amounts of acids or bases are added to a solution.
What makes up a buffer?
It is a mixture of weak acids and its corresponding salt which provides a reservoir of the acid and its anion.
What is an example of a buffer?
An example is carbonic acid (H2CO3) and its salts
What is most abundant organic molecule in nature?
Carbohydrates
What is the primary energy store molecules in most living organisms?
Carbohydrates
What type of bonds are in carbohydrates?
C-C and C-O bonds
What are monosaccharides?
This consists of a single sugar molecule.
What are some examples of monosaccharides?
Glucose and frustose
What are dissacharides?
These contain 2 sugars covalently linked together by
What are some examples of disaccharides?
Examples are sucrose and lactose
What is ratio of H:O in carbohydrates?
Carbohydrates are 2:1
What are polysaccharides?
These contain many sugar units covalently bonded together.
Polysaccharides are also called _________________________
Macromolecules
What is polymerisation?
This is when monomers or individual sugar unit are covalently linked together to create a polymer.
What causes the units to link together?
By the process of condensation (removal of water )
What causes the units to break down?
By the process of hydrolysis which is the opposite of condensation
What are the 3 main types of macromolecules ?
They are polysaccharides
What are polysaccharides used for?
They are used for food storage and structural purposes.
What types of molecules are nucleic acids and proteins?
They are informational molecules
What are some properties of carbohydrates?
Some are all are aldehydes or ketones and all contain several hydroxyl groups
How are monosaccharides classified?
According to the number of carbon atoms such as trioses (3C)
What are the most simplest monosaccharides?
They are trioses
Note 
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