molecular genetics

what does each nucleotide consist of

1. sugar phosphate backbone

   1. nitrogenous base

   2. phosphate group

2. a pentose sugar (for DNA only: deoxyribose)

what is the main role of DNA

it is the long term storage of genetic information, as it contains the specific instructions to make specific polypeptides which determine the traits of an organism

what is complementary base pairing

when each type of base on one strand forms a bond with just one type of base on the other strand

A bind with T and C bind with G

bonds between pentose sugar, nitrogenous base and phosphate

nitrogenous base is attached to carbon-1 of pentose sugar

phosphate group is attached to carbon -5 of its own pentose sugar and carbon -3 of the adjacent pentose sugar

what are the two types of nucleotides and what is their difference

1. purine

   1. adenine

   2. guanine

2. pyrimidine

   1. thymine

   2. cytosine

why is thymine replaced with uracil in RNA

thymine oxidises easily and is protected from oxygen in the nucleus

outside of the nucleus, thymine is quickly destroyed

uracil is resistant to oxidation and used in the RNA that must exist outside of the nucleus

differences between DNA and RNA

1. sugar unit

   1. deoxyribose VS ribose

2. nitrogenous bases are

   1. ATCG VS AUCG

3. ratio of A:T/U and G:C

   1. fixed vs unfixed (single strand)

4. molecular characteristics

   1. large, insoluble molecule vs small, soluble molecule

5. permanence

   1. permanent vs temporary

how is DNA organised inside the nucleus

1. a molecule of DNA is wrapped around proteins to form a single chromatin thread

2. during cell division, the chromatin threads coil more tightly to form chromosomes inside the cell nucleus

what is a chromosome consisting of and what is it made of

• Is consists of many sequence of genes that determines a characteristic of an organism.[1]

• Chromosome is condensed chromatin which is formed from DNA wrapped around proteins.[1] / are tightly coiled and condensed chromatin strands

what is the structure of DNA

1. 2 polynucleotides running anti-parallel strands tied together by hydrogen bonds and are twisted into a double heliX

2. each polynucleotide chain is made up of many nucleotides through condensation

how can the two strands of DNA be pulled apart

enzymes / mechanical force / high temperature

what is a gene

A gene is a hereditary unit consists of a sequence of DNA/nucleotides that occupies a specific location on the chromosome [1]

and the function of the gene is to control the production of ONE protein/polypeptide that determines a specific trait of an organism [1]

function of a gene

enables the formation of structural and regulatory RNA molecules and proteins

(regulatory proteins are stuff like enzymes and what not)

what is a chromatin

a complex formed by DNA molecules and proteins

what is a chromosome

a shortened, thread-like visible structure made up of chromatin threads coiled up and condensed

what are the two basic steps for protein synthesis

1. transcription

2. translation

what happens during transcription

1. inside the nucleus, DNA unfolds

2. one of the DNA strand acts as a template to make mRNA

3. RNA polymerase catalyses this transcription.

4. mRNA molecules copies the genetic code in the DNA template following the base pairing rule

what happens during translation

1. in the cytoplasm, 2 ribosomal subunits approaches mRNA

2. 2 ribosomal subunits bind to mRNA, forming a ribosome

3. tRNA approaches ribosome, anticodon on tRNA binds to codon on mRNA following the base pairing rule

4. the next tRNA carrying an amino acid approaches the mRNA

5. second tRNA binds to mRNA. anti-codon on tRNA binds to codon on mRNA, also following the base pairing rule

6. amino acid moves from first tRNA and joined to second tRNA forming a dipeptide

7. third tRNA approaches mRNA

8. Third tRNA binds to mRNA

9. Anticodon on tRNA binds to codon on the mRNA again following the base pairing rule

10. The process continues until the codons on the mRNA sequence are all translated

what happens to mRNA after translation

mRNA will be broken down into individual nucleotides which can be used for next round of transcription

what happens to tRNA after translation

tRNA remains in cytoplasm, picks up a corresponding amino acids and can then take part in next round of translation

what happens to polypeptide after translation

Polypeptide is folded, modified and packaged  in Golgi apparatus and sent to its designation as proteins 

what happens to ribosome after translation

Ribosome split into its subunits stay in cytoplasm and awaits for the next mRNA to arrive so that translation can take place

what is genetic engineering

• a technique that artificially insert gene / genes from one species into another to produce desirable traits

what is a transgenic organism

an organism which contains DNA form an organism of a different species inserted into its DNA

application of genetic engineering

1. production of substances used in medicine (hormones and drugs)

2. production of substances to enable resistance to diseases (vaccines)

3. mosquito-bone disease control

4. crops with improved qualities

   1. resistant to pests (releases substances to kill pests)

   2. improved shelf-life

   3. nutrients

5. gene therapy

   1.  a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene. generates a functional proteins product from the therapeutic gene restores the target cell to a normal state

6. reduce pollution

ethical considerations of genetic engineering

1. health concerns as new proteins in GM food might cause allergies

2. welfare of animals used in experiments should be taken into consideration

3. certain gene technologies may be accessible only to a select few with financial means

4. Potential risk of creation of new combinations of genes that can be used in chemical of biological warfare.

benefits of GE

1. Affordable medicine – important drugs, such as human insulin, are now more affordable as the cost of production is low.

1. Production of crops that can grown in extreme conditions that would otherwise be unsuitable – e.g: drought-resistant crops and salt-tolerant crops.

1. Crops that produce toxins and pesticide-resistant crops – this reduces the use of pesticides that are harmful to the environment

1. Foods with specific nutrients – e.g: “Golden Rice” with high vitamin A content

why are microorganisms used for genetic engineering as host cells

1. it is cheaper to culture and grow bacteria

2. they can grow much faster and indefinitely and produce large quantities of compound in a shorter period of time

why is animal and plant cells not used for genetic engineering

1. they lose the ability to produce the desired compound after a few rounds.'

2. more expensive to culture plant and animal cells

if the ratio of A is T and C is to G are both close to 1:1, what does t his tell us?

1. AT and CG are complementary bases

2. the DNA is double stranded

what are the two main bonds in a polynucleotide

1. hydrogen bonds

2. phosphodiester bonds (between two nucleotides)

what is a vector in genetic engineering

a DNA molecule, virus, or a bacterium which is needed for the transfer of genes as it is used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated and / or expressed

steps to genetic engineering

1. identify the region on bacterial gene that carries the desired gene [state function too]

2. Cut using restriction enzyme to isolate the desired gene, resulting in a segment of that gene with sticky ends

3. Obtain a plasmid from a bacterium. Cut using the same restriction enzymes the plasmid.

4. the cut desired genes and plasmid has complementary sticky ends

5. use DNA ligase to paste the desired gene and the plasmid at their complementary sticky ends, sealing them together and producing a recombinant plasmid

6. insert the recombinant plasmid into the host cell (this is done by applying temporary electric shock / heat shock to make the bacteria cell more permeable to the recombinant plasmid), known now as transgenic bacterium

7. transgenic bacteria are grown in large industrial fermenters with the right nutrients and optimum conditions. they reproduce, multiply and make copies of the recombinant plasmid

8. using transcription and translation process, these bacteria produce the compound in the cytoplasm

9. bacterial cell is then disrupted and lysed

10. desired compound is separated from bacterial cell and purified

how to transfer gene into a plant

method one — infection

1. [previous steps until you get the transgenic bacterium]

2. The bacterium is allowed to infect the crop plant where it will insert the recombinant plasmid into the cells of the crop plants.

3. D8:Transgenic plant cells will differentiate into shoots and transplanted and grow to become crop

4. D9:When the bacterial gene is expressed, the plant cell will make the protein that kills insects.

method 2 — insert recombinant plasmid into cell of crop plant using gene gun / electric-shock / heat shock with makes the plant’s cell membrane more permeable to the plasmid

why are transgenic bacteria grown in large industrial fermenters

they provide optimum conditions such as temperature and pH and nutrients for the microorganism to grow and reproduce

Methods of getting desired gene into the host cells (which is not microorganism)

1. infecting host cell with transgenic bacterium

2. gene gun

   1. bombarding plant tissues with gold particles coated with recombinant plasmid / or other vector containing the foreign gene

advantages of manufacturing products using fermenters

1. substrate and nutrients used are relatively inexpensive

2. contamination are kept in check, so better quality control

3. microorganism are easy and fast to grow, providing large quantity yields in shorter time

what model of DNA replication is correct and what are its mechanisms

1. semi-conservative

2. two parental DNA strands separate and each makes a copy of itself

3. after one round of replication, the two daughter molecules each comprises old and one new strand

disadvantages of plants that are genetically engineered to produce insect toxims

1. it may kill other insects that are beneficial to other plants, such as bees for pollination

2. there may be pest that becomes resistant to the chemical released by these transgenic plants

3. pest resistance bay be spread to weeds through cross-pollination

pros of the semi-conservative DNA replication method

1. one original strand is conserved in every new DNA molecule, serving as an accurate reference template

2. this minimizes cooing errors and prevents detrimental mutations

3. ensuring that every new generation of cells receives the exact same genetic instructions as the parent cell

4. which is essential for growth and tissue repair