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Biology 🦠 > Chapter 14: Molecular genetics > Flashcards

Chapter 14: Molecular genetics Flashcards

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1
Q

Deoxyribonucleic acid (DNA)

A
  • a molecule that carries genetic information
  • information carried by DNA is important for all cellular functions, such as cell division and cell differentiation
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2
Q

How is DNA organised in the cell

A
  1. a small segment of DNA carries a gene that stores info used to make a single protein which is responsible for determining the characteristics of an orgnaism
  2. Each DNA molecules consists of 2 strands twisted around each other to form a double helix
  3. a DNA molecule is wrapped around proteins to form a single chromosome
  4. DNA can be extracted from the nucleus of the cell. in its purified form, it appears as very fine white threads
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3
Q

honestly, this still requires you to look at your notes, cause its really hard to put a picture here and expect you to memorise it

A
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4
Q

Nucleotide

A
  • basic unit of DNA
  • each nucleotide is made out of a sugar, a phosphate group and a nitrogenous base
  • they can be joined tgt to form long chains called polynucleotides
  • each gene is made out of a sequence of nucleotides. the sequence of nucleotides can vary, resulting in many different genes
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5
Q

Rule of base pairing

A

Adenine (A) — Thymine (T)
Cytosine (C) — Guanine (G)
- they are called complementary base pairings cause A has complementary shape with T and so does C with G
- in DNA molecule, the ratio of T:A and C:G is always 1:1

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6
Q

Genes

A
  • a sequence of DNA nucleotides that controls the formation of a single polypeptide
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7
Q

What do genes do

A
  • a polypeptide is used to make a protein
  • each gene stores a message that determines how a protein should be made in the cell
  • the message stored by a gene is known as the genetic code
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8
Q

How are proteins made

A
  • through transcription and translation
  • transcription occurs when the message in the template has to be copied into a RNA molecule called messenger RNA (mRNA)
  • Transcription occurs in the nucleus
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9
Q

What determines the amino acid sequence of the polypeptide

A

Three nitrogenous bases form a codon
Each codon is a code for 1 acid
Examples:
CAA: Glutamine
CGG: Arginine
CCA: Proline
TTT: Phenylalanine

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10
Q

How DNA template is used to make proteins

A
  • template consists of a sequence of nucleotides
  • 3 base codes are called the triplet code or codon code for 1 amino acid
  • for proteins that made up of more than 1 polypeptide, more than 1 gene will be involved
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11
Q

Process of transcription (1-4)

A
  1. the gene unzips @ segment where gene is located
  2. sequence on bases on one of the DNA strands (template strands) is used to make the mRNA, following rule of base pairing. mRNA does not contain T, but has U (uracil) instead
  3. mRNA leaves nucleus through nuclear pore and attaches to ribosome in cytoplasm
  4. each transfer RNA (tRNA) attaches to a specific amino acid in cytoplasm and each tRNA has 3 bases @ one end which is an anticodon that binds to complementary codon on mRNA
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12
Q

Process of transcription (5-8)

A
  1. first 2 tRNA and their amino acids(aa) fit into a ribosome. anticodons on tRNA binds to codon on the mRNA according to rule of the base pairing. a peptide bond is formed between the 2 aa
  2. ribosome move towards another set of codon responsible for next aa, attaching another aa to the chain
  3. aa are continuously attached until the stop codon is encountered which can be UGA, UAA or UAG and it does not have corresponding tRNA anticodon. ribosomes leave mRNA
    the whole chain of polypeptide is finally produced
  4. ribosome will attach to same mRNA for another round of translation
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13
Q

Genetic engineering

A
  • a technique used to transfer genes from one organism to another. individual genes may be cut off from the cells of one organism of the same or different species. the transferred gene can express itself in the recipient organism
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14
Q

What is needed in genetic engineering

A
  • a vector, another DNA molecules, a bacterium / virus that is used to carry the genes of 1 organism to another, is required
  • plasmid, from bacterium, is used to transfer genes
  • gene-of-interest is a gene that we want to transfer from one organism to another
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15
Q

Transferring insulin gene into bacteria

A
  • insulin needed to treat people suffering from diabetes
  • used to be obtained from animals
  • animal insulin is not the same as human insulin & many diabetics develop antibodies against animal insulin
  • they become allergic to animal insulin and can no longer use it
  • diseases may also be transmitted from animals to humans who used the animal insulin
  • hence, insulin is produced using genetic engineering
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16
Q

Advantages of producing insulin using genetic engineering

A
  • does not induce allergic response in patients
  • cheaper and easier to produce insulin in large quantities
  • less risk of contamination by disease causing microorganisms
  • ethical concerns of vegetarians or religious groups can be overcomes
17
Q

Transgenic organisms

A
  • an organism that acquires genes from another organism of different species
  • this process takes place due to human intervention
  • transferred gene can express itself on the recipient organism
  • this organism is called genetically modified organism
18
Q

Manufacturing insulin using bacteria (1-2)

A
  1. Obtain DNA fragment in human chromosome containing insulin gene. Cut out gene using restriction enzyme. The enzyme cuts the restriction site @ the 2 ends of the gene to produce sticky end. each sticky end is a single strand of sequence of DNA bases. These bases can pair with complementary bases to form a double strand
  2. Obtain a plasmid from a bacterium. Cut plasmid with the same restriction enzyme. This produces sticky ends that are complementary to the ends of the insulin gene
19
Q

Manufacturing insulin using bacteria (3-5)

A
  1. mix plasmid with DNA fragment containing insulin gene. It will bind to plasmid by complementary base pairings between their sticky ends. Add the DNA ligase to seal human insuline gene to plasmid. The plasmid containing DNA from 2 different organisms is called recombinant plasmid
  2. Mix recombinant plasmid with E-coli. Apply temporary electric shock / heat to open up pores in cell membrane of e-coil to let plasmid enter
  3. Transgenic bacterium will use new gene to make insulin. Bacteria is isolated and grown in fermenter for mass production of insulin. Insulin is then extracted and purified
20
Q

Reasons for development of transgenic organsims

A
  • to produce large amounts of human insulin, reducing cost of medicine
  • to produce pest resistant crops hence increasing crop yield
  • to improve nutritional value of current food crop to improve health
21
Q

Benefits of genetic engineering

A
  1. low-cost production of medicines leads to cost of medicines to be low making it more affordable and more people can access them and get treated
  2. Production of crops that grow in extreme conditions allows farmers to grow crops even when environmental conditions are not suitable
  3. Development of pesticide-resistant crops and crops that produce toxins that kill pests, like Bt corn, reducing use of pesticides that are harmful to environment and expensive
  4. Development of foods designed to meet specific nutritional goals like Golden Rice
22
Q

Ethical considerations of genetic engineering

A
  1. New proteins in GM foods may cause allergies in humans
  2. Some biotech companies engineered crops producing seeds that cannot germinate, forcing farmers to buy new seeds, affecting poorer societies
  3. Animals are used for medical research when studying diseases, we need to consider the welfare of the animals
  4. Concerns that genes coded for antibiotic resistance used in genetic engineering accidentally incorporate into disease causing bacteria
  5. Some people create new combinations of genes to use in chemical/biological welfare
  6. Genetic engineering may not be easily accessible to everyone

Biology 🦠 (18 decks)

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