Molecular Genetics Flashcards
DNA stands for?
Deoxyribonucleic acid
What are the four DNA bases and their parings, and the bonding per pair?
Adenine and Thymine (2 hydrogen bonds)
Guanine and Cytosine (3 hydrogen bonds)
Also known as complementary base paring
Nucleotides (DNA molecules) consist of
Deoxyribose sugar, base, phosphate molecule
What is the sugar-phosphate backbone?
Made out of
Deoxyribose sugars, two per DNA molecule, one 3 prime and the other 5 prime (anti parallel, facing different directions)
+ phosphate molecules
What’s the difference between mRNA and DNA?
Uracil replaces thymine (AU instead of AT)
Deoxyribose sugar in DNA, ribose sugar in mRNA
DNA is large and insoluble, mRNA is small and soluble
DNA is double stranded, mRNA is single stranded (no fixed ratio of A:T, C:G)
Definition of a gene
A segment of DNA where its sequence of nucleotides contain information that controls the synthesis of a single polypeptide. Also a unit of inheritence
What’s the difference in the replication of DNA and mRNA?
DNA replicates semiconservatively using DNA polymerase (each daughter molecule has one parent strand), mRNA is synthesised using DNA as a template
What forms a chromatin fibre?
DNA wrapped around histone proteins (bead on string structure)
What is a codon?
Three nucleotides on DNA/mRNA, each codon calls for a specific amino acid during the synthesis of proteins. Each gene can have a multiple of 3 + 2 nucleotides (codons and start/stop nucleotides)
What enzymes create DNA and mRNA, and what molecule aids translation?
DNA: DNA polymerase
mRNA: RNA polymerase
TRNA bring amino acids to ribosomes for protein synthesis
What are transgenic organisms?
Organisms with a gene that has been transferred from another species
Who require insulin injections?
Type 1 diabetes mellitus patients
Cons of animal insulin
Animal insulin isn’t identical to human insulin, transfer of diseases (eg. coronaviruses), ethicality (vegetarians, muslims, killing of pigs), not cost efficient
How are transgenic bacteria produced? (Insulin production)
Human insulin gene is isolated from the human chromosome, ends of the gene cut by a specific restriction enzyme, creating sticky ends. Bacterial plasmid (small circular DNA in prokaryotes) is isolated from bacterial cell, plasmid cut by same restriction enzyme, generating complementary sticky ends which bind to one another. DNA sugar-phosphate backbone between bacterial plasmid and insulin gene repaired with DNA lipase. Recombinant plasmid created (bacterial plasmid wth human insulin gene), inserted into bacterial cell through transformation (electrically or heat shocking them, making cell membrane permeable). Bacteria grown on petri dishes and screened (plasmids contain an antibiotic resistance gene, successfully transformed cells can survive on agar medium with antibiotic, multiplied in the fermenter for large numbers. Recombinant DNA plasmid is transcribed and translated, synthesising human insulin. Transgenic bacteria killed, insulin isolated and purified by crystallisation.
Advantages of asexual reproduction for transgenic organisms
Quick reproduction, copy of recombinant plasmid made during asexual reproduction for more wanted protein production. Cost effective (growth in fermenter)
Case study: golden rice (what is it, benefits, concerns)
Transgenic plant with beta-carotene (pigment) from corn and soil bacteria (converted to vitamin A in body).
Philippines is poor, vitamin A deficiency. Reduces suffering and blindness, cheap, no allergies.
“Playing god”, insufficient beta-carotene in previous strains, animal recombinant gene may be rejected by vegetarians
How to clone an organism
Remove nucleus from an egg cell to form an enucleated egg. Any body cell from cloned placed into enucleated egg through somatic cell transfer. Embryo formed, delivered by surrogate, carbon copy of cloned, no DNA from donor egg cell or surrogate.
State all the enzymes and each of their functions
DNA polymerase: to synthesise new DNA
mRNA polymerase: to synthesis new polymerase
tRNA: carried amino acids to ribosomes for protein synthesis
Restriction enzyme: cuts the ends of bacterial plasmid and gene
DNA lipase: repairs sugar-phosphate backbone of recombinant plasmid
Describe features of a polypeptide molecule that are different from those found in a DNA molecule
Basic unit of a polypeptide is amino acids, and basic unit for DNA is nucleotides
Polypeptide is a single chain while DNA is double stranded
Peptide bonds hold amino acids together in a polypeptide while phosphodiester bonds hold nucleotides together in DNA
20 different subunits for polypeptides, 4 different subunits for DNA
Describe the structure of DNA
Two molecules twisted around one another in double helix
Each molecule is polymer of nucleotides
Each nucleotide consists of deoxyribose sugar, phosphate and nitrogen-containing base
Deoxyribose sugar and phosphate bond to form sugar-phosphate backbone, each molecule’s backbone anti-parallel to each other
Bases paired in complementary way, adenine to thymine and cytosine to guanine
What is the central dogma?
The flow of genetic information within a biological system.
Transcription: in the nucleus, where DNA is copied to form a piece of mRNA, leaving nucleus through nuclear pores
Translation: at ribosomes on RER/in cytoplasm, genetic information on the mRNA is used by a ribosome to synthesis a polypeptide.
Describe the process of protein synthesis from DNA to leaving the cell
Transcription: mRNA synthesised by mRNA polymerase from DNA in the nucleus leaves through nuclear pores into the cytoplasm
Translation: mRNA used by ribosomes to synthesise polypeptides which leave RER in transport vesicles to the Golgi body
Polypeptides are chemically modified and repackaged at the Golgi body, leaving the cell in transport vesicles
