DNA and biothechnology Flashcards
(33 cards)
DNA structure
Nucleotide: 5-carbon sugar (deoxyribose sugar), phosphate group, nitrogenous base
each phosphate group is attached to 2 sugar molecules by ‘ester’ bonds - Phosphodiester bond
Polypeptide
String of amino acids, joined by peptide bonds
phosphodiester bond
A covalent bond that links a 3’carbon in one sugar to 5’ carbon in another sugar in DNA and RNA
Semi-conservative replication
refers to DNA replication
Because one strand is conserved from one generation to the next, while other strand is new
DNA replication
DNA helicase
DNA ligase
Leading strand
lagging strand
DNA helicase
Unzips double stranded DNA into single strands by breaking the weak hydrogen bond between nucleotides thus exposing the nucleotide bases.
small sections at a time
Replication fork
junction between the unwound single strands of DNA and the intact double helix.
Moves along paternal DNA strand so that there is a continuous unwinding of paternal strands
on Leading strand
Polymerase moving towards replication fork and synthesise continuously
on lagging strand
DNA polymerase is moving away from replication fork and synthesises in pieces called Okazaki fragments
DNA replication steps
1. DNA helices unwinds and separates the double strand by breaking the weak hydrogen bonds, each half of the parent molecule is used as a template.
2. Primase attaches a short sequence of RNA, known as a primer, to show DNA polymerase where to start adding nucleotides.
3. Complementary nucleotides are added by the enzyme DNA polymerase, synthesis of new daughter strand is in a 5’ to 3’ direction. Adenine pairs with thymine, and cytosine pairs with guanine.
4. The result is the production of two identical DNA molecules that are each made of one parent strand and one new daughter strand, therefore the process is described as semi-conservative.
5. In eukaryotic organisms, two sister chromatids are now ready for cell division. In Prokaryotes, two circular chromosomes are now ready for binary fission.
Coding DNA
sections of the sequence that codes for proteins
Also called a gene
Essential for protein synthesis
enzymes
codons
Nucleic acid
Amino acids
protein synthesis
Process of synthesising proteins
two parts:
Transcription: the synthesis of mRNA using the stored DNA code. Synthesised mRNA is a chain of complementary RNA nucleotides, except uracil (rather thymine) is base pair of adenine in RNA.
Translation: synthesis of polypeptide using the information in the RNA. The RNA nucleotide code is translated into an amino acid sequence.
Transcription
1. In Nucleus, part of one gene becomes unzipped by the action of RNA polymerase, which breaks the weak hydrogen bonds. RNA polymerase then joins the complementary nucleotides.
2. Template strand is used for transcription. RNA polymerase binds to a promoter region after transcription is initiated.
3. RNA polymerase adds free floating nucleotides according to the complementary base pair rules, but in RNA uracil pairs with adenine. The new strand of mRNA is synthesised in 5’ to 3’ direction
4. The DNA are read in triplets, and the complementary mRNA triplets are called codons. The process continues until there is a termination signal and the pre-mRNA is released.
5. Pre-mRNA consists of introns and exons. Are joined to create mature mRNA. Mature RNA exits the nucleus via the nuclear pore.
Translation
1. The ribosome binds to the mRNA strand.
2. The start codon in mRNA is usually ‘AUG’
3. Amino acids are attached in order according to the order of the codons
4. The polypeptide forms
5. Translation is complete
Apoptosis
programmed cell death
Strategy for disposing of damaged or infected cells and those no longer needed in a multicellular organism.
biotechnology
Refers to the tools and techniques used on organisms or the products of organisms to make a product or solve a problem for human benefit
modern DNA biotechnology uses tools and techniques to extract, analyse and manipulate DNA
Combines biology and technology to improve our lives and the health of our planet.
DNA tools
Restriction enzymes
DNA ligase
DNA polymerase
Primers
types of restrictions enzymes
Ligase
polymerase
Primers
Restriction enzymes
enzymes that cut DNA molecules at recognition sites, usually 4-8 bases long.
2 types of cuts: sticky ends, blunt ends
main source of restriction enzymes are bacteria.
Naturally occurring restriction enzymes protect bacteria by cutting foreign DNA and then removing invading organisms.
Ligase
An enzyme that uses complementary base pairing to seal and reassemble DNA strands in the process of ligation.
Sticks the backbone together.
useful for recombinant DNA technology
Polymerase
A class of enzymes that synthesises new strands of DNA based on a template strand and according to complementary base-pair rules
Vital tools in biotech, enabling efficient and accurate amplification of DNA templates.
used in amplifying DNA during PCR.
Primers
Short fragments of single-stranded DNA or RNA
primers assist in the synthesis of new strands of DNA by acting as a signal for the polymerase to begin synthesis
Primer is synthesised by enzyme primase.
about 20 nucleotides in length and are usually labelled with an enzyme, or radioactive or fluorescent dye tag.
Amplification
used to greatly increase number of copies of a DNA sequence for further laboratory use.
This can be achieved either in vivo by inserting the sequence into a cloning vector that replicates within a host cell, or in vitro, polymerase chain reaction (PCR)
