DNA and biothechnology

Question 1

DNA structure

Answer 1

Nucleotide: 5-carbon sugar (deoxyribose sugar), phosphate group, nitrogenous base
each phosphate group is attached to 2 sugar molecules by ‘ester’ bonds - Phosphodiester bond

Question 2

Polypeptide

Answer 2

String of amino acids, joined by peptide bonds

Question 3

phosphodiester bond

Answer 3

A covalent bond that links a 3’carbon in one sugar to 5’ carbon in another sugar in DNA and RNA

Question 4

Semi-conservative replication

Answer 4

refers to DNA replication
Because one strand is conserved from one generation to the next, while other strand is new

Question 5

DNA replication

Answer 5

DNA helicase
DNA ligase
Leading strand
lagging strand

Question 6

DNA helicase

Answer 6

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

Question 7

Replication fork

Answer 7

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

Question 8

on Leading strand

Answer 8

Polymerase moving towards replication fork and synthesise continuously

Question 9

on lagging strand

Answer 9

DNA polymerase is moving away from replication fork and synthesises in pieces called Okazaki fragments

Question 10

DNA replication steps

Answer 10

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.

Question 11

Coding DNA

Answer 11

sections of the sequence that codes for proteins
Also called a gene

Question 12

Essential for protein synthesis

Answer 12

enzymes
codons
Nucleic acid
Amino acids

Question 13

protein synthesis

Answer 13

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.

Question 14

Transcription

Answer 14

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.

Question 15

Translation

Answer 15

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

Question 16

Apoptosis

Answer 16

programmed cell death
Strategy for disposing of damaged or infected cells and those no longer needed in a multicellular organism.

Question 17

biotechnology

Answer 17

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.

Question 18

DNA tools

Answer 18

Restriction enzymes
DNA ligase
DNA polymerase
Primers

Question 18

types of restrictions enzymes

Answer 18

Ligase
polymerase
Primers

Question 19

Restriction enzymes

Answer 19

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.

Question 20

Ligase

Answer 20

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

Question 22

Polymerase

Answer 22

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.

Question 23

Primers

Answer 23

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.

Question 25

Amplification

Answer 25

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)

Question 26

Anealing

Answer 26

Process of joining two pieces of DNA by complementary base pairing.
the two pieces are joined by weak hydrogen bonds only, and therefore only temporarily.

Question 27

Polymerase chain reaction (PCR)

Answer 27

Is cyclic method used to rapidly amplify relatively small numbers of particular sequences of DNA into extremely large numbers of copies.
The DNA is then suitable for further laboratory uses such as gel electrophoresis and DNA profiling.
Requirements

Question 28

requirements for PCR

Answer 28

Template DNA
a special DNA polymerase (tax polymerase)
Buffer solution to maintain pH
A supply of the 4 nucleotides
two sets of single-stranded DNA primers
A thermocycler that is able to rotate through the necessary temperatures.

Question 29

PCR steps

Answer 29

1. Denaturation
2. Annealing
3. Extensions
4. Repeat

Question 30

Gel electrophoresis

Answer 30

Is a technique that can seperate large charged molecules, according to size and change, so that they can be visualised and identified by comparison with a standard. (DNA profiling)

Question 31

steps of gel electrophoresis

Answer 31

1. Set up apparatus
2. Pipette samples
3. Turn on current
4. Visualise/compare

Question 32

DNA sequencing

Answer 32

Refers to the methods and technologies used to determine the orders of the nucleotide bases in a DNA molecule.
Scientists cut DNA into fragments to sequence one section at a time. The entire set can then be put together to create a whole genome.
Sequencing genes of different species has assisted scientists in determining genetic relatedness and evolutionary links.

Question 33

Recombinant DNA

Answer 33

DNA that is composed of one or more genes from two different organisms, usually from a different species, and is then expressed.
Transgenic organisms are also known as genetically modified organisms.

Question 34

proteins

Answer 34

Are built from a selection of 20 different amino acids.
the amino acids are linked together by peptide bonds to form polypeptide chains, which fold and/or are modified to form the protein.