DNA and genetics

Question 1

Purpose of DNA?

What is it’s structure?

Answer 1

Store, transmit genetic information.

It is circular and unbound in the cytosol of prokaryotes, mitochondria and chloroplasts.

Is bound to proteins(histones) in linear chromosomes in eukaryotes in nucleus.

It is negatively charged

Question 2

Define DNA’s structure

Answer 2

Is a nucleic acid

made of nucleotides which have a phosphate connected to a deoxyribose sugar connected to an N base.

Question 3

Define a gene:

Answer 3

A segment of DNA on a chromosome that contains the complete sequence bases required to direct the manufacture of a polypeptide or an RNA molecule is called a gene.

Question 4

Explain nucleotide bonds:

Answer 4

Adenine double bonds to Thymine

Guanine triple bonds to cytosine

Question 5

Explain important enzymes:

Answer 5

Helicase- separate double strand DNA into single strands

Primase- synthesizes primers, short strands of nucleotides.

Polymerase- catalyses the synthesis of new complementary DNA strands

Ligase- joins fragments of DNA together

Topoisomerases: are involved with the re-coiling of DNA

Question 6

Describe semi-conservative replication of DNA:

Answer 6

Two original strands of DNA act as a template for two new complementary strands.
the two new DNA strands have one new strand and one old strand.

Question 7

Role of DNA in cells:

Answer 7

Compounds in cells need to be manufactured,

in the process are many chemical reactions, each chemical reaction is catalysed by an enzyme which is a molecule made of polypeptide chains(protein)

in which a sequence of DNA (gene) codes for the creation of.

Simple cells need hundreds of genes to make compounds which form its structure, carry out processes, reproduce to survive. Many proteins are structural

Question 8

Explain protein synthesis:

Answer 8

The transcription of a gene into messenger RNA and translation of mRNA into amino acid sequence at ribosomes

Question 9

Describe transcription;

Answer 9

Is the process of copying information from DNA into mRNA.
The part of DNA unwinds, using one of the strands as a template, RNA polymerase links new nucleotides, complementary to the DNA strands using uracil in place of thymine. mRNA passes through the pores in nuclear envelope to ribosomes. Meanwhile, 2 DNA strands rejoin. Start and stop codons indicate where the mRNA is copied from. All polypeptide chains begin with methionine.

Question 10

Describe translation:

Answer 10

The mRNA attaches to ribosome, Made up of ribosomal RNA, produced in the nucleolus and protein. tRNA (transfer) in a clover leaf shape, one end with anticodons that are complementary to a codon on mRNA, the other end with an amino acid. tRNA joins and the amino acids are joined emzymically with a peptide link.

Question 11

Describe introns & exon

Answer 11

They are both sections of DNA, Exons are expressed and are translated into a protein. Introns are transcribed but then cut out of the mRNA but used for alternative splicing and increase variation.

Question 12

Describe protein structure:

Answer 12

Primary- the sequence of amino acids in the polypeptide chain. Determined by the sequence of bases on the mRNA which is determined by the sequence of bases on the DNA that is the gene
Secondary- Coiling or folding of localised sections of polypeptide chain, determined by the primary structure
Tertiary- 3D shape of polypeptide chain, determined by the primary & secondary structure.
Quaternary- where it is made up of more than one polypeptide chain.

Question 13

State 7 functions of proteins:

Answer 13

Structural- hair nails ligaments
Catalyse reactions- enzymes
Contraction- fibers in muscles
Transport- carrying oxygen
Defence- antibodies
Coordination- hormones, receptors
Storage-ferritin

Question 14

Express why protein shape is important:

Answer 14

Specific shapes are required in proteins to be complementary to their counterpart in hormones, receptor proteins, important for self-recognition, and antibodies, with binding sites specific to the shape of foreign substances like bacterium/virus. Enzymes are specific for their substrate
Many genetic diseases are because of abnormal 3D protein structure.

Question 15

State factors affecting transcription;

Answer 15

factors are specific regulatory factors that control gene expression. Some switch genes on, binding to the promoter region on DNA. Some turn genes off by blocking attachment of RNA polymerase. Factors can be activated by specific hormones.

Question 16

Define phenotypic expression & phenotype & genotype:

Answer 16

This refers to the physical, biochemical or physiological characteristics that a gene produces. Pheynotype is the observable ccharacteristics.
Genotype is the gene that an individual organism has for a particular characteristic

Question 17

4 Environmental factors affecting transcription and translation;

Answer 17

Lack of O2- increased blood cell production
Increased UV exposure- change in skin colour
Malnutrition- reduced bosy size
Increased light intensity- increased plant growth

Question 18

Define cellular differentiation:

Answer 18

It is controlled by gene expression. The stem cells differntiate and become specilised cells, they do this by turning off genes which can be done through methylation

Question 19

Describle methylation:

Answer 19

Genes are switched off through methylation of the Cytosine nucleotide. The study of this is epigenetics.

Question 20

Explain how epigenetic changes can cause cancer

Answer 20

There are tumor suppressor genes that regulate cell division, if these genes are methylated, they will not be transcribed and their pprotein products will not be avalible to control cell division, cancer may result.

Question 21

Describe mutations:

Answer 21

random permanent changes in the genes, they result from errors in DNA replication or celldivision or damage by physical or chemical factors in the environment. Such as:
Ionising radiation, mutagenic chemicals, viruses

Question 22

Consequences of mutations:

Answer 22

They can occur in somatic cells, which confine them to an individual, but if they occur in germ cells, then they may be passed on to the next generation these lead to changed in the characteristics of the descendants as the mutations inherited by gametes will appear in the zygote and then in every somatic cell and germ cell of that individual.

Question 23

Describe the process of polymerase chain reaction:

Answer 23

DNA is heated to split the helix into two strands, primers are used to keep the DNA from rejoining when cooled, the single strands act as a template for DNA polymerase to replicate the strands the primer is included in a mixture of free nucleotides so that there is a higher chance that the primer will bond to the DNA strand upon cooling. This is done repeatedly until the primer or free nucleotides are exausted. Using heat resistant enzymes so they dont denature at the melting point of DNA.

Question 24

How was DNA replicated before PCR?

Answer 24

By splicing DNA into the plasmid of bacteria and then introduce the recombinant plasmid into a bacterial host cell under suitable conditions for the cell to reproduce.

Question 25

Describe electrophoresis:

Answer 25

Different length DNA fragments are analysed, separated according to size, placed in the negative end of a gel block or amarose. A current is turned on and, cause DNA is negatively charged It will move towards the positive electrode, the smaller fragments moving faster than the larger fragments.

Question 26

How does DNA profiling help:

Answer 26

It identifies the uniques genetic make up of individuals. Using restriction enzymes, the specific fragment of DNA can be removed, it is then PCR’d and electrophorised.
Analysis of markers on XY chromosomes will reveal the sex of the person, it will match DNA samples at a crime scene to a victim or suspect. It can determine genetic relationships, solving custody disputes. Genetic faults may also be identified.

Question 27

Describe Barcode of life database:

Answer 27

One protein in the mitochondria of all eukaryotes is different for each species. They have a unique sequence which can be used to establish a database of different species. This can be used to catalogue illegal cutting of timber or fishing.

Question 28

Ethical issues with bold:

Answer 28

How will we use the technology, will this inhibit life insurance buyers who’s ancestors have had a disease
Should an employer be entilted to make it a preerequisite for employment
Tests could be carried out without consent or knowledge

Question 29

Economic issues with BOLD:

Answer 29

Cost of storage and administeration of and database
Maintenience costs
Cultural issues with BOLD:
People of culture may believe this predition of disease to be unatural and reject BOLD
Others believe it will disturb the natural harmony of the body.
This may cause some groups to be victimsed because of disease that may be found to be prevalent in them.

Question 30

Explain restriction enzymes:

Answer 30

Used to cut sections of DNA specific to the restriction enzyme. This is used to cut repeating patterns out that are different lengths apart for people. These will cut either blunt or sticky ends.

Question 31

Describe DNA, RNA probes:

Answer 31

A sequence of nucleotides must be known in a gene, radioactive or fluroescent probes bind to specific sequences on dna after the dna has been heated/.

Question 32

Define plasmids and gene cloning:

Answer 32

Small rings of DNA seperate from the bacterial chromosome. Restriction enzymes can cut them, human dna is cut with the same restriction enzyme. Ligase is used to re join the dna into a ring. The recombinant plasmid is introduced back into the cell. This is gene cloning.

Question 33

Explain Vacine making in terms of gene engineering:

Answer 33

Copies of antigen proteins are made from the coat of pathogen.
Insert extra dna into genome of pathogen, render it harmless the stimulate the immune system

Question 34

Describe gene transfer.

Answer 34

Microinjection- gene injected into fertilised ovum, the animal will contain the foreign gene.
vector(bacterial, plasmid)- genes introduced into viral dna, which can infect cells and incorporate its DNA into those cells.
Electroporation- electric pulse , forms holes in plasma membrane of cell, gene inserted through.
liposome fusion- vesicles containing the gene fuse with membrane by endocytosis

Question 35

Define transgenesis:

Answer 35

Introducing a gene into an organism so the gene will be expressed.

Question 36

Issues of genetic manipulation:

Answer 36

New, many implications not understood
Organisms may develop unexpected characteristics, threaten the ecological balance
Food may be harmful to consumers

Question 37

Describe CRISPER:

Answer 37

Bacteria store part of viral dna in a section of their dna called crisper. If attacked again, the bacteria recognises and makes a complementary RNA copy of the dna segment which is loaded into an enzyme CAS9, which cuts the viral DNA at the corresponding site.

Question 38

Describe Cas9:

Answer 38

The protein is programmable, able to cut DNA determined by the RNA sequence loaded onto it, this can accurately cut DNA at a predetermined location.