Module 6: Genetic Change

Question 1

What are the main categories of mutagens?

Answer 1

Electromagnetic radiation
Chemicals
Naturally occuring mutagens

Question 2

What is a point mutation?

Answer 2

When a single base pair of a genome is:
- Insertion, extra nucleotide added
- Deletion, nucleotide not included
- Substitution, wrong nucleotide added

Question 3

What is a chromosome mutation?

Answer 3

A change to the arrangement or structure of a chromosome. Instead of changing a single base a very large section of DNA is being altered. They occur due to errors in cell divisions, more specifically in meiosis.

Question 4

Types of chromosome mutations?

Answer 4

• Deletion - Section is broken off and lost
• Inversion - Section breaks off and reattaches in a different orientation.
• Translocation - Section breaks off to stick to another chromosome.
• Duplication - One section is copied more than once.
• Nondisjunction - When chromosomes dont separate problem.

Question 5

Down syndrome?

Answer 5

The most common disease caused by chromosomal mutation. It is also referred to as trisomy 21, where people have 3 copies of chromosome 21. Occurs due to non disjunction which results in a gamete receiving 2 of chromosome 21, resulting in the zygote have 3.

Question 6

Types of Genetic change? What are they caused by?

Answer 6

Mutations: These are accidental, in which a disruptive process alters the base sequence of DNA. They can be caused by environmental agents called mutagens, or by a cellular error, when a mistake is made during cell division.
Biotechnology: Where we deliberately alter DNA.

Question 7

Types of cellular error?

Answer 7

Chromosomal
Point

Question 8

How does electromagnetic radiation work? (2 examples)

Answer 8

As short wavelength, high energy waves move through matter, they give energy to atoms they hit, causing them to vigorously vibrate and lose electrons in the process. This causes damages as chemical bonds. Examples of EM radiation are UV rays from the sun, and gamma rays from uranium-236.

Question 9

How do chemical mutagens work? (3 examples)

Answer 9

There are many different ways chemicals cause mutations:
- Chemical is incorporated into DNA, instead of proper nucelotides. E.g. 5-bromodeoxyuridine is mistakenly taken to be Thymine by DNA polymerase.
- Chemical inserts itself into DNA. E.g. Actinomycin D creates a bulge in DNA, and prevents replication.
- Chemical makes gaps in DNA, like dimethyl sulfate, which breaks the bond between the base and a sugar of a nucleotide.

Question 10

How do naturally occuring work?

Answer 10

They specifically come from fungi, plants and animals. Mycotoxins are poisonous chemicals produced by fungi. Cycasin is a mutagenic chemical produced in the leaves of cycad plants. Dimethylnitrosamine is produced in the stomach when nitrite is consumed by an animal, which is found in ham and sausage.

Question 11

Why is mutation the ultimate source of genetic variation?

Answer 11

Because it is the only process that can introduce new alleles into the population.

Question 12

What happens if a gene is not fully intact?

Answer 12

Genes produce proteins when they are fully intact. If a gene has been ‘broken’ to allow for the insertion of another gene, or due to mutation, it will not be functional.

Question 13

Effects of UV radiation?

Answer 13

UV radiation is a known carcinogen, meaning that it can cause genetic mutations that lead to cancer. For example, mutations might damage tumour suppressor genes, leading to cell proliferation. A type of skin cancer known as melanoma can occur die to chronic carcinogen (UV radiation) exposure.

Question 14

What is cancer?

Answer 14

Cancer is the term given to a group of diseases that involve abnormal cell growth, typically as a result of genetic mutations.

Question 15

Why is mutation bad?

Answer 15

As DNA is used as a template for mRNA during protein synthesis, if even a single nucleotide is altered, the order of bases on DNA will be changed, resulting in the wrong amino acids being used to build the chain, and creating a different or dysfunctional protein.

Question 16

Effects of point mutation?

Answer 16

Insertion and Deletion will affect the nucleotide sequence, and thus every subsequent codon after the site of mutation. These are called frameshift point mutations.
During substitution, it can either be mis-sense, non-sense or silent.
- Missense mutation is when a substitution results in the codon coding for a different amino acid.
- Nonsense is when substitution results in he formation of a stop codon.
- In a silent mutation, the wrong nucleotide is substituted in, but there is no change that occurs.

Question 17

Example of point mutation disease?

Answer 17

Sickle Cell anaemia is a genetic disorder where people have misshapen RBC. Caused by a single substitution in the gene that creates haemoglobin, going from GAG to GTG. This causes the RBC to fold into an abnormal shape, where they can’t carry oxygen as efficiently and cause blood clots.

Question 18

What are the effects of chromosomal mutations?

Answer 18

In all chromosomal mutations, if breakage occurs in the middle of a gene, the gene is destroyed and becomes inactive. In deletion, inversion and translocation, the genes are moved to a new place. In duplication, we can end up with changes in the amount of proteins produced.

Question 19

What is a germ-line mutation?

Answer 19

A change of DNA in a germ cell, which are the cells that divide during meiosis to form sex cells. These mutations are passed from parents to offspring. They do not affect the parent. Examples of germ-line mutation is Down Syndrome, or trisomy 21, where when a germ cell undergoes meiosis, 2 chromosome 21s go into a sex cell, instead of one (non-disjunction)

Question 20

Somatic mutations?

Answer 20

Somatic cells form the body tissue of an organism. A somatic mutation can only affect the individual, and cannot be passed onto offspring. For example, lung cancer is a disease caused by uncontrolled cell growth in the lungs as a result of mutagens like cigarette smoke.

Question 21

Example of a mutation to coding DNA?

Answer 21

Change to DNA which codes for the amino acid sequence of a protein. For example, sickle cell anaemia is a genetic disorder where people have misshapen red blood cells, caused by a substitution point mutation in DNA which codes of haemoglobin, from GAG to GTG. Changes amino acid from glutamic acid to valine.

Question 22

What are the effects of mutation to non-coding DNA? (1 example)

Answer 22

Change in DNA that doesn’t code for proteins. Instead, they can act as:
- Templates in the creation of functional RNA
Mutation will cause issues with protein synthesis
- Regulatory sequences, that control the amount of proteins produced by coding DNA
Mutation may cause gene transcription levels to change, that is the amount of proteins produced may increase or decrease.
- Repetitive sequences, regions of DNA which have the same sequence repeated many times, which have mostly been introduced to us by viruses.
Mutation will have no effect.
Example is lung cancer, which is a mutation in the regulatory sequences, which control cell division and growth.

Question 23

What is a gene pool?

Answer 23

All the alleles for all genes in a population. Gene pools are dynamic, affected by gene flow, drift, mutations and selection pressures. Larger gene pool is good for genetic diversity

Question 24

Factors affecting gene pool?

Answer 24

Gene flow: Movement of alleles between populations due to movement of organisms. If gene flow between populations is high, their gene pools will be similar, and vice versa
Genetic drift: Random events occuring can lead to changes in gene pool, such as natural disasters. The “lucky” individuals survive, not the “better” ones.
Mutations: Source of new alleles.
Selection pressures: Any external factor that affects an organism’s ability to survive in it environment. The individuals that are better suited in different selection pressures will go on to give their traits to their offspring.

Question 25

What is the founder effect?

Answer 25

When a small group of individuals are separated from their original, larger population, and move to a new location to establish a new population

Question 26

What is bottleneck effect?

Answer 26

When a species experiences an event that suddenly and significantly reduces its population and gene pool

Question 27

Inbreeding?

Answer 27

Occurs when populations become smaller and isolated. Results in an accumulation of mutations, as many mutations are recessive, and inbreeding increases the likelihood that offspring receive two copies of the mutation.

Question 28

Historical examples of biotechnolgy?

Answer 28

- Selective breeding - Fermentation - Traditional medicine

Question 29

Female and Male part of flowers?

Answer 29

Pollen is produced in the stamen The stigma receives the pollen

Question 30

How do we clone whole plants?

Answer 30

- Cutting and grafting Cutting: Section of plant is removed, and placed in soil or water where it develops its own roots, stems and leavings until it grows to full size. Grafting: Cutting from of a plant is bound to the cut stem of another plant with already developed roots, where they fuse and then grow. - Tissue cultures Section of parent plant is pulverised to release individual plant cells. Cells are grown on a medium containing nutrients and hormones that promote growth, which eventually grow into full sized plants.

Question 31

How do we clone animals?

Answer 31

- Artificial Embryo twinning Egg is fertilised, zygote is allowed to develop, forming a clump of unspecialised cells, where each cell is capable of developing into a complete organism. These are then separated and each transplanted into different surrogate mothers, who will give birth to multiple, genetically identical offspring. - Somatic Cell Nuclear transfer Donor cell is taken from the organism that will be cloned, and an unfertilised egg is taken from a female donor. DNA in the egg is removed, and replaced with the DNA from the donor cell. Egg cell is triggered to divide by an electrical impulse, developing into an embryo. This is then transplanted into a surrogate mother, who will give birth to a clone.

Question 32

Why do we clone? (3 reasons)

Answer 32

- Scientific Research Animal testing, as cloned animals will have the same reactions to drugs, providing reliable responses to drugs used in research. E.g oncomouse - Argriculture As desirable traits are able to be passed onto offspring, which can often be faster and more reliable than conventional breeding. For example, tissue cultures enable the production of thousands of genetically identical plants in a short time. - Wildlife Conservation Crucial in prevention extinction of critically endangered species. E.g. northern white rhinoceros, which only have 2 females remaining

Question 33

What is recombinant DNA? How is it cloned?

Answer 33

DNA which contains genes from two or more different sources. DNA is cloned 'in vivo', where a gene is inserted into a bacterium, which makes copies of the gene for us. One example is cloning the human insulin gene in E.coli

Question 33

What is PCR?

Answer 33

Polymerase Chain reaction, where a specific region of DNA is cloned 'in vitro'.

Question 34

Applications of Gene cloning (4)

Answer 34

DNA Sequencing - Gene cloning makes enough gene copies for scientists to perform analysis on base sequence. DNA Profiling - Scientists can create a DNA profile by amplifying (cloning) certain genes. Genetically modified organisms - Genes can be added or removed from organisms to allow understanding of how a gene works Gene Therapy - Scientists replaced a disease-causing gene with a normal gene.

Question 35

Disadvantages of organism and gene cloning?

Answer 35

- Extremely expensive - Ethical concerns, as cloned animals tend to suffer more adverse health issues and higher mortality rates. - Reduces genetic diversity, leaving population more vulnerable to sudden environmental changes.

Question 36

How is recombinant DNA made?

Answer 36

1. Isolation - DNA fragments are extracted from their natural sources, the target gene, which codes for the protein of interest, and scaffold DNA, which the target gene will be inserted into, usually plasmids from bacteria. 2. Digestion - Using the same restriction enzyme on both DNA, which cuts the DNA at a specific base sequence. The enzymes create 'sticky ends' at the ends where there are exposed bases. 3. Insertion - The target gene and open plasmid are mixed together, where they will spontaneously fuse to form a recombinant plasmid at their 'sticky ends'. 4. Ligation - DNA ligase fixes the broken sugar-phosphate backbone of the recombinant DNA.

Question 37

How is DNA amplification done using bacterial transformation?

Answer 37

Bacteria duplicates very quickly, so bacterial transformation is a very effective method of amplifying DNA. We must first introduce the recombinant plasmid to the bacterial cell. First, the plasmids and bacteria are both added to a solution containing calcium ions, which disrupt the cell membrane of bacteria, and allowing recombinant DNA to move into the cell. Next, the bacteria is heat shocked, quickly increasing the temperature in a short time which forces the recombinant DNA into the bacteria cells. Finally, the bacteria is transferred to a nutrient rich broth, at their optimal temperature/ (37 degrees).

Question 37

How many bacteria become transformants during transformation?

Answer 37

Only 1/10000 become transformants and take up the plasmid DNA, as either the bacteria doesn't take up the plasmid by chance, or the heat shocking kills the bacteria.

Question 38

How are transformant bacteria identified?

Answer 38

Scientists use plasmids with a selectable marker, a gene that produces easily observable characteristics, usually an antibiotic resistance gene.

Question 39

What happens to transformants?

Answer 39

Either they are used to make the protein of interest, which is extracted and purified to be used. Or, they could be used to make the recombinant plasmid, extracted from the transformants, which could be used in DNA sequencing, profiling or making transgenic organisms.

Question 40

Advantages of use DNA recombinant technology over artificial selection?

Answer 40

- Allows for the ability to choose from the genes of unrelated organisms for the gene of interest, significantly improving the chance of finding a target gene. - It is faster, as it can be incorporated immediately into the species, while artifical selection can take multiple generations. - It is more controlled, as artificial selection can give rise to different unrelated traits.

Question 41

What is the difference between a transgenic organism and a GMO?

Answer 41

GMO is an umbrella term for any organims that has had their genome modified, while a transgenic organism is one that has had DNA added to their genome, so possesses DNA from two or more different sources.

Question 42

Techniques for making transgenic organisms (4 examples)

Answer 42

- Bacterial plasmids - Microinjection - DNA from one species is inserted into the cell of another using a micropipette - Biolistics - a gene gun shoots small metal bullets coat in DNA into the nucleus of a cell, mostly used for plant cells - Electroporation - cells are exposed to a series of short electrical impulses, which create holes in the cell membrane through which DNA can move into the cell

Question 43

Uses of transgenic organisms? (4 examples)

Answer 43

- Increasing crop and livestock livestock BT cotton contains a gene from a soil bacteria which codes for a toxin that kills cotton-eating caterpillars. - Increasing crop productivity Golden rice contains 2 additional genes from daffodils and a soil bacterium, which allows the plant to produce rice rich in beta-caratene, which is the precursor to vitamin A. - Produce therapeutic products Insulin is created by inserting the human gene that codes for it in E.coli, which will cause the bacteria to produce insulin which can be harvested and purified. - Help study human diseases, by predicting how certain drugs and treatments will affect humans. The OncoMouse contains a human cancer gene, increasing the likelihood for developing cancer, and helping assist the development of cures for human cancer.

Question 44

Ethical concerns with transgenic species? (1 pro 1 con)

Answer 44

Advantage: Provided the ability to produce proteins without the need to extract from animals. Example, human insulin can be produced using bacterial plasmids, instead of extracting it from pigs. Disadvantage: There are ethical concers involving transgenic species that are used for testing. For example, the Oncomouse is genetically modified to develop cancer in the first few weeks of its life, limiting its life span to only eight weeks.

Question 45

Effect of biotechnology on biodiversity? (2 pros 2 cons)

Answer 45

Pros: - Artificial insemination and artifical pollination can be used to cross organism from the same species that would otherwise be unable to breed due to geographical barriers. - Recombinant DNA can move genes between organisms, creating transgenic and biodiverse organisms. Cons: - Intensive farming promotes the growth of crops and animals with "desirable" traits and lead to low biodiversity, leaving them susceptible to sudden envionmental changes. - If GMOs escape into the wild, they may outcompete non-GMOs, decreasing biodiversity in the whild.

Question 46

Ethical concerns of biotechnology? (3 examples)

Answer 46

Examples: - Genetic screening during pregnancy Can be used to determine if an unborn baby has genetic abnormalities, which may lead to suffering of the child or parents, allowing parents to make an informed decision as to whether or not they would like to continue with the pregnancy. - GMOs Transferring genes between organisms can contradict with people's beliefs. - Animal welfare It has positive and negative. For example, insulin can now be extracted from vats of transgenic bacteria, instead of being extracted from pigs. Negatives include GMOs that suffer from poor health. OncoMouse.