Biology Module 6 - Genetic Change Flashcards
What is a Mutation
Any change that occurs in the sequence of bases in DNA - small and large impacts.
What are Point Mutations
Alterations to one or a few bases or have them inserted/deleted at a single point on the strand - substitution, insertion, deletion and inversion. E.g. cytosine substitutes for adenine.
What are Chromosomal Mutations
Significant changes to the chromosome, can be added, deleted, inverted, duplicated or translocated. E.g. Trisomy causes Down syndrome, which uses an extra copy of chromosome 21.
What is the cause of Mutations
When DNA fails to copy accurately, or the chromosome/tid fails to seperate in cell division.
How often do errors occur in replicating DNA? How many base pairs are in DNA?
Errors occur around 1/100,000 bases - 10,000 mutations every DNA replication - repair mechanisms ‘proof read’ and correct mutations.
There are 3 billion base pairs in DNA.
What is it called when a mistake is made when copying DNA?
Typos
External causes of Mutations
Chemicals: Nicotine
Radiation: Electromagnetic, UV.
Virus’s can cause mutagens too: Human Papillomarvirus (HPV) causes mutations associated to cervical cancer.
Effects of Mutations
If in coding-gene, it can alter produced protien positively or to not function. In non-coding it has little effect but can affect regulatory regions outside the gene, increasing or decreasing protein production.
What happens if a Mutation infects a Gamete?
It can be inherited to the offspring - Germ-line mutations, which create variation.
How are somatic mutations compensated?
Some mutations are compensated by surrounding healthy cells, other times the cell with it dies and is replaced in mitosis of healthy cells, can cause uncontrolled cell replication - cancerous tumours.
Are all Mutations harmful?
No, some are beneficial and most do nothing, it creates variation to allow natural selection to favour specific characteristics.
How does radiation cause mutations? Examples?
Any radiation with a shorter wavelength then light can be mutagenic.
Ionising radiation: Radioactive material from nuclear reactions which remove electrons from atoms.
Ultraviolet: Sunlight.
How are chemical mutagens caused? Examples?
‘Free radicals’ are chemically unstable substances in the body that have lost an electron, they try to become stable by capturing electrons in the body.
Examples: Ingested chemicals, fatty foods, preservatives, irritants and poisons.
How do Biological mutagens occur?
Viruses and microorganisms cause them.viruses from transduction, disturbing DNA, repair mechanisms to create mutation. HIV can influence genetically material to change gene functions and make cancer, aging leads to mistakes in mitosis or free radicals from the body, fungi mycotoxins too.
What do radiation, biological and chemical mutations have in common?
They are naturally occurring mutagens
What are somatic mutations? Example and effect on DNA repair cells?
Mutations that occur in the body besides gametes. Can have effect on DNA spontaneously and randomly or induced from mutagens. Can’t be passed to offspring. If the gene is involved in DNA repair and mutated it can cause cancer quickly.
Example: Change in skin cell can cause melanoma and other skin cancers.
What are germ-line mutations? Example?
Mutations on the gamete from the gonads, passes variation to offspring.
Example: Queen Elizabeth passed haemophilia to descendants as recessive mutation.
What are coding DNA mutations
Mutations occurring on exon’s/coding region of DNA for mRNA and protein production. Mutation can change activity if protein/cell and could become inactive.
What are non-coding DNA mutations?
Non-coding DNA is not involved with gene-expression. It’s the introns that turn genes on/off. Mutation has little effect besides switching genes on-off or if introns becomes exon to cause effect.
What is the effect of Electromagnetic radiation?
Radiation breaks bonds in DNA and mutations can occur from errors that rebind the DNA strands, they can also cause molecules to loose electrons.
What is the effect of chemicals as a mutation?
Some are mistaken for substrates and bind into DNA strands when synthesising, creating a replication fork, this causes structural changes creating further miscopies of the template strand DNA when replicating.
Founder effect
When a new population is formed from a small number of individuals, from existing parent population. E.g. beetles dumped on new island after cyclone.
Why can’t founder effect organisms represent the original populations genetic makeup?
Inhabiting a new area will produce varying results who maybe heterozygous but doesn’t show the original populations on dominant and recessive genes there.
What can cause the founder effect and bottleneck?
Genetic drift
Missense mutations
Wrong amino acid is substituted in, changing the result amino acid & protein.
Nonsense - what does non & sense mean?
Creates premature STOP codon.
Non - absent
Sense - sequence of amino acids in polypeptide.
Silent mutation
Point mutation in coding region that doesn’t affect resulting amino acid.
How do fertilisation, meiosis and mutation cause genetic variation.
Fertilisation: combines maternal and paternal material through independent assortment & random segregation.
Meiosis: Crossing Over
Mutation: increase alleles for traits.
Histones
Protien that binds DNA to give chromosomes their shape and control gene activity.
Insulators
DNA sequence element that protects genes from inappropriate signals from environment.
Silencer
DNA element to reduce transcription from target promoters
Enhancers
Cis-acting DNA sequences that increase transcription. Function independent of orientation and distance from promoters.
Promoter
Region of DNA upstream of gene where proteins bind to imitate transcription of gene.
UTR
Untranslated region, at end of 5’ of protein-coding genes that transcribe into mRNA but not translated into protien.
What is CRISPR
(Clustered Regularly Interspaced Short Palindromic Repeats): gene editing tech made from bacteria’s immune system. Modify DNA from specific sequences to introduce changes, delete or insert.
CRISPR Applications
Gene therapy (correct genetic mutations), agriculture (better crops.
CRISPR Ethical issues
Unintended mutations/ecological damage.
Change to earths biodiversity from genetic techniques
Reduces genetic variation, increased susceptibility (others gain resistance).
Whole organism cloning examples
Grafting, tissue culture /micropropagation, artificial embryo twinning, SCNT.
Examples of gene cloning
PCR
