6.1, mutagens/mutations Flashcards
what are mutations and the two type of classes
mutations are the event where a permennt change is made to DNA structure due to spontaneous/envrionmental mistakes during DNA replication. it ultimately alters the genetic sequence of a gene n creates a new allele.
the two main classes are : spontaneous mutatioons (wo the affect of an environmental agent) and induced (environmental)mutations
what are mutagens? - what do mutagens tend to be smth..genic
mutagens are synthetic/environmental agents that alter DNA greatly, enhancing the spontaneous rate of mutations. many mutagens tend to be carcinogenic.
what are chemical mutagens?
they are structurally similar to DNA and hence are often accidently incorporated as nucleotides, causing mutations.
- When DNA replication occurs and polymerase 3 is creating a complementary strand, chemical mutagens can just sneak their way in
what are three key examples of a chemicalmutagen and expand on one heavily
- nitrosamines (nai-tro-se-means)
- cigrates ( polycyclic hyrdocarbons)
asbestos/mesothelioma :
asbestos is carcinogenic causing
mesothelioma acancer which affects mesothelium cells.
- asbestos is a naturally occuring mineral and is extremely fibrous w tiny fibres which are easily inhaled and then trapped in lungs.
- Once inhaled, the fibres migrates the pleura (lining of the lungs) and causes cell death and Inflammation.
- 6% five year survival rate
what r physical mutagens ?
Physical mutagens are agents that can cause changes in the DNA of an organism by physically altering its structure
Explain ionising electromagentic radiation in gamma rays
ionising electromagnetic radiation
-ionising radiation carries enough energy to remove electrons from atoms, causing atoms to become charged or ionised.
GAMMA RAYS
If gamma rays hit into the molecule of water in our bodies which possesses 60% of our body weight, it will likely remove an electron, causing an unstable atom. this atomi would try to find another electron to replace it w from another molecule which is likely to be DNA, creating a mutation in the amino acid sequence. this is indirect ionisation.
explain the connection of nuclear weapons in japan to how it caused Physical mutagens
The use of such weapons caused a massive release of ionising radiation. An increased rate of mutations/birth defects was caused in survivors. Long term consequences included leukemia, transgenerational mutations
explain UV radiation and pyramidine dimerization as a physical mutagen
- UV radiation can join adjacent pyramidines (C/T bases) in the process known as pyramidine dimerization.
- UVA – lowest risk of Pyramidine dimerization , UVB and UVC have higher risks
- DNA repair mechanisms usually correct such mutations, however unrepaired mutations may accumulate alongside other mutations throughout an individual’s life to cause skin cancer
- This prevents them from pairing with bases on the complementary strand, causing the strand to end prematurely.
what are naturally occuring mutagens?
They are mutagens that are present at normal levels within natural environments and may cause mutations.
- The likelihood of mutations increases with increased frequency and length of exposure.
- There are two groups: biological (viruses, fungi, bacteria) non biological (metals)
wat is metabolism’s relevance to naturally occuring mutagens?
When we eat something chemical reactions increase
Chemical reactions increase= wastes production increases. Some of the waste produced is free radical species
* Free radicals are highly reactive species that carries an unpaired electron
* Free radicals aim to become stable hence they can take an electron from DNA, causing a mutation and damaging DNA sequence
naturally occuring mutagens
what are transposons and what is an example
- DNA sequences in the body that randomly detach and reinsert in the genome
o When inserted within a gene, they alter the sequence causing mutation
o If it jumps into coding section 2%, itll cause a mutation - EBV which is transmitted by salive
naturally occuring mutagens
what is cervical cancer and the HPV virus
- the hpv is a common sexually transmitted virus which integrates HPV- DNA impacting the host genome leading to mutations and causing cervical cancer.
what are point mutations?
a change to a single nucleotide base pair in DNA/RNA
what are the three types of point mutations
insertion, deletion and base substitution
what causes point mutations?
spontaneous or induced mutagens
what are the 4 effects created by point mutations
nonsense mutation, missense, silent and frameshift
what is a nonsense mutation
its where the codon in mRNA changes to a stop codon. this causes polypeptide synthesis to end at translation.
what is a missense mutation and a key example of it
its where one codon changes and results in one different AA in polypeptide. this affects the shape and function of protein and has a major effect on phenotypes.
a key example of it is sickle cell anemia, where amino acid is substituted by valine, reducing the flow of oxygen. recessive disorder caused by single substitution which creates haemoglobin
- when there r two copies of the mutation, it results in thin sickle shaped blood cells that cannot carry oxygen properly. impacts 8-10% of african americans
what is a silent mutation?
one codon changes but codes for the same aa. hence, no effect or change to protein
what is a frameshift substation
one base is inserted or deleted, causing the entire sequence of codons to change from point of mutation onwards. worst type as entire sequence is changed
what is a chromosomal mutation
- changes in the arrangement of genes on a chromosome
- occurs during crossing over in meiosis 1
- when chromosomes break and reform, the sequence of genes can be altered
what are the 5 main types of chromosomal mutations
deletion, duplication, translocation, inversion,and rings
what r two examples of deletion in chromosomal mutations
- partial deletion causes (Wolf Hirschhorn Syndrome) on the short arm of chromosme 4 is missing. this causes cranial facial phenotype a disifigurement in the face.
- deletion in the q-arm of chromosome 11 causes jacobsen syndrome, a congenital disorder
what is an example of duplication in chromosomal mutations
huntington’s disease
what is translocation and whats an example
portion of chromosome is moved to a non-homologous chromosome whichmay lead to gene fusion
e.g, translocation down syndrome portion of chromosome 21 attached to 15
what is inversion?
Section of chromosome is removed turned around 180 and reinserted (inverted)
Haemophilia A
what is trisomy and an example
3 copies of chromsomes
- down syndrome- extra set of chromosomes effects the function of the cell, chromo 21 known as trisomy 21
what are rings
A portion of a chromosome that has broken off and caused a circle/ring. Can cause either loss of or none lost genetic info
what is an aneuploidy ?
A gain or loss in the number of chromosomes from the normal 46 or is a different amount to the parents’ chromosomes. down syndrome is an example
what is a polyploidy?
a state of having more than two complete sets of chromosomes. trisomy has three copies of every homologous chromosome instead of the usual two
