6.1, mutagens/mutations

Question 1

what are mutations and the two type of classes

Answer 1

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

Question 2

what are mutagens? - what do mutagens tend to be smth..genic

Answer 2

mutagens are synthetic/environmental agents that alter DNA greatly, enhancing the spontaneous rate of mutations. many mutagens tend to be carcinogenic.

Question 3

what are chemical mutagens?

Answer 3

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

Question 4

what are three key examples of a chemicalmutagen and expand on one heavily

Answer 4

• 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

Question 5

what r physical mutagens ?

Answer 5

Physical mutagens are agents that can cause changes in the DNA of an organism by physically altering its structure

Question 6

Explain ionising electromagentic radiation in gamma rays

Answer 6

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.

Question 7

explain the connection of nuclear weapons in japan to how it caused Physical mutagens

Answer 7

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

Question 8

explain UV radiation and pyramidine dimerization as a physical mutagen

Answer 8

• 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.

Question 9

what are naturally occuring mutagens?

Answer 9

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)

Question 10

wat is metabolism’s relevance to naturally occuring mutagens?

Answer 10

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

Question 11

naturally occuring mutagens

what are transposons and what is an example

Answer 11

• 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

Question 12

naturally occuring mutagens

what is cervical cancer and the HPV virus

Answer 12

• the hpv is a common sexually transmitted virus which integrates HPV- DNA impacting the host genome leading to mutations and causing cervical cancer.

Question 13

what are point mutations?

Answer 13

a change to a single nucleotide base pair in DNA/RNA

Question 14

what are the three types of point mutations

Answer 14

insertion, deletion and base substitution

Question 15

what causes point mutations?

Answer 15

spontaneous or induced mutagens

Question 16

what are the 4 effects created by point mutations

Answer 16

nonsense mutation, missense, silent and frameshift

Question 17

what is a nonsense mutation

Answer 17

its where the codon in mRNA changes to a stop codon. this causes polypeptide synthesis to end at translation.

Question 18

what is a missense mutation and a key example of it

Answer 18

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

Question 19

what is a silent mutation?

Answer 19

one codon changes but codes for the same aa. hence, no effect or change to protein

Question 20

what is a frameshift substation

Answer 20

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

Question 21

what is a chromosomal mutation

Answer 21

• 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

Question 22

what are the 5 main types of chromosomal mutations

Answer 22

deletion, duplication, translocation, inversion,and rings

Question 23

what r two examples of deletion in chromosomal mutations

Answer 23

• 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

Question 24

what is an example of duplication in chromosomal mutations

Answer 24

huntington’s disease

Question 25

what is translocation and whats an example

Answer 25

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

Question 26

what is inversion?

Answer 26

Section of chromosome is removed turned around 180 and reinserted (inverted)

Haemophilia A

Question 27

what is trisomy and an example

Answer 27

3 copies of chromsomes

• down syndrome- extra set of chromosomes effects the function of the cell, chromo 21 known as trisomy 21

Question 28

what are rings

Answer 28

A portion of a chromosome that has broken off and caused a circle/ring. Can cause either loss of or none lost genetic info

Question 29

what is an aneuploidy ?

Answer 29

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

Question 30

what is a polyploidy?

Answer 30

a state of having more than two complete sets of chromosomes. trisomy has three copies of every homologous chromosome instead of the usual two