Section 1 Flashcards
Mutations
A change in the genetic code (DNA structure) altering the sequence of nucleotides
When can mutations occur
They can occur spontaneously (because of mistakes in meiosis and mitosis)
Can happen naturally overtime
Or induced from environmental agents - mutagens
Mutagen
An environmental agent that has the potential to cause mutation
Mutagenesis
The process of mutations occurring that changes normal base pairs to altered pairs
Name a physical mutagen
Electromagnetic radiation sources
What are the main sources of radiation
The higher ends of spectrums; UV rays, X rays and Gamma rays
Why are X rays and gamma rays so dangerous
They have ionising radiation which causes damage to DNA and produces free radicals- reactive molecules
What is ionising radiation
The ability to strip electrons from atoms (ionisation)
How is UV radiation different from X rays and gamma rays
It is non-ionising
How does Uv radiation effect DNA
It penetrates through the skin and has enough energy to hit DNA
What does UV radiation cause
It causes a thymine dimmer
Thymine dimer
When 2 thymine nucleotides next to each other bond together to cause a bulge in DNA (a bump)
Why is thymine dimer a problem to DNA
When copying DNA or making an amino acid (via polypeptide synthesis) it can form a cyclobutane ring and distort DNA
How do chemicals cause mutation
Tricks DNA into thinking they’re part of the sequence = changing nucleotides = directly getting in between nucleotide pairs (desperate bitch)
Chemical mutagens cause
Misreading and changes in polypeptide synthesis
How do chemical mutagens get into the body
They are often ingested like alcohol/ cigarettes
Naturally occurring mutagens
They are mutagenic agents that exist within the natural environment
What are examples of naturally occurring mutagens and biological naturally occurring mutagens
Metals; mercury and cadmium - occur naturally in environment
Viruses, bacteria, fungi and their products are biological mutagenic agents
Name a common naturally occurring mutagen that alters DNA and how it works
Microbes (Specifically viruses)
Viruses will insert their own DNA(rude) into a cell then when the cell reproduces, the cell replicates and alters the function of the cell
Point mutation
Only one base is changed
How are bases impacted by point mutations
They can either be substituted, deleted or added
Out of all the different types of mutation which one has the least impact
Point mutation
Silent mutation
Produces an amino acid of the same type of the original - no change in the proteins
Note: multiple codons can code for the same amino acid
Nonsense mutation
Adds a stop codon in the sequence- changing the amino acid and stopping everything
Often produces a protein that isn’t able to properly function
Missense mutation
Changes original amino acid to something different
[effect on protein depends on how many amino acids are changed and if they can still bond the same way to form protein’s 3D structure]
Frameshift mutation
This impacts all amino acids added to a polypeptide chain
How do frameshift mutation impact sequence
The reading frame is shifted and results in completely different amino acid sequence
Why are frameshift mutations more likely to produce proteins that cannot function properly
They affect large sequences of base pairs - affecting large numbers of amino acids
Chromosomal mutations
Made on large scales - changes to multiple genes occurring on one chromosome
Somatic mutation
Occur in somatic cells (THE BODDYYYYY) and will affect that cell and others that are produce via mitosis
NOTE: WILL NOT BE PASSED TO OFFSPRING (SOO DRAMATIC IT WONT BE GIVEN TO YOU)
Germ-line mutation
Occurs during meiosis
(Like when the sperm is penetrating to the egg - the mutation happens there and then the mutation spreads to the whole body)
NOTE: WILL BE PASSED ONTO OFFSPRING (GERMS SPREAD EW)
What is an example of point mutation
Sickle cell anemia
Sickle cell anaemia
- it is a condition that involves 2 alleles; the normal allele and the mutant sickle allele
-normal allele DNA codes for protein - GLU
-mutated sickle DNA codes protein- VAL because it has base adenine instead of thymine
-normal allele produces normal haemoglobin proteins = normal red blood cells
-people - homozygous- with mutant allele = abnormal haemoglobin - sickle shaped red blood cells = poor oxygen transport
But
-people - heterozygous- produce both normal and abnormal haemoglobin - because they produce this mutant allele, they are less likely to catch malaria since infectious parasite dies inside sickle cells
What are the two parts that makes up DNA
Coding (exons) and non-coding (introns)
Is exons or introns used to produce proteins
Exons
Is DNA exons or introns
Exons - they are expressed
Frameshift mutations
They affect all amino acids added to polypeptide chains
(They shift all the base pairs)
What are the 4 types of chromosomal mutation
Deletion - section is removed
Duplication - section of chromosome is copied
Inversion - section is moved to another section in the same chromosome
Translocation- section is swapped to another section of another chromosome (crossing over but gone wrong type thing)
Chromosomal mutation
Changes to multiple genes on one chromosome
What is an example of chromosomal mutation
Aneuploidy - entire chromosomes being added or removed
How does chromosomal mutation affect large sequence of base pairs
They often have many proteins that aren’t affected, not produced or produced in wrong amounts
What are the 4 types mutation can be
Silent - cause no change in organism
Beneficial - giving organism advantage, improving chances of survival
Neutral - causing change with neither advantage or disadvantage
Deletion (very harmful) - disadvantage organism, lowering chances of survival
Outline how entirely new alleles can be introduced into a gene pool
- mutation must occur that produces a new trait
- mutation must occur in germ-line cells so it can passed to next generation to be part of the gene pool
- mutations will mainly happen in meiosis during cell replication
What is an example of mutations as a source of variation
Blue eyes is a mutation bringing variation into humans
- mutation impacts a cell called OCA2 lowering melanin production = blue eyes that was not seen before
What are coding DNA
DNA sequences that are used directly to make proteins and RNA
Gene pool
The combination of all genes including alleles present in a reproducing population
Gene flow
Changes in allele frequency due to new individuals entering a population or from individuals exiting a population
Genetic drift
Change in allele frequency due to chance - random events -
Since one or more alleles are lost in a population due to random events, the allele frequency of gene pool will decrease
What causes somatic mutation
Environmental factors
What causes germ-line mutation
DNA replication errors
Outline how fertilisation relates to the causes of genetic variation
- increases genetic variation
-combines maternal (mum) and paternal (dad) genetic material in zygote - as a result of independent assortment + random segregation in meiosis
- new gene combinations form in that person and contributes to population
Outline how meiosis relates the causes of genetic variation
- meiosis has a very significant role in making genetic variation
- meiosis introduces new alleles through crossing over and random segregation
(Exchanging genes between homologous chromosomes)
(Two chromosomes separated randomly to reproductive cells’ gametes)
-replication errors in meiosis can also lead to point mutation = errors in crossing over = chromosomal mutation
How does mutation relate to genetic variation
- mutations can increase number of alleles for a trait
- can occur during DNA replication = replication errors
- can occur during disjunction of chromosomes (separating) = chromosomal mutation
Natural selection
Process individuals possessing traits that give them advantage for survival in their environment
Sexual selection
Process where some traits become more common in population because of mating partners being selected based on having certain traits
If the rate of mutation of DNA in germ line cells increase
The frequency of new alleles being passed onto offspring’s increases
Increase in gene pool
=
Decrease in mutation
Bottleneck effect
A type of genetic drift
When chance event causes drastic decrease in population size
Lowering allele frequency
Lowering genetic variation
Decreasing gene pool
Founder effect
A type of genetic drift
New population is stared by small numbers of individuals = founder
New population has different allele frequency from old population
Founders might not carry all genetic variation from old population so it will - lower genetic variation in gene pool
Conservation genetics
Use of data on the DNA and genes of a population
How does conservation genetics help
They help guide management decisions that aim to preserve the population
What does conservation genetic projects usually aim towards
Endangered species and development of suitable preservation plans
Genetic diversity
Assists in the long term survival of a population
