inquiry question 1 module 6 Flashcards
How does mutation introduce new alleles into a population?
main process that contributes to variation
meiosis
crossing over
swapping of genetic material in homologous chromosomes during prophase I and reshuffles/recombines alleles
meiosis
produces gamete that are genetically different from each other
and the main source of variation within a population
- crossing over
- random segregation
- independent assortment
random segregation
homologous chromosomes are distributed in daughter cells randomly in anaphase I
independent assortment
Homologous chromosome pairs align randomly where genes are inherited independently of each other during metaphase I
define a mutation and types
A permanent change in the DNA sequence that occurs that are the source of new alleles within a gene pool spontaneously or as a result of mutagens
- point
- chromosomal
define a mutagen and the types and how they are obtained
natural or synthetic substance that can alter the structure or sequence of DNA and that can dramatically increase the rate of mutation that can occur at the gene or chromosome level
- neutral
- beneficial
- harmful
spontaneous or induced
beneficial mutagens
increase the likelihood of survival and results in allele that allows adaptability to the environment and successful reproduction
neutral mutagens
no effect on the survival (most are neutral as they are in the non-coding region)
harmful mutagen
decrease the likelihood of survival - results in allele that reduces adaptability to environment or increases susceptibility to disease or disability
what process leads to the creation of mutations
mutagenesis which can occur in both somatic and gametic cells but they cant be passed down to offspring from somatic cells as they are bodily cells
- spontaneous
- induced
physical chemical biological
spontaneous mutations
randomly occurs during DNA replication where DNA polymerase can make mistakes while copying the bae sequence which can result in mutations if ot detected and repaired
induced mutations
exposure to caused by mutagens eg. UV radiation, tobacco smoke, HPV etc.
chemical mutagens
- intercalating agents
- base analogues:
- DNA reactive chemicals
eg. tobacco smoke which contain mutagenic compounds that can be carcinogenic, outdoor air pollution, asbestos ( fibres are inhaled and the body is unable to remove)
intercalating agents
chemical mutagen
chemicals that insert themselves into bonds between base pairs preventing hydrogen bonds from forming and bends the DNA double helix out of shape causing to errors in DNA replication
base analogues
chemical mutagen
inhibits DNA from functioning –> chemicals that are structurally similar to the nitrogenous bases in DNA that they are incorporated into DNA sequence during replication instead of the normal base
DNA reactive chemicals
chemical mutagen
chemicals that react directly with the nitrogenous bases of DNA → modify the DNA structure causing a mutation
ultraviolet light
physical mutagen and a form of ionising radiation
- form of radiation not visible to the eyes and has shown to increase skin cancer rates
physical mutagens
- ionising radiation (eg. gamma radiation, ultraviolet light, x-rays)
- non-ionising radiation (not associated with damage to DNA eg. microwaves, visible light)
gamma radiation
physical mutagen and ionising radiation that is a result of radioactive decay interrupt the cellular process and ionise molecules by penetrating cells and breaking or changing chemical bonds that give the double helix its structure
- hiroshima atomic bombs which causes a tenfold increase in cancer deaths and provides evidence for its mutagenic nature
biological mutagens
Living molecules that can cause mutations and canvas by interfering with the functions
of oncogenes and tumour-suppressor genes
eg. viruses, transposable elements
transposable elements
biological mutagen
- short DNA sequences that move around the genomethat cause
errors in normal DNA replication
Interference with gene function
Insertion into the middle of a functional gene
eg.. corn kernel which uses it to manipulate its qualities
viruses
biological mutagen
- Insert DNA into host cell → host undergoes transcription and translation of viral genes → produces viral DNA and viral proteins
-If infected cell does not die → permanent mutation in host genome
eg. HPV
point mutations
A mutation that alters, adds or removes only one nucleotide from a sequence of DNA or RNA and often only effects a single gene
- base substitutions
- frameshift mutations
nonsense mutation
base substitution in point mutations
- codon is changed to a stop codon signalling chain termination
- Stops the translation process as it truncates the polypeptide
- Results in incomplete, usually non-functional protein products
base substitutions
silent mutation: codon is changed which codes for the same amino acid
nonsense mutation: codon is changed to a stop codon signalling chain termination
missense mutation: a codon is substituted with another codon which encodes for a different amino acid
silent mutation
base substitution in point mutations
- codon is changed which codes for the same amino acid
- AGG → CGG (both encode for arginine)
missense mutation
base substitution in point mutations
- a codon is substituted with another codon which encodes for a different amino acid
- Codes for an altered polypeptide sequence → still produces a protein but its function depends on the importance of the amino acid replaced
conservative: specify codons that are chemically similar to the original → Protein function is not altered
non-conservative: codones are dissimilar to the original → often produces non-functional proteins
eg. sickle cell anaemia –> chain in amino acids Aggregates the red blood cells created a distorted, sickle shaped cells that are inefficient in oxygen transport
frameshift mutations
involve one or two nucleotides being either added or removed from a nucleotide sequence, altering every codon in that sequence from that point onwards
- If it occurs in coding regions → non-functioning proteins are produced as the polypeptide is completely different
- insertions
- deletions
insertions
frameshift mutation –> point mutation
- one or more extra nucleotides are added into a DNA sequence
AAG CTT CCT (original)
AAG CTA TCC T (addition of A)
deletions chr
chromosomal mutation
- section of a chromosome breaks off and a segment is permanently deleted
- Results in the loss of genetic information which can have serious effects on the growth and development
eg. cri-du chat syndrome
inversion
chromosomal mutation
-ccurs when a segment of a chromosome breaks off and is inverted before being reinserted back into its original location
- genetic information remains the same
deletion
frameshift mutation –> point mutation
- one or more nucleotides are deleted from the DNA sequence
AAG CTT CCT (original)
AAG CTC CT.. (deletion of T)
chromosomal mutations
Changes in DNA that occur because of the alterations in structure or number of chromosomes
- usually during meiosis
- duplication
- inversion
- deletion
- insertion
- translation
chromosome
macrostructure made up of DNA wrapped around histone proteins and is visible during nuclear division
translocation
chromosomal mutation
- whole chromosome or a segment of a chromosome becomes attached or exchanged with another non-homologous chromosome
balanced: no loss or gain of genetic material
unbalanced: total amount of genetic material is lost
eg. down syndrome
insertions chr
chromosomal mutations
- section of one chromosome breaks off and is inserted into a different chromosome
duplication
chromosomal mutation
- occurs when the same segment of a chromosome is copied, repeated or occurs twice
- Increases gene expression that can be harmful or beneficial depending on the gene involved
aneuploidy
presence of an abnormal number of particular chromosome
- down syndrome
point mutation strength
Nonsense > non-conservative mutation > missense conservative > silent mutation
somatic mutations
4Changes to DNA to specific body cells
- cant be passed down to offspring
- localised effect on individuals
- found everywhere
- mitosis
- diploid
- 6 chromosomes
nondisjunction and what does it result in
two homologous chromosomes don’t separate properly during first division of meiosis
- Results in gametes with incorrect number of chromosomes →
- If gametes are involved in fertilisation → offspring with incorrect chromosomes will be formed → birth defects / genetic disorders
- aneuploidy
- polyploidy
what are chromosomal abnormalities
total number of chromosomes changes
- Detected with a karyotype
- Change in chromosome number can occur due to nondisjunction of chromosomes in cell division in Anaphase I
germline mutations
Changes to the DNA of cells that produces eggs and sperm
- meiosis
- found in gametes
- haploid
- 23 chromosomes
polyploidy
change to the total number of chromosomes → presence of more than two sets of chromosomes
- If this gamete is fertilised → the zygote will have more than the usual two sets of chromosomes
Triploid (3n) → haploid gamete fuses with diploid gamete → low fertility
Tetraploid (4n) → two diploid gametes fuse
how do mutations effect the gene pool of species
They provide genetic variation for the population → if it results in a favourable trait it can increase the survival and effect evolution
cancer
Group of diseases characterised by abnormal, uncontrolled cell division that can result in the formation of a tumour (Undifferentiated group of cells that do follow normal cell division which inhibit the normal functioning of the body)
genes that regulate cell growth and division
mutations of these= cancer
proto-oncogenes (gas pedal)
- code for proteins that stimulate mitosis
- mutation = uncontrolled cell division
tumour suppressor genes (brake pedal)
- codes for proteins that inhibit cell division to help stop mitosis
- mutation = division out of control
non-coding DNA double check this stuff
98% of dna sequence
is the sequence of DNA which DO NOT encode for proteins
- control the action of regulatory proteins
- Introns (within genes) –> spliced out during
- intergenic non-coding DNA (between genes)
coding DNA (check how much we need to know)
sequence of DNA that encodes for proteins
Number of difference in DNA caused by mutations is used to determine how closely related two species are
mutations and variation
higher level of variation and increases diversity in the gene pool
- favourable = increase chance of survival and likely to be passed on
- unfavourable = likely to be fatal to individual and disappear from population
regulatory proteins
proteins that control the rate of transcription
- activator proteins: bind to enhancer regions that increase transcription to reduce mutation
- repressor proteins: bind to silencer regions that decrease transcription and contribute to increased rate of mutations
epigenetics
Study of factors that influence gene expression
- genes can be turned on/off –> chemical tags or activator and repressor genes
- regulatory proteins - proteins that control the rate of transcription
enzymes
catalyses reactions within a cell
- catabolism= breaks molecules apart
-anabolism = joins molecules together
Enzyme 1 converts glutamate to ornithine
Enzyme 2 converts ornithine to citrulline
Enzyme 3 converts citrulline to arginine
enzyme effect on gene mutations
- if gene for enzyme is mutated the enzyme may not be fully functional
- and effects the biosynthetic pathway
biosynthetic pathway
a chain of reactions associated with the formation of complex compounds from simple substances by a living organism
- Check if an enzyme is working in a cell by looking at which product is missing and which substrate has accumulated
gene pool
total number of alleles for all genes found within a population of species
Constantly changing
large=ensure genetic variation and diversity to survive sudden selection pressure in the environments
small = higher chance of extinction and less biodiversity
microevolution
small changes that occur in gene pool from generation to generation
mechanisms for gene pool change
- Mutation and natural selection
- Gene flow
- Genetic drift
evolution
gradual change and development of a living species
mutations and natural selection
darwins theory of evolution by natural selection
- Process by which mutations are advantageous to survival are passed onto future generations
- in order for this to occur there needs to be variation within individuals in a population which is caused by mutations and meiosis
favourable = increases chances of survival and can be passed on
unfavourable = likely to be fatal and disappear from population
gene flow
refers to the movement of alleles between different populations through interbreeding
- genetic differences between two populations is minimised
- breeding between two populations to make the populations more similar to each other = increase in genetic diversity within a population an positive effect son isolated populations
how does gene flow occur
- migration between populations
- horizontal gene transfer in bacteria –> Transfer of DNA from a donor to a recipient by asexual means in prokaryote (antibiotic resistance)
how is gene flow limited
- mobility of organisms –> lower in species that have low dispersal or mobility and fragmented habitats due to bigger distances between populations and smaller sizes
- small isolated populations = increase in interbreeding –> amish population, black footed rock wallaby
genetic drift and two situations
change in allele frequencies in a population due to random fluctuation in the allele frequencies of a particular gene
- does not result in formation of new alleles
- no influenced by environment or selection pressures
- greater effect on smaller populations
two situations:
- genetic bottle neck: occurs when there is a sudden decrease in population size due to environmental factors
- founder effect: New population is established by a small number of individuals being separated from a larger population it results in a small gene pool size in the founder population
founder effect
- type of bottleneck effect
- New population is established by a small number of individuals being separated from a larger population it results in a small gene pool size in the founder population
- population expands = diversity of alleles do not increase
- new colony becomes isolated –> lower genetic diversity
eg. amish
- culturally isolated, reduced genetic diversity –> maple syrup urine disease
genetic bottleneck
Type of genetic drift that occurs when there is a sudden decrease in population size due to environmental factors
- disease, natural disasters –> Devil facial tumour disease in tasmanian devils
- cheetahs = small number survived due to mass extinction , diversity low as few families survived + interbreeding
