evolution

Question 1

Allele
Gene
Proteins
Phenotype
Genotype

Answer 1

Allele: A variant of a gene; brown eyes, blue eyes, etc

Gene: sequences of DNA that code for a protein

Proteins: functional polypeptides

Phenotype: physical expression of a gene; eye colour, hair colour, blood type

Genotype: The genetic make-up of an organism that determines or contributes to the phenotype

Question 2

What causes genetic mutation, it’s impact on genetic diversity, can our bodies fix bad mutations & kinds

Answer 2

**Genetic mutation **

• Can be caused by mutagens or randomly occur
• increases genetic diversity & can change the gene pool
• Our bodies have ways to fix DNA to avoid bad mutations

Kinds: of mutations
- Advantageous
- Neutral
- Deleterious: negative impact on individual fitness

Question 3

Gene pool

How to determine whether evolution has occurred

How to have diversity

Answer 3

Gene pool = all of the alleles present in a population
–> Changes to the gene pool result in evolution
–> The greater the variation and number of alleles within a genetic pool, the greater the genetic diversity

Question 4

• Define evolution
• link b/w changes to gene pools and evolution
• why evolution/change in gene pool may occur

Answer 4

Evolution = change in gene pool over time.

Changes in gene pool = evolution:
- random event [genetic drift]
- natural selection
- reproduction of mutations
- gene flow
- artificial breeding

Question 5

Genetic diversity
define Genetic drift & state diff kinds

Answer 5

**Genetic diversity = **variation of alleles within a population

Genetic drift: A random event that dramatically alters a populations gene pool
- Bottleneck effect
- Founder effect

Question 6

Founder effect

Answer 6

• Reduction in genetic diversity
• when a population is derived from a small unrepresentative sample of the original population

Question 7

Bottleneck effect

Answer 7

• Reduction in genetic diversity
• occurs when a large proportion of a population is removed due to a chance event

Question 8

Point mutations
- Base substitution

Answer 8

Point mutations: change 1 nucleotide; substitution, deletion or insertion.

Can be further differentiated into:
silent → doesn’t change the amino acid
- bc genetic code is degenerate so despite the change to the original DNA sequence the same amino acid is produced and incorporated into the protein

nonsense → codes for STOP codon
- pre-maturely ends the translation of a gene’s mRNA
- the gene will not be completely translated meaning the polypeptide will be too short to function properly
- most dangerous mutation

missense → changes one amino acid**

Question 9

frameshift mutations

Answer 9

• Addition or deletion of a nucleotide that alters the reading frame [read in triplets/codons] of the following nucleotides
• causing a major disruption to the structure and function of proteins as it could alter the base sequence of a gene so that the message it encodes is no longer the right amino acid

Question 10

1. degenerate
2. reading frame

Answer 10

1. a single amino acid can be coded for by more than 1 codon
2. the order in which nucleotide triplets [codons] are divided into consecutive non-overlapping sequences to be read and translated into amino acids

Question 11

Block mutations & the diff types
- occur on a chromosome

Answer 11

• **Deletion: **removal of a section of DNA
• **Duplication: **replication of a section of DNA, lengthening the DNA
• Inversion: reversal of a section of DNA
• Translocation: switching of 2 different sections of DNA on diff chromosomes

Question 12

Aneuploidy

Answer 12

• chromosomal abnormality where an organism has an incorrect number of total chromosomes due to the addition or loss of a chromosome
• can result when homologous chromosomes fail to segregate in anaphase of meiosis stage I or when sister chromatids fail to segregate in anaphase of mitosis or meiosis stage II
• additional chromosome on the 21st gene causes Down syndrome
• turner’s syndrome 1 x chromosome instead of 2

Question 13

Polyploidy

Answer 13

• a change in the number of sets of chromosomes
• most species are diploid -> 2 sets of chromosomes
• some species have more than two sets of chromosomes -> polyploid (eg. 3 sets of chromosomes (3 of each chromosome)
• can occur naturally through crossbreeding/hybridisation or can be induced using chemicals

Question 14

hardy-weinberg equilibrium

Answer 14

In large, randomly mating populations where there are:
- no mutations
- no migration
- all phenotypes are equally suited to the environment

there will be no change in allele frequencies
→ gene pool/allele stability
→ no evolution (remain the same)

Question 15

natural selection

Answer 15

natural selection = a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles

• • these traits are already present in the population
• • can cause an increase or decrease in gene diversity
• • selection pressures lead to natural selection
• • natural selection occurs when any selecting agent acts on a population creating a selective advantage [when selective agents create a selective advantage]
• • the differences in survival and reproduction result in changes to allele frequencies
• –> results in evolution

Question 16

outline the steps involved in natural selection

Answer 16

1. Varitation
   * there is heritable phenotypic variation b/w members in a population.
2. selection pressure
   * A specific environmental selection pressure causes a struggle for survival.
3. trait w/ selective advantage
   * Members with advantageous alleles have increased chances of surviving and reproducing
4. Heritability
   * These “fitter” organisms thus have higher chances of passing on their advantageous alleles to their offspring,** increasing those allele frequencies over successive generations**
   * can only be inherited if the trait mutates in the germline cells

Question 17

Population
Allele frequency

Answer 17

Population = a group of individuals of the same species living in the same location

Allele frequency = The proportion of certain alleles in a gene pool

Question 18

mutations as a source of variation

Answer 18

generally, the genetic material of an organism is stable both in its base sequence and in its chromosomal location and is passed unchanged from generation to generation

• mutations are changes in the DNA sequence
• can be small → changes to nucleotides (point)
• can be larger → changes to sections of chromosomes (block)

Question 19

Inbreeding
Adaptive potential

Answer 19

Inbreeding - Sexual reproduction b/w 2 related individuals
–> keeps harmful alleles in the gene pool

Adaptive potential - The ability for a population to adjust to new environmental selection pressures
–> Lower adaptive potential: Populations become vulnerable to new selection pressures that could challenge and potentially wipe out the entire population due to the absence of advantageous alleles

Question 20

Interbreeding
-> Gene flow
-> Immigration
Emigration

Answer 20

Gene flow - The flow of alleles in and out of a population due to the migration or interbreeding of individuals b/w 2 populations

–> Interbreeding - When 2 individuals living in different populations mate and have offspring

–> Immigration - The movement into a population

Emigration - The movement out of a population

Question 21

Category & effect on genetic diversity of these mechanisms:
- Genetic drift: 2
- Gene flow: 3

Answer 21

Genetic drift:
examples of chance events:
* destruction of habitat
* drought
* bushfire
* introduced diseases

• Bottleneck effect: Decrease genetic diversity
• Founder effect: Decrease genetic diversity

Gene flow
- Immigration: Increase genetic diversity
- Emigration: Decrease genetic diversity
- Interbreeding: Increase genetic diversity

Question 22

Define
- Selective breeding/artificial selection

Answer 22

The changing of a population’s gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait

Question 23

The effect of selective breeding on genetic diversity

Answer 23

• can lead to smaller gene pools
  –> overexpression of deleterious alleles, reducing adaptability and fitness within a population as it also lowers adaptive potential.
• can cause a human-induced genetic bottleneck

Question 24

mechanism of artificial selection

Answer 24

1. there is heritable phenotypic variation within the population’s gene pool
2. humans select individuals with a desired trait
3. humans alter the breeding behaviour of these individuals to breed (reproduce) and pass specific alleles onto the next generation
4. the alleles that lead to the desired phenotype will be inherited by subsequent generations and they can increase in frequency in the gene pool over time

1. variation
2. selection pressure
3. favoured trait & heritability

Question 25

antibiotic resistance is due to:

Answer 25

- patients not finishing an entire course of antibiotics - increased use of antibiotics in livestock farming; enables antibiotic ingestion by humans - misuse of antibiotics e.g. prescription of antibiotics on non-bacterial related infections - doctors overprescribing antibiotics - lack of infection control in medical centres - poor hygiene and sanitation

Question 26

Viral antigenic evolution: Antigenic drift and shift

Answer 26

**Antigenic drift:** when a point mutation alters a virus’s nucleic materials resulting in small changes to its antigens until the accumulation causes the antigen to be unrecognisable **Antigenic shift: **occurs when two or more strains of a virus combine to form a new strain of the virus with antigens from each of the original strains - Antigenic shift often occurs when a species is infected with more than one strain of a virus

Question 27

Darwin vs Lamark's theory

Answer 27

**Darwin: **Giraffes with short neck die, giraffes with long neck pass on the trait **Lamarck:** physical changes in organisms during their lifetime - such as greater development through increased USE, could be transmitted to their offspring.

Question 28

treatments: virus

Answer 28

Rest Hydration Antivirals (vaccines)

Question 29

factors affecting a populations gene pool

Answer 29

Gene pools tend to remain constant (unchanging) Unless something acts to change the gene pool - mutation - selection (natural or sexual) - random events (genetic drift) - gene flow (emigration and immigration) - human intervention

Question 30

selection pressures [- selection pressures can select for or against phenotypes - selection pressures act on the phenotype and change the genotype (gene pool - allele frequencies)]

Answer 30

selection pressure = an external agent which affects an organism’s ability to survive in a given environment physical - climate change, shelter, food availability biological - competition, predators, disease chemical - pollutants, drugs (antibiotics)

Question 31

change in population equation

Answer 31

change in population = births - deaths + immigration - emigration

Question 32

impact of events on genetic diversity

Answer 32

natural selection → decrease in genetic diversity - during natural selection, a particular phenotype has a selective advantage so particular alleles become more common, while others are removed gene flow → increase in genetic diversity - usually, the movement of alleles results in new alleles coming into a population genetic drift → decrease in genetic diversity - random chance events may lead to a loss of alleles in a population bottleneck → decrease in genetic diversity - event leading to the death of many members of a population may lead to a loss of alleles in a population founder effect → decrease in genetic diversity - the population is descended from individuals with limited diversity in their genetic material mutations → increase in genetic diversity - mutations are the source of new alleles

Question 33

outline the process/formation of antibiotic resistance

Answer 33

1. heritable phenotypic?genetic? variation exists b/w bacterium in a population, with some having advantageous alleles that confer antibiotic resistance. 2. an antibiotic acts as an environmental selection pressure, when the antibiotic is added antibiotic-resistant bacteria have a selective advantage and increased chances of surviving and passing on their advantageous alleles via binary fission or bacterial conjugation 3. allele frequencies of those advantageous alleles increase over successive generations and an antibiotic resistant bacterial population has formed

Question 34

consequences of bacterial resistance

Answer 34

- more challenging to treat common infectious diseases - normally treatable diseases can now be life-threatening if they have an antibiotic-resistant strain of bacteria ---> eg. pneumonia, tuberculosis, gonorrhoea, salmonella - WHO sets up the Global Antimicrobial surveillance system to monitor antibiotic resistance ----> solutions: - new antibiotics --> which bacteria aren’t resistant to - new treatment options - time length of treatments being altered

Question 35

mutations of viruses

Answer 35

viruses mutate at a high rate during replication and antigens can change - especially for viruses that have RNA as their nucleic material - no proofreading mechanisms like enzymes that check for mutations in RNA as compared to DNA ---> eg, influenza, stars cov 2, HIV, ebola - the degree to which the antigens are altered will result in either antigenic drift or antigenic shift

Question 36

consequences of antigenic drift and antigenic shift

Answer 36

no mutation of virus (same strain) - full immune response immediately - B memory cells produce antibodies quickly - no illness antigenic drift of influenza - partial immune response - B memory cells can produce antibodies and can form SOME antibody-antigen complexes - no illness antigenic shift of influenza - immune system has no memory of pathogen - time required for adaptive immune response - illness constantly mutating therefore a single vaccination cannot be made and administered to provide long-term protection Australian government make a vaccine covering the most common seasonal strains of influenza for each year

Question 37

State 3 differences between natural selection and selective breeding

Answer 37

**natural selection: ** 1. occurs slowly over numerous generations 2. selected traits increase the chance of survival for the species 3. occurs due to environmental selection pressures **Artificial selection:** 1. humans are the selection pressure 2. selected traits may not be advantageous for the organism 3. occurs faster as humans intervene

Question 38

Compare natural selection to genetic drift

Answer 38

- natural selection selects for favourable traits while genetic drift occurs randomly due to chance events - natural selection occurs over a long period of time, and genetic drift can occur as quick as over one generation

Question 39

Describe how changes in the antigenic properties of viruses can lead to ineffective vaccines

Answer 39

Vaccine target the specific strain of virus (the antibodies produced from the stimulation of the vaccine aren’t specific to that strain)

Question 40

mutation is a source of variation, explain

Answer 40

define mutation, these random mutations can result in changes to amino acid sequences coded by DNA which results in phenotypic variation

Question 41

define mutation

Answer 41

random changes in DNA sequence