UNIT 4 - AOS 2 - CH7 Flashcards
Population
- Interbreeding group of orgs
- Same species
- Living in the same region at same time
Gene pool
“Sum total of genetic info present in a pop”
- Described by the frequencies of alleles of each gene present
- ^ variation of gene pool = ^ genetic diversity
Allele frequency
“Proportion of specific allele in a pop”
CALCULATE:
1. Calculate the total people and total alleles (x2 of total people)
2. Calculate number of the two specific alleles (e.g. B & b)
3. Divide the total number of that allele by the total number of overall alleles = frequency for that specific allele.
Allele frequency in populations and what causes it to change
- Generally, remains stable between generations
- However, can change over time due to (changes iin enviro selection pressures -> natural selection, genetic drift, gene flow
Environmental selection pressures
“External agents that influence the ability for an individual to survive & causes natural selection”
PHYSICAL (climate change, food shortages, availability of shelter)
BIOLOGICAL (Infectious disease, predation, competition )
CHEMICAL (pollutants in air/soil, drugs )
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Natural selection
“When organism that are better adapted to enviro are more likely to survive & pass their genes to next gen”
STEPS
1. Variation (genetic variation in pop gene pool)
2. Selective pressure (acts upon pop)
3. Selective advantage (Individuals better adapted to change = survive & reproduce)
4. Heritability (Advantageous trait are heritable and passed on)
Genetic drift definition
“Random changes that are unpredictable & changes to allele frequencies from one gen to next is from the action of chance events”
2 Types of genetic drift
BOTTLENECK EFFECT:
“Chance effects the allele frequencies in a pop, as a result of major pop decreases”
- The few that survive may not represent the original populations gene pool
FOUNDER EFFECT:
“Chance effects on allele frequency when a new colony is started by a few members (=unrepresentative) of a large pop”
New pop’s gene pool = decreased genetic variation, unrepresentative sample, dependent on size of founder pop
Gene flow ( + difference between immigration and emigration)
“Movement of individuals and their genetic material between populations
IMMINGRATION = movement into pop
EMIGRATION= Movement out of pop
Formula for population change
Pop change = (births - deaths) + (immigration - emigration)
Mutation
“A permanent alteration to a DNA sequence of a gene that leads to the formation of a new allele”
Causes of a mutation
- Radiation (UV, X-ray)
- Chemical (Cardcinagens)
- Pathogenic (bacteria, viruses)
For a gene mutation to be sustained in a pop ….. it is first necessary that the mutation occur in the germline (sez cells) of an org so it is passed to next gen.
TYPES =
POINT MUTATIONS & BLOCK/CHROMOSOMAL MUTATIONS
Point mutations + 2 main types
Effects a single nucleotide
- Substitution mutation
- Frameshift mutation
Substitution mutation types
SILENT MUTATION
Nucleotide substitution in DNA & doesn’t result in a chance in amino acid sequence = gene expression isn’t effected
NONSENSE MUTATION
Stop codon earlier than intended = shorter polypeptide (depends on where mutation occurs along the protein if it will be impacted)
MISSENSE MUTATION -> CONSERVATIVE
Causes amino acid change with a amino acid that has similar properties but protein can carry same function
MISSENSE MUTATION -> NON-CONSERVATIVE
Amino acid change to one with different properties = protein cannot carry out normal function
Frameshift mutations
INSERTION MUTATION
1 nucleotide added to DNA strand (TAC GTA -> TAC GCT A) = codons are changed
DELETION MUTATION
1 nucleotide removed
