Unit 4 - Human Biology Flashcards
Gene Pool
All alleles within an interbreeding population
- Large gene pool indicates high amounts of genetic diversity, decreasing chance of extinction
- Small gene pool indicates low amounts or genetic diversity, increasing chance of extinction
Population
All members of a species living in an area at one time
Allele Frequency
How many copies of each of each allele are in that population - usually a percentage value
Changes to Allele Frequency
Genetic drift (random)
Mutation
Gene flow
Natural selection
Gene Flow
Occurs when member/s of one population move to another and reproduce
Barriers to Gene Flow
Geographical - individuals must be able to physically interact in order to reproduce
Sociocultural - restrictions to reproduction due to sociocultural differences such as: religion, not speaking the same language, ethnicity
Genetic Drift (Random)
Changes to alleles in population due to chance or small population size
Less effect on larger populations
Includes Founder Effect and Bottleneck Effect
Founder Effect
Small group leaves population and forms new population in uninhabited location
Small gene pool
Will have new gene frequency that can be compared to mother population
Bottleneck Effect
Large portion of population is removed
Due to chance catastrophic event
Can result in recovery or extinction
Mutations
Errors in gene replication or mitosis that introduce new alleles
Most are detrimental; it’s rare for one to stay in population
Can be caused by errors in internal processes or mutagens
Natural Selection
Some genotypes produce phenotypes that convey selective advantages or disadvantages
Alleles that make up advantageous genotypes will become more common, vice versa
Types of Mutations
Somatic Mutations (body cells) Germline Mutations (sperm/egg cells) Gene or Chromosome mutations
Somatic Mutations
Only affect individual
no impact on the gene pool
Germline Mutations
Affect the gene pool if mutated cells form offspring
What do mutagens do?
Mutagens can:
- trigger DNA replication errors
- break up DNA
- Lengthen DNA
- Block DNA replication
- Damage DNA structure
- Chemically react with DNA to modify it
Examples of Mutagens
Ionising radiation (X-rays, Gamma rays, UV rays) Mustard gas Formaldehyde Sulfur dioxide Some antibiotics
Gene Mutations
Deletion
Insertion
Substitution
Point mutation
Deletion (gene)
one or more bases are deleted
Insertion (gene)
One or more bases are added
Substitution (gene)
One or more bases are swapped out for another base
Point mutation
Deletion/Insertion or substitution but only affects one base
Frameshift Mutations
Deletion or insertion affects every codon after it
more likely to create a significant effect
Chromosomal Mutations
Duplication/insertion Deletion Inversion Translocation Non-disjunction
Duplication/insertion (chromosomal)
Section of chromosome is doubled up
Deletion
Section of chromosome is missing
Inversion
Part of the chromosome is out of order
Translocation
Part of one chromosome is attached to different chromosome
Non-disjunction
One extra or one missing chromosome
Missense Mutation
Amino acids have changed, protein looks and functions differently
Nonsense Mutation
“stop” code inserted
Protein is either very short or not produced
Neutral Mutation
Change to amino acid but function unaffected
Protein looks different but acts the same
Silent Mutation
No change
Protein appears and functions the same way
