chap 9- genetic changes in a population over time Flashcards
what is a gene
section of DNA that transmits genetic information
what is an allele
different forms of a gene
what is a genotype
the alleles present in an individual
what is a phenotype
observable physical traits
what are the types of variation
structural, biochemical, behavioural, developmental, physiological and geographic
what are allele frequencies
a measure of how common a particular allele is in the gene pool of a population
what are mutations
random/unpredictable changes in DNA. creates new alleles, genes and chromosomes
what are spontaneous mutations
copying errors during DNA replication
what are mutagens
factors that induce mutation
what are somatic mutations
occur in body cells and only affect that individual
what are germline mutations
are heritable because they affect gametes and can be passed on to offspring
what are point mutations
a mutation that alters, adds or removes a single nucleotide from a sequence of DNA or RNA is called a point mutation. typically affect a single gene
what are substitution mutations
a point mutation in which one nucleotide is replaced by another type of nucleotide.
can be silent mutations, missense mutations, or nonsense mutations
what are silent mutations
the new codon still codes for the same amino acid
what is a missense mutation
the new codon codes for a different amino acid
what are nonsense mutations
the new codon is a stop codon and shortens the amino acid chain (which may have severe affects)
what is a frameshift mutation
one nucleotide being either added or removed from a nucleotide sequence. alters every codon in that sequence from that point onwards
what are block mutations
mutations that affect large sections of a chromosome (multiple genes)
when do block mutations occur
in eukaryotic cells during meiosis
what are the types of block mutations
duplication, inversion, deletion, insertion, translocation
what is a duplication mutation
results in multiple repetitions of a sequence of DNA
what is an inversion mutation
mutations involve a broken section of the sequence rotating 180 degrees before reattaching.
what is a deletion mutation
involves the loss of large sequences of DNA from the chromosome
what is an insertion mutation
involves a sequence breaking off one chromosome and attaching to another
what is a translocation mutation
can involve two different chromosomes exchanging segments
what is a chromosomal abnormality
when a mutation involves whole chromosomes or the number of chromosomes
how is chromosomal abnormality detected
through karyotypes
what are the two types of chromosomal abnormality
aneuploidy and polyploidy
what is aneuploidy
abnormal number of a particular chromosome, either an extra chromosome or a missing chromosome
how can aneuploidy be caused
non-disjunction during meiosis
what is polyploidy
cells and organisms that have more than 2 copies of every chromosome
what is natural selection
the influence of environmental pressures on allele frequencies of a population. occurs because of genetic variation between individuals.
what is gene flow
the movement of alleles into and out of a gene pool
how can gene flow occur
when different populations interbreed or individuals migrate between populations
what is genetic drift
the change in allele frequencies in a population due to random events
how can genetic drift occur
the bottleneck effect and the founder effect
what is the bottleneck effect
when an event (often a natural disaster) significantly reduces the size of a population and thus its genetic diversity
what is the founder effect
when a small group of individuals breaks away from the main population and colonises a new habitat
what is selective breeding
where individuals with desirable traits are deliberately interbred to produce offspring with those desired traits
why do people selectively breed plants
to produce higher quality food
why do people selectively breed animals
meat, milk quality. wool quantity/quality etc
how is selective breeding done
1- determine desired trait
2- interbreed parents who show desired trait
3- select the offspring with the best form of the trait and interbreed these offspring
4- continue this process until the population reliably reproduces the desired trait
what are advantages of selective breeding
allows for higher quality products for consumption/use
increase yields from plants/animals
produce fitter/stronger animals, more viable plants
what are disadvantages of selective breeding
can reduce resistance to environmental change
can increase genetic abnormalities
can lower genetic diversity
what is antibiotic resistance
when bacteria become resistant to antibiotic
what are antibiotics
chemicals that are toxic to bacteria
what is a superbug
when a bacterium becomes resistant to 2 or mor antibiotics
why are bacteria ideally suited to develop antibiotic resistance
they are vastly numerous, small in size, have compact genomes, reproduce rapidly
how do new genes for antibiotic resistance arise
by a combination of gene duplication and mutation
what are some strategies to reduce antibiotic resistance
prohibiting sale of over the counter antibiotics
delaying prescription of antibiotics
enforcing tighter management/use of antibiotics
discovering/developing new antibiotics
what is antigen drift
change in the surface of a virus due to gradual accumulation of mutations in the genes that code for virus surface proteins. mutations are small and new antigen is only slightly different
what is antigen shift
a sudden change in the antigen of a virus resulting in the combination of genetic material from 2 or more strains/subtypes of the virus. antigens will be substantially different
how can antigen shift occur
when different host animals live close together, increasing the chances that the two different subtypes will meet in a common host
what is the value of vaccination
prevents outbreaks of new virus strains/subtypes.
how many subtypes of influenza can vaccinations normally protect against
can normally protect against 3-4 subtypes of influenza
