UNIT4 AOS1 Flashcards
-changes in the genetic makeup of a population -changes in biodiversity over time -determining relatedness between species -human change over time
What are mutations?
changes in the DNA base sequence of gene
How do mutations usually occur?
through errors during DNA replication
What are point mutations? and what are the three types?
they alter add or remove a single nucleotide from a sequence of DNA or RNA and typically only effect a single gene. Deletions, substitutions and additions.
Are all mutations negative?
no a mutation may produce a new characteristic that may provide a survival advantage
What are substitution mutations?
occurs when one nucleotide is replaced by another type of nucleotide.
What is a silent mutation? and why can it occur?
a silent mutation is when a substitution results In a new codon that still codes for the same amino acid. it occurs due to the degeneracy of genetic code
What are missense mutations?
is when a base substitution results in a different amino acid being encoded.
What are nonsense mutations ?
is a point mutation that results in a premature stop codon in transcribed RNA and a non-functional protein
What is insertion mutations?
type of frameshift mutation where an nucleotide is inserted into DNA or RNA sequence
What are deletion mutation?
type of frameshift mutation where one nucleotide is removed from DNA or RNA sequence
What are block mutations?
block mutations affect large sections of chromosome, therefor affecting many genes. there are four main types, translocations, inversions, duplications and deletions
What are translocations?
is when a section of one chromosome attaches to the end of another chromosome. abnormally cause b rearrangement of parts between non-homologous chromosomes
What are inversions?
inversions occur when a single chromosome undergoes breakage and a segment of the chromosome is reversed end to end
What are duplications?
duplications are a type of mutation in which part of the second homologous chromosome joins on to its partner
What are deletions?
is a mutation in which a part of the chromosome is missing- part of the chromosome breaks off but does not reattach
What is a chromosomal abnormality?
a mutation that involves the gain or loos of whole chromosome in a cell- occurs due to mistakes in cell division
What is aneuploidy ?
occurs when an organism possesses an abnormal umber 0f chromosomes that is jot a who multiple of a haploid number
When do aneuploidy’s occur?
when there has been a non-disjunction is anaphase 1 or 2 of meiosis.
What is a polyploidy?
when whole sets of chromosomes do not seperate resulting in diploid gametes
Do animals or plants survive when polyploidy occurs?
animals rarely survive as it often results in a miscarriage.
very common in plants, although these plants cannot reproduce
How do we know if organisms are of the same species?
when they can interbreed to produce fertile offspring
What is a subspecies?
when two species interbreed creating infertile offspring
What are three types of phenotypic variation?
structural =appearance, short hair biochemical=colour which are due to protein expression physiological=metabolic rate, body temp behavioural= nest building, observation developmental= young-tadpole, adult-frog geographical= environmental behaviour
What is the ‘formula for phenotype’?
phenotype=genotype X environment
What factors that cause/increase genetic variation
- Sexual reproduction
- Mutation
- Gene Flow
How does sexual reproduction increase variation?
a) crossing over- which results in the recombination of genetic material in chromosomes, occurs in prophase1
b) random assortment of chromosomes into gametes,
c) particular combinations of parents=mixing of gametes
d) the particular combination of gametes
How does mutations increase genetic variation?
A mutation is a change in DNA base sequence, this can then change the structure of DNA making up a gene or chromosome
Define genepool
all the alleles of a gene present in a population
Define allele frequency
the proportion each allele if all genotypes are known must add to 1
Define polymorphic vs monomorphic population
p=individuals show variation in trait
m=all members of population show one form of a trait
Define evolution
the genetic change in a population over time
Define population
organisms of the same species living in the same place at the same time
Define gene flow and how it increases genetic variation?
gene flow is the movement of alleles form one population to another as a result of sexual reproduction between individuals from each population. this adds new Gennes or alleles to a populations gene pool
Define genetic drift
involves the unpredictable changes in allele frequencies in a population due to chance events. two types, the bottle neck effect and founder effect
How does genetic drift effect genetic variation?
creates a small isolated population that has no gene flow, therefor there is decreased genetic variation
Describe the bottle neck effect
results from the reduction in size of a population due to a natural disaster. genetically diverse original population, reduced due to natural disaster, time, genetic;y simplified population
Describe the founder effect
an example of genetic drift caused by the colonisation of an area by a limited number of individuals from a parent population not representative of original population. Decrease in variation, time and sexual reproduction creates a large popular with little variation
How does genetic drift effect the biodiversity of a population?
creates little genetic diversity and terror is unlikely to adapt to changing environmental conditions= more likely to become extinct