Genetic Diversity and Evolution Flashcards
How is genetic variation introduced in metaphase 1?
Independent assortment - during meiosis 1, the 23 pairs of chromosomes are randomly assorted into each side of the cell, and the alleles on separate chromosomes are randomly assorted from each other, meaning that different combinations of alleles are present in each cel
What is the definition of evolution?
Formation of a new species from a pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation
What is non-disjunction, and what conditions can it cause?
Failure of a pair of chromosomes to move to opposite poles of the cell, causing either trisomy or monosomy. Conditions such as Downs syndrome are caused by this error
What is gene flow?
- Movement of genetic material between populations
- can occur between populations of the same species or different species
- e.g. bird crosses a mountain range then breeds with a bird on the other side, bringing it’s genetics across
What is directional selection?
When an environmental change results in all distribution being shifted towards one extreme e.g. peppered moths became darker to blend in with the soot caused by the Industrial Revolution
How is a new species defined?
When the new species can no longer produce fertile offspring with the old species, it is considered a new species
What is the key identifier of meiosis?
Number of chromosomes go from 2n -> n
When are mutations most likely to occur?
During interphase, S phase
How is genetic variation introduced in prophase 1?
Chiasmata - ends of the maternal and paternal chromosomes cross over with each other, resulting in a swapping of the DNA and producing recombinant chromosomes
What are the three ways that genetic variation can produced during meiosis? (no explanation)
Independent assortment, chiasmata, random fusion of gametes
How is genetic diversity determined?
Total number of different alleles in a given population
What is allopatric speciation?
- a species gets split up by a geographic barrier e.g. a newly formed mountain range
- 2 separate environments get formed by the barrier, meaning that there will be different selective pressures
- different mutations will be favoured, eventually resulting in a new species being formed
What is the process of meiosis?
Prophase 1 - chromsomes condense, nuclear envelope disintegrates, chiasmata occurs
Metaphase 1 - spindle fibres attach to kinetochore on centromere and independent assortment occurs
Anaphase 1 - homologous chromosomes are pulled to opposite poles of the cell
Telophase 1 - cytokinesis occurs and the cells are now haploid cells, even though there are two copies of each chromatid, as there is only one type of chromosome
- mitosis then occurs as normal, producing a total of 4 cells from the initial 1
What is frameshift, and why can it cause such big issues?
Frameshift is caused by an insertion or deletion (not in a multiple of 3) mutation that results in all the bases being shifted, causing all the amino acids to be changed. Can result in a completely non functional protein
What is the process of natural selection?
1) Mutation randomly occurs in population
2) Due to mutation, some individuals have favourable alleles, making them more likely to survive and reproduce
3) These favourable alleles are passed onto their offspring
4) Over many generations, a new species is formed
What is a mutation?
Random change in DNA that alters the sequence of bases
What is genetic drift?
- random changes in the allele frequency, caused by a large event
- e.g. volcano erupts, wiping out all the birds that could survive close to the volcano, meaning that the allele for high heat tolerance is completely wiped out
- not selected for
What is the definition of meiosis?
Nuclear division that results in four cells, each with half the DNA of the original organism
What is sickle cell anaemia caused by?
Mutation in the 6th amino acid in haemoglobin, causing the cell to agglutinate due to its altered shape
What are the three types of mutation that affect sections of DNA?
- inversion - sections of DNA becomes detached and then invert when reinserted
- duplication - section of DNA can be repeated in a duplication event
- translocation - chromosomal mutations can cause sections of the chromosome to break off and move to a completely different location
Why can a mutation affect the tertiary structure of a protein?
Difference in amino acid sequence can affect the placement of intermolecular bonding, resulting in an altered tertiary structure of the protein
What are the three types of mutations that affect singular bases?
- substitution - a single base is swapped with a different base, which could result in a different amino acid in the primary sequence of the polypeptide
- deletion - one or more bases are removed, which can result in a frameshift occurring. If a multiple of three bases are removed, no frameshift occurs
- insertion - one or more bases are inserted, which, similar to deletion, can result in frameshift.
What are chromosomal mutations?
Mutations that don’t just affect a single gene
