9.Genetic Diversity Flashcards
What is gene mutation
Any change to the nucleotide bases, or a change in the sequence of bases in DNA
What’s a mutation
Any change to the quantity or base sequence of the DNA of an organism
What is base substitution
When a nucleotide in a DNA molecule is replaced by another nucleotide with a different base
What may be the consequences of base substitution
May result in a non functioning protein, this is if the new triplet codes for a different amino acid to the original then the bonds formed in the tertiary structure will be different resulting in a different shaped protein which means may not function properly.
May not had negative effect, if the new triplet codes for same amino acid due to being degenerate, then amino acid is same and therefore polypeptide is indifferent
What’s deletion of bases
When a nucleotide is lost from the normal DNA sequence
What are the consequences of base deletion
One base deletion means polypeptide is entirely different, as all bases are read differently as all move one place to left so all triplets are different bases
What are chromosome mutations
Changes in the structure or whole number of chromosomes
What are the two forms of chromosome mutations
Change in whole set-when organisms have three or more sets rather than the usual two, called polyploidy and occurs mostly in plants
Change in number of individual-homologous fail to separate in meiosis non-disjunction, results in having one more or one fewer than usual amount, eg Down’s syndrome is the addition of chromosome
What’s hybridisation
Combing of genes of of different species of organisms to produce hybrid
What’s the importance of meiosis
In sexual reproduction gametes fuse together, if each gamete had whole number then the offspring would have 92 chromosomes, the doubling of chromosomes would occur at each generation, so in order to maintain constant number chromosome must be halved at some point
What’s the process of meiosis
1-first division, homologous chromosomes pair up and their chromatids wrap around each other, equivalent portionsmay be exchanged in the process-crossing over. Homologous pairs separate and each one goes to each daughter cell
2-second division, chromatids move apart, daughter cells divide again, giving 4 daughter cells that are genetically different
What’s independent segregation of homologous chromosomes
When chromosomes line up next to homologous partner during meiosis 1, homologous pairs arrange themselves randomly, so she first division occurs, mix of maternal and paternal or all maternal or all paternal
What’s genetic recombination by crossing over
Chromatids twist round eachother
During twisting process tension created and portion of chromatids break off
Broken off parts rejoin with chromatids of homologous’ partner
New genetic combinations of maternal and paternal alleles produced
What’s the formula for possible combinations for each daughter cell
2^n where n is number of homologous chromosomes
What’s the possible combinations of chromosomes through sexual reproduction formula
(2^n)^2
