Genetic diversity - Yr 1 Flashcards
Gene Mutation
A change to one or more nucleotide bases in DNA that could result in a change in genotype which may be inherited
Substitution mutation
If a nucleotide is changed in the DNA sequence
Nonsense mutation
If the base change results in the formation of a stop codon
Mis-sense mutation
If the base change results in a code for a different amino acid completely
Silent mutation
If the base change still codes for the same amino acid as before (as code is degenerate)
Deletion mutation
If a nucleotide is lost from the DNA sequence, resulting in a ‘frame shift’ in translation
Mutagen (mutagenic agent)
A material or other factor which increases the normal mutation rate eg high energy radiation, chemicals
Chromosome mutation
A change that occurs in a chromosome. These changes are most often brought on by problems that occur during meiosis and can result in changes in the number of chromosomes in a cell or changes in the structure of a chromosome.
Polyploidy
The process of the genome doubling that gives rise to organisms with multiple sets of chromosomes.
Non-disjunction
The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
Meiosis
The type of nuclear division in which the number of chromosomes is halved.
Gamete
Reproductive (sex) cell that fuses with another gamete during fertilisation
Diploid
Cell or nucleus containing pairs of homologous chromosomes (two sets of chromosomes)
Haploid
Cell or nucleus containing single, unpaired chromosomes (a single copy of each chromosome)
Homologous chromosomes
A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. They are not necessarily identical as may have different alleles. They are capable of pairing during meiosis.
Crossing over
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged
Chiasmata
A point at which paired chromosomes remain in contact during the first metaphase of meiosis and at which crossing over and exchange of genetic material occur between the strands.
Recombination
The rearrangement of genetic material, especially by crossing over in chromosomes.
Independent assortment
The alleles of two (or more) different genes get sorted into gametes independently of one another. The allele a gamete receives for one gene does not influence the allele received for another gene. This is because homologous chromosomes line up in random orientations at the middle of the cell at metaphase as they prepare to separate, meaning that the same parent cell can produce different combinations of chromosomes in the daughter cells.
Independent segregation
During the formation of gametes, each gamete receives just one gene copy, which is selected randomly. Each pair of alleles segregates independently of the other pairs and all possible combinations of alleles can occur in the resulting gametes.
Variation
Differences between individuals. It can be interspecific (between different species) or intraspecific variation (between individuals of the same species).
