genetic diversity Flashcards
what is a mutation
a random change in the DNA that alters the sequence of bases.
what 3 things is DNA code
it is degenerate so more than one codon can codon for the same amino acid. it is universal so the same codon triple always code for the same amino acid. it is non overlapping so each base is only part of one codon.
what is meiosis
is nuclear cell division that results in 4 daughter cells what have half the DNA of the original organism.
what type of cells does meiosis produce
haploid cells
stages of meiosis
prophase 1, metaphase1, anaphase 1, telophase 1, cytokinesis, prophase 2, metaphase2, anaphase 2, telophase 2, cytokinesis.
what happens in prophase 1
the DNA condenses. 2 chromatids joined at centromere. they are arranged in homologous pairs. crossing over may occur. nuclear envelop breaks down.
what happens in metaphase 1
they line up along the equator of the cell. spindle fibres attach. independent assortment. means the proportion of paternal and maternal chromosomes that end up on each side is due to chance.
what happens in anaphase 1
the spindle fibres pull them to opposite ends of the cell. centromeres do not divide
what happens in telophase 1
chromosomes arrive at opposite poles. spindle fibres break down. nuclear envelope form around the 2 groups of chromosomes.
what is cytokinesis
division of the cytoplasm. cleavage furrow. 2 haploid cells.
what is prophase 2
nuclear envelope breaks down and chromosomes condense.
what is metaphase 2
spindle fibres attach and they line up along the equator of the cell.
what is anaphase 2
chromatids pull to opposite poles. 4 groups of chromosomes.
what is telophase 2
nuclear envelope forma around each group of chromosomes.
what is cytokinesis
cytoplasm divides creating 4 haploid cells
why do chromosomes cross over
the make more genetic diversity
how does crossing over work
chromosomes in each pair they twist around each other. chromatids break and the sections re-join.
what does crossing over result in
the exchange of alleles between homologous chromosomes.
causes of variation
environmental changes (access to food) and genetic changes (mutations)
how is genetic diversity determined
by its total number of different alleles.
what is natural selection
it is the process that organisms with more desired characteristics will survive and reproduce in a habitat
how does natural selection drive evolution
variation in a population due to mutations. some alleles are favourable which held organisms to survive and reproduce. these are passed onto offspring.
example of natural selection in the real world
black peppered moths- after the cities became covered in soot, the peppered moths went from black to white as they were able to camouflage.
what is normal distribution
it is a bell curve
