inheritance Flashcards
haploid
single complete set of chromosomes
diploid
two complete set of chromosomes
gametes why half
nuclei fuse, zygote formed with a complete set of chromosomes
meiosis
prophase 1 + 2 : bivalent = a pair of homologous chromosomes, process = synapsis, chiasma forms between bivalent chromosomes.
metaphase 1 + 2 : bivalents line up along the equator
anaphase 1 + 2 : centromeres don’t divide, whole chromosomes towards the opposite of the poles
telophase 1 + 2 : spindle fibres break down, each cell contains one complete set of chromosomes, one from each homologous pair, haploid chromosomes
genetic variation
crossing over
random orientation (independent assortment)
fertilisation
crossing over
pirces of chromatids can exchange between bivalents = produces different combinations
swapping alleles between two homologous chromosomes
random orientation (independent assortment)
random alignment of bivalents along the equator
many different combinations of chromosomes and therefore many different combinations of allele
fertilisation
any male gamete can fuse with any female gamete
different combinations of alleles
structural genes
a gene that codes for a protein that has a function in the cell
regulatory genes
a gene that codes for a protein that helps control the expression of other genes
repressible enzyme
substrate
lac operon
regulatory gene codes for a protein called repressor
repressor binds to operator region, close to B-galactosidase
repressor is attached to operator so RNA polymerase cannot bind to DNA at promoter region so no transcription
lactose can bind to repressor protein to change the active site
transcription is no longer prohibited and mRNA is produced
genes switched on and trascribed together.
products of mitosis and meiosis
mitosis : 2 identical diploid daughter cells
meiosis : 4 genetically different haploid daughter cells
