mitosis and genetic variation 3 Flashcards
what are chromosome mutations caused by
errors in cell division
in humans,what is the product when meiosis works properly
all four daughter cells will end up with 23 whole chromosomes- one from each homologous pair
but sometimes meiosis goes wrong, when it does what is different about the cells produced
the cells produced contain variations in the numbers of whole chromosomes or parts of chromosomes
when meiosis goes wrong the variation in cells produced are different, for example one cell could have two chromososmes 6’s and others have no chromosome 6’s what is this an example of
chromosome mutation and is caused by errors in meiosis
what can chromosome mutations lead to
inherited conditions because the errors are present in the gametes (the hereditary cells)
what is non disjunction
a type of chromosome mutation, its a failure of the chromosomes to separate properly
what can non disjunction of chromosome 21 in humans during meiosis result in
down syndrome
what is down syndrome caused by
a person having an extra copy of chromosome 21 (or sometimes an extra copy of part of chromososme 21
non disjunction means that chromosome 21 fails to separate properly during meiosis, what does this mean
so one cell gets an extra copy of chromosome 21 and another gets none
when the gamete with an extra copy of chromosome 21 fuses to another gamete at fertilisation, what happens
the resulting zygote will have three copies of chromosome 21
what is a gamete
an organisms reproductive cells (sex cells)
what is a zygote
a` diploid cell resulting from the fusion of two haploid gametes
what is a haploid
a cell that has a single set of unpaired chromosomes
what is a diploid
a cell that has two complete sets of chromosomes one from each parent
what is a chromatid
each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
