INSpiREzine Discovering DNA | Page 39

HOW DO WE SEE CHROMOSONES ?
One parent is Aa and the other is aa : Their child has a 50 % chance of being Aa ( heterozygous ) and a 50 % chance of being aa ( homozygous ). 50 % dominant and 50 % recessive .
One parent is Aa and the other is AA : Their child has a 50 % chance of being AA ( homozygous ) and a 50 % chance of being Aa ( heterozygous ). 100 % dominant .
a
a
A
Aa
Aa
a
aa
aa
A
A
A
AA
AA
a
Aa
Aa

HOW DO WE SEE CHROMOSONES ?

Modern scientific techniques allow scientists to extract DNA from tissue samples and pool together tiny amounts of DNA from thousands of different cells . allowing scientists to distinguish different pairs of chromosomes from one another .
Actually visualizing the double-helical structure of DNA requires special imaging technology , such as X-ray diffraction . But it is still possible to see DNA using a standard light microscope by painting the chromosomes onto a glass slide with chemicals . The resulting banding patterns that appear on the individual chromosomes are unique to each pair of chromosomes ,