ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Biology => Topic started by: emxrang on October 24, 2012, 07:24:52 pm
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okay so my teacher didn't explain this to me but here it goes.
Q1. if a dihybrid cross results in a 9:3:3:1 ratio does it mean that the two genes are linked???
because i red in Nature of biology that two genes are linked if they produce offspring in unequal ratio with more from parental gametes; and two genes are unlinked if they produce offspring in the equal classes.
Q2. also if a dihybrid cross results in a 1:1:1:1 ratio does it mean that the two genes are unlinked???
please answer ASAP
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In both of the cases that you've mentioned, such ratios would indicate that the genes are unlinked.
In Q1, the 9:3:3:1 phenotypic ratio would indicate that the two genes have assorted independently, in a cross between two heterozygotes (at both gene loci)
If two genes are linked, than in a cross between two heterozygotes, expect offspring in a proportionally high:proportionally low:proportionally low: proportionally high, phenotypic ratio. Eg. 50:10:12:50
In Q2, the 1:1:1:1 phenotypic ratio indicates that a cross between a heterozygote (eg. AaBb) and a homozygous recessive individual has occurred (eg.aabb)
If the two genes are linked, once again expect offspring in a proportionally high:proportionally low:proportionally low: proportionally high, phenotypic ratio. Eg. 50:10:12:50