BIOLOGY NEED HELP ASAP

Question

If the offspring of two similar plants appears to look like the "parent" plants, then the plants have actually bred "true."  

In your experimental design be sure that you are being precise in your language and that you are thinking clearly about and clearly identifying any controls, independent, and dependent variables.

Answer 1

Hi Jead. Let me restate the question:

If the offspring of two similar plants appears to look like the "parent" plants, then the plants have actually bred "true."  

In your experimental design be sure that you are being precise in your language and that you are thinking clearly about and clearly identifying any controls, independent, and dependent variables.

This feels like there is some information missing, and that may be why no one has answered yet.

But I can still offer some help.

The help comes mostly from the information in the first paragraph:

If the offspring of two similar plants appears to look like the "parent" plants, then the plants have actually bred "true."  

1. Two similar plants = the plants have the same PHENOTYPE
2. offspring...look like the "parent" plants = offspring have the same PHENOTYPE as the parents

Classic genetics says that for traits controlled by a single gene there would be a dominant and a recessive form of the gene, so that the possible GENOTYPES are DD, Dd, and dd (homozygous dominant, heterozygous, homozygous recessive). And the possible PHENOTYPES from crossing would be:

1. DD x DD = 100% (4 DD's) dominant looking
2. DD x dd = 100% (4 Dd's) dominant looking, but the parents would not look the same
3. dd x dd = 100% (4 dd's) recessive looking
4. Dd x Dd = 75% (1 DD + 2 Dd) dominant looking and 25% (1 dd) recessive looking, but some of the offspring would not look like the parents

Now comes the guessing, because you do not tell us what your experiment is about. If you are trying to determine the GENOTYPES of the parents, then the experiment would cross the offspring to see if their offspring are still 100% the same PHENOTYPE (the grandparents would then be proven to be homozygous).

If the experiment is to determine if a particular trait is dominant (DD) or recessive (dd) or single gene (RR) vs co-dominance (RRWW), then the cross would be with the same species but a different appearance (tall x short, red x white).

If you are trying to test how environmental factors effect a trait's expression, for example how does soil pH effect flower color in Hydrangea macrophylla, then your dependent variable is flower color and your independent variable is soil pH.

Hope that helps.