09) Na mandioca existem dois pares de genes situados em dois pares de cromossomos diferentes, que atuam respectivamente sobre a cor da raiz e a largura dos folíolos. As relações de dominância para os fenótipos e genótipos são as que se seguem:

Faça o cruzamento entre os indivíduos indicados e verifique a descendência:

a) Marron (homozigoto) Estreito (heterozigoto) x Branco e estreito (heterozigoto)

b) Marron (homozigoto) largo x branco e largo

[Incomplete question. I found these data in other source]

Brown: BB and Bb

White: bb

Narrow: LL and Ll

Long: ll

Answer:

This means that long is recessive and narrow is dominant, and also brown is dominant and white is recessive.

root color - > Alleles: narrow (L) and long (l)

leaflets length - > Alleles: brown (B) and white (b)

a) A brown (homozygous) narrow (heterozygous) mandioca is BBLl, so it can produce BL or Bl gametes

A white mandioca is always homocygous, so a white narrow (heterozygous) mandioca is bbLl - this means it can produce bL and bl gametes.

So here is the Punnett square:

---| - - BL-|--Bl--

bL|BbLL| BbLl

-bl|BbLl-| Bbll

So 75% of the offspring will be brown and narrow and 25% will be brown and long.

b) A long mandioca is always homocygous, so a brown (homocygous) long mandioca is BBll - this means it can only produce Bl gametes. As white has to be homobygous as well, a white long mandioca has to be bbll - this means it can only produce bl gametes. So here is the Punnett square:

---| - Bl

bl-|Bb ll

So all the offspring is going to be brown and long.