A breeder wants to set up a program to produce zebrafish with long fins. Having long fins is a dominant trait compared to the short-finned wild type. Before she can market her zebrafish, she needs to perform a test cross on the long-finned fish she plans to use as a breeder. How can she tell whether her fish are homozygous or heterozygous for the long-finned trait? A. Cross the long-finned fish with short-finned fsh; if three-fourths of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous. B. Cross the long-finned fish with short-finned fish; if three-fifth of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous. C. Do several test crosses between the long-finned fish and short-finned fish; if the offspring are always long-finned, the long-finned parent is probably homozygous.

Option C

Explanation:

Let the allele for long fin trait be "L" and the allele for short fin trait be "l"

Given L is dominant over l

If he crosses a long fish and short fin to produce three fourth long fins and one fourth short fins, it is not confirmed that the long fin species are homozygous as represented in the cross below

Ll * Ll

LL, Ll. Ll, ll

The two parent species are long (but not homozygous). Hence, option A is incorrect

However, if this test cross is carried out several times, the recessive trait may disappear thereby producing only homozygous long finned species.

Hence, option C is correct

1: the largest region of the brain is the:

  cerebrum

2. the term "psychology" literally means:

the process or procedure of the science or study of the mind.

3. the area of the brain responsible for respiration, heart rate, and smooth muscle control of our blood vessels is t

medulla oblongata

4. the structure that conducts nerve impulses to and from the brain and serves as a reflex center for some sensory information without input from the brain is the:

spinal cord

5. the three-layered membrane that covers the brain and spinal cord and literally means membrane is called the:

meninges

6. the cord-like (string-like) structures that carry bio-electrical impulses from one part of the body to another are called

nerves

7. a group of nerve cell bodies that are found outside of the spinal cord and brain are referred to as:

ganglions or ganglia (pl.) “literal meaning knot”

8. the term that means spinal cord inflammation is:

myel/itis

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.