Chapter 17, Due November 16th

Multiple Choice and/or True-False Review Questions

(Circle the single best answer for each question.)

   1.      Each sperm and ovum carries the:

            A.  diploid       B.  haploid  --  number of chromosomes.

 

  2.       Replication of body cells during tissue maintenance and growth is termed:

            A.  mitosis       B.  meiosis

 

  3.       The gene for the polled trait (P) is dominant and the gene for horns (p) is recessive.  Therefore, the dominant gene will mask the expression of the gene for horns.

            A.  True                       B.  False

 

  4.       The term, phenotype, is used to denote the genes or gene combinations on the chromosomes in the body cells of an individual.

            A.  True                       B.  False

 

  5.       An animal that carries the genotype (Pp) for the polled trait will be:

            A.  horned       B.  polled

 

  6.       Mating of individuals that are heterozygous for a particular trait (e.g., Pp) will enable the recessive genes to express themselves in the phenotype in about 25 percent of the offspring.

            A.  True                       B.  False

 

  7.       Most economically important traits are influenced by:

            A.  one or two gene pairs

            B.  several to many gene pairs

 

  8.       In two herds averaging the same genetic merit for a particular trait, more genetic progress should be possible in the herd with:

            A.  more          B.  less  --  variation in performance.

 

  9.       More rapid genetic progress would be expected in species with:

            A.  shorter       B.  longer  -- generation intervals.

 

Chapter 18, November 17

Multiple Choice and/or True-False Review Questions

(Circle the single best answer for each question.)

   1.      Heritability can be defined as “the proportion of the differences in a trait that exists among animals that is caused by heredity.”

            A.  True                       B.  False

 

  2.       A heritability estimate of 40 or greater is considered by geneticists to be high.

            A.  True                       B.  False

 

  3.       If a trait is low in heritability, the environment often “masks” the genotype, making it more difficult to select herd or flock replacements with confidence that genetic progress will be made.

            A.  True                       B.  False

 

  4.       An example of a trait that is low in heritability is:

            A.  feed lot gain                       B.  carcass length        C.  conception rate

 

  5.       Selection within herds or flocks where all prospective breeding animals receive the same management reduces variation in animal performance and provides greater accuracy in selection.

            A.  True                       B.  False

 

  6.       The selection differential for a particular trait can be accurately defined as  --  the difference between the selected animals to be parents and:

            A.  the average of that particular breed of animals.

            B.  the average of all animals available for selection within the herd or flock.

            C.  that portion of the difference in performance passed on to the next generation.

 

  7.       Predicted improvement in a trait can be calculated by multiplying the “selection differential” times the “heritability” of that trait.

            A.  True                       B.  False

 

  8.       Regardless of the trait, one should always  add  the value of the predicted improvement of a trait to the herd or flock average to best predict the expected performance of the offspring.

            A.  True                       B.  False

           

 

Chapter 20, November 17

Multiple Choice and/or True-False Review Questions

(Circle the single best answer for each question.)

   1.      Relationship of animals generally can not be determined when random mating is practiced so it is most practical for use in commercial herds.

            A.  True                       B.  False

 

  2.       Inbreeding should result in relatives being more:

            A.  heterozygous          B.  homozygous  --  in their genetic make-up.

 

  3.       Highly inbred animals tend to be more vigorous than more distantly related animals.

            A.  True                       B.  False

 

  4.       Inbreeding provides:

            A.  more          B.  less  -- opportunity for the recessive genes to express themselves in the phenotype.

 

  5.       The system of outcrossing is sometimes used to introduce a desired trait into a “line or strain” of breeding stock.

            A.  True                       B.  False

 

  6.       As compared to crossbreeding, inbreeding generally results in more “heterosis.”

            A.  True                       B.  False

 

  7.       At least part of the explanation for increased heterosis as a result of the mating of more distantly related animals is that greater gene heterozygosity is possible, and  “Good genes are more likely to be dominant genes and mask the effects of recessive genes.”

            A.  True                       B.  False

 

  8.       Crossbreeding of superior animals is effective in obtaining rapid improvement in traits that have a low heritability.

            A.  True                       B.  False

 

  9.       A two breed criss-crossing system is as effective in maintaining high amounts of heterosis as a three-breed rotational crossbreeding system.

            A.  True                       B.  False