AGR 3303 - Genetics 16 Oct 2000

University of Florida - Fort Lauderdale

Exam #1, Part B: PARTICULATE GENETICS (Bonus)

Short answer (20 pts.)

1. In a diploid organism with several genes, the number of possible genotypes increases as the number genes increases. For example, assuming each gene has two alleles, there are three possible genotypes involving one gene. If there are two genes, there are nine possible genotypes. In fact, the number of possible genotypes involving genes with two alleles is equal to the number three raised to the power of the number of genes (see table).
   
   Answer either a or b below.
   
   

Number of genes each with two alleles (x):	1	2	3	4	Any number x
Number of possible genotypes (y):	3	9	27	81	y=3x


a. Why? (one word or a few words can be sufficient)

 

b. If you cannot explain why, then in these cells list the 27 genotypes involving three genes A, B, and C (alleles are A vs. a, B vs. b, and C vs.c):


2. If Mendel had been able to use a microscope to explain his postulates, he would have looked at the dividing germ cells, that is, those that produce the gametes. What is the name of the type of cell division (also, first or second?), what is the name for the objects involved that Mendel would have seen, and how exactly would their behavior explain three of his four postulates? (Hint, it may help to just draw a dividing cell which contains four of the objects, and use labels and arrows to describe their behavior.)
   
   
   
   
   
   
   
   
   
   
   
   
   
   
3. What are the four main genetic capabilities and very briefly describe how each is important to a species:

 

(1)_________________ ______________________________________________

 

______________________________________________________

 

(2)_________________ ______________________________________________

 

______________________________________________________

 

(3)_________________ ______________________________________________

 

______________________________________________________

 

(4)_________________ ______________________________________________

 

______________________________________________________




4. The difference between phenotype and genotype involves both the effect of environment and the interrelationship of alleles and genes. Ignoring the environment, what are the names for relationships among alleles and/or genes that explain the phenotypic variations. (The numbered allelic designations, e.g., H1, H2 etc. are arbitrary and are not meant in this case to imply any particular relationship. However, A vs a and B vs b are used in their traditional sense.)
   
   

Fill-in the blank (20 pts.)

Please write your answers in the blanks.

5. A form of a gene _________________
   
6. A type of cell division which can lead, ultimately, to new genetic combinations
   
   ____________________
   
7. In human blood types the alleles coding for the A antigen and the B antigen are related by
   
   ____________________
   
8. Two similar chromosomes that pair and then separate during the first stage of meiosis are called
   
   ____________________
   
9. In a dihybrid cross, phenotypic ratios that differ from the classical 9:3:3:1 ratio of Mendel are due to a nonreciprocal masking effect called
   
   ____________________
   
10. Among Mendel's four postulates, the one which deals with gene expression is:
    
    ____________________
    
11. This law holds that the probability of two independent events occurring simultaneously is found by multiplying their independent probabilities.
    
    ____________________
    
12. Recessive alleles are expressed only when they occur in a condition of:
    
    ____________________
    
13. A tabular method that is used to predict the ratio of progeny genotypes based on knowing the parental genotypes. This method uses a series of rows to represent the various possible female gametes, and it uses a series of columns to represent the various possible male gametes (or vice-versa). Where the rows and columns form cells are the various possible progeny genotypes. The method is called:
    
    ____________________
    
14. The kind of cross necessary in order to observe independent assortment
    
    ____________________
    
15. What is one of the words we have used to describe the inheritance of a trait controlled by many genes with small effects?
    
    ____________________
    
16. The nature of the chromosomal condition for a cell or an organism with a single set of unpaired chromosomes, and which results from meiosis.
    
    ____________________
    
    
17. A genetic feature that men always receive from their mothers but not their dads:
    
    ____________________
    
18. Assuming that a gene controls for an enzyme, if an organism receives a normal copy of the gene from one parent, but receives a defective copy of the same gene from the other parent, the phenotype is likely to be:
    
    ____________________
    
19. Transcription, translation, and various modifications of polypeptides result in generally functional proteins. What kind of protein helps catalyze chemical reactions in organisms?
    
    ____________________
    
20. Which type of allele is mostly likely to remain hidden in a population of organisms, dominant or recessive?
    
    ____________________
    
21. An allele is mostly likely to remain hidden in a population of organisms, based on the location of the gene on what kind of chromosome, autosomal or X-linked?
    
    ____________________
    
22. The diploid cell resulting from the union of two haploid gametes:
    
    ____________________
    
23. Homologous chromosomes do this, only in meiosis
    
    ____________________
    
24. The concept or idea that is tested with the Chi-Square test
    
    ____________________