Answer:
a) 28 cases
b)  3 cases
Explanation:
a) From the table of genetic codes, there are 28 codons that specify more than one amino acid assuming only the first two nucleotides are considered. In these cases, one cannot outrightly specify the amino acid the genetic codes are coding for without knowing the last nucleotide of the codes. <em>For example, UU can be for Phenylalanine or Leucine, CA can be for Histidine or Glutamine, etc. </em>
b) From the table of genetic codes, the first two nucleotides of Arginine can be either of CG or AG, that of Serine can be either of UC or AG while that Leucine can be either of CU or UU. Only in these <u>3 cases</u> would one fail to know which are the first two nucleotides assuming the name of the amino acids are given.
<em>See the attached image for the genetic code.</em>
 
        
             
        
        
        
Genes in DNA or responsible for the traits an organism has. This is caused by Dominant and Recessive Traits. Remember that Genotypes are the genetic letters such as RR, Rr, and rr. Phenotype is physical traits.
Dominant Traits are more likely or always show in the offspring. The Dominant Genotype uses Capital letters such as RR. 
Recessive Traits are less likely to show up. Their Genotype use lower case such as rr. Now genotypes of Rr have one dominant trait and one recessive trait. If the dominant trait was black fur and the recessive white fur, the offspring will be black fur because dominant traits overpower the other.
To understand how to know if an organism will have Dominant or Recessive Genes, you have to use something called a Punnet Square. Lets imagine 2 parents both have the genotype Rr. R is Black fur and r is white fur. As you can see from the chart, 3 of 4 boxes have Rr and 1 rr. Since there is a Dominant Trait with a Recessive, they will show a Dominant Phenotype, or Black fur. This has 3/4 chance and a 1/4 chance for white fur in the offspring.
 | R. r
-----------------------------------
 R | Rr. Rr 
-----------------------------------
 r | Rr. rr
 
        
             
        
        
        
Answer:
Nitrate deficiency
Explanation:
Plants absorb nitrates in water through their roots. Nitrates are present in high levels in plant fertilisers. Without nitrates, the amount of chlorophyll in leaves reduces. This reduces the plant's ability to photosynthesise and grow properly, which reduces the farmers' crop yield .
 
        
             
        
        
        
Answer:
Proteins can carry nutrients across the plasma membrane. There are also differnet receptros outside the cell that recieve signals as well as inside the cell. 
Explanation:
 
        
             
        
        
        
The answer is nucleus (structure A) 
because nucleus DNA would be destroyed