1. The four nucleotides found in human DNA (G, A, T, C) combine in groups of thr
ID: 49504 • Letter: 1
Question
1. The four nucleotides found in human DNA (G, A, T, C) combine in groups of three to create potentially 64 different amino acids, but only 20 amino acids, one start codon and three stop codons are used to construct proteins. Why is this so?
a.Many amino acids are not considered complete until they bind with a second amino acid.
b.64 amino acids are produced, but the body only integrates
c.42 of them into proteins. 64 amino acids are initially produced, but 42 of them are unstable and degrade immediately. Different d.nucleotide combinations code for the same amino acid.
2.What term is used to describe the phenomenon that there are 64 different groups of 3 nucleotides to code for amino acids but only 20 amino acids, 1 start codon, and 3 stop codon used in protein construction.
a.Crossing over
b.Redundancy
c.DNA structure
d.Transcription
Suppose a male and a female with chromosomes "DD" (male) and "dd" (female) crossbreed. How likely is their offspring to exhibit the DD genotype?
100%
25%
50%
0%
4.What term best describes the genotype of "dd"?
a.heterozygous
b.monohybrid
c.homozygous
d.haploid
5.Suppose a male and a female with chromosomes "DDBb" (male) and "ddBB" (female) interbreed. How likely is their offpsring to exhibit the DdBb genotype? 100% 50% 25% 0%?
6. What term best describes the breeding perfomed when a male and female with chromosomes "DDBb" (male) and "ddBB" (female) interbreed?
Dihybrid cross
Codominance
Incomplete dominance
Monohybrid cross
Explanation / Answer
1. d.nucleotide combinations code for the same amino acid.
The information present in the DNA consists of a sequence of “genetic words,” which indicate four bases, adenine (A), guanine (G), cytosine (C), and uracil (U). Three bases form a triplet genetic word, which codes for a specific amino acid, this triplet code is called a “codon.”
At each of the three positions of a codon, there are four possible bases which can form a total of 64 mRNA codons. These 64 codons collectively form the “genetic code.” Each triplet codon codes for an amino acid (Eg; AUG codes for methionine). As per the sequence of these codons in an mRNA, the order of amino acids in the polypeptide chain that will be translated from it is determined. There are twenty naturally occurring amino acids which are specified by 64 codons in the genetic code
As the genetic code is redundant, a single amino acid may have more than one codon. For example, the amino acid glutamic acid can be coded by two different codons such as GAA and GAG. As both the triplets code for the same amino acid, no functional change in the protein synthesis occurs.
2. b.Redundancy
3. d. 0% (the genotype of the offpsring will be 100% Dd).
4. c. homozygous
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