Questions - All Essay Questions Must Be Answered In Detail

Questions; - All essay questions must be answered in details

Find the primary structure of the protein. DNA sequence is = AGCATGTTACCCATTGATGGGTGAUAA

Given is the amino acid sequence. Find the possible DNA sequences. (AUG)Methionine- proline-lysine-glycine-stop condone(UAA)

Mendel found that crossing wrinkle-seeded plants with pure round-seeded plants produced only round-seeded plants. What genotypic & phenotypic ratios can be expected from a cross of a wrinkle-seeded plant & a plant heterozygous for this trait (seed appearance)?

What are the genotypic and phenotypic ratios of the following crosses

  • A. Heterozygous dominant Red flower * Homozygous white flower (Red is the dominant trait)
  • B. Homozygous Dominant cross with heterozygous dominant

a. Round pea ( R), oval pea (r )

b. Color Green ( G), color brown ( b)

c. Incomplete dominant of the color results in eclipse shape pea , and white color pea.

Paper For Above instruction

The assignment encompasses a spectrum of biological concepts, including protein structure, genetic coding, Mendelian inheritance, and phenotypic ratios resulting from various genetic crosses. Analyzing these questions requires a detailed understanding of molecular biology's fundamentals and classical genetics.

Primary Structure of Proteins and DNA Sequencing

The primary structure of a protein refers to its sequence of amino acids linked together by peptide bonds. It determines the protein's ultimate shape and function. However, when given a DNA sequence, one can decode the corresponding amino acid chain by translating codons—triplet nucleotide sequences—into amino acids. The provided DNA sequence is AGCATGTTACCCATTGATGGGTGAUAA, where the presence of Uracil (U) indicates an RNA molecule or a transcription error, as DNA should have thymine (T) instead of uracil.

Assuming the sequence is a DNA strand, the correct sequence should be AGCATGTTACCCATTGATGGGTGATAA, replacing U with T. To find the primary amino acid structure, the DNA must first be transcribed into mRNA, and then translated into amino acids.

Transcription produces mRNA: AGCATGTTACCCATTGATGGGTGATAA

While the reading frame is crucial, assuming standard reading frames, the codons would be:

  • AGC
  • ATG
  • TTT
  • ACC
  • CCT
  • TGA
  • TGG
  • GTG
  • ATA

However, this presentation is simplified, and actual translation would involve determining the correct start codon and reading frame. The start codon AUG (methionine) marks the beginning of translation, and the sequence's start point influences the entire amino acid chain produced.

Possible DNA Sequences for Given Amino Acid Sequence

The second part involves reverse engineering amino acids to possible DNA sequences. The amino acid sequence provided is: Methionine- proline-lysine-glycine- stop. The corresponding codons are:

  • Methionine (AUG)
  • Proline (Pro) – CCU, CCC, CCA, CCG
  • Lysine (Lys) – AAA, AAG
  • Glycine (Gly) – GGU, GGC, GGA, GGG

To form possible DNA sequences, reverse translation is necessary. Since DNA codons source from mRNA, and the mRNA codons are established, their DNA equivalents are obtained by replacing uracil with thymine and reversing the transcription process. For example, AUG in mRNA corresponds to DNA: TAC; similarly, proline could be coded by the DNA template strand with options like CCT, CCC, CCA, CCG, depending on the choice.

One possible DNA sequence that encodes the amino acid chain could be:

  • ATG (Methionine)
  • CCG (Proline)
  • AAG (Lysine)
  • GGT (Glycine)
  • Stop codon: TAA, TAG, TGA

This demonstrates the degeneracy of the genetic code, where multiple codons can encode the same amino acid, allowing for various DNA sequences.

Mendelian Inheritance and Phenotypic Ratios

Proceeding to Mendel’s classical experiments, the expected genotypic and phenotypic ratios of offspring depend on the parental genotypes. When crossing a wrinkle-seeded plant (assuming heterozygous Rr) with a pure round-seeded plant (RR), Punnett squares reveal the possible outcomes.

In this case, the heterozygous wrinkle seed (Rr) crossed with a homozygous round seed (RR):

- Genotype ratios: 50% RR, 50% Rr

- Phenotype ratios: 100% round seeds (since round is dominant over wrinkle)

Similarly, crossing a heterozygous wrinkle seed (Rr) with a pure wrinkle seed (rr) yields:

- Genotype ratio: 1 Rr : 1 rr

- Phenotype ratio: 1 round : 1 wrinkle

The classical Mendelian ratios illustrate the predictable inheritance patterns based on genotype combinations and dominance relationships.

Genotypic and Phenotypic Ratios in Crosses

A. Cross of heterozygous dominant red-flowered plants with homozygous white-flowered plants:

The heterozygous red (Rr) crossed with homozygous white (rr):

- Genotypic ratio: 1 Rr : 1 rr

- Phenotypic ratio: 1 red : 1 white

B. Crosses between homozygous dominant and heterozygous plants:

  • a. Round (Rr) × (RR):
  • Genotypic ratio: 1 RR : 1 Rr
  • Phenotypic ratio: 2 round : 0 oval (if oval is recessive)
  • b. Color green (Gg) × (GG):
  • Genotypic ratio: 1 GG : 1 Gg
  • Phenotypic ratio: 2 green : 0 brown
  • c. Incomplete dominance in pea color resulting in eclipse-shaped (heterozygous) and white peas (homozygous recessive):
  • Genotypic ratio: 1 heterozygous : 1 homozygous recessive
  • Phenotypic ratio: 1 eclipse shape : 1 white

Conclusion

Understanding the genetic basis behind protein synthesis and inheritance patterns is pivotal for comprehending biological processes. The correlation between DNA sequences and amino acids showcases the genetic code’s degeneracy, while Mendelian ratios underscore the predictability of genetic inheritance. Accurate interpretation of these foundational principles deepens our grasp of biological diversity and inheritance mechanisms, essential for advancements in genetics, molecular biology, and biotechnology.

References

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