Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

11. Translation

Translation

Genetics

11. Translation

Translation

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2:59 minutes

Problem 5b

Textbook Question

A portion of a DNA template strand has the base sequence
5′-...ACGCGATGCGTGATGTATAGAGCT...-3′
Assume the mRNA is written in the correct reading frame. Determine the amino acid sequence encoded by this fragment. Identify the N- and C-terminal directions of the polypeptide.

Verified step by step guidance

Step 1: Identify the complementary mRNA sequence by transcribing the DNA template strand. Remember that RNA uses uracil (U) instead of thymine (T). The DNA template strand is read in the 3′ to 5′ direction, so the mRNA will be synthesized in the 5′ to 3′ direction. For example, A pairs with U, C pairs with G, G pairs with C, and T pairs with A.

Step 2: Divide the mRNA sequence into codons (groups of three nucleotides). Each codon corresponds to a specific amino acid or a stop signal during translation.

Step 3: Use the genetic code table to translate each codon into its corresponding amino acid. For example, AUG codes for methionine (start codon), and UAA, UAG, or UGA are stop codons.

Step 4: Determine the directionality of the polypeptide chain. Translation begins at the N-terminal (amino group) and proceeds toward the C-terminal (carboxyl group). The first amino acid corresponds to the start codon, and the sequence ends at the stop codon.

Step 5: Write out the amino acid sequence in order, starting from the N-terminal and ending at the C-terminal. Ensure that you include the start codon and stop translation at the stop codon.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Transcription

Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA). During this process, RNA polymerase binds to the DNA template strand and synthesizes a complementary RNA strand, replacing thymine (T) with uracil (U). Understanding transcription is essential for determining how the DNA sequence translates into an mRNA sequence, which is the first step in protein synthesis.

Translation

Translation is the process by which the mRNA sequence is decoded to synthesize a polypeptide chain, which will fold into a functional protein. This occurs in the ribosome, where transfer RNA (tRNA) molecules bring specific amino acids to the growing polypeptide chain based on the codon sequence of the mRNA. Recognizing how codons correspond to amino acids is crucial for determining the final amino acid sequence from the mRNA.

Amino Acid Structure and Polypeptide Directionality

Amino acids are the building blocks of proteins, each consisting of a central carbon atom, an amino group, a carboxyl group, and a variable R group that determines the specific properties of the amino acid. In a polypeptide chain, the N-terminus refers to the end with a free amino group, while the C-terminus has a free carboxyl group. Understanding this directionality is important for correctly identifying the ends of the synthesized polypeptide and its functional implications.

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Textbook Question

You conduct a study in which the transcriptional fusion of regulatory sequences of a particular gene with a reporter gene results in relatively uniform expression of the reporter gene in all cells of an organism. A translational fusion with the same gene shows reporter gene expression only in the nucleus of a specific cell type. Discuss some biological causes for the difference in expression patterns of the two transgenes.

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Textbook Question

The human mitochondrial genome encodes only 22 tRNAs, but at least 32 tRNAs are needed for cytoplasmic translation. How are all codons in mitochondrial transcripts accommodated by only 22 tRNAs? The Plasmodium mitochondrial genome does not encode any tRNAs; how are genes of the Plasmodium mitochondrial genome translated?

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Textbook Question

Contrast the roles of tRNA and mRNA during translation, and list all enzymes that participate in the transcription and translation process.

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Textbook Question

Outline the events that occur during initiation of translation in E. coli.

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Textbook Question

During translation, what molecule bears the codon? the anticodon?

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Textbook Question

The α chain of eukaryotic hemoglobin is composed of 141 amino acids. What is the minimum number of nucleotides in an mRNA coding for this polypeptide chain?

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Textbook Question

Assuming that each nucleotide in an mRNA is 0.34 nm long, how many triplet codes can simultaneously occupy the space in a ribosome that is 20 nm in diameter?

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Textbook Question

Describe the central dogma of molecular genetics and how it serves as the basis of modern genetics.

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