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

1. Introduction to Genetics

Fundamentals of Genetics

Genetics

1. Introduction to Genetics

Fundamentals of Genetics

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1:22 minutes

Problem 29c

Textbook Question

Consider the following segment of DNA:
5'-...ATGCCAGTCACTGACTTG...-3'
3'-...TACGGTCAGTGACTGAAC...-5'
If the lower strand of DNA serves as the template transcribed into mRNA, how many peptide bonds are present in the polypeptide fragment into which the mRNA is translated?

Verified step by step guidance

Identify the template strand of DNA, which is the lower strand in this case (3'-...TACGGTCAGTGACTGAAC...-5'). This strand will be used to synthesize the complementary mRNA sequence.

Determine the mRNA sequence by transcribing the template strand. Replace each base with its complementary RNA base: A pairs with U, T pairs with A, G pairs with C, and C pairs with G. The resulting mRNA sequence will be 5'-...AUGCCAGUCACUGACUUG...-3'.

Locate the start codon (AUG) in the mRNA sequence. This codon signals the beginning of translation and the synthesis of the polypeptide chain.

Divide the mRNA sequence into codons (groups of three nucleotides) starting from the AUG codon. Each codon corresponds to a specific amino acid, except for stop codons, which terminate translation.

Count the number of codons that encode amino acids (excluding the stop codon). The number of peptide bonds in the polypeptide will be one less than the number of amino acids, as each bond links two amino acids together.

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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 encoded in DNA is copied into messenger RNA (mRNA). During transcription, RNA polymerase binds to the DNA template strand and synthesizes a complementary RNA strand. The mRNA then carries the genetic code from the nucleus to the ribosome, where it will be translated into a protein.

Translation

Translation is the process by which the sequence of nucleotides in mRNA is decoded to produce a specific polypeptide or protein. This occurs in the ribosome, where transfer RNA (tRNA) molecules bring amino acids to the mRNA template according to the codon sequence. Each codon, a sequence of three nucleotides, corresponds to a specific amino acid, and the polypeptide chain is formed through peptide bonds between these amino acids.

Peptide Bonds

Peptide bonds are the chemical bonds that link amino acids together in a polypeptide chain. They form during the translation process when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water. The number of peptide bonds in a polypeptide is always one less than the number of amino acids, as the first amino acid does not form a bond with a preceding one.

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Related Practice

Textbook Question

Shorter fragments of DNA (those with fewer base pairs) have a higher electrophoretic mobility than larger fragments. Thinking about electrophoresis gels as creating a matrix through which fragments must migrate, briefly explain why the size of a DNA fragment affects its electrophoretic mobility.

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Textbook Question

Four nucleic-acid samples are analyzed to determine the percentages of the nucleotides they contain. Survey the data in the table to determine which samples are DNA and which are RNA, and specify whether each sample is double-stranded or single-stranded. Justify each answer.

[A table of nucleotide percentages appears below the problem]

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Textbook Question

Consider the following segment of DNA:

5'-...ATGCCAGTCACTGACTTG...-3'

3'-...TACGGTCAGTGACTGAAC...-5'

How many hydrogen bonds are present in this DNA segment?

424

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Textbook Question

Consider the following segment of DNA: