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: minutes

Problem 29a

Textbook Question

Consider the following segment of DNA:
5'-...ATGCCAGTCACTGACTTG...-3'
3'-...TACGGTCAGTGACTGAAC...-5'
How many phosphodiester bonds are required to form this segment of double-stranded DNA?

Verified step by step guidance

Identify the number of nucleotides in the given DNA sequence. Count the number of bases in one strand (e.g., the 5'-3' strand) since both strands are complementary and will have the same number of nucleotides.

Recall that each nucleotide in a DNA strand is connected to the next nucleotide by a phosphodiester bond. Therefore, the number of phosphodiester bonds in a single strand is equal to the number of nucleotides minus one.

Since the DNA is double-stranded, calculate the total number of phosphodiester bonds by multiplying the number of bonds in one strand by two (as each strand has its own set of phosphodiester bonds).

Note that the phosphodiester bonds are only within each strand and not between the two strands. The two strands are held together by hydrogen bonds between complementary bases, not phosphodiester bonds.

Combine the results to determine the total number of phosphodiester bonds required to form the double-stranded DNA segment.

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Key Concepts

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

Phosphodiester Bonds

Phosphodiester bonds are covalent linkages that connect the 5' phosphate group of one nucleotide to the 3' hydroxyl group of another nucleotide in a DNA strand. These bonds form the backbone of the DNA molecule, providing structural integrity and allowing for the formation of long chains of nucleotides. Each bond is crucial for maintaining the continuity of the DNA strand.

Double-Stranded DNA Structure

Double-stranded DNA consists of two complementary strands that run in opposite directions, known as antiparallel orientation. Each strand is made up of nucleotides, which pair specifically (adenine with thymine, and cytosine with guanine) through hydrogen bonds. Understanding this structure is essential for determining how many phosphodiester bonds are present, as each strand contributes to the overall length of the DNA segment.

Counting Nucleotides

To determine the number of phosphodiester bonds in a DNA segment, one must count the nucleotides in each strand. Each nucleotide, except for the terminal ones, is linked to its neighbor by a phosphodiester bond. Therefore, the total number of bonds is equal to the total number of nucleotides minus one for each strand, as the ends do not form bonds with additional nucleotides.

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Suppose a genotype for a protein-producing gene can have any combination of three alleles, A₁, A₂, and A₃.

List all the possible genotypes involving these three alleles.

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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?

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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?

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Textbook Question

A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):

Chromosome 1RNMDHBGKWU

Chromosome 2RNMDHBDHBGKWU

What term best describes this situation?

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Multiple Choice

In a genetic cross between flies heterozygous for body color and wing size, 16% of the offspring show recombinant phenotypes. What is the recombination frequency between the genes for body color and wing size?

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