A cell’s genetic information provides the instructions needed for its structure and functions, and it must be passed on when cells reproduce. This lesson introduces the genome and explains how DNA is organized in prokaryotic and eukaryotic cells. It also explores chromosome sets, genes, and how inherited gene combinations contribute to variation.
A cell’s genome is its complete complement of DNA. The form in which this DNA is organized differs between prokaryotes and eukaryotes.
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What is a genome?
A genome is the complete complement of DNA in a cell or organism.
How is DNA commonly organized in prokaryotes and eukaryotes?
Prokaryotes typically have one circular, double-stranded DNA molecule in a nucleoid, sometimes with additional plasmids. Eukaryotes have several linear, double-stranded DNA molecules associated with proteins to form chromosomes.
What is the difference between diploid and haploid cells?
Diploid cells have two sets of chromosomes and are represented by 2n. Haploid cells have one set and are represented by n. Human somatic cells are diploid, while eggs and sperm are haploid.
What are homologous chromosomes?
They are a matched pair of chromosomes, one inherited from each parent. They carry the same genes at corresponding loci, although the versions of those genes may differ.
How can inherited genes contribute to variation?
Individuals can inherit different combinations of gene versions from their parents. Those combinations contribute to differences in traits, such as blood type, eye color, and height.
Quiz questions
How is DNA organized in a typical eukaryotic genome?Answer: Several linear DNA molecules associated with proteins form chromosomes.
How many chromosomes are in a typical human gamete?Answer: 23 chromosomes.
In a human diploid cell, where does each homologous chromosome pair come from?Answer: One chromosome comes from each parent.
What is true of plasmids found in some prokaryotes?Answer: They are small DNA loops that may carry conditionally useful genes.
How do human X and Y chromosomes compare in the genes they carry?Answer: They share a small homologous region but carry mostly different genes.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.