Cell division passes genetic information from one cell to new cells. To understand how this happens, we first need to know how DNA is organized and how chromosomes carry inherited information.
A cell’s genome is its complete genetic information, packaged as DNA. In prokaryotes, the genome is typically one circular, double-stranded DNA molecule located in a region called the nucleoid. Some prokaryotes also contain smaller DNA loops called plasmids. Plasmids are generally not essential for normal growth, but they can carry useful genes. Bacteria can exchange plasmids, allowing traits such as antibiotic resistance to spread between cells.
All flashcards
What is a genome?
A cell’s complete genetic information, packaged as DNA.
What are plasmids, and why can they matter?
Plasmids are small loops of DNA found in some prokaryotes. They can carry useful genes and may be exchanged between bacteria, spreading traits such as antibiotic resistance.
What is the difference between diploid and haploid cells?
Diploid cells have two chromosome sets, written 2n; haploid cells have one set, written n or 1n. Human body cells are diploid, while sperm and egg cells are haploid.
What makes two chromosomes homologous?
They form a matched pair, generally have the same length, and carry the same genes at corresponding loci. One is inherited from each biological parent, and their alleles may differ.
How do alleles contribute to variation?
Alleles are different versions of a gene. The combination inherited from both parents can contribute to differences in traits among individuals.
Quiz questions
In prokaryotic cells, where is the region containing the main chromosome typically located?Answer: In the nucleoid.
How many chromosomes are in a typical human haploid gamete?Answer: 23 chromosomes.
What is a nucleosome composed of?Answer: DNA wrapped around a core of eight histone proteins.
During which part of the cell cycle is DNA replicated before mitosis?Answer: During the S phase of interphase.
What is generally true of genes on homologous chromosomes?Answer: They occur at corresponding loci, though their alleles may differ.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.