Chapter 6: DNA Structure and Replication Flashcards
What does DNA stand for?
Deoxyribonucleic Acid
What is DNA?
An information molecule that is the universal basis of an organism’s genetic material; it contains instructions, written in a chemical code, for the production of proteins by the cell
What are genes?
A unit of heredity that transmits information from one generation to the next; a segment of DNA that codes for a polypeptide
Where is DNA located in a eukaryotic cell?
In the nucleus
What is chromatin?
A complex of proteins and DNA in eukaryotic chromosomes
What are chromosomes?
A structure composed of DNA and protein that contains along its length linear arrays of genes carrying genetic information; prokaryotes have one circular chromosome whereas eukaryotes have a number of linear chromosomes
What is histone?
A protein that DNA winds around in eukaryotic cells
What are sister chromatids?
The two identical copies of a single chromosome, formed by replication and connected by a centromere
What is centromere?
The waist-like constriction in a chromosome required for the movement of chromosomes during cell division. Refer to figure 6.1.4 pg 128 for more detail
What are homologous chromosomes?
A pair of chromosomes that have the same size, shape, and genes at the same locations
What is a karyotype?
A display of the number and appearance of the chromosomes of an organism or cell observed at metaphase
How many pairs of chromosomes do humans have?
23 (46 chromosomes)
What chromosomes are not homologous?
Sex chromosomes (usually male) are not homologous
What is the endosymbiotic theory?
A theory that suggests that chloroplasts and mitochondria arose from ancient prokaryote cells that were ingested by other prokaryote host cells
Where is DNA located in prokaryote cells?
They form a single circular chromosome that lies in direct contact with the cytoplasm
What is a nucleoid?
The region within a prokaryotic cell that contains the genetic material
What are plasmids?
A small circular piece of DNA found in bacteria, which can replicate independently of the cell’s chromosomes; plasmids carry antibiotic resistance markers
What is a nucleotide?
The basic building block of nucleic acids (DNA and RNA) linked together by phosphodiester bonds; each nucleotide is made up of a five-carbon sugar, a phosphate group, and a nitrogenous base
What are the three distinct chemical components of a nucleotide?
A five-carbon sugar (deoxyribose in DNA), a negatively charged phosphate group, and an organic nitrogen-containing compound called a base. Refer to figure 6.2.4 pg 133 for more detail
What are the four kinds of nitrogenous bases in DNA?
Adenine (A), thymine(T), Guanine (G), and cytosine (C)
What are complementary bases?
Nitrogenous bases on nucleotides that bind to each other (e.g. A-T and C-G)
What does RNA stand for?
Ribonucleic Adic
What is RNA?
A molecule consisting of a single strand of nucleotides; plays an essential role in protein synthesis (as messenger RNA and transfer RNA) and as a structural component of ribosomes
What are the three major differences between DNA and RNA?
Composed of a single chain of nucleotides, the base thymine is replaced by the base uracil (U) and ribose sugar replaces the deoxyribose of DNA
What is a daughter cell?
Either of the two cells formed when a cell undergoes cell division
What are the periods involved in the interphase?
Active growth (G1 phase), synthesis of DNA (S phase), and preparation for the next division (G2 phase)
What is the stage between nuclear divisions called?
Interphase
What is DNA helicase?
An enzyme that helps the two strands of the DNA double helix unwind and separate - begins DNA replication
What is the replication fork?
The junction between the unwound single strands of DNA and the intact double helix during replication
What is DNA polymerase?
An enzyme capable of making exact copies of fragments of DNA
What is semiconservative replication?
The production of two new DNA double helix molecules, each consisting of one parental strand and one daughter strand
