DNA structure and Chromosome composition

DNA is double stranded, and the strands are antiparallel because they run in opposite directions. Explanation: Each DNA molecule has two strands of nucleotides. Each strand has sugar phosphate backbone, but the orientation of the sugar molecule is opposite in the two strands. Both of the strands of DNA double helix can grow in 5’ to 3’ direction, but they grow in opposite directions due to opposite orientation of the sugar molecule in them. The antiparallel orientation allows for the base pairs to compliment one another. Antiparallel DNA is also more structurally stable than parallel DNA. The antiparallel orientation of DNA has important implications for DNA replication, as at the replication fork one strand allows steady replication, thereby known as leading strand while the other becomes lagging strand. A histone is a protein that provides structural support to a chromosome. In order for very long DNA molecules to fit into the cell nucleus, they wrap around complexes of histone proteins, giving the chromosome a more compact shape. Some variants of histones are associated with the regulation of gene expression. Problems: What is meant by the description “antiparallel“ regarding the two strands that make up the DNA double helix? A) The 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand. B) One strand contains only purines and the other contains only pyrimidines. C) Base pairings create unequal spacing between the two DNA strands. D) The double helix structure of DNA creates nonparallel strands. Eukaryotic chromosomes are composed of which of the following macromolecules? A) DNA only B) DNA and proteins C) DNA and RNA D) DNA and phospholipids #DNA #hitones #chromosome #dnaStructure #chromosomeStructure #purine #pyrimidine #base #rybose #Deoxyribose #euchromatin #Heterochromatin