DNA Structure Analysis Questions Answered The twisted ladder structure of DNA is called a Double Helix. The backbone of DNA is made up of deoxyribose sugar and phosphate group. The ladder-like rungs of DNA are made up of nitrogenous bases. Adenine always pairs up with Thymine. Cytosine always pairs up with Guanine. A nucleotide is the basic building block of DNA. A nucleotide is made up of one deoxyribose sugar, one phosphate group, and one nitrogenous base.

DNA Replication

DNA Packaging A cell’s nucleus contains chromosomes made up of DNA.

Each nucleosome consists of DNA wound around histones Chromatin Fibers Each super coil is made up of coils. A coil is a chain of beadlike structures called nucleosomes Each nucleosome consists of DNA wound around histones Each chromatin fiber is a tightly wound supercoil

DNA replication Before a cell divides, it duplicates its DNA in a copying process called replication this process insures that each resulting cell receives a complete set of DNA molecules

During replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for a new strand

DNA Replication In Eukaryotic Cells replication occurs in hundreds of places at once Replication proceeds in both directions until each chromosome is completely copied

Creating a New Strand ATGCAA Two strands of the double helix separate allowing two replication forks to form Each new strand forms following the rules of base pairing. For example: The original strand has the bases: TACGTT What would the complementary strand be? ATGCAA

CCGTACTTACG GGCATGAATGC The result is two DNA molecules identical to each other and to the original NOTE: each DNA molecule will have one original strand and one new strand. More practice. Create the complementary strand CCGTACTTACG Answer GGCATGAATGC

How Replication Occurs DNA replication is carried out by a series of Enzymes The enzymes “unzip” a molecule of DNA by breaking the hydrogen bonds between the base pairs DNA polymerase joins individual nucleotides to produce a DNA molecule and proofreads each new DNA strand