DNA Structure, Replication & Mitosis Review

A model of a DNA molecule is shown in the picture. The arrow indicates -

• the bond between adjacent phosphate and deoxyribose molecules
• the junction of introns and exons in the sense strand of DNA
• the hydrogen bond between complementary nucleotides
• the junction of a codon and a DNA triplet

Characteristics such as a widow’s peak or attached earlobes are determined by the genetic code. Which components of DNA are referred to as the genetic code?

• Phosphate groups
• Nitrogenous bases
• Deoxyribose sugars
• Hydrogen bonds

How does DNA in cells determine an organism’s complex traits?

• DNA contains codes for proteins, which are necessary for the growth and functioning of an organism.
• DNA separates into long single strands that make up each part of an organism.
• DNA produces the energy an organism needs in order to grow.
• DNA folds into the nucleus of each of the cells of an organism.

The sequence of nitrogenous bases in DNA varies widely. The sequence of the bases in DNA is most important for which of the following?

• Allowing the DNA to have the shape necessary for replication
• Providing the instructions for the traits of an organism
• Helping form the sugar-phosphate backbone of DNA molecules
• Preventing mutations from occurring during DNA replication

In 1952 Rosalind Franklin took the x-ray photograph shown below, which gave the world its first look at DNA. By studying this photograph, scientists gained knowledge about the —

• role of DNA in protein synthesis
• mutation of nucleotide sequences in DNA
• sequence of DNA that makes up the human genome
• double-helix structure of DNA

Organisms can be classified based on homology, which is shared characteristics inherited from a common ancestor. In the past, homologies were based on studies of anatomical structures and patterns of embryonic development. In more recent years, the use of molecular biology techniques has allowed homologies to be compared at the level of nucleotide sequences. Nucleotide sequence comparisons are possible because all organisms share which of the following?

• DNA bases
• Cellular organelles
• Division of the nuclear chromosomes
• Types of proteins needed for cellular functions

A segment of DNA is represented in the illustration. How is information for a specific protein carried on the DNA molecule?

• As a sequence of nucleotides
• In the double-helix shape of the condensed chromosome
• In the ratio of adenines to thymines
• As a pattern of phosphates and sugars

A student builds a model of a DNA strand as shown in the photo. Which of these models of a DNA strand shows bases that are complementary to the ones on the student’s DNA model? 

• CTACCGAC
• GUCGGUAG
• GTCGGAAG
• GTCGGTAG

A photomicrograph of onion root tip cells during mitosis is shown below. Which phase of mitosis is occurring in the cell indicated by the arrow?

• Prophase
• Metaphase
• Anaphase
• Telophase

Cells typically respond to DNA damage in three ways: by ceasing to grow and divide until the damage is repaired, by permanently ceasing to grow and divide, or by dying. In 2010 a group of scientists reported that a certain kind of immune reaction can cause DNA damage that leads to a fourth response. DNA damage can turn off genes involved in cell-signaling pathways. Turning off these genes can cause less-mature cells to divide too rapidly, often leading to the development of —

• tumors
• allergies
• hemophilia
• cardiovascular disease