Study Guide
Chapter 3: Sections 3 & 4
Know the information listed below. (In addition, review your warm-ups, guided reading sheets,
and lab activities)
Section 3. The Cell & Inheritance
1. The Chromosome Theory of Inheritance states that genes are carried from parents to their
offspring on chromosomes.
2. Chromosomes are rod-like bundles of coiled DNA. They contain a string of genes packaged
in a single unit. Genes are located on chromosomes.
3. Genes are the structures that carry the information for the inheritance of traits. They contain
the information that specify for the making of a particular protein.
4. Meiosis is the process by which the number of chromosomes is reduced by half to form sex
cells – sperm and eggs. During meiosis chromosome pairs separate. There are two division
in the process of meiosis.
5. A Punnett square is a short-hand way to show the events that happen in meiosis.
6. Sex cells are haploid. They have half the number of chromosomes as body cells.
(Advanced Information: Sex cells are called gametes. Other body cells are called
autosomes.) Body cells are diploid. They have the full number of chromosomes.
7. Only one chromosome from each chromosome pair ends up in each sex cell.
Section 4. The DNA Connection
1. The nitrogen bases, Adenine, Thymine, Cytosine and Guanine, form the rungs of the
DNA double helix. These nitrogen bases are arranged to form codes.
2. A, T, C, and G are the letters of the genetic alphabet. In different sequences or order,
these four letters create the codes that spell out the 20 different amino acids that serve
as the building blocks for all of the proteins that are needed for the functioning of a
living organism.
3. DNA contains the genetic code. It is a double stranded molecule that has a double helix
structure. Deoxyribose is the sugar that makes up this molecule. DNA is contained in the
nucleus of the cell.
4. RNA is a single stranded molecule. It is made up of the sugar ribose. It can usually be found
in the cytoplasm of the cell.
5. The triplet code or codons found in the DNA molecule direct the order in which amino acids
are put together to form specific proteins.
6. Amino acids are small molecules that are linked together chemically to form proteins.
Amino acids are referred to as the building blocks of proteins.
7. A codon is a group of 3 nitrogen bases that make up the code for a specific amino acid.
8. Protein synthesis is the process by which cells use information from a gene on a
chromosome to produce a specific protein.
9. During protein synthesis, messenger RNA copies the coded message from the DNA in the
nucleus and carries the message into the cytoplasm.
10. Transfer RNA adds amino acids to form the string-like structure of proteins.
11. Proteins are assembled or made on ribsomes in the cytoplasm.
12. Proteins are large organic molecules that are made up of smaller molecules called amino
acids. Although there are only 20 different amino acids they can combine in many ways to
form thousands of different proteins.
13. Cells use proteins for many different things. Proteins form part of the cell membrane.
Proteins make up many of the cell’s organelles. Proteins are used by the body for growth and
repair. Proteins make up certain body parts such as hair. Enzymes, which control many of
life’s activities, are proteins.
14. A mutation is a change in a gene or chromosome. Some mutations are harmful, some are
helpful, and some are neutral.
15. Whether a mutation is helpful, harmful or neutral for an organism partly depends on the
environment.