Flashcards for Biological Basis of Heredity
Topic 5:  Molecular Level of Genetics
(19 cards)

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The category of organic molecules that include sugars and starches.


The category of organic molecules that include fats, oils, and waxes.


A large chain-like molecule that is normally twisted and folded back on itself in a complex pattern. Molecules of this type serve as structural material for the body, gas transporters, hormones, antibodies, neurotransmitters, and enzymes.


The term for a protein that causes or regulates specific chemical reactions within cells.


A kind of organic molecule that is a building block of proteins. Proteins are composed of different combinations of 20 different kinds of these molecules assembled in chain-like molecules.

amino acid

The largest kind of molecule in humans and other organisms. DNA and RNA are types of this kind of molecule.

nucleic acid

A large organic molecule that stores the genetic code for the synthesis of proteins. It is composed of sugars, phosphates and bases arranged in a double helix shape. Segments of this molecule correspond to specific genes.

DNA (deoxyribonucleic acid)

A type of nucleic acid that is found in both the nucleus and the cytoplasm of cells. Unlike DNA, this molecule is single stranded. Different forms of it play important roles in the synthesis of proteins.

RNA (ribonucleic acid)

The four chemical bases in DNA molecules.

guanine, cytosine, adenine, and thymine

The basic building block of nucleic acids. It consists of any one of four specific chemical bases attached to a sugar and phosphate group.


A sequence of three nucleotides in a DNA or RNA molecule that codes for a specific type of amino acid that will be used in the synthesis of a protein.


The name for the twisted ladder shape that is characteristic of DNA molecules.

double helix

DNA base pairs that code for proteins and, therefore, are part of genes. Only 1.1-1.5% of DNA consists of these kinds of base pairs.


DNA base pairs that do not code for proteins and, therefore, are not part of genes. These kinds of base pairs have been referred to as "junk" DNA, however, it is now known that they perform important functions. Some are subtle enhancers or suppressors of genes, while others act as buffers against mutations.


Small rod-like structures in the cytoplasm that produce fuel for the cell in the form of adenosine triphosphate (ATP). A small amount of DNA is located in these structures. This DNA is normally inherited only from mothers and is distinct from DNA that makes up the chromosomes.

Mitochondria (singular mitochondrion)

The form of RNA that carries a copy of a specific sequence of genetic information (a gene) from the DNA in the cell nucleus to the ribosomes in the cytoplasm where it is translated in order to synthesize a protein. This form of RNA is assembled on one sequence (one strand) of DNA bases.

mRNA (messenger RNA)

A form of RNA that binds to specific amino acid molecules and transports them to the ribosomes for the assembly of proteins. This form of RNA temporarily bonds with corresponding mRNA codons at the ribosomes in this process of protein synthesis.

tRNA (transfer RNA)

Small roughly spherical structures near the endoplasmic reticula in the cytoplasm of cells. These structures are the sites where proteins are assembled by the momentary bonding of mRNA and tRNA.


The process at the beginning of mitosis and meiosis by which a DNA molecule is duplicated or copied. One DNA molecule becomes two identical ones. This is accomplished by the DNA molecule unwinding and unzipping along its base pairs so that both sides can be copied by free nucleotides. This process is triggered and controlled by enzymes.

DNA replication