TEAS 2.2 Genetic Material & Protein Structure

What is a gene?

A sequence of DNA that is the basic unit of heredity and contains instructions to make proteins or regulate protein production.

What are chromosomes?

Structures that contain genetic information, consisting of tightly coiled DNA wrapped around histone proteins.

How many chromosomes do humans have?

46 chromosomes (23 pairs).

What is the difference between prokaryotic and eukaryotic chromosomes?

Prokaryotes have a single circular chromosome, while eukaryotes have multiple linear chromosomes.

What are the two purposes of DNA coiling around histones?

1) Condenses DNA to fit inside the nucleus, and 2) Regulates genes on that chromosome.

What is DNA?

Deoxyribonucleic acid, a macromolecule containing genes that provide coded instructions for cells to produce proteins.

What are the four nucleotide bases in DNA?

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

What is a codon?

A sequence of three nucleotides that codes for a specific amino acid or a stop signal during protein synthesis.

What is complementary base pairing in DNA?

The specific pairing of nucleotide bases where A pairs with T (2 hydrogen bonds) and G pairs with C (3 hydrogen bonds).

Why are hydrogen bonds used in DNA instead of covalent bonds?

Individual hydrogen bonds are weak but strong in large numbers, maintaining DNA integrity while being easier to break than covalent bonds, allowing strands to separate for replication and transcription.

What is the sense strand?

The DNA strand that runs in the 5' to 3' direction where information is coded.

What is the anti-sense strand?

The DNA strand that runs in the 3' to 5' direction and is used as the template for replication and transcription.

What is DNA replication?

The process before cell division where chromosomes containing DNA are copied to make two identical copies called chromatids.

What is a mutation?

A permanent change in the nucleotide sequence of DNA that may arise during replication.

What are the three types of mutations?

1) Substitution (one base pair replaced), 2) Deletion (base pair removed), and 3) Insertion (base pair added).

What is RNA?

Ribonucleic acid, a molecule that acts as a messenger carrying instructions from DNA to control protein synthesis.

What are the structural differences between RNA and DNA?

RNA is single-stranded, contains ribose sugar (vs. deoxyribose), and uses uracil (U) instead of thymine (T).

What is messenger RNA (mRNA)?

RNA that carries genetic information from DNA to ribosomes; it's a copy of DNA's template strand with uracil replacing thymine.

What is transfer RNA (tRNA)?

RNA that transfers amino acids to ribosomes and contains anticodons (codon complements).

What is ribosomal RNA (rRNA)?

RNA that is a component of ribosomes and catalyzes peptide bond formation between amino acids.

What is transcription?

The synthesis of RNA from a DNA template; the process of copying DNA's code to mRNA in the nucleus.

What is translation?

Protein synthesis that occurs after mRNA exits the nucleus and binds to a ribosome in the cytoplasm.

Where does transcription occur?

In the nucleus.

Where does translation occur?

In the cytoplasm at the ribosomes.

What is the role of mRNA in protein synthesis?

It carries genetic information from DNA to ribosomes and is small enough to exit the nucleus.

What is the role of tRNA in protein synthesis?

It transfers amino acids to the ribosome and delivers the anticodon (codon complement).

What is the role of rRNA in protein synthesis?

It catalyzes peptide bond formation between amino acids.

What is a peptide bond?

The link between amino acids in a protein.

What are structural genes?

Genes that are converted into mRNA, decoded by ribosomes, and assembled into proteins that build cellular structures.

What are regulatory genes?

Genes that control expression of protein-coding genes by turning genes "on" or "off" either directly or through protein intermediaries.

What is gene expression?

The process by which cells make different proteins based on their function by expressing different genes.

What is keratin?

A tough protein made by epithelial keratinocytes in skin cells.

Why don't all cells express the same genes?

Different cell types need different proteins, so regulatory genes turn off genes that code for unneeded proteins in specific cell types.

How many genes do humans have approximately?

Approximately 25,000 genes.

What is the size range of genes?

From a few hundred DNA bases to over 1 million bases.

What is a genome?

The complete set of genetic information in a cell.

What are nucleotides?

The monomers used to build DNA and RNA.

What is a complementary strand?

A molecule of RNA (or a strand of DNA) synthesized from a complementary template strand.

What is a template strand?

A sequence of bases on a strand of DNA that is used to form a complementary mRNA molecule.

What is a hydrogen bond?

A type of non-covalent bond; a weak attraction between a hydrogen atom bound to an electronegative atom and a second highly electronegative atom.

What is the hierarchy of genetic organization?

Chromosomes → DNA → Genes → Codons → Proteins.

What happens during the translation process (step-by-step)?

1) mRNA enters cytoplasm through nuclear pores, 2) rRNA in ribosomes attaches to mRNA, 3) Each mRNA codon designates a specific amino acid, 4) tRNA transfers amino acids to the ribosome, 5) tRNA delivers the anticodon, 6) When a match is made, tRNA releases the amino acid, 7) Catalytic rRNA binds amino acids together via peptide bonds, 8) Result is the desired protein chain.

What are chromatids?

Two identical copies of DNA made during replication before cell division.

What is deoxyribose sugar?

The sugar portion of a deoxyribose nucleotide found in DNA.

How many chromosomes do dogs have?

78 chromosomes.

What makes up the sides of the DNA ladder?

Phosphate and deoxyribose sugar molecules.

What makes up the rungs of the DNA ladder?

Four nucleotide bases (A, T, G, C).

What is the double helix?

The twisted ladder structure of DNA.

Are most mutations harmful?

No, most mutations are harmless except when they lead to cell death or tumor formation.

What base does RNA use instead of thymine?

Uracil (U).

What is the base pairing in RNA?

A-U (adenine-uracil) and G-C (guanine-cytosine).

Why can't DNA leave the nucleus?

DNA is too large to leave the nucleus.

What is an anticodon?

The codon complement found on tRNA that matches with mRNA codons.