Understanding DNA, Genes, and Chromosomes
ITEM 5: DNA
Deoxyribonucleic acid (DNA) is a molecule that contains all the genetic information, dictating traits like body structure and eye color.
DNA Components
- Monosaccharides
- Phosphoric acid
- Nucleobases
Nucleotide Components: A nucleotide consists of a nucleobase, a monosaccharide, and phosphoric acid.
Nitrogenous Bases:
- Cytosine
- Guanine
- Thymine (DNA)
- Uracil (RNA)
- Adenine
Double Helix: The double helix is the shape created when two nucleotide chains face each other, forming a structure resembling a spiral staircase.
Clone: Stem cells that have the same genetic material as their parent.
Parts of a Chromosome
Chromatids joined by a centromere.
Constituents of a Chromosome: DNA and proteins (protamine or histone).
Karyotype: A set of chromosomes of an individual, ordered in pairs. Humans have 46 chromosomes, comprising 22 homologous pairs and one pair of sex chromosomes (Men: XY, Women: XX).
Gene: A segment of DNA with instructions to produce a particular protein.
Genotype: The set of genes of an individual.
Phenotype: The external appearance of a genetic character.
Protein Function
Proteins protect and provide consistency, transport substances, activate defense mechanisms, produce movements, package hereditary material, receive signals, and facilitate biochemical reactions.
Codon: A triplet of bases that encodes an amino acid, which are the building blocks of protein.
Degenerate Codon: A codon is considered degenerate because there are more base triplets than necessary.
Difference between RNA and DNA: Ribosomes are present in RNA, but not in DNA.
Types of RNA
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
- Nucleolar RNA
Translation: The process of converting information from mRNA to protein.
Transcription: The process of transferring information from tRNA to mRNA.
Anticodon Location: Anticodons are found in tRNA.
Mutations and Polymorphisms
Mutation: A change in the nucleotide sequence of DNA.
Polymorphism: A mutation in a DNA region that does *not* encode any gene, and therefore does not cause any change in the protein.
Pathological Mutations: Mutations that cause significant changes in proteins and can lead to diseases.
Founder Effect: When a subspecies founder carries a relatively rare allele, that allele can become fixed in the new population with a high frequency.
Key Terms
- Hereditary Material: Nucleic acids.
- DNA: Molecules made up of four repeated and differently combined units (nucleotides).
- Nucleotides: Composed of a phosphate group, a pentagonal sugar, and a nucleobase.
- Nucleobases: Cytosine, guanine, thymine, adenine.
- One chromosome contains one DNA molecule.
- Humans have 46 chromosomes, in 23 pairs.
- Homologous Chromosomes: Chromosomes that are the same.
- Karyotype: The set of chromosomes of an organism.
- Gametogenesis: The production of reproductive cells from a cell with 46 chromosomes.
- Alleles: Different variations of the same gene.
- Mutation: A change in the nucleotide sequence of DNA.
- Polymorphism: When a mutation occurs in a DNA region that does not encode any gene.
- Polydactyly: A disease that causes the appearance of extra fingers on the hands and feet.
- Gene: A fragment of DNA that encodes a specific protein.
- Protein: Formed by amino acids and having various functions.
- Messenger RNA Function: Carries information to the ribosome for protein synthesis.
- Pathogenic Mutation: A change in DNA that causes a disease.