DNA, RNA, and Heredity

• DNA (deoxyribonucleic acid) is an organic chemical containing genetic information and instructions for protein production.
• RNA (ribonucleic acid) is a nucleic acid with structural similarities to DNA found in all living cells, and is often single-stranded.
• Genes are DNA segments that control single genetic traits.
• Chromosomes are long, thin strands of genetic material made of DNA and proteins.
• A chromatid constitutes one strand of a chromosome.
• Chromosomes are classified into autosomes and sex chromosomes.
• Autosomal chromosomes are non-sex chromosomes.
• Hereditary refers to traits or characteristics passed down from ancestors through inheritance.
• Sex chromosomes determine an individual's sex.
• Nitrogen bases include adenine, thymine, guanine, and cytosine, with uracil present in RNA.
• DNA contains the instructions needed for an organism's development, survival, and reproduction.
• DNA has a double helix structure, with a nucleotide which is the basic unit that contains a phosphate, sugar, and nitrogen bases.
• Phosphate and sugar form the backbone of DNA.
• Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G) during DNA replication.
• DNA replication is the process of copying DNA.
• A nucleotide consists of phosphate, deoxyribose sugar, and one of four nitrogen bases (A, C, G, T).
• Haploid cells contain one chromosome of the homologous pair, with only 23 chromosomes.
• Diploid cells contain full homologous pairs, totaling 46 chromosomes.
• Mitosis is the division of a cell's nucleus.
• Mitosis functions in growth and repair.
• Mitosis increases the number of cells in a living organism aiding in regeneration and replacement of worn-out tissues.
• The stages of mitosis are interphase, prophase, metaphase, anaphase, and telophase.
• Meiosis is cell division that produces reproductive cells in sexually reproducing organisms.
• Meiosis functions in the production of gametes.
• Meiosis increases genetic variation via chromosomal crossing, where chromosome regions are exchanged, producing unique combinations.
• Each gamete contains a different set of DNA because of recombination and independent assortment in meiosis, which leads to a unique combination of genes in the resulting zygote.
• Recombination or DNA crossing occurs during prophase I.
• The stages of meiosis include interphase, prophase I, metaphase I, anaphase I, telophase I, cytokinesis, prophase II, metaphase II, anaphase II, telophase II, and cytokinesis.
• Mitosis involves the division of body cells, which occurs once.
• Meiosis involves the division of sex cells, which occurs twice.
• A typical human karyotype contains 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes (allosomes).
• Females usually have two X chromosomes (46, XX).
• Males usually have an X and a Y chromosome (46, XY).
• Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA) are the three types of RNA.

Messenger RNA (mRNA)

• The 3' ends typically contain a poly(A) tail post-transcription consisting of multiple adenosine monophosphates .
• mRNA carries protein information from DNA in a cell's nucleus to the cytoplasm.

Transfer RNA (tRNA)

• The tRNA molecule folds into a distinctive structure with three hairpin loops, forming a three-leafed clover shape.
• tRNAs are adaptor molecules that translate genetic information into protein sequence by delivering amino acids to the protein synthesis machinery during translation.

Ribosomal RNA (rRNA)

• rRNA forms part of the protein-synthesizing organelle known as a ribosome.
• The primary function of rRNA is in protein synthesis through binding mRNA and tRNA to ensure accurate translation of the codon sequence of the mRNA into amino acids sequence in proteins.
• Protein synthesis involves cells making proteins.
• Transcription involves transferring genetic instructions in DNA to mRNA in the nucleus.
• Translation occurs at the ribosome, which consists of rRNA and proteins.
• Helicase, DNA primase, DNA polymerase, RNA polymerase, and ligase are enzymes involved in DNA replication.
• Helicase untwists the double helix of DNA at replication forks.
• DNA primase synthesizes short RNA sequences complementary to a single-stranded piece of DNA, serving as its template.
• DNA polymerase I fills DNA gaps that arise during DNA replication, repair, and recombination.
• RNA polymerase copies a DNA sequence into an RNA sequence during transcription.
• DNA ligase catalyzes the formation of a phosphodiester bond between nucleotides on one strand of a double-stranded DNA molecule.
• Genetics studies inheritance.
• Inheritance involves the passing of genes from one generation to another.
• Alleles are alternate forms of a gene.
• A dominant allele is the trait that always shows up in the organism when the allele is present.
• A recessive allele is masked when a dominant allele is present.
• Homozygous refers to two identical alleles for a trait (e.g., BB).
• Heterozygous refers to two different alleles for a trait (e.g., Bb).
• Phenotype is an organism's physical appearance or visible traits.
• Genotype is an organism's genetic makeup or allele combinations.

Albinism Example

• a - albinism (recessive)
• A - normal pigmentation
• aa genotype results in albino phenotype.
• Aa and AA genotypes result in normal pigmentation phenotype.
• A monohybrid cross involves one pair of contrasting traits.
• Mutations are permanent changes in DNA.
• Chromosomal mutation types include: deletion, duplication, inversion, insertion, translocation, don disjunction.
• Mutations can improve an organism's chance of surviving in its surroundings.
• Mutagens are chemical or physical agents that interact with DNA and cause a mutation.
• A gene mutation is a change in the base sequence of a gene.
• A chromosomal mutation is a change in the structure of a chromosome.
• A somatic mutation occurs in a body cell.
• A germ line mutation occurs in gametes and is passed on to offspring.
• Codons are a three-letter sequence.
• Maternal refers to of or like a mother.
• The stages of protein synthesis are transcription and translation.
• Transcription is where the DNA sequence in a gene is copied into mRNA.
• Translation is the process by which mRNA is decoded and a protein is produced.