Genetics

RNA: messenger, transfer, ribosomal Both made of nucleotides: pentose sugar, phosphate group, nitrogenous base DNA: [deoxy]ribose, double stranded with covalent bonds between sugar and phosphate, hydrogen bonds between bases, anti-parallel RNA: C-G, A-U DNA: C-G, A-T

Happens in synthesis (S) phase of interphase DNA copies for replication Occurs in nucleus with presence of enzymes (helicase and DNA polymerases) and free nucleotides 1) helicase initiates separation between 2 strands by breaking hydrogen bond 2) free floating nucleotides find complementary partners on open strands polymerase catalyzes covalent bond between nucleotides; both sides happen simultaneously in different directions 3) other polymerase proofread each nucleotide for the template and correct if needed Catch most mistakes, others are mutations (usually harmless) Semi-conservative because new strands are 1/2 old DNA (1/2 is conserved)

Cell cycle: interphase (G1, S, G2), miotic phase (mitosis, cytokinesis) Mitosis is in somatic cells Phases: prophase, metaphase, anaphase, telophase 2 Genetically identical cells that are diploid (two copies of each chromosome)

Meiosis makes sex cells (egg and sperm) or gametes Have 1/2 the number of chromosomes when done (haploid) Has homologous chromosome pairing and crossing over Produces cells with variable genetics

Prophase 1: cell has 2n chromosomes (double chromatid), homologous chromosomes pair in synapsis, crossing over and swapping occurs further from centromere Metaphase 1: chromosomes line up on metaphase plate in pairs independently assorted Anaphase 1: sister chromosomes separate from pairs and move to poles Telophase 1: chromosomes uncoils, cytokenisis divides cell on equator, haploid Meiosis 2: non-identical sister chromatids line up (single file), cytokinesis creates 4 haploid cells, in females only 1 egg is used

Genetic variation: swapping between chromosomes, independent assortment, random fertilization Non-disjunction: homologous chromosomes don’t separate in anaphase 1, usually lethal or down syndrome, intersex Translocation and deletion: incorrectly transfer or delete fragment of chromosome

Gene: sequence of bases coding for a trait, found on a locus Codon: 3 base pairs which code for 1/20 amino acids (triplet) Anti-codon: tRNA bases that compliment the amino acid it has Protein bond: condensation reaction → covalent peptide bond DNA [CAGT] → RNA [GUCA]

Transcription: DNA into RNA. Gene in DNA is unzipped by RNA polymerase, RNA nucleotides float in, attach via RNA polymerase, stop at stop codon → complementary mRNA of gene which leaves nucleus through pore Only 1 side of DNA is transcribed, polymerase re-zips Translation: tRNA is a single strand with complementary anti-codons on the bottom culd-e-suc, other end has corresponding amino acid found in cytoplasm. tRNA and mRNA go to ribosome, 2 tRNAs at once which match the RNA codon. Peptide bond between the amino acids, then moves to next codon. tRNA floats away, stop codon allows amino acids to break off and morph into a protein

Belief that every gene coded for 1 enzyme, amended to include all proteins because many proteins are polypeptides Recent understanding that 1 gene may lead to a single mRNA molecule, but mRNA may be modified by spliceosomes, resulting in many different polypeptides

Mutation: change in sequence of bases in gene, most mistakes are caught Usually don’t have an impact, but can be good/bad Creates genetic variability → if mutation happens in meiosis it can be inherited Sickle cell anemia: angular red blood cells that clog capillaries, developmental problems, pain. Primarily in black folks and Hispanics. Heterozygotes don’t have sickle cell but are more resistant to malaria. Caused by base substitution in hemoglobin (GAG → GUG)

Gene: heritable factor that controls a specific characteristic (length of DNA occupying a position on a chromosome known as a locus) Allele: specific form of version of a gene that differs from others by 1 or a few bases, occupies the same gene locus as other alleles Genotype: alleles passed down by an organism (AA or Aa) Phenotype: outward expression or characteristics of an organism Dominant allele: same affect on phenotype whether homo- or hetero- (capitalized) Recessive allele: only affects phenotype if homo- (lowercase) Homozygous: 2 identical alleles of a gene Heterozygous: 2 different alleles of a gene

Dominant allele carries code for protein, recessive doesn’t on its own Capital / lowercase letters

More than 1 dominant allele: partial phenotypic affect when hetero- more when homo- Capital letter same for an alleles with differing capitalized superscript

Genes with > 2 alleles (blood type) Similar to codominance notation but recessive (O blood type) is lowercase

Alleles carried on X chromosome (females have 2, males have 1) Notation with capital X and / or Y, superscript on X with capital or lowercase Ex: hemophilia, colorblindness

1) choose a letter if not set 2) write parental cross (ex: Tt x tt) 3) gametes, space to show haploid ( ex: T t t t) 4) fill in Punnett Square 5) write genotype and phenotypic ratios (do not simplify, specify carriers)

Record of an organism’s ancestry through a diagram of 1 trait Circle is female, square is male Filled in means with trait | is parent / offspring — is parents with offspring ^ is twins Prove method of inheritance by disproving all others