Genetics final study guide intro to molecular genetics mls 400 oakland

Genetics final study guide intro to molecular genetics mls 400 oakland Genetics Final Exam Important definitions Base: pyrimidines & purines (C, U, T) (A, G) Nucleoside: base + sugar (phosphorylated to become a nucleotide) Nucleotide: phosphate group + sugar + base Sugar may be ribose (RNA) or deoxyribose (DNA - missing hydroxyl group) Antiparallel: 2 sequences have opposite orientation with regard to their 5’ & 3’ ends Complementary: AT/GC rule; purines bond to pyrimidines, and vice versa Intron: Sequence of nucleotides that do not code for proteins (removed during splicing) Exon: Coding sections of an RNA transcript, or the DNA encoding it, that are translated into protein. Codon: a sequence of 3 nucleotides Start codon: AUG Stop codons: UAG, UAA, UGA Amino Acid: protein encoded for by specific codons (in 3’s) Polypeptide: Sequence of amino acids Gene: a unit of inheritance; a sequence of polypeptides Open Reading Frame: Nucleotide sequence that can be translated; start codon to stop codon Allele: Alternate form of a gene at a locus on a chromosome Genome: complete set of genetic instructions (blueprint) Central Dogma: DNA replication → RNA → Protein Semi-Conservative Replication: each DNA molecule composed of ½ of parent & ½ of new complementary strand Law of Segregation: alleles randomly separate into two daughter cells Law of Independent Assortment: the separation of alleles is independent of the separation of other pairs Inherited: Receive genetic information from predecessors Congenital: “Born with,” not necessarily heritable, but present at birth Hot spots: region of the gene more frequently mutated Loci physical location of a gene on a chromosome Alleles alternate forms of genes Homologous Chromosomes similar but not identical chromosomes Each carries the same genes in the same order, but the alleles for each trait may not be the same. Homologous ● same structure, value, or position Heterologous ● different structure, value, or position Diploid ● somatic cells ● 2 copies (pair) of homologous chromosomes Haploid ● gametes ● 1 copy of each chromosome Phenotype ● an expressed, observable trait Genotype ● actual sequence of genetic information Wild Type ● original (normal) DNA sequence Mutant ● alteration in the “normal” DNA sequence Dominant ● allele that is expressed as the phenotype independent of zygosity Recessive ● allele that is expressed as the phenotype only when it is homozygous Protein Structure Primary The amino acid sequence Secondary Folding or coiling from H-bonding Tertiary Folding that provides 3D structure interactions between R groups Domains ● DNA binding ● Signal molecule binding Quaternary Assembly of more than one polypeptide chain RNA Class Name Function Translated Messenger (mRNA) encodes DNA sequence Transfer (tRNA) transfers an amino acid to the polypeptide chain being assembled during translation Transfer Ribosomal (rRNA) catalyze the assembly of amino acids into protein chains bind tRNAs & various accessory molecules necessary for protein synthesis Minor Heterogeneous nuclear (hnRNA) Small nuclear (snRNA) Chromosomal Organization Purpose Enzymes Involved Supercoiling further compacts chromosome Topoisomerase ● Topo II - introduces negative supercoils to help separate tangled DNA following replication ● Topo I - relaxes negative supercoils; breaks one strand to relieve tension Chromosomal Structure Function Origins of Replication several per chromosome initiate DNA replication Centromere constricted region in center of chromosome chromosome segregation kinetochore: protein that links centromere to spindle apparatus Telomere ends of chromosome prevents translocations maintenance of chromosome length tether to nuclear membrane to position chromosome Structure of Dividing Cells Structure of Nondividing Cells Euchromatin Less condensed regions of chromosomes Transcriptionally active Radial loop domains formed Heterochromatin Tightly compacted regions of chromosomes Transcriptionally inactive Radial loop domains compacted Structural Maintenance of Chromosomes Function Condensin chromosome condensation (short & fat) Cohesion binding (cohesion) between sister chromatids Chromosomal Alterations Effect Structural: Unbalanced Deficiencies/Deletions - subtraction loss of a chromosomal segment Duplications - addition repetition of a chromosomal segment Structural: Balanced Inversions change in direction Translocations Breakpoint segment broken Position Effects repositioned Simple one-way transfer Reciprocal two-way transfer Number Monosomy missing chromosome Trisomy extra chromosome Mitosis - End Result Cells Chromosome Content 2 diploid daughter cells genetically identical 46 chromosomes per daughter cell Meiosis - End Result Cells Chromosome Content 4 haploid daughter cells NOT genetically identical 23 chromosomes 1 chromosome from each homologous pair different combinations of homologs Meiosis I & II Event Meiosis I Meiosis II no chromosomal replication prior to meiosis II Prophase Pairing of homologous chromosomes homologous recombination Start with 6 chromatids joined as three pairs of sister chromatids Prometaphase Metaphase Anaphase Alignment of chromatids along metaphase plate Two pairs of sister chromatids separate from each other (kinetochore intact) Heterozygous alleles separate from each other Alignment of chromatids along metaphase plate Separation of sister chromatids (kinetochore broken) Telophase Attachment of sister chromatids to both poles Gamete Formation Spermatogenesis Oogenesis Process Diploid spermatogonial cell divides mitotically to produce 2 cells: ● spermatogonial cell ● primary spermatocyte Diploid oogonia produce diploid primary oocytes ● undergo Meiosis I & arrest at Prophase I until puberty (dormant phase) ● 1 per month proceeds through Meiosis I after puberty ● division in Meiosis I is asymmetric ○ large secondary oocyte ○ small polar body End Result Progresses through Meiosis I & II to produce haploid sperm Secondary oocyte begins Meiosis II, arrested until ovulation ● Meiosis II complete if fertilized ○ haploid egg & 2nd polar body produced Genetic Recombination Recombinants Mechanisms Outcome Combination of alleles offspring receive that differs from those in the parental generation Law of Independent Assortment Homologous recombination (crossing over) Genes at different loci are transmitted to offspring independently of one another Exchange of DNA between non-sister chromatids of homologous chromosomes, producing new combinations of DNA sequences Dosage Compensation -Level of gene expression on sex chromosomes is similar in both sexes -How much gene product is generated from a single allele (male) or a pair of alleles (female) is often equal Males have one copy (dose) Females have two copies Lyonization One X chromosome randomly inactivated in somatic cells of XX female X-Inactivation 1. Initiation - X chromosome selected for inactivation (during embryonic development) 2. Spreading - Xist expressed on chromosome to be inactivated, Xist transcripts (RNA) coats chromosome, Proteins are recruited to chromosome to condense it 3. Maintenance - Remains as a Barr body for life X- linked Y-linked Pseudoautosomal Gene location X-chromosome only Y-chromosome only both X- & Y-chromosomes Hemizygous: Single copy of X-linked gene in males More likely to be affected by recessive X-linked disorders. Pattern of Inheritance Effect X- linked dominant Mother with trait ● daughters can have trait ● sons can have trait ○ all of affected son’s daughters have trait Father with trait ● all daughters have trait ● no sons have trait X- linked recessive Mother without trait (but with mutated gene) ● no daughters have trait (unless father also contributes a mutant allele) ● all sons have trait Y-linked Only males affected