BIO FINAL

• Gregor (Johann) Mendel 

  • Father of genetics
  • Established the principle of inheritance
  • Austrian monk 
  • Bred different varieties of garden pea plants (Pisum sativum) with contrasting characteristics
• • Dominant strong & noticeable (capital)
• • Recessive weaker and often masked by dominant (small)
• • Law of inheritance 

  1. Variations in the inherited traits of offspring are attributed to alleles
  2. Every offspring contains two copies of a particular gene (one from each parent)
• allele - gene variant or different form of genes
• genes - units of heredity that carry genetic information
• Law of Dominance - two different alleles are present only one is dominant and will be expressed.
• Law of Segregation

  • Pairs of alleles for a specific trait separate from one another and result in gametes that carry only a single inherited trait
  • An individual possesses two alleles and only one allele is passed on to the offspring
• TYPES OF ALLELE

  1. Homozygous dominant
  2. Homozygous recessive
  3. Heterozygous
• • Homozygous dominant two dominant alleles (BB)
• • Homozygous recessive two identical copies of the recessive gene (bb)
• • Heterozygous two different alleles of a particular Gene (Bb)
• • Monohybrid cross involves one pair of contrasting traits
• • Punnet squares allow geneticists to predict the possible genotypes and phenotypes of offspring
• Genotype - the genetic material passed between generations
• Phenotype -the observable characteristics or traits of an organism.
• Law of Independent Assortment

  • One gamete is different from the alleles of the genes in another gamete
  • The alleles of two (or more) different genes get sorted into gametes independently 
• Dihybrid inheritance/cross  - Involves two pairs of contrasting traits; breeding experiment between two organisms that are identical hybrids for two traits
• • Complete dominance traits segregated during gamete formation and were assorted independently into particular gametes
• NON-MENDELIAN PATTERNS OF INHERITANCE 

  1. Incomplete dominance
  2. Codominance  
  3. Multiple alleles
  4. Polygenic inheritance
• • Incomplete dominance the blending of phenotypes; does not dominate the other allele completely
• • Codominance both traits are expressed equally 
• • Multiple alleles three alleles or more within a population

  Example: person’s ABO blood
• • Polygenic inheritance single trait influenced by numerous genes; many alleles that can affect phenotype
• SEX DETERMINATION AND LINKAGE 

  • 46 chromosomes, 23 pairs

  Autosomes first 22 pairs

  • Sex chromosomes last pair
• Sex-linked inheritance 

  • Sex-linked genes - traits unrelated to the biological sex of an individual result from a gene located on an X or Y chromosome
  • Sex-linkage - the processs where a gene linked to a sex chromosome; Alleles attached to the X-chromosome express the X-linked traits, while Y-chromosomes in males expressed their Y-linked traits
• • Sex limited traits characteristics are expressed only  in the presence of sex hormonse and are observed in one sex of a specie like changes during puberty
• • Sex-influenced traits autosomal traits influenced by sex chromosomes; occur differently in both sexes but more frequent in the other like baldness
• • DNA (Deoxyribonucleic acid) the material that carries the genetic informatio of organisms
• Made of nucleotides

  • five-carbon sugar (deoxyribose)
  • nitrogenous base: adenine (A), thymine (T), guanine (G), and cytosine (C).
  • Phosphate group
• Purines - Adenine and guanine are the double-ring (bicyclic) bases
• • Pyrimidines cytosine and thymine are  the single-ring (monocyclic) nitrogenous bases.
• (Erwin) Chargaff’s rules

  (1) purine content = pyrimidine content 

  (2) adenine = thymine, cytosine = guanine
• DNA replication duplicated during cell division 

  • Happen in a semiconservative manner new DNA strand formed from an old DNA strand
  • running from 5’ to 3’ direction
• antisense strand (non-coding strand, minus strand, or template strand) is in 3’ to 5’ direction.
• Stages of DNA Replication

  STAGE 1: initiation

  STAGE 2: elongation

  STAGE 3: termination
• DNA helicase - unzips the double-stranded DNA
• DNA polymerase adds new nucleotides to form the new strand complemented to the template strand through base pairing rules; an enzyme responsible for forming new copies of DNA
• DNA replication fork - Y-shaped region where the parent DNA double helix splits into two strands, subsequently copied
• • Leading strand (5’ to 3’) and lagging strand (3’ to 5’)