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Both chapters help explain away the complex science behind genetics.…

- - - - Gregor Mendel was an Austrian monk with a strong interest in plants
        
        Known as the Father of Genetics
        
        Mendel discovered the basic principles of heredity by breeding garden pea plants
        
        His discoveries are what we know as Mendelian Genetics
        
        Oversimplified Genetics
        
        The study of how traits are inherited through generations, based on principles established by Gregor Mendel
      - Pea Plants Experiment
        
        Reasons
        
        Many varieties of Pea Plants
        
        Ex. Purple and/or White Flowers
        
        Short Generation Time
        
        Large Number of Offsprings
        
        Could Control Mating between Plants
        
        Technique
        
        Mendel tracked characters that occurred in two distinct, alternative forms, such as purple or white flowers
        
        He removed stamens from the purple flowers
        
        Transferred sperm bearing pollen from stamens of the white flower to egg bearing carpel of the purple flower
        
        These are known as the Parental (P) Generation
        
        Waited for pollinated carpel to mature into pod
        
        Plants seeds from pod
        
        Examined offspring
        
        This is known as the First Filial (F1) Generation of Offsprings
        
        Key Vocabulary
        
        Mendel's Reasoning
        
        Character
        
        An observable heritable feature that may vary among individuals
        
        Ex: Flower's color or Seed shapes in pea plants
        
        Trait
        
        One or two more detectable variants in a genetic character
        
        Ex: Purple flower or White flower
        
        Mendel's Experiment
        
        True-Breeding
        
        Referring to organisms that produce offspring of the same variety over many generations of self-pollination
        
        These were used to ensure consistent and predictable results
        
        Hybridization
        
        The mating, or crossing, of two true-breeding varieties
        
        P Generation
        
        The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived
        
        P stands for Parental
        
        F1 Generation
        
        The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross
        
        F2 Generation
        
        The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation
        
        F2 stands for second filial
    - - Law of Segregation
        
        The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
        
        This occurs during Meiosis
        
        Meiosos
        
        A specialized type of cell division that reduces the chromosome number by creating four haploid cells from one diploid cell
        
        Alleles segregate so that each gamete contains only one allele for each gene
        
        This is why offpsring inherit one allele from each parent
      - Law of Independent Assortment
        
        The two alleles of two (or more) different genes get sorted into gametes independently of one another
        
        The allele a gamete receives for one gene doesn't influence the allele for another gene
        
        This occurs during Meiosis Metaphase I
        
        Chromosomes align independently
        
        This leads to genetic variations; results in the combinations of traits in offspring
      - Key Vocabulary
        
        Laws
        
        Alleles
        
        Any of the alternative versions of a gene that may produce distinguishable phenotypic effects
        
        Dominant Allele
        
        An allele that is fully expressed in the phenotype of a heterozygote
        
        Recessive Allele
        
        An allele whose phenotypic effect is not observed in a heterozygote
        
        Punnett Square
        
        A diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype
        
        Monohybrids
        
        An organisms that is heterozygous with respect to a single gene of interest
        
        Ex: AA x aa = Aa
        
        Monohybrid Cross
        
        A cross between two organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant)
        
        Dihybrids
        
        An organism that is heterozygous with respect to two genes of interest
        
        Ex: AABB x aabb = AaBb
        
        Dihybrid Cross
        
        A cross between two organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters)
        
        Useful Vocabulary
        
        Homozygote
        
        An organism that has a pair of identical alleles for a gene (encoding a character)
        
        Homozygous
        
        Having two identical alleles for a given gene
        
        Homozygous Dominant
        
        Two dominant alleles
        
        Homozygous Recessive
        
        Two recessive alleles
        
        Heterozygote
        
        An organism that has two different alleles for a gene (encoding a character)
        
        Heterozygous
        
        Having two different alleles for a given gene
        
        Phenotype
        
        The observable physical and physiological traits of an organism, which are determined by its genetic makeup
        
        Genotype
        
        The genetic makeup, or set of alleles, of an organism
        
        Testcross
        
        Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype
  - - - Pedigree Analysis
        
        Pedigree
        
        A diagram of a family tree with conventional symbols, showing the occurrence of heritable characters in parents and offspring over multiple generations
        
        Resembles a family tree but focuses on specific genetic traits, helping deduce the genotypes of family members and predict future offspring's traits
        
        Symbols
        
        Shapes
        
        Males are represented by a square
        
        Females are represented by a circle
        
        Shaded
        
        Shaded symbols indicate individuals with the trait
        
        Nonshaded symbols indicate individuals without the trait
        
        Numbers
        
        Arabic Numbers
        
        Used to denote the order of individuals in each generation
        
        Roman Numerals
        
        Used to denote the generation
      - Inherited Disorders
        
        Fetal Testing
        
        Two types of testing can be done to look for genetic disorders in the fetus
        
        Types
        
        Amniocentesis
        
        A technique associated with prenatal diagnosis in which amniotic fluid is obtained by aspiration from a needle inserted into the uterus
        
        The fluid and fetal cells it contains are analyzed to detect certain genetic congenital defects in the fetus
        
        Chorionic Villus Sampling
        
        A technique associated with prenatal diagnosis in which a small sample of the fetal portion of the placenta is removed for analysis to detect certain genetic congenital defects in the fetus
        
        Dieases
        
        Cystic Fibrosis
        
        A genetic disorder that affects the respiratory and digestive systems
        
        It's caused by mutations in the CFTR gene, which leads to the production of thick and sticky mucus that can clog airways and lead to severe respiratory and digestive problems
        
        It's inherited in an autosomal recessive manner
        
        This indicates an individual must have two copies of the recessive gene to exhibit the disease
        
        Sickle-Cell Diease
        
        A genetic disorder resulting from a single amino acid substitution in the hemoglobin protein of red blood cells causing for the hemoglobin molecules to form long fibers under low oxygen conditions, deforming red blood cells into a sickle shape
        
        Huntington's Diease
        
        A human genetic disease cause by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system
    - - Degrees of Dominance
        
        Complete Dominance
        
        The situation in which the phenotypes of the heterozygote and dominate homozygote are indistinguishable
        
        When an organism has one dominant allele and one recessive allele, the dominant trait is expressed
        
        Ex: PP = Pp
        
        This means no matter the genotype, both will expressed the dominant trait which is the Purple Flower
        
        Incomplete Dominance
        
        The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele
        
        This occurs when neither allele is completely dominant over the other
        
        This results in the heterozygous phenotype is a blend of the two homozygous phenotypes
        
        Ex: RR x WW = RW
        
        This means that the cross between an incomplete dominant red flower and an incomplete dominant white flower will produce a pink flower
        
        Codominance
        
        The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways
        
        A genetic scenario where both alleles in a heterozygous organism are fully expressed, resulting in a phenotype that clearly shows both traits WITHOUT blending
        
        Different from Incomplete Dominance
        
        Ex: Blood Type AB
        
        This means this blood type expresses both antigen A and antigen B
      - Genetic Phenomena
        
        Pleiotrophy
        
        The ability of a single gene to have multiple effects
        
        Multiple phenotypic effects
        
        This occurs because the gene product, such as a protein, can be involved in various biological processes or pathways, affecting different characteristics of an organism
        
        Ex: Cystic Fibrosis and Sickle-Cell Disease
        
        Cystic Fibrosis
        
        Individuals inherit two recessive alleles for the disease, leading to a defective or absent chloride transport channels in cell membranes
        
        Sickle-Cell Disease
        
        A genetic disorder resulting from a single amino acid substitution in the hemoglobin protein of red blood cells causing for the hemoglobin molecules to form long fibers under low oxygen conditions, deforming red blood cells into a sickle shape
        
        How it's caused
        
        The intricate molecular and cellular interactions in a organisms development and physiology
        
        Epistasis
        
        A type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene
        
        One gene affects the phenotype of another due to interactions of their products
        
        This occurs when the product of one gene affects the phenotypic expression of another gene at a different locus
        
        Polygenic Inheritance
        
        An additive effect of two or more genes on a single phenotypic character
        
        Polygenic Traits
        
        A characteristic influenced by multiple genes, each contributing to the phenotype
        
        These exhibit a range of variations and are often quantitative characters
        
        Quantitative Character
        
        A heritable feature that varies continuously over a range rather than in an either-or fashion
        
        Multifactorial
        
        A phenotypic character that is influences by multiple genes and environmental factors
- - - - A gene located on either sex chromosome; the ones responsible for determining the sex of an individual
        
        For humans, these are the X and Y chromosomes
        
        Most sex-linked genes are found on the X chromosomes
        
        It's larger and houses more genes compared to the Y chromosome
      - X-Linked Genes
        
        A gene located on the X chromosome; such gene show a distinctive pattern of inheritance
        
        Women have the ability to be carriers of a gene compared to a man because they have two X chromosomes instead of one
        
        Ex: Hemophilia and Duchenne Muscular Dystrophy
        
        Hemophilia
        
        A human genetic disease caused by a sex-linked recessive allele resulting in the absence of one or more blood-clotting proteins; characterized by excessive bleeding following injury
        
        Duchenne Muscular Dystrophy
        
        A human genetic disorder cause by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue
        
        X Inactivation
        
        A process that occurs in female mammals to ensure that they don't produce double the amount of proteins from X-linked genes compared to males
        
        Barr Body
        
        A dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome
        
        It's mostly not expressed
      - Y-Linked Genes
        
        A gene located on the Y chromosome
        
        Very few genes are on the Y chromosome, and they're typically involved in male sex determination and development
    - - Genes located close enough together on a chromosome that they tend to be inherited together
      - Genetic Recombination
        
        General term for the production of offspring with combinations of traits that differ from those found in either parent
        
        Parental Offspring type
        
        An offspring that inherits a phenotype matching one of the parental phenotypes
        
        Recombinant Offspring
        
        An offspring that exhibits new combinations of traits not found in either parent
        
        % of Recombinant Offspring
        
        Recombinant + Frequency
    - - Aneuploidy
        
        A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number
        
        Can occur due to nondisjunction during meiosis
        
        Nondisjunction
        
        An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair or sister chromatids fail to separate from each other
        
        Caused by a mess up in the Law of Segregation
        
        Types
        
        Monosomy
        
        Zygote has only one copy of a particular chromosome
        
        Ex: Turner (XO) Syndrome
        
        A chromosomal condition that affects females; characterized by the presence of only one X chromosome
        
        Trisomy
        
        Zygote has three copies of a particular chromosome
        
        Ex: Trisomy 21 (Down Syndrome)
        
        A genetic disorder caused by the presence of an extra chromosome 21
      - Polyploidy
        
        A chromosomal alteration in which the organisms possesses more than two complete sets of chromosomes
        
        Caused by an accident during cell division where chromosomes fail to separate properly
        
        Types
        
        Autopolyploidy
        
        An individual has multiple chromosome sets derived from a single species
        
        Allopolyploidy
        
        Combining chromosomes sets from different species
        
        Results an a hybrid who is often sterile
      - Alterations in Chromosome Structure
        
        Deletion
        
        A deficiency in a chromosome resulting from the loss of a fragement through breakage
        
        Results in missing certain genes
        
        Can be lethal if the deletion is large or affects certain genes
        
        Duplication
        
        A aberration in a chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated
        
        Can be beneficial by providing extra copies of genes that may evolve new functions
        
        Inversion
        
        An aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated
        
        Results in a segment of the chromosome being flipped
        
        Can alter phenotypes if the inversion disrupts a gene or changes its regulatory environment
        
        Translocation
        
        An aberration in a chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome
        
        Most commonly associated with Chronic Myelogenous Leukemia (CML), where a reciprocal translocation between chromosomes 9 and 22 create the Philadelphia chromosome, leading to cancer
        
        Forms
        
        Reciprocal Translocation
        
        Most common type, where two nonhomologous chromosomes exchange segments
        
        Nonreciprocal Translocation
        
        Less common type, a chromosome transfers a fragment to another chromosome without receiving any segment in return
  - - - A phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent
        
        Results in the silencing of one allele based on its parental origin
      - The phenotype can vary depending on whether the allele is inhertied from the mother or father
        
        Not the case for most genes, as most will be expressed regardless of origin
        
        During gamete formation, certain genes are imprinted
        
        This means one is slienced
        
        Imprinted genes are crucial for embryonic development and are involved in body functions such as temperature regulation and metabolism
        
        Imprinting resets each in generation, ensuring the same genes are consistently imprinted in the same way
    - - An ordered list of the genetic loci (genes or other genetic markers) along a chromosome
        
        Loci = Location
      - Linkage Map
        
        A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes
        
        These don't provide precise physical distances; the frequency of crossing over is not uniform across a chromosome
      - This helps scientists understand the arrangement of genes and their relative distances from ech other on a chromosome
      - Constructed of...
        
        Map Units
        
        Distances, where one map units corresponds to a 1% recombination frequency
        
        Recombinant Frequency
        
        A measure use in genetics to determine the distance between genes on a chromosome
        
        This is caused by crossing over
        
        Linkage Groups
        
        Genes that are close together on the same chromosome
      - The more physically distance two genes are, the more likely crossing over is to occur