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Genetics: Heredity & Biotechnology

94 cards · 🇺🇸 English

Mendelian genetics, inheritance problems, genetic engineering and CRISPR.

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Genetics

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  1. 1Genetics
    The study of genes, genetic variation, and heredity in organisms
  2. 2Gene
    A discrete unit of heredity that codes for a specific trait and is passed from parents to offspring
  3. 3Allele
    Different versions of the same gene that control variations of a trait (e.g., purple or white flower color)
  4. 4genotype vs phenotype
    Genotype is the genetic makeup (alleles) of an organism; phenotype is the observable physical or biochemical characteristics
  5. 5Homozygous
    An organism has two identical alleles for a particular gene (e.g., AA or aa)
  6. 6Heterozygous
    An organism has two different alleles for a particular gene (e.g., Aa)
  7. 7Dominant allele
    An allele that expresses its phenotype even when only one copy is present (masks the recessive allele)
  8. 8Recessive allele
    An allele that only expresses its phenotype when two copies are present (homozygous recessive)
  9. 9Mendel's Law of Segregation (First Law)
    During gamete formation, the two alleles for a trait separate so that each gamete receives only one allele
  10. 10Mendel's Law of Independent Assortment (Second Law)
    Alleles for different traits are distributed to gametes independently of one another (applies to genes on different chromosomes)
  11. 11Punnett square
    A diagram used to predict the genotypes and phenotypes of offspring from a genetic cross
  12. 12Monohybrid cross
    A genetic cross that examines the inheritance of a single trait
  13. 13In a cross between two heterozygous individuals (Aa × Aa), what is the expected phenotypic ratio?
    3:1 (3 dominant phenotype : 1 recessive phenotype)
  14. 14In a cross between two heterozygous individuals (Aa × Aa), what is the expected genotypic ratio?
    1:2:1 (1 AA : 2 Aa : 1 aa)
  15. 15Testcross
    A cross between an individual with a dominant phenotype (but unknown genotype) and a homozygous recessive individual to determine the unknown genotype
  16. 16If a testcross produces any recessive offspring, what is the genotype of the parent with the dominant phenotype?
    Heterozygous (Aa), because the recessive allele must have come from that parent
  17. 17If a testcross produces only dominant phenotype offspring, what is the likely genotype of the parent?
    Homozygous dominant (AA), though a small sample size might not reveal heterozygosity
  18. 18Dihybrid cross
    A genetic cross that examines the inheritance of two different traits simultaneously
  19. 19In a dihybrid cross between two heterozygous individuals (AaBb × AaBb), what is the expected phenotypic ratio?
    9:3:3:1 (9 both dominant : 3 first dominant/second recessive : 3 first recessive/second dominant : 1 both recessive)
  20. 20Incomplete dominance
    A pattern of inheritance where heterozygous individuals show an intermediate phenotype between the two homozygous phenotypes (e.g., red × white = pink)
  21. 21Codominance
    A pattern of inheritance where both alleles are fully expressed in heterozygous individuals (e.g., AB blood type shows both A and B antigens)
  22. 22Genotypic ratio in incomplete dominance for a cross between two heterozygotes
    1:2:1, but the phenotypic ratio is also 1:2:1 (not 3:1) because heterozygotes show an intermediate phenotype
  23. 23Epistasis
    When one gene affects or masks the expression of another gene (e.g., a gene for albinism can mask color genes)
  24. 24Sex-linked trait
    A trait determined by genes located on sex chromosomes (usually the X chromosome)
  25. 25Why are X-linked recessive disorders more common in males?
    Males have only one X chromosome (XY), so a single recessive allele will be expressed; females need two copies (XX) to show the disorder
  26. 26Typical notation for an X-linked trait
    X^A for dominant allele, X^a for recessive allele; males are X^A Y or X^a Y; females are X^A X^A, X^A X^a, or X^a X^a
  27. 27Examples of X-linked recessive disorders
    Color blindness, hemophilia, and Duchenne muscular dystrophy
  28. 28Carrier
    An individual who is heterozygous for a recessive trait (doesn't show the trait but can pass it to offspring)
  29. 29Polygenic inheritance
    When multiple genes contribute to a single trait, producing a continuous range of phenotypes (e.g., human height, skin color)
  30. 30Pedigree chart
    A diagram that shows the inheritance pattern of a trait through multiple generations of a family

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