Heredity: 60 flashcards
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1. What is heredity?
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Heredity is the transmission of characters from parents to offspring.
2. What are variations?
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Variations are differences in characteristics among individuals of a species.
3. Why are variations important for a species?
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Variations help a species adapt to environmental changes and survive.
4. What is a gene?
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A gene is a segment of DNA that codes for a specific protein or trait.
5. What is an allele?
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An allele is one of two or more alternative forms of a gene.
6. Define dominant trait.
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A dominant trait is a trait that is expressed even when only one copy of the allele is present.
7. Define recessive trait.
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A recessive trait is a trait that is expressed only when two copies of the recessive allele are present.
8. What is genotype?
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Genotype is the genetic makeup of an organism, e.g., TT, Tt, or tt.
9. What is phenotype?
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Phenotype is the observable physical or biochemical characteristics of an organism.
10. State Mendel's Law of Dominance.
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In a cross between two pure breeding contrasting traits, the F1 generation shows only the dominant trait, while the recessive trait reappears in the F2 generation.
11. State Mendel's Law of Segregation.
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Alleles segregate during gamete formation, so each gamete receives only one allele of a gene.
12. What is the phenotypic ratio in the F2 generation of a monohybrid cross?
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3:1 (dominant:recessive).
13. What is the genotypic ratio in the F2 generation of a monohybrid cross?
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1:2:1 (homozygous dominant:heterozygous:homozygous recessive).
14. In a monohybrid cross between pure tall (TT) and pure dwarf (tt) pea plants, what is the phenotype of the F1 generation?
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All tall (Tt).
15. What is a dihybrid cross?
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A cross between two individuals that differ in two pairs of contrasting traits.
16. What is the phenotypic ratio in the F2 generation of a dihybrid cross?
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9:3:3:1.
17. What is sex determination in humans?
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Sex in humans is determined by the sex chromosomes: females have XX and males have XY.
18. Who determines the sex of a child in humans?
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The father determines the sex of the child because the mother always contributes an X chromosome, while the father can contribute either an X or a Y.
19. What are the chances of a boy or a girl in humans?
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50% chance of a boy and 50% chance of a girl.
20. What is evolution?
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Evolution is the gradual change in the characteristics of a population over generations.
21. What is a fossil?
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A fossil is the preserved remains or traces of ancient organisms.
22. How do fossils provide evidence for evolution?
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Fossils show the sequence of organisms over time and help trace evolutionary relationships.
23. What is homologous organs?
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Homologous organs are organs that have the same basic structure but perform different functions, indicating common ancestry.
24. Give an example of homologous organs.
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Forelimbs of humans, birds, and whales.
25. What are analogous organs?
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Analogous organs are organs that perform similar functions but have different structures, indicating convergent evolution.
26. Give an example of analogous organs.
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Wings of insects and birds.
27. What is natural selection?
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Natural selection is the process by which individuals with favorable traits are more likely to survive and reproduce.
28. Who proposed the theory of natural selection?
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Charles Darwin.
29. What is genetic drift?
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Genetic drift is a random change in allele frequencies in a small population.
30. What is speciation?
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Speciation is the formation of new species from existing ones.
31. What is a species?
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A species is a group of organisms that can interbreed and produce fertile offspring.
32. What is the role of variation in evolution?
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Variations provide the raw material for evolution by natural selection.
33. What is the significance of DNA in heredity?
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DNA carries genetic information and is responsible for the transmission of traits from parents to offspring.
34. What is a monohybrid cross?
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A cross between two individuals that differ in one pair of contrasting traits.
35. What is the F1 generation?
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The first filial generation, the offspring of the parental generation.
36. What is the F2 generation?
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The second filial generation, the offspring of the F1 generation.
37. What is a Punnett square?
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A Punnett square is a diagram used to predict the genotypes of offspring from a cross.
38. What is the genotype of a tall pea plant if it is heterozygous?
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Tt.
39. What is the genotype of a dwarf pea plant?
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tt.
40. What is the phenotypic ratio of a cross between two heterozygous tall pea plants (Tt x Tt)?
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3 tall : 1 dwarf.
41. What is the genotypic ratio of a cross between two heterozygous tall pea plants (Tt x Tt)?
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1 TT : 2 Tt : 1 tt.
42. What is the probability of a dwarf offspring from a cross between two heterozygous tall pea plants (Tt x Tt)?
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1/4 or 25%.
43. What is the probability of a tall offspring from a cross between two heterozygous tall pea plants (Tt x Tt)?
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3/4 or 75%.
44. What is the genotype of the F1 generation in a cross between pure tall (TT) and pure dwarf (tt) pea plants?
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Tt (heterozygous tall).
45. What is the phenotype of the F1 generation in a cross between pure tall (TT) and pure dwarf (tt) pea plants?
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All tall.
46. What is the genotype of the F2 generation in a monohybrid cross between pure tall and pure dwarf pea plants?
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1 TT : 2 Tt : 1 tt.
47. What is the phenotype of the F2 generation in a monohybrid cross between pure tall and pure dwarf pea plants?
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3 tall : 1 dwarf.
48. What is the law of independent assortment?
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The law states that alleles of different genes assort independently of one another during gamete formation.
49. What is the significance of Mendel's experiments?
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Mendel's experiments established the fundamental laws of inheritance.
50. What is the difference between acquired and inherited traits?
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Acquired traits are acquired during lifetime and not passed to offspring; inherited traits are genetically passed from parents to offspring.
51. Why are acquired traits not inherited?
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Acquired traits do not cause changes in the DNA of germ cells, so they are not passed to the next generation.
52. What is the role of germ cells in inheritance?
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Germ cells carry genetic information from parents to offspring.
53. What is the significance of sex chromosomes?
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Sex chromosomes determine the sex of an individual.
54. What are the sex chromosomes in human males?
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XY.
55. What are the sex chromosomes in human females?
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XX.
56. What is the probability of a child being a boy if the father contributes a Y chromosome?
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100% (if the father contributes Y, the child will be a boy).
57. What is the probability of a child being a girl if the father contributes an X chromosome?
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100% (if the father contributes X, the child will be a girl).
58. What is the evolutionary significance of homologous organs?
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Homologous organs indicate common ancestry and divergent evolution.
59. What is the evolutionary significance of analogous organs?
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Analogous organs indicate convergent evolution due to similar functions.
60. What is the role of fossils in studying evolution?
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Fossils provide direct evidence of past organisms and help in tracing evolutionary history.
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