Explain Genetic Causes of Variation - Biology

1. What is the primary genetic source of new alleles in a population?

   Mutation. Creates entirely new alleles that didn't exist before.

2. Which type of mutation generally is not inherited because it occurs in body cells?

   Somatic mutation. Only affects the individual, not their offspring.

3. Which point mutation replaces one nucleotide with another?

   Substitution. One of three types of point mutations affecting single bases.

4. Identify the mutation type: one nucleotide is removed from a coding sequence, shifting codons.

   Frameshift due to deletion. Loss of nucleotide disrupts reading frame downstream.

5. What is the number of possible chromosome combinations per gamete from independent assortment for $n=4$?

   $2^4=16$ combinations. Formula $2^n$ where $n$ is number of chromosome pairs.

6. What is random fertilization as a source of genetic variation?

   Any sperm can fertilize any egg, creating new genotypes. Combines genetic material from two different parents.

7. Identify the genetic mechanism: a DNA base is replaced by a different base at one position.

   Substitution (point mutation). Single nucleotide change at one specific position.

8. Which process increases variation by mixing maternal and paternal chromosomes into gametes?

   Independent assortment. Distributes parental chromosomes randomly among offspring.

9. Identify the genetic mechanism: alleles enter a population when individuals migrate and reproduce.

   Gene flow. Movement of individuals introduces new alleles.

10. Which genetic process can introduce alleles from one population into another?

    Gene flow. Migration connects previously isolated gene pools.

11. Which mutation creates a premature stop codon?

    Nonsense mutation. Truncates protein synthesis early, often affecting function.

12. What is a locus?

    A gene's specific location on a chromosome. Each gene has a fixed chromosomal address.

13. Which chromosomal mutation reverses a segment within a chromosome?

    Inversion. Flips gene order but keeps genes on same chromosome.

14. During which meiotic phase does crossing over typically occur?

    Prophase I. When chromosomes pair and exchange genetic material.

15. Which meiotic event creates new allele combinations by exchanging DNA between homologs?

    Crossing over (homologous recombination). Occurs between paired homologous chromosomes in meiosis.

16. What is a gene pool?

    All alleles present in a population. Contains all possible genetic variants in the group.

17. What is a mutagen?

    An agent that increases the rate of DNA mutation. Environmental factors like radiation or chemicals cause mutations.

18. Which chromosomal mutation repeats a segment of a chromosome?

    Duplication. Creates extra copies of genes within a chromosome.

19. Which process produces gametes and increases genetic variation in sexually reproducing organisms?

    Meiosis. Combines crossing over and independent assortment for variation.

20. Which meiotic stage directly produces independent assortment of chromosomes?

    Metaphase I. When homologous pairs align randomly at cell equator.

21. What is aneuploidy?

    An abnormal number of specific chromosomes. Can result from nondisjunction during meiosis.

22. Identify the genetic mechanism: homologous chromosomes exchange segments during meiosis.

    Crossing over. Physical exchange of DNA between paired chromosomes.

23. Which source of variation is described: new alleles are created rather than reshuffled?

    Mutation. Only mutation introduces completely novel genetic material.

24. What is an allele?

    An alternative form of a gene at a specific locus. Different versions of the same gene exist.

25. What is independent assortment?

    Random orientation of homologous pairs in meiosis I. Each homolog can go to either pole during division.

26. What is heterozygosity in genetics?

    Having two different alleles at a locus. Provides maximum genetic diversity at that locus.

27. Which mutation changes an amino acid in a protein sequence?

    Missense mutation. Results in a different amino acid in the protein product.

28. Which chromosomal mutation moves a segment to a nonhomologous chromosome?

    Translocation. Transfers genetic material between different chromosomes.

29. What is the genetic cause of variation in asexual reproduction compared with sexual reproduction?

    Mainly mutation; little or no recombination. Sexual reproduction adds recombination for greater variation.

30. What is homozygosity in genetics?

    Having two identical alleles at a locus. Reduces genetic diversity at that specific locus.

31. What is a frameshift mutation?

    Insertion or deletion that shifts the reading frame. Changes how codons are read downstream from mutation site.

32. What is the difference between mutation and recombination as sources of variation?

    Mutation creates new alleles; recombination reshuffles alleles. Mutation adds novelty; recombination rearranges existing material.

33. Identify the mutation type: a codon becomes a stop codon, shortening the polypeptide.

    Nonsense mutation. Point mutation creates premature termination signal.

34. Which mutation changes a codon but not the amino acid it codes for?

    Silent mutation. Due to genetic code redundancy, protein remains unchanged.

35. What is genetic recombination?

    Formation of new allele combinations in offspring. Shuffles existing alleles into new arrangements.

36. Which process increases variation by creating new combinations of alleles on the same chromosome?

    Crossing over. Links alleles that were previously on different homologs.

37. What is a mutation?

    A heritable change in DNA nucleotide sequence. Can be passed to offspring and affect protein function.

38. Which broad category of mutations affects an entire chromosome segment?

    Chromosomal mutation (structural rearrangement). Involves large-scale DNA changes beyond single nucleotides.

39. Identify the genetic mechanism: chromosomes line up randomly in meiosis I, forming varied gametes.

    Independent assortment. Random chromosome orientation creates genetic diversity.

40. Which two meiosis-related mechanisms create recombination without creating new alleles?

    Crossing over and independent assortment. Both processes occur during meiosis I.

41. Which mutation adds one or more nucleotides to a DNA sequence?

    Insertion. Adds extra genetic material to the DNA strand.

42. What is gene flow?

    Movement of alleles between populations via migration. Increases allelic diversity between connected populations.

43. Which mutation removes one or more nucleotides from a DNA sequence?

    Deletion. Removes genetic material from the DNA sequence.

44. Which source of variation is described: existing alleles are rearranged into new genotypes?

    Recombination in sexual reproduction. Mixes existing alleles without creating new ones.

45. What is the number of possible chromosome combinations per gamete from independent assortment for $n=3$?

    $2^3=8$ combinations. Each chromosome can orient independently: $2^n$ possibilities.

46. What is genetic variation within a population?

    Differences in alleles and genotypes among individuals. Describes the diversity of genetic forms within a species.

47. What is polyploidy?

    More than two complete sets of chromosomes. Often results from errors in meiosis or mitosis.

48. Which term describes a new allele arising in a gamete that can be inherited by offspring?

    Germ-line mutation. Can be passed to next generation through reproduction.

49. What is nondisjunction in meiosis?

    Failure of homologs or sister chromatids to separate. Results in gametes with incorrect chromosome numbers.

50. Which type of mutation changes a single nucleotide in DNA?

    Point mutation. Affects only one DNA base position at a time.

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