Genetic variation is produced within populations through mutations, sexual reproduction, and meiosis. Mutations introduce new alleles and variation when genes change through single-base mutations or chromosomal rearrangements. Sexual reproduction and meiosis increase variation by recombining alleles through crossing over during prophase I to form new combinations not seen in either parent. This genetic variation provides the raw material for natural selection to act upon.

1. How is variation produced in
a population?
Jennifer Oh (SL)

2. What is genetic variation?

3. What is genetic variation?
Variation in alleles of
genes

4. What is genetic variation?
Variation in alleles of
genes
Occurs within and
among populations

5. What is genetic variation?
Variation in alleles of
genes
Occurs within and
among populations
The “raw material” of
natural selection

6. Sources of Genetic Variation

7. Sources of Genetic Variation
Mutations

8. Sources of Genetic Variation
Mutations
Gene mutations

9. Sources of Genetic Variation
Mutations
Gene mutations
Chromosome
mutations

10. Sources of Genetic Variation
Mutations
Gene mutations
Chromosome
mutations
Sexual Reproduction

11. Sources of Genetic Variation
Mutations
Gene mutations
Chromosome
mutations
Sexual Reproduction
Recombination

12. Sources of Genetic Variation
Mutations
Gene mutations
Chromosome
mutations
Sexual Reproduction
Recombination
Mate selection

13. Assessment Statements
These are the assessment statements that
deal with this topic:

14. Assessment Statements
These are the assessment statements that
deal with this topic:
4.1.2 Define gene, allele, and genome
4.1.3 Define gene mutation
State that meiosis is a reduction division of a diploid nucleus
4.2.1 to form haploid nuclei
Outline the process of meiosis, including pairing of
4.2.3 homologous chromosomes and crossing over, followed by t wo
divisions, which results in four haploid cells
Define genotype, phenotype, dominant allele, recessive allele,
4.3.1 codominant alleles, locus, homozygous, heterozygous, carrier
and test cross

15. Basic Vocabulary

16. Basic Vocabulary
Before diving into the details of genetic
variation, here are some basic terms that you
need to know for this topic.

17. Basic Vocabulary
Before diving into the details of genetic
variation, here are some basic terms that you
need to know for this topic.
From assessment statement 4.1.2

18. Basic Vocabulary
Before diving into the details of genetic
variation, here are some basic terms that you
need to know for this topic.
From assessment statement 4.1.2
Gene, Allele, Genome

19. Basic Vocabulary
Before diving into the details of genetic
variation, here are some basic terms that you
need to know for this topic.
From assessment statement 4.1.2
Gene, Allele, Genome
From assessment statement 4.3.1

20. Basic Vocabulary
Before diving into the details of genetic
variation, here are some basic terms that you
need to know for this topic.
From assessment statement 4.1.2
Gene, Allele, Genome
From assessment statement 4.3.1
Genotype, phenotype

21. 4.1.2 Vocab

22. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic

23. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic

24. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic

25. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic
Allele - one specific form of a gene, differing
from other alleles by one or a few bases only
and occupying the same gene locus as other
alleles of the gene

26. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic
Allele - one specific form of a gene, differing
from other alleles by one or a few bases only
and occupying the same gene locus as other
alleles of the gene

27. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic
Allele - one specific form of a gene, differing
from other alleles by one or a few bases only
and occupying the same gene locus as other
alleles of the gene

28. 4.1.2 Vocab
Gene - a heritable factor that controls a
specific characteristic
Allele - one specific form of a gene, differing
from other alleles by one or a few bases only
and occupying the same gene locus as other
alleles of the gene
Genome - the whole genetic information of
an organism

29. 4.3.1 Vocab

30. 4.3.1 Vocab
Genotype - the alleles of an organism;
determines the genetic potential

31. 4.3.1 Vocab
Genotype - the alleles of an organism;
determines the genetic potential
Phenotype - the characteristics of an
organism

32. Mutation

33. Mutation
Mutations are the source of all new genetic information

34. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial

35. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial
Can be accumulated over many generations

36. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial
Can be accumulated over many generations
Gene mutation (4.1.3)

37. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial
Can be accumulated over many generations
Gene mutation (4.1.3)
Change in the base sequence of an allele

38. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial
Can be accumulated over many generations
Gene mutation (4.1.3)
Change in the base sequence of an allele
Chromosome mutation

39. Mutation
Mutations are the source of all new genetic information
Not always harmful, some are neutral or beneficial
Can be accumulated over many generations
Gene mutation (4.1.3)
Change in the base sequence of an allele
Chromosome mutation
Pieces of chromosomes may be rearranged during
meiosis

40. Mutation

41. Sexual Reproduction

42. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations

43. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations
Crossing over - Recombination

44. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations
Crossing over - Recombination
Pieces of chromosome are often exchanged with a
chromosome’s homologue

45. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations
Crossing over - Recombination
Pieces of chromosome are often exchanged with a
chromosome’s homologue
Increases shuffling of allele combinations

46. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations
Crossing over - Recombination
Pieces of chromosome are often exchanged with a
chromosome’s homologue
Increases shuffling of allele combinations
Mate Selection

47. Sexual Reproduction
Provides rearrangement and shuffling of the genetic
material into new combinations
Crossing over - Recombination
Pieces of chromosome are often exchanged with a
chromosome’s homologue
Increases shuffling of allele combinations
Mate Selection
Different combinations of genes will come together
in the offspring depending on which t wo parents
mate together

48. Meiosis

49. Meiosis
Meiosis is a reduction division of a diploid nucleus to form
haploid nuclei (4.2.1)

50. Meiosis
Meiosis is a reduction division of a diploid nucleus to form
haploid nuclei (4.2.1)
For this topic, the important part is: crossing over

51. Meiosis
Meiosis is a reduction division of a diploid nucleus to form
haploid nuclei (4.2.1)
For this topic, the important part is: crossing over
At Prophase I, the homologous chromosomes pair up
(synapsis), and segments of the chromosome can be
exchanged

52. Meiosis
Meiosis is a reduction division of a diploid nucleus to form
haploid nuclei (4.2.1)
For this topic, the important part is: crossing over
At Prophase I, the homologous chromosomes pair up
(synapsis), and segments of the chromosome can be
exchanged
Important source of variation for the gene pool of a
population

53. Watch this video!
GREAT video lesson about genetic variation:
http://www.khanacademy.org/video/
variation-in-a-species?playlist=Biology

54. i-Biology Link
4.1 Presentation
http://i-biology.net/?s=4.1
4.2 Presentation
http://i-biology.net/?s=4.2
4.3 Presentation
http://i-biology.net/?s=4.3

55. More exercises
For more exercises on this topic, look at these
pages from the Biozone workbook.
Mutations: p. 197 - 8
Meiosis: p. 185 - 8
Genetic Variation: p. 181 - 2

56. The End!