Types of Cell Division Mitosis - Body cell replication Meiosis - Sex cell replication

1. Types of Cell Division Mitosis - Body cell replication Meiosis - Sex cell replication

2. Meiosis - Sex cell replication What is sex?

3. Sexual reproduction: The production of offspring whose genetic constitution is a mixture of that of two potentially genetically different gametes. -Futuyma, p. 771

4. Sexual reproduction in diploid organisms: -Chromosomes come in pairs

5. Sexual reproduction in diploid organisms: -Chromosomes come in pairs -One member of each pair comes from each parent

6. Sexual reproduction in diploid organisms: -Chromosomes come in pairs -One member of each pair comes from each parent - Cells that will turn into gametes are sequestered early in development - minimizing replication.

7. Sexual reproduction in diploid organisms: -Chromosomes come in pairs -One member of each pair comes from each parent - Cells that will turn into gametes are sequestered early in development - minimizing replication. -At sexual maturity, gamete production begins.

8. Sexual reproduction in diploid organisms: -Chromosomes come in pairs -One member of each pair comes from each parent - Cells that will turn into gametes are sequestered early in development - minimizing replication. -At sexual maturity, gamete production begins. -Gametes are haploid. Their union produces a new diploid organism.

9. Sexual reproduction in diploid organisms: -Chromosomes come in pairs -One member of each pair comes from each parent - Cells that will turn into gametes are sequestered early in development - minimizing replication. -At sexual maturity, gamete production begins. -Gametes are haploid. Their union produces a new diploid organism. -Non-chromosomal cell matter comes from the mother.

10. Barbara McClintock

11. Barbara McClintock Nobel Prize: 1983 Discoverer of transposition & recombination

12. Meiosis Sex cell division, aka gametogenesis During meiosis, chromosome pairs double, then the center two chromatids recombine, or “cross-over”

13. Meiosis - Sex cell division, aka gametogenesis Sampling error 3 chromosomes = 64 combinations but only 1 to 4 gametes

14. Mutation- An error in replication of a nucleotide sequence, or any other alteration of the genome that is not manifested as reciprocal recombination. Mutation is the ultimate source of all hereditary variation

15. Basic types of mutations- Point mutation Insertion/Duplication Deletion Translocation Inversion Fis Horizontal transfer sion /Fusion

16. Point mutation -An error in replication of a nucleotide sequence. For example, a daughter cell might end up with a guanine molecule where the parent cell had a adenine molecule at that same position in its DNA sequence. G

17. Point mutation -An error in replication of a nucleotide sequence. Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet For example, a daughter cell might end up with a guanine molecule where the parent cell had a adenine molecule at that same position in its DNA sequence. G

18. Point mutation -An error in replication of a nucleotide sequence. Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet Why would the position matter? G

19. Point mutation -An error in replication of a nucleotide sequence. Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet Why would the position matter? Because the DNA code is redundant. G

20. Point mutation -An error in replication of a nucleotide sequence. Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet Why would the position matter? Because the DNA code is redundant. DNA nucleotide triplets code for amino acids. G

21. Point mutation -An error in replication of a nucleotide sequence. But there are 64 possible triplet combinations (“codons”) yet only 20 amino acids. Why would the position matter? Because the DNA code is redundant. DNA nucleotide triplets code for amino acids. G

22. Point mutation -An error in replication of a nucleotide sequence. But there are 64 possible triplet combinations (“codons”) yet only 20 amino acids. Some combinations are synonymous. Why would the position matter? Because the DNA code is redundant. DNA nucleotide triplets code for amino acids. G

23. Point mutation -An error in replication of a nucleotide sequence. But there are 64 possible triplet combinations (“codons”) yet only 20 amino acids. Some combinations are synonymous. For example CCC codes for the amino acid proline. But so do CCA, CCT, and CCG fmi see Futuyma, p. 45 G

24. Insertions & Deletions During meiosis, chromosome pairs double, then the center two chromatids recombine, or “cross-over”

25. Insertions & Deletions Sometimes, the recombination is not perfectly reciprocal, producing “unequal crossing-over” Deletion Insertion

26. From Futuyma

27. Translocation Sometimes, chromosomal material is exchanged among non-homologous chromosomes. Also, copies of certain nucleotide sequences can be transposed --inserted on other chromosomes. Transposition events sometimes occur in plants, eg flax, during times of ecological stress. It is a quick way to disrupt the phenotype, giving rise to new morphologies and physiologies in one generation, thus allowing rapid evolution of new adaptations. Equal crossing over Unequal crossing over Deletion Duplication or Equal crossing over with Translocation

28. Inversion Sometimes, a bit of chromosomal material is excised during recombination and ends up back in place, but upside down.

29. Doublets Game post from Carl Zimmer’s blog: www.corante.com/loom/ The challenge of a doublet is to turn one word into another. You are allowed to change one letter at a time, but each change must produce a real word. Here's a doublet that suits a post on evolution: Change APE to MAN. APE APT OPT OAT MAT MAN

30. Doublets Game post from Carl Zimmer’s blog: www.corante.com/loom Now imagine that having solved the APE-to-MAN puzzle, you tell a friend about your triumph. Your friend scoffs. "That's ridiculous," he says. "I don't believe you've found a missing link between APE and MAN. It doesn't exist." You furrow your brow. "Wait," you say. "No, I think maybe you didn't hear how the puzzle works--" "I mean, what comes in between?" "Well, there's APT, and then--." "APT? Please! That's nothing like MAN. They don't have a single letter in common. It's just a completely separate word on its own." "But then there's OPT--" "OPT? Are you kidding me? That's just as irrelevant. You can't just go from APE to MAN through OPT." "But what about MAT? That's a lot like MAN." "Sure," your friend says, rolling his eyes. "But what on Earth does it have to do with APE?"

31. Doublets Game MAN RAN RAM RIM RIB ROB > translocation adds MAN ROB MAN > deletion takes away the B & the space ROMAN WOMAN

32. Structure of the genome

33. Structure of the genome -integrated system of modules of various kinds

34. Structure of the genome -integrated system of modules of various kinds -10,000-100,000 genes in most metazoans

35. Structure of the genome -integrated system of modules of various kinds -10,000-100,000 genes in most metazoans -90% or more is non-genic & “junk DNA”

36. Structure of the genome -integrated system of modules of various kinds -10,000-100,000 genes in most metazoans -90% or more is non-genic & “junk DNA” -repetitive sequence

37. Structure of the genome -integrated system of modules of various kinds -10,000-100,000 genes in most metazoans -90% or more is non-genic & “junk DNA” -repetitive sequence -highly repetitive satellite DNA eg. alu repeats have been inserted all over the genome of Drosophila

38. Structure of the genome -integrated system of modules of various kinds -10,000-100,000 genes in most metazoans -90% or more is non-genic & “junk DNA” -repetitive sequence -highly repetitive satellite DNA eg. alu repeats have been inserted all over the genome of Drosophila -introns

39. DNA that codes for protein is arranged within the gene in a series of exons. The non-coding introns are spliced out during transcription and translation.

40. A gene generally forms part of a gene family, a group of genes descended from an ancestral gene. Gene families evolve primarily via insertions. When a second copy of a functional gene is inserted downstream (or sometimes on another chromosome), the second copy (and often the original as well) is free to accumulate additional mutations without compromising gene product volume or quality. Gene families often have numerous member genes which specialise in producing subtly different forms of the gene product at different stages of organismal development (eg. fetal hemoglobin)

41. Complex additive loci model -Most traits arise from many genes working together Locus 1 2 3 4 5 Alleles (versions) equals any Combination

42. Locus 1 2 3 4 5 Alleles (versions) nearly translucent skin Virtually no one would have all 10 of the same allele Locus 1 2 3 4 5 Alleles (versions) nearly black skin

43. So, in our hypothetical example: Locus 1 2 3 4 5 Alleles (versions) So these two very different gene combinations both produce the same skin tone, but share no alleles

44. Locus 1 2 3 4 5 Alleles (versions) nearly translucent skin Person 1 1 2 3 4 5 Person 2 medium tone skin Each shares more alleles with the translucent person than with each other