Mutations

1. Suppose that eye gene is sex linked, and wing is autosomal. A red eyed female, long wing is crossed to a male with yellow eyes, vestigial wings. Diagram the cross if the female is heterozygous for both traits.

2. -Gene Mutation- Chromosome Mutation Mutations Compiled by Siti Sarah Jumali Room 14, Level 3 06-4832123

3. 5 Ways of Creating Genetic Diversity in Bacteria A. Mutations B. Transformation C. Conjugation D. Transposition E. Transduction

4. MUTATIONS Mutation– any changes in the DNA sequence that affects genetic information and the appearance of offspring. • Occur naturally at low level (also known as spontaneous mutations), during DNA replication ; or • Caused by UV Light, X-Rays, mutagens error during DNA replication by the effects of chemical agents called mutagens; or by physical agents like radiation.

5. Types of Mutations • Gene mutation – a mutation that occurs in a single gene and affects one trait. Eg: Eye color, Sickle cell Anemia, Hemophilia • Chromosome mutation – a mutation that occurs in many genes and affects many traits at once. Eg: Down Syndrome (an extra 21st chromosome) • Genome mutation – mutation on ploidy

6. 1. GENE MUTATIONS

7. Gene Mutation • Involve insertion or removal of 1 or more base pairs • Gene mutation is a change in single base pair within DNA sequences

8. Effects of Gene Mutations Most mutations are neutral - they have no effect on the polypeptide. Some mutations result in a less active product; Less often an inactive product; Very few mutations are beneficial.

9. Effects of Gene Mutations cont’d • Affects molecular changes in the DNA sequence of a gene • Alter the coding sequence within a gene • Causes permanent change in DNA sequence

10. Body (Somatic) and Gamete (Germ)mutation Body cell mutations can cause cancer. - only the individual is affected. Gamete cell mutations affect the egg and the sperm. - all offspring of the individual can be affected. In multicellular organisms (plants or animals) mutations may occur in the somatic cells of the organism. Somatic cells are the cells involved in growth and repair and maintenance of the organism. A mutation in these cells may lead to cancer and certain of chromosomal mutations may be involved in aging. Other mutations happen in the germ cells and these mutations  may appear in the gametes and then in the offspring produced by sexual reproduction.  These sorts of mutations are called germ cell mutations.

11. Types of Mutations • Point mutations - a one base change in DNA. • Frame Shift Mutations - the addition or deletion of 1 or more bases. These are due to powerful mutagens; chemical or physical.

12. DNA (antisense strand) mRNA Polypeptide Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons ↓ Pro-Glu-Glu-Cys-Gly Amino acids Normally.. The antisense strand is the DNA strand which acts as the template for mRNA transcription © 2010 Paul Billiet ODWS

13. The amino acid chart

14. The amino acid chart with diseases

15. 1. Point Mutation 3 types: a. silent mutation - single base substitution in the 3rd base nucleotide position of a codon. This results in NO change in amino acid. Note that the first 2 letters of the genetic code are the most critical. b. missense mutation - single base substitution in 1st or 2nd base nucleotide position. This results in changed amino acid. • nonsense mutation - single base substitutions that yield a stop codon. Note: there are 3 nonsense codons in the genetic code = NO PROTEIN

16. Silent or neutral mutation • Silent mutation can result in enhancing new protein, but all other mutations reduce the function

17. Silent mutation

18. Missense mutation

19. Nonsense mutation

21. 2. Frameshift Mutations Additions Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons ↓ Pro-Glu-Glu-Cys-Gly Amino acids Addition mutation GGTGCTCCTCACGCCA ↓ CCACGAGGAGUGCGGU ↓ Pro-Arg-Gly-Val-Arg © 2010 Paul Billiet ODWS

22. 2. Frameshift Mutations cont’s Deletion Deletion mutation GGTC/CCTCACGCCA ↓ CCAGGGAGUGCGGU ↓ Pro-Gly-Ser-Ala-Val Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons ↓ Pro-Glu-Glu-Cys-Gly Amino acids © 2010 Paul Billiet ODWS

23. Frameshift mutation

24. Frameshiftmutation

27. Mutations Can Be Neutral • They may have little or no effect on the survival of an organism or on its ability to reproduce. • They may result in the same kind of organism - meaning that the change still tells the cell to do what it should, so there is no difference. • It is estimated that the average human has 50-100 mutations within their DNA - most (if not all) are neutral or beneficial

28. Mutations Can Be Beneficial • Bacterial resistance to antibiotics • Insecticide resistance in bugs • Rapid mutation rates in virus’s proteins allowing them to adapt to new “hosts”

29. Mutations Can Be Beneficial • In humans, it can be a different set of circumstances… Here’s an example: • Sickle-Cell Anemia is a genetic disorder in which there is a defect in the structure of red blood cells. This leads to fatigue and anemia when not treated. • However, it has been found that people who are carriers for Sickle-Cell Anemia also has some genetic protection against another disease, malaria.

30. Mutations Can Be Beneficial • In evolutionary studies, scientists have connected the presence of a brain chemical microcephalin (a proposed mutation) with the human’s development of art, music, and complex tool-making practices • This same research indicates that the human brain is still evolving and becoming more and more capable of more complex tasks • Some humans have been found to have mutations that protect them from other diseases, such as AIDS

31. Compare the following types of base-substitution mutation.

32. Self-Quiz • Describe the effects of sickle cell disease on sufferers in terms of: • Hemoglobin production • Symptoms and mortality • Identify parts of the world where a single sickle cell (Hbs) allele could be beneficial

33. 2. CHROMOSOME MUTATION

34. Chromosome Mutation Chromosome structure become influenced by • Change in amount of genetic information in chromosome because of • Deletion • Duplication • Similar amount of genetic information but the materials are rearranged • Inversion • Translocation

35. Chromosome Mutation cont’d • Deletion • Loss of chromosomal segment • Duplication • Repetition of chromosomal segment • Inversion • A change in the direction of the genetic material along a single chromosome • Translocation • A segment of one chromosome becomes attached to a different chromosome • Simple translocation • One way transfer • Reciprocal translocation • Two way transfer

37. Duplications • Insertion of an extra copy of a region of  a chromosome into a neighboring position. • Zygotes produced from gametes involving duplications are often viable and may or may not have any serious problems. • Various sorts of duplications are  related to color vision conditions many of which are quite subtle in their effects e.g certain anemias involving abnormal hemoglobins  called the thalassemias.

38. Deletions • Deletions result when a gene is mistakenly removed from a chromosome, as a result of  unequal crossing over. • Often zygotes produced by gametes  involving deletions are not viable since they do not have the full compliment of genes.

39. Inversions • Inversions happen when a whole region of genes on a chromosome gets flipped around . • 2 types of inversions. • paracentric inversions the centromere is not included in the inversion. • pericentric inversions, the centromere is involved in the inversion. Both these types of inversions lead to abnormalities in crossing over and meiosis resulting in some chromosomes which are not viable, while others are viable but have new combinations of genes. These sorts of  inversions are thus important in reshuffling genes on a chromosome.

40. Translocations • Movement of part of a chromosome to another part of the genome. • May happen with the same chromosome. • translocation is an intrachromosome translocation. Other translocations involve transfer of a region of a chromosome to a non homologous chromosome. For example certain types of Down syndrome involve translocations between chromosome 14 and chromosome 21. This type of  translocation between non homologous chromosomes is called an inter-chromosomal translocation.

41. Base substitution changes is in pair • 2 types of changes • Transition (within same group AT and GC) • Transversion (between 2 groups)

42. Transition vsTransversion

43. Inversion mutation Inversion mutations, also, only affect a small part of the gene Inversion mutation GGTCCTCTCACGCCA ↓ CCAGGAGAGUGCGGU ↓ Pro-Gly-Glu-Cys-Gly Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons ↓ Pro-Glu-Glu-Cys-Gly Amino acids © 2010 Paul Billiet ODWS

44. GENOME MUTATION

45. Changes in chromosome number • Aneuploidy • Polyploidy • Autopolyploidy • Allopolyploidy

46. Aneuploidy • Normally 2N ends up either with extra copies of homologous chromosomes or fewer than the normal diploid number. • Happens when homologous chromosomes fail to segregate properly during meiosis (non disjunction). • Monosomy (2n-1) in which the diploid  individual has only one member of a  certain homologous chromosome. • The other common type of aneuploidy is called trisomy (2n+1) because the individual has three copies of the chromosome.Aneuploidy leads to a number of syndromes in humans. For example trisomy 21 leads to Down syndrome, characterized by mental retardation and other abnormalities. Aneuploidy involving the sex chromosomes is common. XYY males are normal but XXY males and XXXY males have a syndrome called Klinefelter syndrome. These males are often actually intersexed or hermaphroditic with partially developed sexual organs of both genders. These individuals are sterile and are often subjected to hormones and surgery to bring them into conformance with social gender roles.

47. Polyploidy • 3N or sets of chromosomes in a nucleus.   • Can happen because of a failure of the spindle fibers in mitossis or meiosis to segregate chromosomes into separate groups. • Many organisms have specialized polyploid tissues even organisms we typically consider as diploid.   • For example in plants a so called double fertilization leads to the genesis of a diploid zygote from the union of two gametes produced by the haploid gametophytes, but also a specialized triploid tissue (3N) called endosperm. This tissue is produced when a male gamete fertilizes special diplid tissue from the flower. In mammals, cells of the liver are typically polyploid. • Believed to be an important mechanism in the development of new species and a common pattern in plants is to find populations of two species both of which might be diploid. Where the species overlap a series of localized polyploid populations are often found. These polyploid populations are often effectively reproductively isolated from the parent species and thus can be considered species in their own right. • E,g plant species and some fish and amphibians; • domestic wheat is hexaploid(6N). ‘ • Seedless' plants are usually triploid (3N). Consider a  tetraploid plant (4N). The gametes of this plant are going to be effectively diploid (2N) and if they are fertilized by a normal haploid gamete (N), the result is a triploid plant. Since triploid plants have an odd number of chromosomes, typically the gametes have variable number of chromosomes are usually not viable. This is why triploid plants are used to produce seedless plants.  Since most plants can self fertilize, the tetraploid plant can breed with itself and produce viable tetraploid populations.

48. Autopolyploidy • Autopolyploidy is polyploidy in which all the chromsomes originate from the same diploid parent species. Domestic banana and various seedless plants are often triploid autoployploids.

49. Allopolypoidy • Allopolypoidy is a polyploidy in which the sets of chromosomes are from differrent species. Usually hybrid plants (N1 + N2) from such crosses are not fertile since proper pairing of chromsomes does not occur in meiosis. But sometimes the the chromosome number spontaneously doubles leading to tissues with 2N1 + 2N2. If this tissue is germ tissue, tissue that can give rize to haploid tissue via meisosis the result can be gametes with the N1 + N2 chromosome complement. When two of these gametes fuse, the result is an allopolyploid plant with a viable chromosome complement (2N1 + 2N2).

50. Factors that causes mutation • Chemical mutagens - used in research to study mutagenesis. There are 3 kinds of chemical mutagens. 1. Alkylating agents. Adds alkyl group, CnH(2n+1) Eg. formalin, nitrogen, mustard, and ethylene oxide (reacts with G changing it to bind with T). 2. Base analogs. Mimics a nitrogen base. Ex. AZT is a modified sugar that substitutes for T. Eg. 5 - bromouracil binds with A or G. 3. Intercalating agents. Inserts into DNA and pushes bases apart. Eg. AFLATOXIN - a chemical produced by peanut and grain molds. The mold is Aspergillusflavus (fungus).