Chapter 11

1. Chapter 11 Section 3-Genetic Changes

2. I) Mutations • Mutation-def-pg296-any change in the DNA sequence • Mutations can be caused by: • Errors in replication • Errors in transcription • Errors in cell division • External agents

3. B)Mutations in reproductive cells Mutations can affect reproductive cells by changing sequence of nucleotide w/in gene in sperm/ egg cell If mutated sperm/egg cell is part of fertilization will change genetic makeup of offspring Mutation can result in: New trait Non-fxnal protein = structural/fxnal problems in cell/organism Negative affects-At times mutation can result in death of embryo Positive affects-Gene mutation can make an org: faster, stronger or better adapted to survive in their environment I) Mutations

4. C)Mutations in body cells Mutations that occur in body cells don’t get passed on to next generation of organisms only to new body cells Mutation in body cells can cause problems for individual suffering from mutation Ex/ damage to gene  impaired fxn of cell: (1) Stomach loses ability to make acid for digestion (2) Skins loses elasticity Mutations thought to be an imp cause of aging I) Mutations

5. I) Mutations C)Mutations in body cells • Some mutations in DNA in body cells can affect genes that ctrl cell division  can result in cells growing & dividing rapidly & producing cancer • Cancer-def-pg296- disease believed to be caused by changes in the genes that ctrl the cell cycle, the uncontrolled dividing of cells • Results from gene mutation • Ex/Can be caused by: • Too much UV radiation in sunlight  skin cancer

6. II) Gene Mutations A) The effects of point mutations • Point Mutation-def-pg298-a change in a single base pair in DNA • A single mistake (i.e. pt mutation) can affect the entire structure of the entire protein molecule • In general, point mutations less harmful to an org because they only disrupt a single codon

7. II) Gene Mutations B) Frameshift mutations • What would happen if a single base pair was removed? • The reading frame would shift causing new sequence to be transcribed leads to mistakes in the amino acids being made • What is a reading frame? • Reading Frame-a contiguous and non-overlapping set of three-nucleotide codons in DNA or RNA • Frameshift mutation-def-pg299-a mutation in which a single base is added or deleted from DNA is called a frameshift mutation, because it shifts the reading of the codon by one base

8. II) Gene Mutations • Ex/No Deletion = No Frameshift • Original DNA TACGGTTCCCCGGGT • mRNA AUGCCAAGGGGCCCA • A.A. Chain (Protein) • Ex/ Deletion = Frameshift Mutation • Original DNA TACGGTTCCCCGGT • mRNA AUGCCAAGGGGCCA • A.A. Chain (Protein) • How did that one base deletion change the Protein made?

9. III) Chromosomal Alterations • Changes/mutations can occur in genes or chromosomes B) How chromosomal mutations occur? • Parts of chromosomes broken off in mitosis/meiosis • Part of chromosomes are lost in mitosis/meiosis • Parts of chromosomes can break & then be rejoined incorrectly or backwards

10. B) How chromosomal mutations occur? Chromosomal mutations-def-pg.299- mutation that occurs at the chromosomal level resulting in changes in the gene distribution to gametes during meiosis; can be caused when parts of chromosomes break off or rejoined incorrectly. Chromosomal mutation most common in plants but can affect all org C)How homologous chromosomes are affected? Homologous chromosomes-def-paired chromosomes with genes for the same traits arranged in the same order III) Chromosomal Alterations

11. C) How homologous chromosomes are affected? Normally homologous chromosomes pair up-see human karyotype When there is a chromosomal mutation the homologous chromosomes don’t pair correctly  separation of homologous chromosomes doesn’t occur  resulting in some gametes having: extra chromosomes or missing chromosomes Few chromosomal mutations are passed on to next generation b/c zygote usually dies In cases where zygote lives & develops-mature org: Often sterile (incapable of producing offspring) Can have developmental or physical delays or difficulties Don’t survive to reproductive age III) Chromosomal Alterations

12. III) Chromosomal Alterations Normal Human Male Karyotype Human Karyotype-Turner’s Syndrome

13. Fragile X syndrome Progeria Edward’s sydrome Turner’s Syndrome Klinefelter’s Syndrome Marfan Syndrome

14. D)Types of Chromosomal Mutations: They are 4 basic types of chromosomal mutations: ii) Deletions Occurs when part of the chromosome is left out/deleted iii) Insertions Occurs when part of a chromatid breaks off & attaches to sister chromatid The result  duplication of genes on the same chromosome III) Chromosomal Alterations

15. D) Types of Chromosomal Mutations: iv) Inversions Occurs when part of a chromosome breaks off & reattached backwards v) Translocations Occurs when part of one chromosome breaks off a& is added to a different chromosome III) Chromosomal Alterations

16. A) What can cause mutations? i) Spontaneous mutations Mistakes in base pairing during DNA replication ii) Environmental factors  causing mutations Mutagen-def-pg.300-any agent that can cause a change in DNA IV) Causes of Mutations

17. A) What can cause mutations? iii) Types of Mutagens: Radiation-dangerous b/c of the energy they contain can break apart/damage DNA: X-rays Cosmic rays UV light Nuclear radiation Can cause: Deletions Conversion of bases Fusion of bases IV) Causes of Mutations

18. A) What can cause mutations? iii) Types of Mutagens: Chemicals Dioxins Asbestos Benzene Formaldehyde Some of these substances are commonly found in buildings & environment Can cause: Substitution mutations High temperatures IV) Causes of Mutations

19. B) Repairing Mutations Repair mechanisms have evolved to fix mutations that may be caused by: Mutagens Cosmic rays ii) How mutations are repaired? Enzymes proofread DNA Any mistakes (i.e. incorrect nucleotides) are replaced with correct nucleotides Repair mechanisms work well but more exposure to mutagens  more likely mistake will not be corrected Prevent mistakes & limit exposure to mutagens IV) Causes of Mutations