WHAT IS A MUTATION?  A mutation is a permanent change in the DNA sequence of a gene. Alters the amino acid sequence of the protein encoded by the gene. Telematics for N-Cape by C G Oppelt & L Kuun 2

 MISTAKES……… when?  Replication  Crossing over  Meiosis Telematics for N-Cape by C G Oppelt & L Kuun 3

MUTATIONS IN REPLICATION OCCUR THROUGH ONE OF TWO PROCESSES: Mistakes that occur when a cell copies its DNA in preparation for cell division. Telematics for N-Cape by C G Oppelt & L Kuun 4

MUTATIONS FROM ENVIRONMENTAL AGENTS OCCUR THROUGH ONE OF TWO PROCESSES: DNA damage from environmental agents such as ultraviolet light (sunshine), nuclear radiation or certain chemicals EFFECT? A protein that functions differently Telematics for N-Cape by C G Oppelt & L Kuun 5

MUTATIONS – any change in the genetic composition of an organism Telematics for N-Cape by C G Oppelt & L Kuun 6

Like words in a sentence, the DNA sequence of each gene determines the amino acid sequence for the protein it encodes. Thesunwashotbuttheoldmandidnotgethi shat. = GENE The sun was hot but the old man did not get his hat. Telematics for N-Cape by C G Oppelt & L Kuun 7

 The DNA sequence is interpreted in groups of three nucleotide bases, called codons. Each codon specifies a single amino acid in a protein. triplet amino acid Telematics for N-Cape by C G Oppelt & L Kuun 8

SOURCES OF GENOTYPIC VARIATION Meiosis ReproductionMutations Crossing over during phase Prophase Random arrangement of chromosomes during phase Metaphase Fusion of many types of sperm cells and egg cells can produce many different types of offspring Gene mutations Alteration in the sequence of nitrogenous bases on DNA Chromosome mutations Extra chromosomes added  One or more sets of chromosomes are added (a)Lethal: the mutated organism dies and the harmful characteristics are not passed on to the next generation (b) Neutral: has no effect on the structure and functioning of the organism (c) Fixed: advantageous/sometimes the advantageous mutation wipes out all the other alleles controlling the same characteristic within the population Outbreeding Telematics for N-Cape by C G Oppelt & L Kuun 9

Outbreeding  /Gene flow Random assortment  /segregation/ recombination of chromosomes during meiosis in the formation of gametes OR meiosis  Crossing over  Chance/random fertilisation of gametes  /sexual reproduction Mutation  Telematics for N-Cape by C G Oppelt & L Kuun 10

 Mutations Molecular – changes gene: lethal, neutral, established/fixed Cellular – change to karyotype. Telematics for N-Cape by C G Oppelt & L Kuun 11

Telematics for N-Cape by C G Oppelt & L Kuun 12

Telematics for N-Cape by C G Oppelt & L Kuun 13

1. POINT MUTATION Telematics for N-Cape by C G Oppelt & L Kuun 14

Telematics for N-Cape by C G Oppelt & L Kuun 15 EACH WORD BELOW REPRESENTS A CODON AUG GAA GCU UGC CUG AAA EACH CODON CODES FOR AN AMINO ACID Met Glu Ala Sis Leu Gly

Telematics for N-Cape by C G Oppelt & L Kuun 16 ONE AMINO ACID WILL CHANGE

POINT MUTATION: INVERTION Telematics for N-Cape by C G Oppelt & L Kuun 17

Telematics for N-Cape by C G Oppelt & L Kuun 18 ONE AMINO ACID WILL CHANGE

Telematics for N-Cape by C G Oppelt & L Kuun 19

Telematics for N-Cape by C G Oppelt & L Kuun 20

Telematics for N-Cape by C G Oppelt & L Kuun 21

Telematics for N-Cape by C G Oppelt & L Kuun 22

Telematics for N-Cape by C G Oppelt & L Kuun 23

24 Telematics for N-Cape by C G Oppelt & L Kuun

Trisomy 21  Chromosomes of homologous pair 21 do not separate during meiosis  One gamete (♀) may have two chromosomes for chromosome 21 and the other (♀) does not have a chromosome 21. Telematics for N-Cape by C G Oppelt & L Kuun 25

 Fertilisation: 2 x 21 (♀) + 1 x 21 (♂) = 3 x chromosomes 21  Extra chromosome 21 (trisomy) - baby  This process is called non- disjunction (failure to separate ) Telematics for N-Cape by C G Oppelt & L Kuun 26 +

Telematics for N-Cape by C G Oppelt & L Kuun 27

28 Homologous chromosomes do NOT separate – Anaphase I Chromatids of single chromosomes do NOT separate – Anaphase II Telematics for N-Cape by C G Oppelt & L Kuun

29 3 x chromosome 21- trisomy Telematics for N-Cape by C G Oppelt & L Kuun

30 3 sex chromosomes – XXY Trisomy - XXY

Telematics for N-Cape by C G Oppelt & L Kuun 31 female has 1 X chromosome – monosomy Monosomy - X0

HOW DOES THIS OCCUR? Telematics for N-Cape by C G Oppelt & L Kuun 32  During Meiosis I, a homologous pair on chromosome pair number 21  did not separate / During Meiosis II a chromosome did not separate  As a result of non-disjunction during Anaphase I/ Anaphase II  And resulted in an extra chromosome /3 chromosomes  On chromosome pair number 21  Known as Trisomy 21/ Down Syndrome