Introduction to

1. Introduction to Genetics Wild Type Head Mutant Head (Antennapedia)

2. Genetics • DNA – hereditary information found in nucleus; directs activity in cell • Chromosome – DNA and chromatin tightly coiled together • Gene – a portion of DNA that codes for a specific trait Ex. Seed color

3. Genetics • Allele – alternateform of a gene that controls the expression of the gene • 1 from Mom and 1 from Dad

4. Genetics • Genetic traits • Dominant – an allele that prevents/masks the expression of a recessive allele (Use Capital letters) • Recessive – an allele that is hidden by a dominant allele (Use lower case letters)

5. Genetics • Example: T = Tall (dominant) t = short ( recessive) Sooooo….. TT = Tall Tt = Tall tt = short (recessive must have two alleles to be expressed)

6. Try it.... • If Y = Yellow and y = green then... YY = yellow Yy = yellow yy = green

7. Genetics • Homozygous – two identical alleles for the same trait (ex. YY or yy) • Heterozygous – two different alleles for a trait (ex Yy) • Genotype – genetic combination of alleles (ex. YY, yy, BB, bb) • Phenotype – the appearance or way an organism’s genes are expressed (ex. Yellow, green, Brown, blue)

8. Genetics • Testcross – a way to determine purelines • TT = tall = homozygous pureline • Tt = tall = heterozygous (hybrid) • tt = short = homozygous pureline 6 Basic crosses :AA x AA = All AA AA x aa = All Aa aa x aa = All aa Aa x AA = 2Aa : 2AA Aa x aa = 2Aa : 2aa Aa x Aa = 1AA : 2Aa : 1aa

9. Genetics • Incomplete dominance – heterozygous alleles expressed by blending (neither is dominant) Ex. Red carnation x White carnation = Pink carnation R R W W

10. Genetics • Codominance – heterozygous alleles both expressed together (NOT blended) • Ex.Brown cow x White cow = Brown & White cow (called a roan) B B W W

11. Genetics • Polygenic inheritance - traits determined by more than one allele • Ex. eye color (melanin = pigment) • a little melanin = blue • a little more = green • a little more = brown

12. Genetics • Sex-linked traits – humans have 23 pairs of chromosomes 22 pairs are autosomes 1 pair (23rd pair) are sex chromosomes Sex chromosomes determine the sex of the individual Female = XX Male = Xy Men determine sex of child

13. Genetics • Sex linkage – genes located on the sex chromosomes (ex. baldness) Female Male Normal XBXBXBy Normal XBXb Balding XbXb Bald Xby

14. Blood Types • Blood type is an example of a multipleallele (a gene with more than two alleles) • Three alleles exist for Blood types: A, B, O • A and B are dominant over O • A and B are codominant (both expressed) when present together

15. Blood Types Genotypes Phenotypes AA A BB B OO O AO A BO B AB AB AB is the Universal recipient O is the Universal donor

16. Blood Types • Rh factor – a marker on the surface of red blood cells • + is dominant over - Rh+ = the marker is present Rh- = the marker is NOT present If mom is Rh- and fetus is Rh+, mom must be given a drug to prevent antibodies from forming against Rh+ fetus

17. Let’s Practice Mom is OO and Dad is AB. What are the genotypes for the possible offspring ? A B O O ratio for genotype: 2AO : 2BO ratio for phenotype: 2A : 2B

18. MUTATIONS

19. Mutations • A random change in the sequence of nucleotides in DNA is called a mutation. • Two groups of mutations: 1. Gene mutation 2. Chromosome mutation

20. Gene Mutations

21. Gene Mutations Gene mutations: Point mutation = one nucleotide in a gene is changed Ex. The cat ate the fat rat. The bat ate the fat rat. The result is a single amino acid change within a protein.

22. Gene Mutations Frameshift mutations 1. Deletion – loss of a nucleotide Ex. The cat ate the fat rat. The ata tet hep atr 2. Insertion – addition of a nucleotide Ex. The cat ate the fat rat. The cca tat eth efa tra.

23. Gene Mutations • Frameshift mutations are more damaging than point mutations because many amino acids are changed within a protein instead of just one.

24. Chromosome Mutations

25. Chromosome Mutations 1. Inversion – when a chromosome is broken and reinserted backwards. ex. abcd -> bacd 2. Translocation – when a part of a chromosome breaks off and attaches to another chromosome

26. Chromosome Mutations

27. Chromosome Mutations • Deletion – a piece of chromosome is broken off and lost ex. Cri du chat • Duplication – a segment of chromosome is repeated ex. abcdabcdefgh

28. Chromosome Mutations 5. Non-disjunction – chromatids fail to separate during meiosis; one daughter cell will be missing an entire chromosome and the other will have an extra chromosome Monosomy = gamete is missing a chromosome Trisomy = gamete has an extra chromosome

29. Chromosome Mutations In trisomy, if the gamete fuses with another gamete to become a zygote, the zygote will have 3 copies of that chromosome ex. Down’s syndrome = Trisomy 21 (there is an extra # 21 chromosome)

30. Chromosome Mutations Polyploidy – extra sets of chromosomes (fatal in animals but common among plants)

31. Chromosome Mutations • Karyotype – a picture of the chromosomes that are paired and numbered in order this is a normal karyotype for a boy

32. Chromosome Mutations this is a karyotype for a boy with Trisomy 21

33. Mutations Mutations in the somatic cells (body cells) are NOT inherited. These mutations cause cancer. Mutations in the gametes will be passed to the offspring

34. Mutagen • Something that increases the chance for a mutation • Ex. exposure to UV radiation, x-rays, pesticides

35. The End