Genetics -the scientific study of inheritance

1. Genetics-the scientific study of inheritance inheritance- the process in which genetic material is passed from parents to their offspring

2. Gregor Mendel • Austrian monk-studied pea plants • Mathematical basis for experiments • Kept careful records of numbers • Studied simple traits (seed color, shape, flower color, height, etc.)

3. Monohybrid Cross • A cross between two parents that are identical in all but one characteristic. • Example: cross a short pea plant and a tall pea plant • P is parent generation, • F1 is first filial generation, • F2 is second filial generation • Result of cross: F1-all tall, F2-3 tall:1 short

4. Modern Genetics • Allele: Alternate forms of the same gene. Each trait has two alleles: • Dominant: masks the effects of the recessive (ex. T) • Recessive: is masked by the dominant (ex. t)

5. Modern Genetics cont’d • Gene Locus: the place on a homologous pair of chromosomes where the alleles occur, one on each chromosome. • Homozygous (true-breeding): Both copies of the allele are identical (TT or tt) • Heterozygous: Each copy of the allele is unique (Tt)

6. Genotype vs. Phenotype • Genotype: the alleles an individual receives at fertilization. TT is homozygous dominant, tt is homozygous recessive, and Tt is heterozygous. • Phenotype: refers to the physical characteristics of an individual. Homozygous dominant and heterozygous individuals both show the dominant phenotype (tall), while homozygous recessive shows the recessive phenotype (short).

11. Classes of chromosomes autosomalchromosomes sexchromosomes

12. Genetics of Sex • In humans & other mammals, there are 2 sex chromosomes: X & Y • 2X chromosomes • develop as a female: XX • an X & Y chromosome • develop as a male: XY X Y X XX XY XX XY X 50% female : 50% male

13. Sex-Linked Traits • Sex-linked traits are produced by genes only on the X chromosome. • They can be Dominant or Recessive. • A = dominant a = recessive • What would be the genotypes of a male and female that have a Sex-linked Dominant trait and do not express the trait? • Expresses Trait: Male - XA Y Female - XAXA or XAXa • No Expression: Male - Xa Y Female - XaXa • What would be the genotypes of a male and female that have a Sex-linked Recessive trait and do not express the trait? • Expresses Trait: Male - Xa Y Female - XaXa • No Expression: Male - XA Y Female - XAXA or XAXa (Carrier) • Most Sex-linked traits are Recessive!

14. Dihybrid Cross • A cross between two individuals that differ from each other in regards to two traits. • Ex: pod color and pea color: GGYY and ggyy. • F1 generation will be GgYy.

16. Polygenic Inheritance • phenotype determined by combination effects of 2 or more genes at a different loci on different chromosomes. • Phenotypes usually found on a bell-shaped curve • human traits • skin color • height • weight • intelligence • behaviors

17. Multiple alleles- more than 2 forms of a gene controlling the expression of a trait • Ex: Blood type: • In humans, 3 alleles: A,B,O • Co-dominance- A pattern of inheritance in which the phenotypic effect of two alleles in a heterozygous genotype express each phenotype of each allele fully and equally; a phenotype which would not be expressed in any other genotypic combination. • Ex: Checkered chickens have both white and black feathers.

18. Environmental Effects • Phenotype is controlled by both environment & genes Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fox influenced by heat sensitive alleles Color of Hydrangea flowers is influenced by soil pH

19. What are Chromosomal Mutations? Damage to chromosomes due to physical or chemical disturbances or errors during meiosis. • Mutations might also be inherited from the sex cells of your parents. If you inherit a mutation from your parent, all of your DNA will be made with the mutation already in it. • The only way to inherit mutations from your parent is through sex cells – not through other types of cells. • Ex: Skin cancer is not passed on to your kid. • Mutations may cause certain types of diseases or make you susceptible to certain types of diseases. • Two Types of Chromosome Mutations: • Chromosome Structure • Chromosome Number

20. Problems with Chromosome Structure: 2 main types of chromosome structure mutations: 1. Point mutation - A point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence. 2. Frameshift mutation- a change in the bases that causes the sequence to be read in different sets of codons. Equivalent to changing the spacing of the sentence.

21. Gene Mutations • Nonsense substitution- a change in 1 base that changes an amino acid to a stop codon • Silent substitution- a change in 1 base that does not cause a change in the amino acid produced OR a change in the DNA that causes a change in the protein, but not the function of the protein. • Missense substitution- a change in 1 base that changes the amino acid produced • Deletion- a deletion of a base • Insertion- an addition of a base

22. Chromosomal Mutations • translocation- a portion of a chromosome breaks off and attaches to a non-homologous chromosome • inversion- a portion of a chromosome breaks off and reattaches “upside down” • deletion- a portion of a chromosome breaks off • duplication- a portion of a chromosome is duplicated

23. Problems with Chromosome Number nondisjunction – members of homologous chromosomes do not move apart in Meiosis I or sister chromatids do not separate during Meiosis II leaves one cell with too few chromosomes and one cell with too many. monosomy – only one of a particular type of chromosome (2n -1) trisomy – having three of a particular type of chromosome (2n + 1) polyploidy – having more than two sets of chromosomes; triploids (3n = 3 of each type of chromosome), tetraploids (4n = 4 of each type of chromosome).

24. Biotechnology • -any procedure or methodology that uses biological systems or living organisms to develop or modify either products or processes for specific use. • Genetic engineering- a technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally. • genetically modified organism- an organism whose genetic material has been altered through some genetic engineering technology or technique.

25. gene therapy- the intentional insertion, alteration, or deletion of genes within an individual’s cells and tissues for the purpose of treating a disease. • gene splicing- a type of gene recombination in which the DNA is intentionally broken and recombined using laboratory techniques • Cloning- a process in which a cell, cell product, or organism is copied from an original source • DNA cloning- making exact copy of a DNA fragment • Reproductive cloning- transfer of genetic material from the nucleus of a donor adult cell to an egg that has had its nucleus removed ; the embryo is an exact genetic copy of the donor organism. • Therapeutic cloning- using STEM cells for use in research • STEM cells- undifferentiated cells; have not decided “what they want to be” when they “grow up”