1. Genetic Variation

2. The Law of Segregation Mendel’s 1 st Law The 2 alleles of each gene pair separate into different gametes (egg or sperm) during meiosis.

3. The Law of Independent Assortment Mendel’s 2 nd Law Independent Assortment: NOTGenes that are inherited separately… Do NOT influence the inheritance of others Alleles segregate independently during meiosis Some ALLELES go to one gamete and some to another

4. INCOMPLETE DOMINANCE Incompletely dominance Incompletely dominance: mixGenes are neither dominant nor recessive= they mix!!! Genotype is heterozygous (hybrid--Hh) Phenotype is between two parents Dominant gene cannot fully mask the recessive redEx: white flower x red flower = pink flowers

5. CODOMINANCECodominance: neitherOffspring shows phenotype of neither parent Both alleles are DOMINANT!!! Ex: black chicken x white chicken = checkered chicken

6. MULTIPLE ALLELES Multiple alleles (Polygenic Traits: Two OR More alleles control a trait You still will only have two of these alleles.You still will only have two of these alleles. Ex: height, hair color, eye color and blood type –There are 3 different alleles for blood: –I A (Type A) = I A I A or I A i –I B (Type B) = I B I B or I B I –I A I B (Type AB) = I A I B –ii (Type O) = ii

7. Sex-Linked Alleles Sex-linked alleles: controlled by genes located on sex chromosomes (XX or XY) Usually carried on X chromosome Since females are XX, they are usually carriers of the trait Since males are XY, they have a higher tendency for inheritance of trait

8. If trait is X-linked, MALES: –pass it to all daughters –none –none to sons If trait is X-linked, MOTHERS: all –have 50/50 chance of passing it to all of their children Ex: colorblindness, hemophilia, male pattern baldness

9. Mutations Mutation: Any mistake or change in the DNA sequence Point mutation: Change in one nitrogen base in DNA Ex: albinism

10. Changes in chromosome structure 1) INVERSION: the order of genes on a chromosome is inverted Chromosomal Mutation: 2) TRANSLOCATION: the movement of a chromosome fragment to a nonhomologus chromosome

11. 3. DELETION Loss of a few bases Loss of large regions of a chromosome 4. DUPLICATION Duplication of a few bases Duplication of large regions of a chromosome

12. Crossing Over Occurs when chromosomes exchange genes. 2 chromosomes overlap. Some genes cross over and switch places

13. NONDISJUNCTION Nondisjunction: chromosome pair fails to separate properly during meiosis Monosomy: gamete has 1 less chromosome than it should 45 chromosomes is the result Ex: Turner syndrome –Missing a sex chromosome

14. Trisomy: Gamete has 1 more chromosome than it should Result is 47 chromosomes Ex: Down’s Syndrome –Extra #21 chromosome

15. Methods of Detection Ultrasound: Sound waves are used to generate an image of the unborn child. Used to detect abnormalities of limbs, organs, etc. Amniocentesis: Fluid surrounding the fetus is drawn out by needle Fetal cells are collected and grown in a lab. Chromosomes can be then Karyotyped Chorion villi sampling: Take sample of the chorion –(membrane surrounding fetus) Chemical tests and Karyotyping performed