Heredity

1. Heredity Genetics: study of the mechanisms of heredity Sex chromosomes: X & Y; one pair Autosomes: 22 pairs Karyotype: diploid chromosomal complement; shown in homologous chromosome pairs from longest to shortest 5. Homologous chromosomes: one from each parent

2. Gene Pairs 1. Alleles: matched genes at same locus on homologous chromosomes; may code same or different expression of the a trait 2. Homozygous: two alleles controlling a trait are alike 3. Heterozygous: two alleles are different for same trait 4. Dominant: allele that masks the expression of the other 5. Recessive: masked allele 6. Genotype: Ll, Mm, etc.; your genetic makeup 7. Phenotype: expression of the genotype; what you look like

3. Genotype An organism�s genotype is the set of genes that it carries. Phenotype: An organism�s phenotype is all of its observable characteristics�which are influenced both by its genotype and by the environment. This flamingo is pink because of the food the bird eats.

4. Sources of variation Why are we different? Independent assortment of chromosomes Crossover of homologues Random fertilization of eggs by sperm

5. 1. Large circle is metaphase of mother cell with 6 chromosomes 2. Purple = paternal Green = maternal 3. Small circle is genetic compliments of gametes from each alignment 4. Some contain all maternal or paternal, some have varying combinations. Independent assortment

6. Crossing over 1. Homologous chromosomes synapse during prophase of meiosis 1. Each chromosome has 2 sister chromatids 2. One chromatid segment exchanges positions with another, crossing over and forming a chiasma H = brown hair h= blond hair E = brown eyes e = blue eyes

8. Random fertilization Gametogenesis creates many variations by Independent assortment random crossovers And, a single egg will be fertilized by a single sperm at random Adding all this variation, any offspring represents one of about 72 trillion possible zygotes Independent assortment 8.5 million 223 Random fertilization 8.5 million 8.5 x 8.5 = 72 trillion

9. Types of Inheritance 1. Dominant - recessive 2. Incomplete dominance 3. Multiple allele 4. Sex- linked 5. Polygene

10. Dominant recessive Interaction of dominant and recessive alleles: one allele masks the other Punnett square to figure possible combination of genes for a single trait from 2 known genotypes. Predicts the probability of having a certain % of offspring with a specific genotype

12. Dominant traits Recessive Tongue roller ZZ or Zz Can�t roll zz Free earlobes Attached earlobes Freckles Absence of freckles Dimples Absence of dimples Widow�s peak Straight hairline Double-jointed thumb Tight thumb Genetic diseases by dominant genes are uncommon because they are lethal and result in embryo death. Most genetic disorders are inherited as recessive traits.

13. Incomplete dominance If the phenotype of a heterozygote is intermediate between the homozygous recessive and dominant the locus is said to display ID:

14. Sickle - cell anemia Co-dominance (Ss) -individuals with Sc make both normal and sickling hemoglobin. Confers malaria resistance

15. Sex-linked inheritance Traits determined by genes on the sex chromosomes Remember, one gene for a given trait comes from male, other from female Many traits are not on X so have no matching gene on the smaller Y Females follow rules of expression because they get two X chromosomes Males receive 1 copy of gene on X chromosome and they ALWAYS exhibit what is on that X gene Males receive no X from their father, so it never goes from father to son

16. Results in continuous phenotypic variation between 2 extremes Skin color is an example is controlled by 3 inherited genes Alleles for dark skin are dominant and each contributes a unit of darkness (dark circle) Homozygotes at each end of the range Polygene Inheritance

17. Environmental factors of gene expression Maternal factors during embryonic development Pesticide contamination - allegators in south, acid rain and its affect on tiger salamanders include deformed embryos low doses of pesticides, especially mixtures of them, mimic, block or disrupt natural hormones which effects embryonic development Poor nutrition after birth influencing brain growth; tall genes stunted by insufficient nutrition

18. Nontraditional Inheritance The same allele can have a different effect dependent on from which parent it came During gametogenesis, genes are tagged as paternal/maternal The embryo reads the tags and expresses the genes differently

19. Nontraditional Inheritance

20. Fetal testing Amniocentesis - amniotic fluid extracted for testing Enzymes Karyotyping for chromosomes of fetal cells for normalcy in number and microscopic appearance Performed before 14th week Chorionic sampling -tube to cervix and suctions from placenta-chorionic villi Karyotyping Performed at 8 weeks