Heredity and Genetics

1. Heredity and Genetics “Why We Look the Way We Do”

2. What is Heredity? • Heredity = the passing on of traits from one generation to the next.

3. What is a Trait? A trait is a specific characteristic that is unique. Traits affect the way we look Traits affect how our bodies function Traits are inherited • Examples are hair color, eye color, handedness, etc.

4. How Do We Keep Track of Traits? • We use a pedigreechart to keep track of how traits are passed on from generation to generation.

5. What is a Pedigree? Apedigree is a diagram that shows the history of a trait as it is passed from one generation to the next. Pedigrees indicate patterns Pedigrees identify carriers of genetic disorders Pedigrees are useful for genetic counseling • Example: a pedigree is like a family tree for one trait.

6. Rules For Making A Pedigree • Females are represented by circles • Males are represented by squares • Mother/Father couples are connected by a line • Offspring are shown oldest on the left to youngest on the right • Half-shadedcircle represents a femalecarrier for the trait • Half-shaded square represents a male carrier for the trait • Full-shaded circle represents a female with the trait • Full-shaded square represents a male with the trait

8. Trait: Parents Offspring Youngest to Oldest A Pedigree

11. What is Mendelian Genetics? • Gregor Mendel was an Augustinian monk who lived in the late 19th century and, through studying peas, developed the basis for the science of Genetics still used today.

14. What Kinds of Traits Are There? • Traits are either Dominant or Recessive.

15. Dominant Trait A dominant traitis a trait that isalwaysexpressed, or shown. • Examples are brown hair, brown eyes, right handed

16. Recessive Trait Arecessive traitis a trait thatis covered upor seems to disappear. • Examples are blonde hair, blue eyes, left handed

18. Where Do Traits Come From? Factors that make up an individual come from both parents. The trait information is passed on from generation to generation in the form of genes.

19. What are Genes? A gene is a specific location on a chromosome that controls a certain trait.

20. Where Do Genes Come From? • An individual needs 2 genes for each trait – one gene from each parent. • This gene pair is called an allele. • One gene comes from the sperm cell (from the Father) • One gene comes from the egg cell (from the Mother)

21. How Do Genes Get Their Information? A chromosome is a structure in the cell that contains the genetic information. • This information is passed on from one generation to the next generation.

23. Gene RepresentationHow Do We Write Our Genetics? • The name of the dominant trait determines what letter is used to represent the gene. • Use a capital of the first letter of the dominant trait to represent the dominant gene. • Use a small version of the first letter of the dominant trait for the recessive gene. Example: Right-handedness is the dominant trait so use R for the dominant gene and use r for the recessive gene forLeft-handedness. Example 2: Tall is the dominant trait so we use T and we use t for the recessive gene for Short.

24. How Are Genes Expressed? Traits are how our genes show and since traits are formed from two genes, they are described by the combination of genes that make the pair. Traits are described as either: • homogeneous, (pure) • heterogeneous, (mixed)

25. Homozygous = Pure (Homogeneous) • Pure Dominant:the individual onlyhasgenes for the dominant trait. • Example: TT = a pure tall individual has onlytall (T) genes. • Pure Recessive:the individual only has genes for the recessive trait. • Example: tt = a pure short individual has onlyshort (t) genes.

26. Heterozygous = Mixed(Heterogeneous) Aheterozygousindividual has one dominant gene and one recessive gene for a trait. The result is the dominant gene is the one expressed, or shown. • Example:Tt= a heterozygote tall individual hasboth tall (T) and short (t) genesbut looks tall.

27. How Do We Predict Offspring? A PunnettSquare is a way to show the possible combinations of genes that offspring of parents could have.

28. Punnett Square

32. What is Phenotype? Phenotype is the way that we look or appear. • Example: brown eyes, blonde hair, tall

34. What is Genotype? Genotype: is the genetic make up for a trait. Example: Homozygous brown; BB = pure brown: (both genes are the same)

38. Results: Phenotypes:100% Right handed75% Tall 25% Short Genotypes: 50% RR, homozygous right25% TT, homozygous tall 50% Rr, heterozygous right50% Tt, heterozygous tall 0% rr, homozygous left25% tt, homozygous short

39. Results: Phenotypes: 100% Blue-eyed100% Right-handed Genotypes: 100% bb, homozygous blue100% Rr, heterozygous right-handed

40. What Is Incomplete Dominance? • Incomplete dominance is when neither gene that determines a trait dominates, so the recessive trait is not fully hidden. • The result is a “mixed” genetic trait that is neither dominant nor recessive. • Example: Red (RR) x White (WW) flowers yield Pink (RW)

41. How Do Genes Control Traits?Deoxyriboneucleic Acid DNA is the “instruction code” that the genes use to form traits. • DNA is long threads of material found in all cells. • DNA contains the “master code” that instructs all cells in their daily jobs. Genes are short pieces of DNA that make up our chromosomes. Each piece of DNA that is related to a gene makes up one trait.

42. Structure of DNA DNA looks like a twisted “ladder” made of chemical compounds called bases.

43. Models of DNA

44. How Bases Make Up DNA • There are 4 types of bases in DNA:Adenine,Guanine,CytosineandThymine. • These bases fit together like puzzle pieces • AdeninewithThymine • CytosinewithGuanine

45. But What ARE Genes? • Genes are pieces of DNA that make up a trait • Different genes consist of different arrangements of the Adenine, Thymine, Cytosine, Guanine bases. • These bases can be arranged to form different proteins (chemical messages) • These messages control different traits (some determine how we look, some determine how we feel and function). • There are many millions of possible combinations of these 4 bases – this accounts for the differences, and similarities, between life forms on earth.

46. Traits from Proteins • All characteristics are affected by the DNA in the cells of the individual organism. • These characteristics are called traits. Traits depend on the types of proteins that the 4 bases (A,C,G,T) make up.

47. How Do We Look The Way We Do? • Parents pass on copies of their DNA to their offspring. • The DNA from each parent combines to form the DNA of the offspring. • How the offspring develops depends on the instructions coded in the DNA donated by both parents. • Offspring are similar to parents, but different due to the many possible combinations of the 4 bases. • Every individual is unique.

48. How Can We Use Genetics? • To predict looks of offspring • To predict risks of diseases/defects • …

49. Genetics Help Predict Diseases • Sickle-cell Anemia is a genetically inherited disease where red blood cells are misshaped. • Red blood cell shape is an inherited trait. • Sickle-cell shape vs Normal cell shape • Sickle-cell anemia is cause by incomplete dominance.

50. Advances in Genetics • We have an increased understanding of certain diseases that are inherited. • We have increased knowledge of many health conditions (treatment, prevention, and cure). • Example: Down Syndrome is caused by an extra chromosome.