The Laws of Inheritance Biology 1 Mrs. Wilkemeyer Image taken from kentsimmons.uwinnipeg.ca/cm1504/mendel.htm

Q - Space How do scientists predict what traits offspring will receive when genetic counseling is needed? How might researchers use the laws of inheritance in agriculture?

Agenda SOL Knowledge Objectives Genetics Gregor Mendel's work Law of segregation Law of probability The use of punnett squares Law of independent assortment Summary of laws of inheritance Beyond dominant and recessive

SOL Knowledge Bio.6 d  Students will investigate and understand common mechanisms of inheritance and protein synthesis Including the prediction of inheritance of traits based on Mendelian laws of heredity

Objectives We will...  Understand the difference between genotypes and phenotypes  Understand how to identify homozygous and heterozygous individuals  Apply the law of probability to determine patterns of inheritance with a punnett square  Understand the difference between complete and incomplete dominance

What is Heredity? The study of genetic traits and how they are passed from one generation to the next.  Where did you get your green eyes, red hair or tall height? Gregor Mendel pioneered genetics  Studied pea plant traits  A trait = a specific characteristic that varies among individuals Color or height By crossing peas of different traits Gregor Mendel formed the laws of heredity Image taken from

Genes & Dominance Hybrids – the offspring of crosses between parents with different traits Genes – a sequence of DNA that determines a particular trait  Alleles – one of a number of different forms of a gene Image taken from dj003.k12.sd.us/SCHOOL%20NOTES/chapter_03.htm Link to baby: mport/modules/genome/fullscreenflash19f9.cfm? flash=en- flash/eyecolour.swf&title=Eye+colour&version= 6 mport/modules/genome/fullscreenflash19f9.cfm? flash=en- flash/eyecolour.swf&title=Eye+colour&version= 6

Early Ideas on Inheritance Gregor Mendel  Concluded from his research that certain traits pass from one generation to the next  Some alleles are dominant and others are recessive Aka the principle of dominance  During reproduction alleles segregate into separate gametes Aka the law of segregation Image taken from Image taken from

Gambling Heredity Probability – the likelihood that a particular event will occur  Toss a coin – the chance of a heads is 50%  Principles of probability can be used to predict the outcomes of genetic crosses

Punnett Squares Punnett squares – used to predict and compare the genetic variations that will result from a cross  Homozygous – TT or tt  Heterozygous – Tt  Phenotype – physical characteristics  Genotype – genetic makeup

Punnett Squares Image taken from:

Do all traits segregate together? Gregor Mendel performed a dihybrid cross to test this  Proved genes for different traits can segregate indep. Later known as the law of independent assortment Accounts for much of the genetic variation observed in plants and animals. Image taken from

Summary of Mendel's Principles Characteristics are inherited from parent to offspring through genes When two or more forms of a trait exist (alleles) some forms may be dominant and some recessive In sexually reproducing organisms adults have 2 copies of each gene that are segregated when gametes are formed  Offspring receive one allele from each parent's gamete Alleles for different genes segregate independently of one another

Beyond Dominant vs Recessive Some alleles are neither and many traits are controlled by multiple alleles or genes  Incomplete Dominance No allele is dominant Heterozygous phenotypes are “in between” as in pink snapdragons when red is crossed with white  Codominance Both alleles contribute to the phenotype  Multiple Alleles More than two alleles exist Human genes for blood type  Polygenic Traits Gene interactions result in a wide range of phenotypes as in skin tone

Blood Types A case of multiple alleles Human blood type is determined by 3 alleles. Both A and B are co-dominant, while type O is recessive.