Transcript File
Ch 10.1 Mendel’s Laws of Heredity Take 5: 11/11/10 ► Round Seeds (R) are dominant to wrinkled seeds. Finish the following crosses: ► Rr x rr : what percentage of the offspring would be round? ► Rr x Rr : What percentage of the offspring would be round? Take 5 ► Which phase in meiosis do the tetrads break and are pulled to opposite poles of the cell? ► Which phase in meiosis do the chromosomes (paired chromatids) line at the equator of the cells? ► Which phase results in formation of 4 haploid cells? ► A haploid cell has ___________ as many chromosomes than a diploid cell. ► Austrian monk of the mid 19th century who studied pea plants: _______________ aka “Father of Modern Genetics” ► Mendel studied __________ (the passing on of characteristics from parents to offspring) ► ________ are inherited characteristics ► Mendel was the first person to succeed in predicting how traits are transferred from one generation to the next. ► This branch of biology that studies heredity is called ___________ ► Mendel studied _____________ ► Garden pea plants reproduce sexually (this means that they produce both male and female sex cells) called ________ ► The male gamete of a plant is referred to as _______ ► The process by where male gametes unite with female gamete is called _________________ ► In plants, the transfer of pollen to female reproductive organ is called ________________ ►A fertilized cell is known as a _______ and in plants it later develops into a seed Mendel’s Monohybrid Crosses ► Mendel experimented with many different traits of pea plants and he recorded this information and … For example, he looked at seed shape, seed color, flower color, flower position, pod color, pod shape, and plant height. ► Let’s look at one example: _____________ ► Pea plants came in two varieties: _____& _______ ► Mendel noticed that when he crossed a short (Mom) plant and a tall (Dad) plant, that all the offspring (Children) were _______ ► Then X when he crossed two of the offspring (children plants) with each other, ___ out of 4 were tall and ___ out of 4 where short. ► Mendel began noticing patterns like this and began developing ideas for explanations. first law is the LAW OF SEGREGATION: which states that every individual has two alleles for each gene and when gametes are produced, each gamete receives one of these alleles ► The second law (LAW OF INDEPENDENT ASSORTMENT) states: each allele of any one pair is free to combine with any allele from each of the remaining pairs during the formation for the gametes. This developed while Mendel examined dihybrid crosses. ► The Now let’s explore the terminology: ► The parent generation is P called: ___ first born generation is called: ___ F1 X ► The ► The second generation is F2 called: ___ X you are crossing (breeding) organisms and only looking at ONE characteristic, you are conducting a ______________ cross ► When you are crossing (breeding) organisms and only looking at TWO characteristics, you are conducting a ___________ cross ► When you are crossing (breeding) organisms and only looking at THREE characteristics, you are conducting a ___________ cross ► When ►We now know that genes are found on _____________. Genes exist in alternative forms. We call these different gene forms _______. An organism has two alleles for each trait and these two alleles are found on different copies of the chromosome (one from Mom and one from Dad). Alleles are often represented by _________. The Allele ►A capital letter indicates a ___________ trait (what is observed) ►A lowercase letter indicates a ___________ trait (often hidden) ► There are three different combinations that can arise from having only a capital and a lowercase letter: ____, ____, ____. Alleles for the height trait Tall Tall Short ► Each of these letter combinations has a science description that corresponds with it. ► _____ is called homozygous dominant ► _____ is called homozygous recessive ► _____ is called heterozygous ►When talking about the genes of an organism, these letter (allele) combinations are referred to as the ___________. ►When talking about the physical appearance of an organism, we use the term ___________. How to use and complete a Punnett Square: 1)___________________________________ _________________________________ How to use and complete a Punnett Square: 2)________________________________ ______________________________ How to use and complete a Punnett Square: 3)__________________________________ __________________________________ How to use and complete a Punnett Square: 4)_________________________________ _________________________________ How to use and complete a Punnett Square: 5)__________________________________ __________________________________ How to use and complete a Punnett Square: 6)__________________________________ __________________________________ How to use and complete a Punnett Square: 7)__________________________________ __________________________________ How to use and complete a Punnett Square: 8)__________________________________ __________________________________ Starting with the Parent Generation…. IV. Mendel’s Dihybrid Crosses A. Mendel performed another set of crosses in which he used peas that differed from each other in ________________ 2 traits. The first generation B. The second generation ► Round Yellow 1. Mendel took true-breeding pea plants that had __________________ seeds (RRYY) and crosses them with true-breeding pea plants that had _____________________ Green Wrinkled seeds (rryy). 2. F1 Generation all had __________________________ Round Yellow (RrYy) seeds. 1. Mendel let the F1 plant __________________ Pollinate themselves. 2. In the F2 generation, he found that hey appeared in a definite ratio of 9 phenotypes _______ round yellow ____ 3 wrinkled 3 round green, ____ yellow, _____ 1 wrinkled green. V. Punnett Squares Dihybrid Crosses * A Punnett square for a dihybrid cross four will need to be ________ boxes on 16 each side for a total of ________ boxes. B. Dihybrid cross: RrYy X RRyy ► Round is dominant to wrinkled and Yellow is Dominant To Green Genotypic Ratio: ______________ Phenotypic Ratio: ______________ VI. Probability ► Punnett squared are good for showing combinations all the possible ______________ of gametes and the likelihood that each will occur. ► It is important to remember that the results predicted by probability are more ____________ likely to be seen when large there is a ___________ number of offspring.