Parent 2 : SpongeSusie Name: : Patterns in Genetics Do Now: Answer the following question based on the information below. As we know, Spongebob is hertereozygous for his yellow body color and his squarepants, while his wife Spongesusie is blue and roundpants. (A) What are their genotypes? a. Spongebob = SpongeSusie = (B) Complete the Punnet square. Remember to distribute the letters so that every combination is on the punnet square. Parent 1: Spongebob (C) What are the chances ( / 16) for having a baby with the following genotypes? a. Square and Yellow: b. Square and green: c. Round and Yellow: d. Round and Green: 1
Multiple Alleles Certain genes have multiple alleles instead of just two. An individual still only has 2 of these alleles but there are more possibilities of what can be chosen from. EX: M&M s can be more than just 2 colors. This means that the gene for their color has multiple alleles. They can be brown (M), green (m g ), yellow (m y ), and orange (m o ). Brown is dominant to all other colors Green is dominant to yellow and orange Yellow is dominant to orange Orange is recessive to all other colors M > m g > m y > m o What are the possible genotypes of each phenotype? Brown: MM, Mm g,,, Green:,, Yellow:, Orange: 2
Co-dominance The prefix CO means together. With some genes, the two alleles are considered to be co-dominant. This means that when both alleles are present, they are both fully visible. Alleles are represented by different, capital letters EX: Certain plants have co-dominant alleles for their petal color gene. Allele for red petals R Allele for white petals is W Genotype = RW RW x RW 3
Simple Dominance Mono-hybrid Punnet Squares A mono-hybrid cross focuses on only 1 gene. Simple dominance means that there are only 2 alleles for the gene and that one is recessive and one is dominant. EX: Two parents have unattached earlobes. Both are heterozygous (Uu). They want to know what the possibility is of their offspring having attached earlobes. (Unattached earlobes is a dominant trait U) How many have Unattached earlobes /4 Attached earlobes /4 How many are Homozygous dominant? Homozygous recessive? Heterozygous? Create another punnet square that crosses the 2 highlighted offspring. (on the back) 4
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Independent Assortment Di-hybrid Punnet Squares Independent assortment means that different traits do not influence each other s inheritance (seed shape and seed color). The 9: 3: 3: 1 ratio shows that heterozygous plants that show the dominant phenotype can produce offspring that look nothing alike the parents; therefore, we use a di-hybrid punnet square to determine all of the possibilities two traits can pass on to the offspring. Spongebob has round eyes and long nose (RrLl), while his wife now also has round eyes and long nose (RrLl). If they were to have children (RrLl x RrLl), what fraction would have the following genotypes: (A) What are the chances ( / 16) for having a baby with the following genotypes? a. Square and Yellow: b. Square and green: c. Round and Yellow: d. Round and Green: Incomplete Dominance 6
When one allele is not completely dominant over another, it is called incomplete dominant. This means that the heterozygous phenotype is somewhere in between the two homozygous phenotype (aka blending of traits) Alleles are represented by different, capital letters EX: red allele + blue allele purple In humans, the hair type is an incomplete dominant allele. Straight Hair: S Curly Hair: C Wavy Hair: CS Problem: While both parents have wavy hair, how come their child has straight hair? What is the probability for an offspring to have straight hair? Cross: 7
Polygenic Traits controlled by two or more genes are polygenic ( many genes ). This means that at least three genes (ex: gene A, B, C) and its different combinations of alleles make different phenotypes. Ex: Eye color, skin color and height all show a wide range of phenotypes. Based on this example, how many genes are determining skin color? How do you know? Why may polygenic traits increase variation in the population? 8
Practice: Human Blood Type The genes for human blood type combine many patterns in genetics, such as dominance, multiple alleles and codominance. This creates 4 phenotypes or blood types: Type A, Type B, Type AB, and Type O. Pattern of Genetics Genotype Rule Multiple Alleles I A, I B, i There are 3 alleles Simple Dominance I, i I is dominant. I is recessive. Ex: I A i is hetereozygous Type A. Codominance I A and I B They are codominant (1) Based on the table above and your knowledge from today, fill in the missing genotypes and phenotypes. Phenotype Type A Type B Type Type O Genotype I A i, I A I A, I A I B ii (2) If both parents are homozygous I A I A and I B I B, use a punnet square to prove that their child will have a completely different blood type. (3) What is the blood type of the child? (4) What pattern of genetics does this show? 9