University:
High School
Course:
High School Genetics
Academic year:

2022
Views:

70

Pages:

16
Author:

Bailee C

In Class Genetics Worksheet KEY Good directions as well as the practice problems for the Genetics unit: Part 1 Introduction: 1. Describe the genotypes given (use your notes). The first two are already done. A. DD homozygous, dominant B. Dd heterozygous C dd homozygous recessive. D. SS bomugens Dominant E. Yy hetercations F. ww homozygous Domenant 2. In humans, brown eye color (B), is dominant over blue eye color (b). What are the phenotypes of the following genotypes? In other words, what color eyes will they have? A. B. bb blue C Bb Broun The Five (5) Steps Associated With Solving a Genetics Problem: If you take the time tofollow the directions below, you will be able to solve most genetics problems. 1. Determine the genotypes of the parents or whatever is given in problem. 2. Set up your Punnett square as follows: "# sq. based on possible gametes that can be formed. 3. Fill in the squares. This represents the possible combinations that could occur during fertilization. 4. Write out the possible genotypic ratio of the offspring. 5. Using the genotypic ratio determine the phenotypic ratio for the offspring. Part 2: Sample Problem (Just read this over, it is a practice problem) A heterozygous male, black eyed mouse is crossed with a red eyed female mouse. Predict the possible offspring! Step 1: Determine the genotype of the parents. The male parent is heterozygous which means he has one allele for black eyes and one allele for red eyes. Since his eyes are black, this means that black allele must be dominant over the red allele. So the male parents genotype is "Bb" (B= allele for black eye, ballele for red eye). The female parent has red eyes, there is only one way to have this recessive phenotype, so she must to be homozygous recessive. Homozygous recessive means that her genotype must be "bb". Therefore, genotype of the parents is Bb x bb. STEP 2: During meiosis (the formation of sex cells) one member (allele) of each gene pair separate. The male mouse (Bb) produces some sperm containing "B" (the allele for black eye) and some sperm containing "b" (the allele for red eyes). On one axis of the Punnett square you put the two possible gametes for the male. Possible Sperm b B b Possible Eggs b Repeat this for the other axis for the possible female gametes. Since she is "bb" you must put "b" and "b". Step 3: During fertilization sperm meets the egg. The Punnett square show us the various possibilities during fertilization. The offspring must be one of these genotypes listed in the squares. b B b If. the sperm contains a "B"and it fertilizes-an-egg-containing the "b" allele,, the resultant offspring will-have the genotype- "Bb". b Repeating the process we can see all of the possible genotypes. B b b Bb bb b Bb bb Step 4: The genotypic ratio is detetmined by counting each possible genotype. You'll note there are two "Bb" for every two "bb". Therefore, we write the ratio as 2:2 Normally we reduce to the lowest terms: 1:1 Bb: bb Bb: bb Part 6: Multiple Allele So far we have studied traits or genes that are coded for by just two alleles. Like in rabbits, there was one allele for brown hair color and one allele for white hair. However, some traits are coded for by more than two alleles. One of these is blood type in humans. This is a violation of Mendel's Principle of unit characteristics. In humans, there are four types of blood; type A, type B, type AB, and type 0. The alleles A and B are codominant to each other and the O allele is recessive to both A and B allelex. So a person with the genotype AA or AO will have A type of blood. The proper way to write blood type alleles is like this: Por it it is the recessive O I = A protein B I = B protein i = no protein a. What poss ble genotypes will produce B type of blood? IIL b. What is the only genotype that will produce 0 type of blood? ii d. Whatisthe only genotype that will produce AB type of blood? IIB L You are blood type Oand you marry a person with blood type AB. e-ii a. Complete a Punnett square for this cross. 07 b. List the possible blood types (phenotypes) of your offspring. AB 50% of each me you A III B B 2. In the 1950's, a young woman sued film star/director Charlie Chaplin for parental support of her illegitimate child. Charlie Chaplin's blood type was already on record as type AB. The mother of the child had type A and her son had type 0 blood. Complete a Punnett square for the possible cross of Charlie and the mother. Charlle TAB) Charter mom A I A VII VI Gust fr II Check Ow VI VII IB DIVI 5080 type A 50% Type AB 72/4-50% Type A 1/4=25% Type AB 1/4 = 25% Type B b. The judge ruled in favor of the mother and ordered Charlie Chaplin to pay child support costs of the child. Was the judge correct in his decision based on blood typing evidence? Explain why or why not. refer to any Pruamett squares to support your answer. No! In order to produce a child of Oblood type each parent has to be heterozygars for the AB- absolutdy Charter was? not heterozygous bel he has AB Blood type.