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Phenotype and genotype




Help in document BSC1020_UnitE_Homework-2;Attachment Preview;BSC1020_UnitE_Homework-2.doc Download Attachment;BSC 1020 Homework;Unit E;Meiosis, Mendel, Oh My!;This homework is worth 25 points. Please use the textbook, the PPT lecture handouts of;Chapter 8 and 9, and the internet, to answer the following five questions;Question 1 (8 points);You are unique, just like everyone else! In this activity, you will be using;several recognizable traits to demonstrate the diversity in humans. These traits are;controlled by a single gene with two alleles. Remember that alleles are alternative forms;of the same gene.;Dimpled chin A cleft in the chin is a dominant trait (D), while the absence of a cleft is;recessive (d).;Free earlobes The E allele for a free earlobe is dominant over the recessive e allele for;attached earlobes.;Freckles The presence of freckles is a dominant trait (F), while their absence is;recessive (f).;Mid-digit hair Hair on the middle segment of fingers (between two joint knuckles) is a;dominant trait (M), while the absence of hair is recessive (m).;Hitchhikers thumb The S allele for a straight thumb is dominant over the recessive s;allele for a bent thumb (i.e.: the tip of the thumb can bend backwards more than 45o);Widows peak The W allele for widows peak is dominant over the recessive w allele;for a straight hairline. (Note: The hairline in widows peak forms a distinct point in the;middle of the forehead);You can see pictures of all of these traits in Figure 9.12 (p 153) of your textbook, and;in the PDF file that is posted alongside the homework handout.;i);For each of these traits, record your phenotype and genotype in Table 1. For the;phenotypes, use one of the following terms: Dimpled chin or Normal chin, Free earlobes;or Attached earlobes, Freckles or No freckles, Mid-digit hair or No hair, Hitchhikers;thumb or No hitchhikers thumb, Widows peak or Straight hairline.;For the genotypes, do the following: If your phenotype is recessive, indicate this with two;lower case letters (Example: dd), and if it is a dominant phenotype, use a single;uppercase letter followed by a big dash (Example: D).;TABLE 1;Trait;Dimpled chin;Free earlobes;Freckles;Mid-digit hair;Hitchhikers thumb;Widows peak;Your Phenotype;Your Genotype;ii);Determine your overall genotype by tracing your probable genotypes from trait 1;through trait 5 until you reach the genotype number. Indicate that number in the box below.;TABLE 2;Earlobes;Freckles;Mid-digit;hair;Hitchhikers;Thumb;S;M;ss;F;S;mm;ss;E;S;M;ss;ff;S;mm;ss;S;M;ss;F;S;mm;ss;ee;S;M;ss;ff;S;mm;ss;My genotype number is =;Widows;Peak;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;W;ww;GENOTYPE;NUMBER;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21;22;23;24;25;26;27;28;29;30;31;32;Question 2 (6 points);Use the media available to you to research and describe the following diseases.;Disease;Cystic;fibrosis;Duchenne;Muscular;Dystrophy;Hemophilia;Huntington;Chorea;Sickle Cell;Anemia;Tay-Sachs;Disease;Brief description of;underlying problem;Is the disease;Dominant;Recessive or;Sex-linked?;Is the disease;common in a;particular group?;Which ones?;Question 3 (4 points);The ability of humans to taste the bitter chemical phenylthiocarbamide (PTC) is;an inherited trait, under the control of the two alleles of a single gene. The T allele for;tasting is dominant to the recessive t allele for non-tasting.;i);Could two non-taster parents have a child able to taste PTC? Explain your answer.;ii);Could two parents able to taste PTC have a non-taster child? Explain your answer.;iii);Minnie and Mickey are married and both can taste PTC. Minnies mom and;Mickies dad are non-tasters. The couple is expecting their first child. What is the chance;that the child will be able to taste PTC? Show your work.;Question 4 (3 points);As discussed on p. 165, red-green colorblindness results from a sex-linked recessive;allele. The dominant allele, N, produces normal color vision, and the recessive n allele is the;colorblind allele. A man with normal color vision marries a color-blind woman.;i);What is the probability of their having a color-blind son? Explain your answer.;ii);The woman gives birth to a color-blind daughter (who has no other chromosomal;abnormality). The husband sues for a divorce on the grounds of adultery. Will his case stand;up in court? Explain your answer.;Question 5 (4 points);A mule is the offspring of a male donkey and a female horse. A donkey sperm;contains 31 chromosomes and a horse egg 32 chromosomes, so the zygote contains a total;of 63 chromosomes. The zygote develops normally. The combined set of chromosomes is;not a problem in mitosis, and the mule combines some of the best characteristics of horses;and donkeys. However, a mule is sterile, meiosis cannot occur normally in its testes and;ovaries. Explain why mitosis is normal in cells containing both horse and donkey;chromosomes, but the mixed set of chromosomes interferes with meiosis.


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