Pre-AP Biology Tuesday February 20. Introduction to Pedigrees

Transcription

1 Pre-AP Biology Tuesday February 20 Introduction to Pedigrees

2 If you were absent: 1. See slides 3 7 for review question/answers 2. See slides 9 11 for background on how to read pedigrees 3. Try practice problems on slides See slide 15 for the overall strategies for interpreting pedigrees 5. Practice applying the steps to the six pedigrees that you have on the bottom of P. 4 in your packet and then check your work using the answers on the remaining pedigrees in this presentation

3 In a diploid organism with the genotype AaBbCcDdEe, how many genetically distinct type of gametes would be produced?

4 In a diploid organism with the genotype AaBbCcDdEe, how many genetically distinct type of gametes would be produced? Aa = 2 options Bb = 2 options Cc = 2 options Dd = 2 options Ee = 2 options Multiply: 2 x 2 x 2 x 2 x 2 = 32

5 A certain species of plants has four unlinked genetic loci, A, B, C, and D. Each genetic locus has one dominant and one recessive allele. For a plant with the genotype AABBCcDd, what is the probability that the plant will produce a gamete with a genotype of ABcd? Give your answer as a fraction or as a value between 0 and 1 to four decimal places. AABBCcDd ABcd 1 x 1 x ½ x ½ = ¼ or 0.25

6 Freckled (F) and PTC-tasting ability (T) are dominant traits in humans. Show a Punnett square and phenotype outcome for this cross: FfTt x fftt FT Ft ft ft ft FfTt Fftt fftt fftt 1 : 1: 1: 1 Freckled taster Freckled Non-taster Non-freckled Taster : : : Non-freckled Non-taster

7 When a woman who is a carrier has children with a color-blind man, one would expect which of the following outcomes: a. 50% carrier females, 100% color-blind sons b. 100% carrier females, 100% color-blind sons c. 50% color-blind females, 50% color-blind sons d. 100% carrier females, 50% color-blind sons Justify your answer with a Punnett square X N X n x X n Y

8 When a woman who is a carrier has children with a color-blind man, one would expect which of the following outcomes:

9 Symbols & Structure Used for a Pedigree Shaded = is affected Shaded = not affected

10 1. Select autosomal or sex-linked Name Description Clue Autosomal Gene found on non sex chromosome Sex-linked Gene found on X chromosome Males and females equally affected Many more males than affected females

11 2. Select recessive or dominant Name Description Clue Recessive Dominant Must have two copies of gene to express the condition Only need one copy to express the condition Skips generations, carriers: parents without condition have children with it Found each generation, no carriers

12 1. Autosomal or sex-linked? Justify: Autosomal males & females equally affected 2. Dominant or recessive? Justify: Recessive two unaffected individuals (carriers) have an affected offspring 3. Genotype of * individual? aa *

13 1. Autosomal or sex-linked? Justify: Autosomal males & females affected 2. Dominant or recessive? Justify: Dominant found in each generation, no carriers observed 3. Genotype of * individual? Aa *

14 1. Autosomal or sex-linked? Justify: Sex-linked males disproportionately affected 2. Dominant or recessive? Justify: Recessive skips generations, carriers observed 3. Genotype of * individual? X n Y *

15 1. Select autosomal or sex-linked 2. Select recessive or dominant 3. Figure out genotype of * individual Name Description Clue Autosomal Gene found on non sex chromosome Sex-linked Recessive Dominant Gene found on X chromosome Must have two copies of gene to express condition Only need one copy to express the condition Males and females equally affected Males disproportionately affected Skips generations, carriers: parents without condition have children with it Found each generation, no carriers

16 1. Autosomal males & females equally affected Dominant every generation, no carriers observed *Aa

17 2. Sex-linked males disproportionally affected Recessive skips generations *X n Y

18 3. * Autosomal because both males and females affected Dominant because affected individuals in all generations *Aa

19 4. * Autosomal males & females equally affected Recessive skips generations, carriers *Aa

20 5. Autosomal males & females equally affected Recessive skips generations & carriers seen *Aa

21 6. Sex-linked males disproportionately affected Recessive skips generations *X N X n