V4 Inheritance 7

Welcome!
Have the following ready:

  • Notebook/document to take notes in
  • Sex-linked inheritance worksheet (have it open)
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Welcome!
Have the following ready:

  • Notebook/document to take notes in
  • Sex-linked inheritance worksheet (have it open)

Slide 1 - Diapositive

Roadmap for today:
Goal: Introducing the last new topics (multiple alleles and lethal alleles) + reviewing the chapter
  • Discuss sticky note question from last lesson
  • Presentation: introduction to multiple alleles and lethal alleles (take notes!)
  • Kahoot (review of chapter)
  • Time to study/finish worksheets

Slide 2 - Diapositive

Question from last lesson:
How does sex-linked inheritance affect the phenotypic ratio of the F1?
- The trait is expressed in the offspring (boys) more often than if the allele was not sex-linked.



Slide 3 - Diapositive

Phenotypic ratios with sex linkage:
  • If the father is XᵃY and mother XᵃX, then half of girls have the trait, half of girls are carriers, half of boys have the trait (1:1, same as if parents were aa and Aa)
  • If the father is XY and the mother is XᵃXᵃ: all girls are carriers, all boys have the trait (1:1 instead of 1:0 if the parents were AA and aa).
  • If the father is XY and the mother is XᵃX: half of boys have the trait, half of girls are carriers (3:1 instead of 1:0 if the parents were AA and Aa).
  • What if the father is XᵃY and mother XᵃXᵃ?

Slide 4 - Diapositive

What will be the genotypic and phenotypic ratio if the father is XᵃY and mother XᵃXᵃ?

Slide 5 - Question ouverte

Multiple alleles
A gene with more than two alleles.

Example: blood type in humans

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I stands for isoagglutinogen, which is the name for the  type of antigen on red blood cells.

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A heterozygous woman with blood type A is married to a man with blood type O. What are all the possible genotypes of the offspring?

Slide 10 - Question ouverte

Lethal alleles
Alleles which cause an organism to die only when the organism is homozygous for the allele.

You can recognize the presence of a lethal allele by looking at the phenotypic ratio of the offspring. The ratio will be different than 

Question: why do we only find lethal alleles which are recessive?

Slide 11 - Diapositive

  • Which phenotypic ratio would you expect to observe if the allele was not lethal?
  • Which phenotypic ratio do you actually observe?

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What sex ratio would you expect among the offspring of a cross between a normal male mouse and a female mouse heterozygous for a recessive X-linked lethal gene?

Slide 13 - Question ouverte

Write a legend for this image: 
What does square vs. circle mean?
What does grey vs. white mean?
1
2
Person 1 is female and healthy. 
Person 2 is female and has an inheritable disease. 
pedigree chart for the family Jones

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5 minute break

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Self-directed work time:
Use this time to prepare for the test
Study the book and the lessonups, finish any unfinished worksheets, ask questions etc.

Homework for Tuesday:
  • finish the codominance worksheet
  • prepare to do a practice test
You may work together (put everyone's names in the worksheet title)

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