Mendel and Genetics. Mr. Nagel Meade High School

Transcription

1 Mendel and Genetics Mr. Nagel Meade High School

2 What is inheritance? Question? Inheritance: Passing on traits by transmitting them from parents to offspring How does it relate to you personally? Why does it matter to you and your future family members?

3 Once Upon a Time Gregor Mendel (1865) Austrian Monk A PAIR of factors control the expression of each inherited trait in an organism Sutton (1900) These factors are on chromosomes Modern Thought These factors are called GENES and are segments of DNA

4 Give Peas A Chance Why use pea plants? What physical features could you monitor?

5 Factors Observed by Mendel

6 Down With the Lingo? Gene Allele Genome Dominant Recessive Homozygous Heterozygous Self-Pollination Cross-Pollination Parental Generation Filial Generation Independent Assortment Segregation Genotype Phenotype

7 Down With the Lingo? Gene segment of DNA on a chromosome that controls a particular trait Allele equivalent of Mendel s factor - several alternative forms of a gene {one from each parent} Genome entire genetic makeup of an organism Dominant dominates the other factor of the trait Recessive masked in the presence of a dominant factor Homozygous when both alleles of a pair are the same Heterozygous when both alleles of a pair are NOT the same Self-Pollination mating with self (same plant) Cross-Pollination mating with a different plant Parental original generation Filial children (generation of offspring) Independent Assortment there is no connection AT ALL between any given inherited trait (color and height, etc.) Segregation two factors (alleles) that a parent possess for a trait are separated during egg/sperm formation Genotype genetic makeup of an organism Phenotype external appearance of an organism

8 Mendel and Meiosis Discuss with a partner: What does independent assortment mean in terms of what is observed in Meiosis? Hint: Linkage is when two traits are known to commonly exist together. What does segregation mean in terms of what is observed in Meiosis? Hint: Disjunction is when the chromosomes separate, sending one trait to each sex cell.

9 Mendel s First Experiment What are the genotypes for each seed? Which trait is dominant? Which trait is recessive? Is the parental Spherical seed homozygous or heterozygous?

10 Punnett Grids Graphical representation of possible offspring Each parent occupies one side Each parental gene occupies one side of a box Based on ideas of Probability In Meiosis, there is a 50/50 possibility that each trait is passed on. (Think coin flip) Parental Genes Mom 1 Mom 2 Dad 1 Kid 1 Kid 2 Dad 2 Kid 3 Kid 4

11 Punnett Grids

12 Punnett Grids What are the two parental genotypes? What are the two parental phenotypes? What are the offspring s genotypes? Ratio? What are the offspring s phenotypes? Ratio?

13 Homozygous Dominant (YY) x Homozygous Recessive (yy) What are the two parental genotypes? What are the two parental phenotypes? What are the offspring s genotypes? Ratio? What are the offspring s phenotypes? Ratio? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

14 Homozygous Dominant (YY) x Heterozygous (Yy) What are the two parental genotypes? What are the two parental phenotypes? What are the offspring s genotypes? Ratio? What are the offspring s phenotypes? Ratio? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

15 Heterozygous (Yy) x Heterozygous (Yy) What are the two parental genotypes? What are the two parental phenotypes? What are the offspring s genotypes? Ratio? What are the offspring s phenotypes? Ratio? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

16 Dihybrid Cross Parental Genes Dad 1 Dad 2 Dad 3 Dad 4 Mom 1 Kid 1 Kid 2 Kid 3 Kid 4 Mom 2 Kid 5 Kid 6 Kid 7 Kid 8 Mom 3 Kid 9 Kid 10 Kid 11 Kid 12 Mom 4 Kid 13 Kid 14 Kid 15 Kid 16

17 Parental Genes Homozygous Dominant (TTYY) x Homozygous Recessive (ttyy) Dad 1 Dad 2 Dad 3 Dad 4 Mom 1 Kid 1 Kid 2 Kid 3 Kid 4 Mom 2 Kid 5 Kid 6 Kid 7 Kid 8 Mom 3 Kid 9 Kid 10 Kid 11 Kid 12 Mom 4 Kid 13 Kid 14 Kid 15 Kid 16

18 Parental Genes Heterozygous (TtYy) x Heterozygous (TtYy) Dad 1 Dad 2 Dad 3 Dad 4 Mom 1 Kid 1 Kid 2 Kid 3 Kid 4 Mom 2 Kid 5 Kid 6 Kid 7 Kid 8 Mom 3 Kid 9 Kid 10 Kid 11 Kid 12 Mom 4 Kid 13 Kid 14 Kid 15 Kid 16

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20 Gizmo Observe outcomes predicted in Punnett Grids for: Mice: Single Trait/Two traits Aliens

21 Beyond Mendel What other systems exist for gene expression? Simple Dominance (A or a) Co-Dominance (equal expression of alleles) Sex-Linked (alleles only on X chromosome) Girls = XX = two alleles Guys = XY = one allele How do we test for unknown genotypes? Testcross to determine AA or Aa

22 Codominant I Imagine a cat that is black, and another that is white. What if all the offspring were gray? What if half the offspring were gray and half were white? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

23 Codominant II Consider two parents, one with type A blood and one with type B. How could a child of this mating have type O blood? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

24 Sex-Linked I Imagine a colorblind mom mating with a noncolorblind dad. What predictions could you make about the offspring? What do you notice about the boys? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

25 Sex-Linked II Imagine a hemophilic dad mating with a nonhemophilic mom. What predictions could you make about the offspring? Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

26 Testcross What if we know the offspring phenotypes and/or genotypes, but don t know one of the parents? Breed with a homozygous recessive! Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

27 Fun With Traits Pick a few traits from the list below: Dominant Widow s peak Dimples Bent little finger Mid-digital hair Dwarfism L-over-R Thumb folding Detached Earlobes Tongue Rolling Recessive Hitch-hiker s Thumb (90 ) Chin cleft Sex-Linked Hemophilia Red-green Colorblindness Male Pattern Baldness Co-Dominant Blood type Flower Color (Red/White) Map out a Punnett Square based on the trait you selected, where mom and dad are both heterozygous for the condition or trait.

28 Where are Genes Located? m.nih.gov/books/n BK22266/

29 Assessment Imagine a parent that is blue and another that is red. Construct a Punnett Square for each that demonstrates this mating if: ALL the offspring are Purple. ALL the offspring are Blue. ALL of the sons are red. Parental Genes Dad 1 Dad 2 Mom 1 Kid 1 Kid 2 Mom 2 Kid 3 Kid 4

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31 Intro sc431/mendel/mendel9.htm

32 Pedigrees

33 Let s take a look at Queen Victoria s son Leopold s family. His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other children a boy and a girl whose status is unknown. What is the probability that her other son was hemophilic? What is the probability that her daughter was a carrier? Hemophilic? What is the probability that both children were normal? Pedigrees

34 Now for the Spanish connection: Victoria s youngest child, Beatrice, gave birth to one daughter, one normal son, and two hemophilic sons. Looking at the pedigree of the royal family, identify which of Beatrice s children received the hemophilic gene; why can you make this conclusion? Notice that Beatrice s daughter, Eugenie, married King Alfonso XIII of Spain and had six children, one of whom was the father of Juan Carlos, the current King of Spain. Would you predict that Juan Carlos was normal, a carrier, or a hemophilic? What is the probability that her unnamed son was hemophilic? Pedigrees

35 Lastly, the royal line of Russia. What are the probabilities that all four of the girls were carriers of the allele hemophilia? Supposing Alexis had lived and married a normal woman, what are the chances that his daughter would be a hemophiliac? What are the chances his daughters would be carriers? What are the chances that his sons would be hemophiliacs? Pedigrees

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37 Polygenes Polygenes have an additive effect the more dominants you have, the more intense the feature: Fingerprint Ridge Count Eye Color Skin Color