Genetics:Inheritance And Variation Made just for You by the Grade 10 Science Team International School Bangkok

Human Genetics

Human Genetic Illness Examples Dominant: Huntington’s Disease – H, h Recessive: Cystic Fibrosis – F, f Codominant: Sickle-cell anemia – Hb A, Hb S X-linked (recessive): Hemophilia – X H, X h

The Human Condition Cystic Fibrosis: A Recessive Allele Genotypes:  FF = normal  Ff = normal  ff = Cystic Fibrosis A sad story. A hopeful story. Informational Video

Cystic Fibrosis Punnett Grids Claire’s parents are both carriers of cystic fibrosis. If they have another child, what is the chance it will have CF? Kerry has CF. Her husband is homozygous normal. What is the chance that their son would have CF? What is the chance he would be a carrier of CF? Ff ff FF FfFf FfFf 25% Ff f F 0% 100%

The Human Condition Huntington’s Disease: A Dominant Allele A degenerative brain disorder A degenerative brain disorder Onset usually occurs later in life (30’s to 40’s) Onset usually occurs later in life (30’s to 40’s) People lose the ability to walk, reason, talk People lose the ability to walk, reason, talk Associated with aggression and other personality changes Associated with aggression and other personality changes Informational Video Personal Story

Huntington’s Disease: A Dominant Allele Genotypes:  Hh = Huntington’s Diesase  hh = normal  HH = Huntington’s Disease (but very rare) A pregnant woman was just diagnosed with Huntington’s Disease. Her husband has tested negative for the Huntington’s allele. What is the chance that the baby will also have Huntington’s Disease? Hhhh h HhHh 50%

The Human Condition Hemophilia: A Sex-Linked (Recessive) Allele Informational Video Teens Speak about Hemophilia

Hemophilia Punnett Grids A woman who carries hemophilia has children with a man with normal blood. What is the chance of a son having hemophilia? What is the chance for a daughter? A man with hemophilia has children with a women who is homozygous normal. What is the chance that their child will have hemophilia? What is the chance that a son will be a carrier? XHXhXHXh X H Y XHXH XhYXhY 0% XHXHXHXH X H Y XHXhXHXh X H Y 50% 0% XHXhXHXh X h Y

The Human Condition Sickle-Cell Anemia : Codominant Alleles Genotypes:  Hb A Hb A = normal  Hb A Hb S = protection from malaria  Hb S Hb S = Sickle Cell Anemia Informational VideoPersonal Story

The Human Condition Sickle-Cell Anemia: Codominant Alleles % of Population with the Hb S allele Two parents are both heterozygous for the sickle- cell allele. What is the chance that their child will have protection against malaria? What is the chance that their child will have sickle cell disease? Hb A Hb S Hb A Hb S 50% 25% Hb A Hb S Hb S

Pedigrees

Visually represent genetic relationships over generations

Symbols in Pedigrees MaleFemale Marriage / Mating Offspring / Children I II Marriage / Mating Generation Number 1 2 What is the relationship of person II 2 to person I 1? Individuals with the trait being studied are shaded. Daughter Number of individual

Do you have a Pedigree? Of course you do!

Ms. Soule’s Pedigree How many children does Ms. Soule have? How many sons and daughters? How many cousins does Ms. Soule have? How many brothers and sisters does Ms. Soule’s mother have? How many brothers and sisters does Ms. Soule’s father have? 2, 1, 1 4 1, 1 0, 1

Ms. Soule’s Pedigree The trait is “red hair”. Assume it is a recessive single-gene trait. What is the chance than Ms. Soule’s sister is a carrier? What is the chance that Ms. Soule is a carrier if her father does not have the allele? 100% 50%

What pattern of inheritance does this show? Recessive! How can you tell?

What pattern of inheritance does this show? Sex-linked recessive! How do you know?

What pattern of inheritance does this show? Dominant! How do you know?

What pattern of inheritance does this show? Recessive! How do you know?

Pedigrees, Probability, and Punnett Grids! 1.What is the chance that person III 1 is a carrier? 2.What is the chance that a new child of people II 3 and II 4 would have the trait? 3.What is the chance that the next child of people III 2 and III 3 will have the trait? 4.What is the chance that a sister of person II 1 would have at least one copy of he allele? 5.What is the chance that the grandchild of person III 5 will be a carrier if no people marrying into the family have the allele? 100% 25% 100% 25%

Remember Karyotypes? Turning a picture of a jumble of chromosomes into... an orderly array like this!

Could you diagnose conditions like Cystic Fibrosis or Sickle-Cell Anemia with a Karyotype? No, those alleles involve changing only a few base pairs. Karyotypes show chromosomes which are many millions of base pairs long