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Inheritance

This article explains how genetic characteristics are inherited, with a focus on human reproduction and the role of genes in determining our features. It discusses important terms such as alleles, homozygous, heterozygous, genotype, and phenotype. It also explores specific examples like albinism and the inheritance of wizardry in the Harry Potter series.

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Inheritance

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  1. Inheritance Who are they? What has he inherited?

  2. Objective • To explain the inheritance of genetic characteristics

  3. Reproduction: • Thegametes (sex cells of humanseachcontain 23 chromosomes. Thisishalfthenumber of allothercells. • When the sperm meets the egg their nuclei fuse giving 23 pairs (46) chromosomes. The number present in all of our cell nuclei (except our sperm and eggs)

  4. Features • Many of our features are controlled by the genes on our chromosomes. • This is why we often look like our parents. • But we don’t always. • We will discuss the reasons.

  5. Important terms • Alleles:These are alternativetypes of one gene. • Homozygous:Youhavethesametwoallelesfor a gene. • Heterozygous:Yourtwoalleles are different • Genotype:Thecombination of allelesthatyouhave. • Phenotype:Thefeaturesyouactuallyhave. This is a human karyotype – all the chromosomes laid out. You can see they are in pairs

  6. Other important terms Dominant: You only need one of your two alleles to be this to see it. It means the phenotype is the same whether you are homozygous (have two dominant alleles) or heterozygous (have one dominant allele) Example Huntington’s disease: you have it if you inherit the allele from one parent Recessive: you need both of your alleles to be this to see its affects. Your phenotype only shows this if you are homozygous: have two recessive alleles. E.g. Cystic fibrosis and others…….

  7. Albinism • Albinos don’tnormallyhave albino parents. Itis a recessivecondition and an albino musthavetwo albino alleles. • Thatmeanstheymusthavegotone albino allelefromeachparent. • One in every 130 individualscarriesthe gene foralbinismbuttheconditionismuchlesscommonbecausebothparentsmustbecarriers and thechildmustinheritthe albino allelefromboth (a 1 in 4 chance). • Onechild in every 17000 is albino.

  8. Harry Potter and the recessive gene ¿What makes wizards?

  9. How are wizards formed? • It is down to their genes. • Wizards receive an allele from each parent. • The ability to be a wizard is recessive. We call the allele ‘m’. The fact that we use a lower case letter shows that it is recessive. Dominant alleles are indicated by capitals. • mm is the genotype needed to have the phenotype of wizard.

  10. The genes of wizardry • The allele for a muggle is ‘M’ • Muggles can be ‘Mm’ or ‘MM’ • M is dominant over m, so you can only be a wizard if you are homozygous for the recessive allele. Your genotype must therefore be ‘mm’

  11. The Malfoys Narcissa Malfoy (mm) Lucius Malfoy (mm) Draco Malfoy ( ) m m The Malfoys are a pure blooded wizard family. All are homozygous for the recessive ‘m’ allele for wizardry. All their ancestors were wizards so they must all be ‘mm’.

  12. The Potters James Potter (mm) Lily Potter (mm) Harry Potter m m Both parents are wizards so Harry is as well. Harry is not considered a pure blood because one of his maternal grandparent was a muggle.

  13. The Weasleys are pure blooded wizards as well. All of them must be ‘mm’

  14. Hermione is as powerful a wizard as them. Logically she must be mm Both her parents were muggles. They must have been heterozygous (Mm) for her to be a wizard (mm) Mm Mm mm

  15. Tom Riddle is half blood His mother was a wizard (mm)and his father a muggle. Therefore his father must have been heterozygous (Mm)for him to be a wizard (mm) Mm mm mm

  16. ¿What alleles would the children of Ron and Hermione have? Ron (mm) Hermione (mm) Babies m m

  17. Their children would both have recessive alleles because the parents are both homozygous recessives. m m m m m m m m

  18. What alleles would the children of Ginny and Dudley have? Ginny mm Dudley Mm Children Mm or mm

  19. Half of their children would be wizards and the other half would be muggles carrying the recessive gene. m m M m M m m m

  20. What alleles would their children have had if Dudley had been MM? Ginny mm Dudley MM Children Mm

  21. All of their children would have been muggles but carrying the ability to be wizards. M m M m m M M m

  22. What alleles could the brothers and sisters of Hermione have?

  23. Her siblings would have only a 25% chance of being wizards, 50% chance of being heterozygous muggles carrying the wizard allele and 25% chance of being homozygous muggles. m m M m M M M m

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