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What is a pedigree?

What is a pedigree? . Shows a pattern of inheritance in a family for a specific trait (phenotype) Why would we want to use a pedigree in genetics? It is a good way to follow the inheritance of genetic disorders through generations. . Pedigree Analysis. I, II, III. 1, 2, 3.

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What is a pedigree?

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  1. What is a pedigree? • Shows a pattern of inheritance in a family for a specific trait (phenotype) • Why would we want to use a pedigree in genetics? • It is a good way to follow the inheritance of genetic disorders through generations.

  2. Pedigree Analysis I, II, III 1, 2, 3 Children (in birth order) Non-identical twins Carrier (heterozygote) Died in infancy Generations Affected male Identical twins Normal male Affected female Normal female Sex unknown

  3. More Symbols

  4. Pedigree Chart Symbols Carrier (heterozygote) In this example, the arrow indicates the propositus or person through which the pedigree was discovered.

  5. Dominant AutosomalTrait I 2 1 II 1 2 3 4 5 6 III 1 2 3 4 5 6 7 8 9 10 . both males and females can be affected • all affected individuals have at least one affected parent • once the trait disappears from a branch of the pedigree, it does not reappear • in a large sample, approximately equal numbers of each sex will be affected.

  6. X-LinkedDominant Traits • • a male with the trait passes it on to all his daughters and none of his sons • • a female with the trait may pass it on to both her daughters and her sons • • every affected person has at least one parent with the trait • • if the trait disappears from a branch of the pedigree, it does not reappear • over a large number of pedigrees, there are more affected females than males. • .

  7. Inheritance of AutosomalRecessive Traits both males and females can be affected • two unaffected parents can have an affected child • the trait may disappear from a branch of the pedigree, but reappear in later generations • equal numbers of affected females and males.

  8. Inheritance of X-LinkedRecessive Traits all the sons of a female with the trait are affected all the daughters of a male with the trait will be carriers of the trait • in a large sample, more males than females show the trait.

  9. Y-Linked Inheritance • Traits on the Y chromosome are only found in males, never in females. • The father’s traits are passed to all sons. • Dominance is irrelevant: there is only 1 copy of each Y-linked gene (hemizygous).

  10. Mitochondrial Genes • Mitochondria are only inherited from the mother. • If a female has a mitochondrial trait, all of her offspring inherit it(matrilineal).

  11. D loop mtDNA • Is a non coding area of a mtDNA

  12. Sex Determination Y X • In most cases, the determination of the sex of an organism is controlled by the sex chromosomes provided by each parent. • In humans and other mammals, males are the heterogametic sex because each somatic cell has one X and one Y chromosome (i.e. the two sex chromosomes are different). • Males are not always the heterogametic sex.In birds and butterflies, the female is the heterogametic sex, and in some insects the male is simply X whereas the female is XX.

  13. XY Sex Determination XY XY XY XX XX XX Female Male X Parents X X X Y Gametes Possiblefertilizations Offspring Sex: Male Male Female Female • In the XY type, sex determination is based on the presence or absence of the Y chromosome; without it, an individual will develop into a female. • XY sex determination occurs in: • Mammals (including humans) • Fruit fly Drosophila • Some dioecious (separatemale and female) plantssuch as kiwifruit. • Females are homogametic withtwo similar sex chromosomes(XX). The male has two unlikechromosomes (XY) and isheterogametic. • Primary sex characteristics areinitiated by genes on the X.‘Maleness’ is determined by the Y.

  14. WZ Sex Determination ZZ ZZ ZZ ZW ZW ZW Female Male X Parents Z W Z Z Gametes Possiblefertilizations Offspring Sex: Female Male Female Female • In the WZ type,the female determines the sex of the offspring. • The male is the homogametic sex (ZZ), while the female has two unlike chromosomes (ZW). • WZ sex determination occurs in: • Birds • Butterflies and moths • Some fish

  15. XO Sex Determination XX XX XX Female Male X X Parents X X X Gametes Possiblefertilizations X X Offspring Male Male Female Female Sex: • In some insect orders, the female has two similar sex chromosomes (XX) while the male only has one (XO). • In the sperm produced by males, there is a 50% chance that it will have a sex chromosome and create a female offspring when it fertilizes an egg. • XO sex determination occurs in: • Grasshoppers • Aphids • Honey bees • Hemiptera (bugs)

  16. Sex Determination in Honey Bees Queen Drone XX XX XX X Not given royal jelly Given royal jelly Queen (Fertile female) Worker (Sterile female) X XX Egg fertilized X X X Egg not fertilized X Drone (Fertile male) • In honey bees sex is determined by the number of sex chromosomes, but environment in the hive has an influence too. • Males or drones • Result from unfertilized eggs and have one sex chromosome (monoploid). • Females • Females have two sex chromosomes but diet determines if they are reproductively active. • Queens are supplied with a diet of royal jelly. • Sterile workers are not given royal jelly.

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