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General Genetic

General Genetic. Exceptions to Simple Inheritance (Non-Mendelian inheritance). Bio 221 Lab 7. 1-Widow's Peak ( W, w) front hairline : Dominant allele in heterozygous or homozygous individuals results in a V-shaped

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General Genetic

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  1. General Genetic Exceptions to Simple Inheritance (Non-Mendelian inheritance) Bio 221 Lab 7

  2. 1-Widow's Peak (W, w) front hairline : Dominant allele in heterozygous or homozygous individuals results in a V-shaped • 2-Ear lobes (A, a): Ear lobes may be either adherent or free and pendulous. Homozygous recessives The dominant trait is for lobes to hang free, a bit of lobe hanging down prior to the point where the bottom of the ear attaches to the head. With the recessive phenotype, the lobes are attached directly to the head • 3-Hitchhiker's thumb (H, h): Homozygous recessives can bend the distal joint of the thumb backward to a nearly

  3. 4-Tongue rolling (R, r) : Persons with a dominant allele in heterozygous or homozygous condition can roll • 5-Bent pinky (B, b) inward toward the fourth (ring) finger : Dominant allele causes the distal segment of the fifth finger to bend distinctly • 6-Cleft chin:  the dominant  gene causes the cleft chin while the recessive genotype presents without a cleft. 

  4. 7-Thumb crossing (C, c): In a relaxed interlocking of fingers, left thumb over right indicates the dominant 8-PTC tasters (T, t) : Phenylthiocarbamide (PTC) tastes bitter to heterozygous or homozygous dominant individuals, but is tasteless to homozygous recessives 9-Blue eyes (E, e) : Blue-eyed persons are homozygous recessive and lack pigment in the iris 10-Middigital hair (M, m): People lacking hair in the middle segments of the fingers are homozygous recessive.

  5. 11- clockwise (CW) or counterclockwise (CCW) direction:  the allele for clockwise is dominant to the allele for counterclockwise.  12- Darwin's tubercle: The allele for Darwin's tubercle is dominant.  13- Toe length: The big toe is longer than the second toe ( L), while other people have the big toe shorter than the second toe ("S").  The allele for S dominant to the allele for L

  6. Exceptions to Simple Inheritance (Non-Mendelian inheritance) Non – Mendelian inheritance : is trait do not segregate in accordance to Mendel Laws . Some traits are carried on sex chromosomes X and Y . Most traits carried are present on only the X chromosome while the Y Chromosome is smaller and very few genes are located on this chromosome . There are 3 Categories of genes that may have different effects depending on an individuals gender : 1- Sex – Limited genes . 1-Beard and Breast . 2- Milk Production . 3-White and yellow color of special specie of butterfly . 4-Feathering in birds . 2- Sex – Influenced genes . 1- Baldness . . 3- X– Linked inheritance . 1- Dominant sex – linked traits. 2- Recessive sex linked traitsa-Whit eye (rr) in Drosphilia . b- Red / Green color blindness .c Example : Hemophilia (hh)

  7. 1- Sex – Limited genes . • Definition : • That are inherited by both men and women but are normally only expressed in the phenotype of one of them . • Example : • 1- Beard and Breast . • Beard and Breast are secondary sexual characters that depend on sex hormones . • In female lacks in beard and male lacks in developed breasts . • 2- Milk Production . • Is trait expressed by cows and affected by gene on Somatic chromosome 14 . Both Bulls and Cows carry this gene and both contribute an allele to their daughters which affects the quantity of milk that daughter produces . • 3- White and yellow color of special specie of butterfly . • That male always have yellow color while (WW) the female have in two color white and yellow (ww) .

  8. Example : 4- Feathering in birds . Males have long , pointed curved fringed feathers on tail and neck , but feathers of female are shorter , rounded , straighter . t had been early established that hen-feathering is a trait controlled by a simple autosomic dominant gene, whose expression is limited to the male sex.

  9. 2- Sex – Influenced genes . • 1-The sex hormones of the animal affect the expression of a trait by the heterozygous and provide different cellular environments in males and females . • 2-The genes behave differently in two sexes . • Ex : amount of body hair and muscle mass. Example : 1- Baldness (BB). *In male physiological factors helps in the expression of hair ( Recessive allele ) in males than females . *The gene for baldness behaves as a dominant in males but as a recessive in females . *Heterozygous males are bald and will pass the gene to about 50% of their offspring of either sex . *The amount of thinning of the hair or balding that is observed depends both on genotype and the amount of testosterone exposure . male BB x bb Female

  10. male BB x bb Female

  11. 3- X– Linked inheritance . Information : That inheritance is different males than females , and That inheritance controlled by Genes on X – Chromosomes . - Mother 1- pass X-linked alleles to only sons . 2- Females ( homozygous) have 2 allele for each gene 3-Female can be : Normal , Affected , Carrier . 4-Females have 2 X- Chromosomes that good chance of having the normal gene on one of the two . - Fathers 1-pass X-linked alleles to only daughters . 2-Male can be : Normal , Affected . 3- males ( hemizygous) have one X – Chromosomes and have recessive condition much more commonly than females . 4-Males have 1 X- Chromosome does not carry of the same genes , so there is no normal gene to counter the defective X .

  12. Probabilities inheritance of sex linked traits 1- Unaffected father with affected mother

  13. 2- Unaffected father and carrier mother

  14. 3- Affected father and unaffected Mother

  15. 3- X-Linked Dominant Inheritance • A male or female child of a mother affected with an X-Linked dominant trait has a 50% chance of inheriting the mutation and thus being affected with the disorder. • All female children of an affected father will be affected (daughters possess their fathers' X-chromosome). No male children of an affected father will be affected (sons do not inherit their fathers' X-chromosome).

  16. 4-X-Linked Recessive Inheritance • Females possessing one X-linked recessive mutation are considered carriers and will generally not manifest clinical symptoms of the disorder. • All males possessing an X-linked recessive mutation will be affected (males have a single X-chromosome and therefore have only one copy of X-linked genes). • All offspring of a carrier female have a 50% chance of inheriting the mutation. • All female children of an affected father will be carriers (daughters possess their fathers' X-chromosome). No male children of an affected father will be affected (sons do not inherit their fathers' X-chromosome).

  17. Kinds of : 1-Autosomal Dominant Inheritance: The child of an parent affected with autosomal dominant inheritance has a 50% chance of inheriting the parent's mutated allele and thus being affected with the disorder. A mutation can be transmitted by either the mother or the father. All children, regardless of gender, have an equal chance of inheriting the mutation.

  18. 2-Autosomal Recessive Inheritance a- An individual will be a "carrier" of autosomal recessive inheritance if they possess one mutated allele and one normal gene copy. There is a 50% chance that a carrier will transmit a mutated gene to a child. b- If two carrier parents have a child there is a 25% chance that both will transmit the mutated gene; in this case, the child will inherit only mutated copies of the gene from both the mother and the father and thus will be affected with the disorder. There is a 50% chance that one carrier parent will transmit the mutated gene and the other will transmit the normal gene; in this case, the child will have one mutated gene and one normal gene and will be a carrier of the disorder. Finally, there is a 25% chance that both carrier parents will transmit the normal gene; in this case the child will have only normal genes and will not be affected.

  19. Examples: 1-White eye (rr) in Drosophila . *Consider the red /white eye allele of Drosphilia . Red eyes are dominant (Normal) and codes (RR) , (Carrier ) (Rr) and White eyes are codes ( rr) . *The recessive phenotype is more common in males , because the R/r locus is on X – Chromosome that means the males are haploid , the only genotype have R or r for that R male has red eyes and r males have white eyes .

  20. Examples: • 2- Red / Green color blindness .(cc) • * Is condition of color vision . It appears to normal state of animals that active at night . • Because , the vision is mediated not by cone receptors but by rods which respond to low intensity of light . • (Normal) code (CC) , (Carrier ) (Cc) and Affected ( cc) .

  21. 3-Example : Hemophilia (hh) Most male lethal 1-Male can be : Normal (HH) , Affected (hh) . 2-Female can be : Normal (HH) , Carrier (Hh) , Affected (hh) . When a female with hemophilia has children , she will pass the gene to each of her sons. .

  22. Question : A color blindness man marries a woman with normal vision . Her mother was color blind . What kind of : 1- Children would you expect from this marriage ? 2- Which kind of this inheritance?

  23. The experiment of today white eye cross in Drosophila

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