a) How are X-linked genes inherited in humans Be able to use this i.pdf
- 1. a) How are X-linked genes inherited in humans? Be able to use this information to perform monohybrid and dihybrid crosses and to interpret pedigrees. (SHOW WORK & EXPLAIN) b) Describe dosage compensation/X-inactivation and its consequences. (SHOW WORK & EXPLAIN) c) Describe Y-linked inheritance and be able to use this information in monohybrid and dihybrid crosses and pedigrees. (SHOW WORK & EXPLAIN) d) Explain complete dominance, incomplete dominance, codominance, penetrance, expressivity, lethal alleles and multiple alleles and give examples of each. (SHOW WORK & EXPLAIN) Solution If cross is made between XY MALE and Xx carrier female then offspring will as shown below 50% hemophilic Xx ( carrier) female and hemophilic boy Yx 50% normal XX and XY. 2.In many animals male have one and female have two X chromosome . The difference in X chromosome dosage between the two sexes is compensated by mechanism that regulate X chromosome transcription. Mainteneance of chromosome dosage is necessary in normal development. X chromosome contain many gene that are important in both sexes male contain single X and female contain two X chromosome. .To compensate for X chromosome dosage difference between sexes different mechanism have evolved to equalize x linked transcript level in male and female.. polypoidy refers to increase in dosage in all chromosome while aneuploidy refers to change in dosage of one chromosome with respect to rest of the genome. Consequence of X gene inactivation is visibly mosaic phenotypes exhibited by mammalian female heterozygous for X linked genes affecting hair and skin . Answer 3: Y linked inheritance can be seen in male members as only male has Y chromosome. Y-linked inheritance is appearance of traits in an organism due to the presence of an alelle on the Y-chromosome e.g hypertrichosis and pattern baldness are due to Y linked inheritance. Answer 4; Complete dominance is form of dominance in hetrozygous allele that is dominant completely mask the effect of allele that is recessive flower on mendel's pea plant is example of complete dominance Blue flower has dominant allele B whle b is recessive cross will be dominant are BB, Bb,Bb with blue flowers Incomplete dominance is a form of inheritance in which one allele for a specific trait is not completely expressed over its paired allele .As a result third phenotype appear which is the combination of both allele e. g snapdragon flower is pink when cross between red flower and
- 2. white flower here neither white is dominant nor red Codominance is form of dominance where in allele of a gene pair in a heterozygote are fully expressedXYXXXXYxXxxY