1. THE CHROMOSOMAL BASIS OF INHERITANCE
CHAPTER 15

2. What you must know:
How the chromosome theory of inheritance connects the physical movement of chromosomes in meiosis to Mendel’s laws of inheritance.
The unique pattern of inheritance in sex-linked genes.
How alteration of chromosome number or structurally altered chromosomes (deletions, duplications, etc.) can cause genetic disorders.
How genetic imprinting and inheritance of mitochondrial DNA are exceptions to standard Mendelian inheritance.

3. Chromosome theory of inheritance:
Genes have specific locations (loci) on __________________
Chromosomes segregate and assort _________________
Chromosomes tagged to reveal a specific gene (yellow).

4. Thomas Hunt Morgan Drosophila melanogaster – ______________
Fast breeding, 4 prs. chromosomes (XX/XY)
________________ gene: located on X or Y chromosome
Red-eyes = wild-type; white-eyes = mutant
Specific gene carried on specific chromosome

5. Sex determination varies between animals

6. Sex-linked genes Sex-linked gene on ________ Females (XX), male (XY)
Eggs = __, sperm = ________
Fathers pass X-linked genes to _____________, but not sons
Males express recessive trait on the single X (_______zygous)
Females can be affected or ____________

7. Transmission of sex-linked recessive traits
Affected __________  __________ Daughter
_____________ Mother  Affected _________
Affected __________ + Carrier ___________  _________ Daughter & Son

8. Sex-linked disorders ________________________
Duchenne muscular dystrophy

9. X-Inactivation
__________________= inactive X chromosome; regulate gene dosage in females during embryonic development
Cats: allele for fur color is on X chromosome
Only __________ cats can be tortoiseshell or calico.

10. Human development ___ chromosome required for development of testes
Embryo gonads indifferent at 2 months
_______gene: sex-determining region of Y
Codes for protein that regulates other genes

11. Genetic Recombination: production of offspring with new combo of genes from parents
If offspring look like parents  _______________
If different from parents  _______________

12. If results do not follow Mendel’s Law of Independent Assortment, then _____________________________

13. Linked genes: located on ______ chromosome and tend to be inherited ________________ during cell division

14. Crossing over: explains why some linked genes get separated during meiosis
the further apart 2 genes on same chromosome, the higher the probability of ________________ and the higher the ________________________

15. Calculating recombination frequency

16. ____________________: genetic map that is based on % of ________________events
1 map unit = 1% recombination frequency
Express relative distances along chromosome
50% recombination = far apart on _____ chromosome or on 2 ____________________ chromosomes

17. Exceptions to Mendelian Inheritance

18. Genomic Imprinting
Genomic ___________: phenotypic effect of gene depends on whether the gene is inherited from M or F parent
Methylation: _____________ genes by adding ____________ groups to DNA

19. Non-Nuclear DNA Some genes located in organelles
_______________, _______________, plastids
Contain small circular DNA
Mitochondria = ____________ inheritance (eggs)
Variegated (striped or spotted) leaves result from mutations in pigment genes in plastids, which generally are inherited from the maternal parent.

20. Genetic Testing Reasons for Genetic Tests:
_______________ testing (genetic disorders)
Presymptomatic & _______________ testing
___________ testing (before having children)
Pharmacogenetics (medication & dosage)
Prenatal testing
_________________ screening
Preimplantation testing (_______________)

21. Prenatal Testing May be used on a fetus to detect genetic disorders
_____________________: remove amniotic fluid around fetus to culture for karyotype
_________________________sampling: insert narrow tube in cervix to extract sample of placenta with fetal cells for karyotype

23. _____________________: chromosomes fail to separate properly in Meiosis I or Meiosis II

24. __________________ can detect nondisjunctions.
Down Syndrome = Trisomy ____

25. ______________ Syndrome: 47XYY, 47XXY
Nondisjunction
______________ Syndrome: 47XYY, 47XXY

26. ____________ Syndrome = 45XO
Nondisjunction
____________ Syndrome = 45XO

27. Chromosomal Mutations

28. Chromosomal Mutations

29. Nondisjunction _________________: incorrect # chromosomes
Monosomy (__ copy) or Trisomy (___copies)
_________________: 2+ complete sets of chromosomes; 3n or 4n
Rare in animals, frequent in ____________
A tetraploid mammal. Scientists think this species may have arisen when an ancestor doubled its chromosome # by errors in mitosis or meiosis.

30. Review Questions
What is the pattern of inheritance of the trait (shaded square/circle) shown in the pedigree?
How many chromosomes are in a human cell that is:
a) Diploid? b) Triploid?
c) Monosomic? d) Trisomic?

31. Chi-Square Analysis Practice
Two true-breeding Drosophila are crossed: a normal-winged, red-eyed female and a miniature-winged, vermillion-eyed male. The F1 offspring all have normal wings and red eyes. When the F1 offspring are crossed with miniature-winged, vermillion-eyed flies, the following offspring resulted:
233 normal wing, red eye
247 miniature wing, vermillion eye
7 normal wing, vermillion eye
13 miniature wing, red eye
What type of conclusions can you draw from this experiment? Explain your answer.