1. Mrs. Howland Biology 10 Rev. Feb 2016
4/28/2017 7:27 PM
Unit 8: Human Heredity
Mrs. Howland
Biology 10
Rev. Feb 2016
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2. What can be INHERITED?
TRAITS

3. Why LOOK at inheritance?
Can predict DISORDERS
Pedigree analysis
Inheritance patterns
Phenotypes  Genotypes

4. Information about INHERITANCE
Inheritance may be studied by looking at:
Karyotypes
Pedigrees
Physical traits to determine genotypes
Patterns: sex-influenced, X-chromosome inactivation
Heterozygous advantage
Mistakes in meiosis (nondisjunction)
Prenatal genetic screening

5. LOOKING BACK…
HOMOLOGOUS CHROMOSOMES = Chromosomes that are the same size and have the same gene sequence
PAIRS of homologous chromosomes have 2 different alleles of the same gene, located at the gene locus

6. Karyotypes Looking at chromosomes
KARYOTYPE = Display of condensed chromosomes arranged in pairs

7. Karyotypes
REMEMBER ~ Each chromosome has 2 sister chromatids joined at the centromere; karyotype shows chromosome pairs
MAKING A KARYOTYPE:
Pictures are taken during meiosis
Pictures are cut and arranged to show all pairs of chromosomes in one view

8. Sex Determination 22 pairs are autosomes (the same for everyone!)
1 pair determines sex (male or female)
XX pair = female
XY pair = male
SEX-DETERMINING CHROMOSOMES
NOTE: This shows both X and Y as single types, but they are present as a PAIR! (XX or XY)

9. Male vs. Female KARYOTYPE
SEX CHROMOSOMES
SEX CHROMOSOMES
AUTOSOMES
AUTOSOMES

10. MISTAKES during meiosis
NONDISJUNCTION = Paired chromosomes do not properly separate during cell division

11. NONDISJUNCTION can occur during Meiosis I OR Meiosis II, causing different effects:

12. VIDEO: Chromosomal Disorders

13. Down Syndrome
Down syndrome is caused by an extra copy of chromosome 21. This is called trisomy

14. Downs Syndrome Affects 1 in every 800-1000 babies
Caused by NONDISJUNCTION
Caused by TRISOMY in chromosome 21

15. Turner Syndrome
Turner Syndrome = chromosomal disorder in which female is born with only ONE ‘X’ chromosome

16. Turner Syndrome What happens when a female has only ONE X chromosome?
SYMPTOMS:
Short stature
Webbed neck
Swollen hands and feet
Spots on skin
Underdeveloped ovaries; no menstruation; infertility

17. Klinefelter Syndrome
Klinefelter Syndrome = Chromosomal disorder in which individuals have TWO ‘X’ chromosomes and ONE ‘Y’ chromosome

18. Klinefelter Syndrome
What happens when an individual has XXY sex chromosomes?
SYMPTOMS:
Tall; long lets
Poor muscle tone
Female breasts
Small testicular size
Poor or no male hair growth

19. Williams Syndrome
Williams Syndrome = autosomal dominant disorder in which several of specific genes) are DELETED from chromosome 7
NOT inherited
Caused by mistake in formation of gametes
Only needs 1 chromosome with deletion(s) to cause disease
Occurs every 1/10,000 births

20. Williams Syndrome SYMPTOMS: Low birth weight
Characteristic facial features
Cardiovascular disease
Excessively social personality
Developmental delays; learning disorders

21. SEX DETERMINATION
During segregation, egg and sperm cells get one sex chromosome, X or Y
OFFSPRING:
50% MALE
50% FEMALE

22. SEX-INFLUENCED TRAITS
Some inherited traits are located on the sex chromosomes = sex-influenced traits (also called sex-linked)
Traits located on the X chromosome
Are usually recessive
FEMALES can have 3 phenotypes, including carrier (heterozygous genotype)
MALES have only ONE X chromosome  if the X chromosome has the recessive allele, the male WILL express the trait!

23. SEX-INFLUENCED TRAITS EXAMPLE: Colorblindness
A recessive trait carried on the X chromosome
KEY:
XB = Dominant, Normal
Xb = Recessive, Colorblind
Males have only one X chromosome, so if the X has the recessive gene, then they are colorblind!

24. SEX-INFLUENCED TRAITS EXAMPLE: Colorblindness
A recessive trait carried on the X chromosome
KEY:
XB = Dominant, Normal
Xb = Recessive, Colorblind
Males have only one X chromosome, so if the X has the recessive gene, then they are colorblind!

25. SEX-INFLUENCED TRAITS EXAMPLE: Male pattern Baldness
A recessive trait carried on the X chromosome

26. SEX-INFLUENCED TRAITS EXAMPLE: Male pattern Baldness
A recessive trait carried on the X chromosome
KEY:
XB = Dominant, Normal
Xb = Recessive, Baldness

27. Hemophilia ~ Sex-linked disorder

28. SEX-INFLUENCED TRAITS YOU TRY IT!
Hemophilia = bleeding disorder where blood does not clot normally XH Xh
KEY:
XH = Dominant, Normal
Xh = Recessive, hemophilia X
* What is the ratio for the offspring (phenotype/genotype)?
* What are the phenotypes of the parents? Y

29. VIDEO: Sex-linked disorders