1. Non-Mendelian Inheritance…another pattern
Genes rarely operate in isolation from other genes.
Epistasis = the action of one gene affects whether another gene will be turned “on”

2. cc= has NO color (despite what B gene is)
Epistasis
Cc or CC= has color
cc= has NO color (despite what B gene is)
Bb or BB= Black
bb= brown

4. Epistasis

5. PEDIGREES
AP Biology
Ms. Gaynor

6. Many human traits follow Mendelian patterns of inheritance
Humans are not convenient subjects for genetic research
However,
We use pedigrees!

7. The Study of Human Genetics Continues to Advance…
Can’t use humans
We use pedigrees
A family tree that describes the interrelationships of parents and children across generations
Can also be used to make genetic predictions about future offspring

8. Inheritance patterns of particular traits can be traced and described using pedigreesWw ww WW or
First generation
(grandparents)
Second generation
(parents plus aunts
and uncles)
Third
generation
(two sisters) Ff ff
FF or Ff FF
Widow’s peak
No Widow’s peak
Attached earlobe
Free earlobe
(a) Dominant trait (widow’s peak)
(b) Recessive trait (attached earlobe)
Figure A, B

11. Example of Pedigree Charts
Is it Autosomal or X-linked?
Take a minute and try to decide if this slide is autosomal or X-linked.

13. Recessively Inherited Disorders
Many genetic disorders are inherited in a recessive manner
Need 2 recessive alleles (ex: ff)
Some people can be carriers
heterozygous individuals, who carry recessive allele but are show “normal” phenotype
Ff  carry the cf gene (“f”) but don’t have the disorder b/c you have to be ff (recessive)

14. Mating of Close Relatives
Matings between relatives
Can increase the probability of the appearance of a genetic disease…especially recessive traits!
Are called consanguineous matings
Increases changes of inheriting mutated alleles (ex: lethal mutations)

15. HUMAN DISORDERS
AP Biology
Ms. Gaynor

16. Cystic Fibrosis Example of recessive autosomal disorder
Affect mostly people of European descent
Symptoms
Mucus buildup in the some internal organs
Abnormal absorption of nutrients in the small intestine

17. Sickle-Cell Disease Another recessive autosomal disorder
Affects one out of 400 African-Americans
Is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells
Symptoms
Physical weakness, pain, organ damage, and even paralysis

18. Autosomal dominant Inherited Disorders
Some human disorders
due to autosomal dominant alleles  only need 1 dominant allele
Ex: Achondroplasia
Lethal when homozygous for the dominant allele
AA’s CAN’T live

19. Another Autosomal Dominant Disorder
Huntington’s disease (HD)
degenerative disease of nervous system
No obvious phenotypic effects until about 35 to 40 years of age HD
Normal

20. Nondisjunction of sister chromatids in meiosis II
Figure 15.12a, b
Meiosis I
Nondisjunction
Meiosis II
Gametes
n + 1
n  1
n – 1
n –1 n
Number of chromosomes
Nondisjunction of homologous
chromosomes in meiosis I
Nondisjunction of sister
chromatids in meiosis II
(a)
(b)

21. Alterations of Chromosome Structure
Breakage of a chromosome can lead to four types of changes in chromosome structure
Deletion
Duplication
Inversion
Translocation

22. Alterations of chromosome structure
Figure 15.14a–d A B C D E F G H
Deletion
Duplication M N O P Q R
Inversion
Reciprocal
translocation
(a) A deletion removes a chromosomal
segment.
(b) A duplication repeats a segment.
(c) An inversion reverses a segment within
a chromosome.
(d) A translocation moves a segment from one chromosome to another,
nonhomologous one. In a reciprocal
  translocation, the most common type,
nonhomologous chromosomes exchange
fragments. Nonreciprocal translocations
also occur, in which a chromosome
transfers a fragment without receiving a
fragment in return.

23. Human Disorders Due to Chromosomal Alterations
Down syndrome
Is usually the result of an extra chromosome 21
trisomy 21

24. Klinefelter syndrome
a result of an extra chromosome in a male, producing XXY individuals
1/2000 live births

25. Triple X Syndrome XXX individuals
Females
Healthy
Same phenotype as XX individuals
1/1000 live births

26. Turner syndrome
Is the result of monosomy X, producing an X0 karyotype
1/5000 live births
Only known monosomy in humans
Normal intelligence
Sterile

27. Cri Du Chat Caused by a deletion of part of chromosome #5
Mentally retarded; small head
Cries like a cat sound

28. Disorders Caused by Translocations
Certain cancers caused by translocations of chromosomes
Example: Chronic Myelogenous Leukemia
Short Chromosome #22/ Long Chromosome #9
Figure 15.16
Normal chromosome 9
Reciprocal
translocation
Translocated chromosome 9
Philadelphia
chromosome
Normal chromosome 22
Translocated chromosome 22

29. Genetic Testing and Counseling
Genetic counselors
Can provide information to prospective parents concerned about a family history for a specific disease

30. Tests for Identifying Carriers
For a growing number of diseases
Tests are available that identify carriers and help define the odds more accurately
Examples
Tay Sachs & CF

31. Blood test @ 10 weeks after conception

32. Can make karyotypes, too!
Fetal Testing
In amniocentesis
The liquid that bathes fetus is removed & tested
In chorionic villus sampling (CVS)
A sample of the placenta is removed and tested
Can make karyotypes, too!

33. (b) Chorionic villus sampling (CVS)
(a) Amniocentesis
Amniotic
fluid
withdrawn
Fetus
Placenta
Uterus
Cervix
Centrifugation
A sample of
amniotic fluid can
be taken starting at
the 14th to 16th
week of pregnancy.
(b) Chorionic villus sampling (CVS)
Fluid
Fetal
cells
Biochemical tests can be
Performed immediately on
the amniotic fluid or later
on the cultured cells.
Fetal cells must be cultured
for several weeks to obtain
sufficient numbers for
karyotyping.
Several
weeks
Biochemical
tests
hours
Chorionic viIIi
A sample of chorionic villus
tissue can be taken as early
as the 8th to 10th week of
pregnancy.
Suction tube
Inserted through
cervix
Karyotyping and biochemical
tests can be performed on
the fetal cells immediately,
providing results within a day
or so.
Karyotyping
Fetal testing
Figure A, B

34. Newborn Screening Some genetic disorders can be detected at birth
Simple tests are now routinely performed in most hospitals in the United States
Example- PKU test