1. Then, pick up the handouts at the front of the classroom.
March 14 & 15, 2006
Warm-up
Describe the following aspects of the genetic disorder you have researched:
What is your disorder?
Is it Dominant or Recessive?
Is it Autosomal or X-linked?
When you are done, put your warm-up and your brochure in your folder, and turn it in.
Then, pick up the handouts at the front of the classroom.

2. Beyond Mendel… Mutations, Gene Linkage, Gene-Mapping,
Polygenic Traits,
Non-disjunction disorders,
Prenatal Diagnosis

3. Back to “Beyond Mendel”
Mutations
Definition
Mutations in Genes
Point Mutations
Frame-shift Mutations
Mutations in Chromosomes
Deletion
Duplication
Inversion
Translocation
Back to “Beyond Mendel”

4. Mutations Definition: A change in the genetic material of a cell
Somatic: Affects body cells; can’t be passed on to next generation
Germ-line: Affect gametes; can be passed on to next generation
Back to Mutations

5. Mutations in Genes
Point Mutation: Affects one nucleotide (One nucleotide is replaced by another)
Types of point mutations
Silent mutations: Codes for same amino acid
Missense mutations: Code for a different A.A.
Nonsense mutations: Code for a stop codon
Example: Sickle-cell Anemia

6. Mutations in Genes
Frameshift Mutation: An insertion or deletion that shifts the reading frame
Example of Insertion: TA
Example of Deletion:
CGCATGGAATACC
TEF
THE H
FAT
ATC
CAT
ATA
TET
ATE
THE
HER
RAT AT
Back to Mutations T

7. 1. Deletion: A segment of the chromosome is removed
2. Duplication: A segment of the chromosome is repeated A B C D E F G H A B C E F G H A B C D E F G H A B C B C D E F G H
3. Inversion: A segment within a chromosome is reversed
4. Translocation: A segment from one chromosome moves to another, non-homologous one A B C D E F G H A D C B E F G H
Back to Mutations
Examples:
Deletion: Duchenne Muscular Dystrophy (on X chromosome)
Duplication: Huntington’s Disease (Chromosome 4)
Inversion & Translocation: Phenotypically normal, but increased risk of having gametes with abnormal numbers of chromosomes A B C D E F G H M N O C D E F G H M N O P Q R A B P Q R

8. Predict a cross between GgWw and ggww.
Linked Genes
In flies, grey bodies (G) and normal-wing size (W) are dominant to black bodies (g) and small wing size (w).
Predict a cross between GgWw and ggww.

9. Predicted Cross GW Gw gW gw gw gw gw gw 25% GgWw 25% Ggww 25% ggWw

10. Actual Results
8.5%
8.5%
41.5%
41.5%
41.5%
41.5%

11. Back to “Beyond Mendel”
Linked Genes
The genes for body color and wing size are linked.
That is, they are inherited together and do not undergo Mendel’s Law of
Independent Assortment
Back to “Beyond Mendel”

12. Back to “Beyond Mendel”
Gene Mapping
Genes are mapped on a chromosome based upon how frequently they cross over together.
Grey Body
Black Body
Normal wings
Small wings
Back to “Beyond Mendel”

13. Polygenic Traits Definition: Traits controlled by two or more genes
Examples: Skin color, height

14. Back to “Beyond Mendel”
Polygenic Traits
Skin Color
Height
What about our height? Does it form the same pattern?
Back to “Beyond Mendel”

15. Non-disjunction Disorders
Definition: When members of a pair of homologous chromosomes fail to separate during Meiosis I – or – when sister chromatids fail to separate during Meiosis II.
Examples: Down Syndrome, Turner’s syndrome, Klinefelter’s syndrome
Meiosis I
Meiosis II
Gametes
Back to “Beyond Mendel”

16. Prenatal Diagnosis: Amniocentesis
1. Amniotic fluid withdrawn
Fetus (14 – 16 weeks)
2. Centrifuge
Fluid
Several weeks later
Fetal Cells
Placenta
3. Karyotype
Uterus
Cervix
Cell culture

17. Prenatal Diagnosis: Chorionic villus sampling (CVS)
1. Suction tube inserted through cervix
Fetus (8 – 10 weeks)
Fetal cells
Placenta
Chorionic villi
2. Karyotype
Several hours

18. Interpret these karyotypes
Klinefelter’s syndrome

19. Interpret these karyotypes
Sex: Male

20. Interpret these karyotypes
Down Syndrome