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.

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

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”

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

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

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

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

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.

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

Actual Results 8.5% 8.5% 41.5% 41.5% 41.5% 41.5%

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”

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”

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

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

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”

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

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

Interpret these karyotypes Klinefelter’s syndrome

Interpret these karyotypes Sex: Male

Interpret these karyotypes Down Syndrome