2. AP Biology March 22, 2012  BellRinger  If two genes are located close together on the same chromosome, how might this affect expected inheritance predictions?  Objective  Calculate recombination frequencies  Differentiate between various chromosomal disorders  Homework  Chp 14 & 15 quiz

3. AP Biology © 2011 Pearson Education, Inc. Animation: Crossing Over Right-click slide / select”Play”

4. AP Biology Recombination of Genes:  Mendel observed that combinations of traits in some offspring differ from either parent  Parental types  Offspring with a phenotype matching one of the parental phenotypes are called  Recombinant types/Recombinants  Offspring with nonparental phenotypes (new combinations of traits)  A 50% frequency of recombination is observed for any two genes on different chromosomes © 2011 Pearson Education, Inc.

5. AP Biology Figure 15.UN02 Gametes from green- wrinkled homozygous recessive parent ( yyrr ) Gametes from yellow-round dihybrid parent ( YyRr ) Recombinant offspring Parental- type offspring YR yr Yr yR yr YyRr yyrr Yyrr yyRr

6. AP Biology Figure 15.10a Testcross parents Replication of chromosomes Gray body, normal wings (F 1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b  vg  b vg b  vg  b  vg b vg  b vg b  vg  b  vg b vg b vg  Sperm b vg

7. AP Biology Figure 15.10b Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspringRecombinant offspring Recombination frequency 391 recombinants 2,300 total offspring  100  17%  b  vg  b vg  b  vg b vg Eggs Recombinant chromosomes b  vg  b vg b  vg b vg 

8. AP Biology  As genes are located closer to one another, what happens to their recombination frequency? Learning Check

9. AP Biology  If gene A recombines 12% of the time with gene B, but 16% of the time with gene C, which gene is closer to gene A?  If gene B and C recombine with one another 28% of the time, what is the order of genes A, B, and C along the chromosome? Recombination frequencies BAC 1612 28

10. AP Biology  The following is a map of four genes on a chromosome:  Between which two genes would you expect the highest frequency of recombination?  A) A and W  B) W and E  C) E and G  D) A and E  E) A and G  Learning Check

11. AP Biology 2006-2007 Errors of Meiosis Chromosomal Abnormalities

12. AP Biology Karyotyping Activty  Read through the first page of the Karyotyping activity 1. What is a karyotype? 2. How are they made?

13. AP Biology Chromosomal abnormalities  Incorrect number of chromosomes  nondisjunction  chromosomes don’t separate properly during meiosis  breakage of chromosomes  deletion  duplication  inversion  translocation

14. AP Biology Nondisjunction  Problems with meiotic spindle cause errors in daughter cells  homologous chromosomes do not separate properly during Meiosis 1  sister chromatids fail to separate during Meiosis 2  too many or too few chromosomes 2n n n n-1 n+1

15. AP Biology Alteration of chromosome number all with incorrect number1/2 with incorrect number error in Meiosis 1 error in Meiosis 2

16. AP Biology trisomy 2n+1 Nondisjunction  Baby has wrong chromosome number  trisomy  cells have 3 copies of a chromosome  monosomy  cells have only 1 copy of a chromosome n+1n monosomy 2n-1 n-1n

17. AP Biology Human chromosome disorders  High frequency in humans  most embryos are spontaneously aborted  alterations are too disastrous  developmental problems result from biochemical imbalance  imbalance in regulatory molecules?  hormones?  transcription factors?  Certain conditions are tolerated  upset the balance less = survivable  but characteristic set of symptoms = syndrome

18. AP Biology Down syndrome  Trisomy 21  3 copies of chromosome 21  1 in 700 children born in U.S.  Chromosome 21 is the smallest human chromosome  but still severe effects  Frequency of Down syndrome correlates with the age of the mother

19. AP Biology Down syndrome & age of mother Mother’s age Incidence of Down Syndrome Under 30<1 in 1000 301 in 900 351 in 400 361 in 300 371 in 230 381 in 180 391 in 135 401 in 105 421 in 60 441 in 35 461 in 20 481 in 16 491 in 12

20. AP Biology Genetic testing  Amniocentesis in 2nd trimester  sample of embryo cells  stain & photograph chromosomes  Analysis of karyotype Rate of miscarriage due to amniocentesis:  1970s data 0.5%, or 1 in 200 pregnancies  2006 data <0.1%, or 1 in 1600 pregnancies

21. AP Biology Sex chromosomes abnormalities  Human development more tolerant of wrong numbers in sex chromosome  But produces a variety of distinct syndromes in humans  XXY = Klinefelter’s syndrome male  XXX = Trisomy X female  XYY = Jacob’s syndrome male  XO = Turner syndrome female

22. AP Biology  XXY male  one in every 2000 live births  have male sex organs, but are sterile  feminine characteristics  some breast development  lack of facial hair  tall  normal intelligence Klinefelter’s syndrome

23. AP Biology Klinefelter’s syndrome

24. AP Biology Jacob’s syndrome male  XYY Males  1 in 1000 live male births  extra Y chromosome  slightly taller than average  more active  normal intelligence, slight learning disabilities  delayed emotional maturity  normal sexual development

25. AP Biology Trisomy X  XXX  1 in every 2000 live births  produces healthy females  Why?  Barr bodies  all but one X chromosome is inactivated

26. AP Biology Turner syndrome  Monosomy X or X0  1 in every 5000 births  varied degree of effects  webbed neck  short stature  sterile

27. AP Biology Changes in chromosome structure  deletion  loss of a chromosomal segment  duplication  repeat a segment  inversion  reverses a segment  translocation  move segment from one chromosome to another error of replication error of crossing over

28. AP Biology 2006-2007 Don’t hide… Ask Questions!!