Science 300:31 April 2003

1. Environment-induced disruptions in meiosis BPA treated Chromosome number error (aneuploidy) rose from 1-2% to 40% in mouse eggs! Reason- bisphenol A (BPA), a component of plastic.. Meiosis ….. results in meiosis errors in mouse eggs normal Science 300:31 April 2003

2. Chromosomes and Cancer Chromosomes andHuman Genetics Genes on chromosomes drive ___________ __________ is uncontrolled cell division Philadelphia Chromosome • First abnormal chromosome to be associated with a cancer • Associated with a chronic ________ • Overproduction of white blood cells • Due to _____________________ Chapter 11

3. Genes • Units of information about _______________ • Each has a particular __________ • Location on a _______________ • _______________ are identical in length, size, shape, and gene sequence Alleles • Different __________ forms of a gene • Arise through _____________

4. _______________- display of chromosomes Fig. 11.4, p. 173

5. Sex Chromosomes • Discovered in late ______ • Mammals, fruit flies • XX is _______, XY is _________ • In other groups XX is male, XY female Sex determination

6. The Y Chromosome • < ____ genes • Includes ____ gene- dictates ______ phenotype The X Chromosome • > ______ genes • Most genes - _______ traits • Genes expressed in both males and females

7. appearance of structures that will give rise to external genitalia appearance of “uncommitted” duct system of embryo at 7 weeks Effect of YChromosome 7 weeks Y present Y absent Y present Y absent testes ovaries 10 weeks ovary testis birth approaching

8. Red eyes White eyes Normal is called “_________” Non-normal is called “______” • Thomas Hunt Morgan - first to associate a specific gene with a specific chromosome in the early 20th century. • Morgan’s model-Drosophila melanogaster, a fruit fly • - have three pairs of __________ and a pair of • _____________ chromosomes (XX in females, XY in males).

9. Know these symbols = _ ______ = ________ • Morgan’s experiments- Red eye X White eye F1 All Red eye 3:1 Red:white F2 Conclude- classic _ ________ _ genetics But- all __________were white, all females red Morgan concluded that a fly’s eye color was linked to the _ ________________. Fig. 15.3

10. Chromosome- 1.5 x 108 base pairs containing about ______ genes Linked genes tend to be inherited together because they are located on the same chromosome • Genes located on the same chromosome,___ ______ _______, tend to be inherited together because the chromosome is passed along as a unit. 0.4% of a chromosome, containing 10 genes • Results of crosses with linked genes deviate from those expected according to __ _______________________.

11. Linkage Groups • Genes on one type of chromosome • Fruit flies • __ homologous chromosomes • __ linkage groups Crossover Frequency -____________to the distance that separates genes A B C D Crossing over will disrupt linkage between _________ more often than _________ Frequencies can be used to construct a _______________

12. A a a c c C A C Incomplete Linkage AC ac x Parents: F1 offspring All AaCc meiosis, gamete formation Unequal ratios of four types of gametes: a a A A C c C c Most gametes have parental genotypes A smaller number have recombinant genotypes

13. Linkage Mapping in Humans Called a “________” • Chart that shows _____________ connections among individuals • Knowledge of probability and Mendelian patterns used to suggest basis of a trait Pedigree for __________ Unusual number of toes or fingers

14. _________ conditions that cause mild to severe medical problems Genetic Disorders Autosomal _________ • Many people are _________ • Heterozygous parents-- child will have a _____ chance of being affected Autosomal __________ • Trait typically appears in _______ generation • Most of these ________ from population. WHY?

15. Autosomal dominant diseases 1. Huntington Disorder • Causes involuntary movements, nervous system deterioration, death • Symptoms don’t usually show up until person is past age ___ • People often pass allele on before they know they have it 2. Acondroplasia • In homozygous form usually leads to _______ • Heterozygotes display a type of _________ • Have short arms and legs relative to other body parts

16. X-Linked Recessive Inheritance • Males show disorder _________ females • Son _______ inherit disorder from his father Examples 1. Color blindness- 2. _________, Blood-clotting disorder; 1/7,000 males 3. ________- Allele has repeated segments of DNA; causes mental retardation 4. ____________________ - Appears to be dominant; spontaneous mutation; premature aging effect, early death

17. The wrong number of chromosomes is bad Usually due to ________________ n + 1 n + 1 n - 1 n - 1 chromosome alignments at metaphase I nondisjunction at anaphase I alignments at metaphase II anaphase II

18. Nondisjunction results in too many or to few chromosomes termed ______________. • some gametes receive two of the same type of chromosome and another gamete receives no copy. • _______cells - three copies of a particular chromosome type and have _______ total chromosomes. • _________cells - one copy of a particular chromosome type and have 2n - 1 chromosomes. • Normally results in embryonic death, but some survive Organisms with more than two ________sets of chromosomes, have undergone_________, e.g. 3n or 4n (rare in ____________) • Polyploids are more nearly normal in phenotype than ___________.

19. Other chromosome problems A ________- a chromosome fragment lacking a ________ is lost during cell division A ___________- a fragment becomes attached as an extra segment to a sister chromatid Fig. 15.13c & d • An inversion - a chromosomal fragment ________to the original chromosome but in the reverse orientation. • In_ _______, a chromosomal fragment joins a _________chromosome. • Some translocations are ___________others are not.

20. Homozygous embryos with a large ________ normally die A deletion in the X chromosome is _______ in males A __ ________________ can alter phenotype because a gene’s expression is influenced by its location. Results of chromosome errors Example- Leukemia is due to a growth gene being placed next to an active region resulting in cancer • Approx. _____ of human embryos are aneuploid and die early in development • Some are viable- • Chromosome 15 trisomy- die at birth • Chromsome 21 trisomy- ________syndrome

21. Down syndrome- trisomy 21. • One in 700 children born in the United States. • result from ___________________ during gamete production • correlates with the age of the mother. Fig. 15.14 Karyotype Phenotype

22. Extra sex chromosomes are allowed • ______________________an XXY male, occurs once in every 2000 live births. • Male sex organs, but are_ ________. • Feminine characteristics; normal intelligence. • Males with an extra Y chromosome (XYY) tend to somewhat _______ than average. • Trisomy X (XXX), which occurs once in every 2000 live births, produces _ _________ females. • Monosomy X or _____________ (X0), which occurs once in every 5000 births, produces phenotypic, but immature females. • XYY and XXYY- males often found in _________.

23. Fig. 14.17a • Fetal cells extracted from amniotic fluid are cultured and __________. • In utero testing for genetic screening. 1. _____________- beginning at the 14th to 16th week of pregnancy to assess the presence of a specific disease. • 2. _____________ ________(CVS)- performed as early as the eighth to tenth week of pregnancy. • Extracts a sample of fetal tissue from the chrionic villi of the placenta are karyotyped. Fig. 14.17b

24. Other techniques- ____________________________ allow fetal health to be assessed visually in utero. • usually reserved for cases in which the risk of a genetic disorder or other type of birth defect is relatively great. • If fetal tests reveal a serious disorder, the parents face the difficult choice of terminating the pregnancy or preparing to care for a child with a genetic disorder.