Download 12 Units of Heredity

3/4/13 Chapter 12 12. Units of Heredity Units of Inheritance •  Genes •  Sex-­‐linked traits •  Pedigrees •  Anuploidy •  Chromosomal mutaCons 2 1 3/4/13 QuesCons: •  What kind of traits are heritable? •  How can we tract heritable diseases within families? •  What are some ways chromosomal changes can cause mutaCons? 3 Heredity •  Trait inheritance •  The transmission of traits from parents to children •  Inherit genes (units of heredity) from parents •  Inherit traits from parents 4 2 3/4/13 GeneCc Disorders •  GeneCc disorders may be recessive or dominant •  What is the probability that two carriers of the recessive Sickle Cell Anemia gene (Ss) will have a child with sickle cell anemia? •  What is the probability that someone with the dominant HunCngton disease gene (Hh) will have a child with HunCngton disease? 5 Inheritance of recessive genes •  Sickle Cell Anemia –  Recessive trait –  Need two copies ¼ (25%) chance of having a child with sickle cell anemia 6 3 3/4/13 Inheritance of dominant genes •  HunCngton’s disease –  Dominant trait –  Need one copy ½ (50%) chance of having a child with HunCngton’s 7 Sex-­‐linked genes •  Found on the X chromosome (usually) •  X-­‐linked disorders mostly affect male children. Why? •  Examples: red-­‐green colorblindness, hemophilia 8 4 3/4/13 Inheritance of colorblindness •  Normal mom (XXb) x Normal dad (XY) •  The mom is a carrier for colorblindness 9 X Chromosome InacCvaCon •  Females have 2 the copies of x-­‐
chromosome genes •  SomeCmes have to turn off the second chromosome for normal expression –  Barr Body 10 5 3/4/13 Mosaics -­‐ Calico Cats Xo/-­‐ = Orange Xb/-­‐ = Black -­‐/-­‐ = White; Double InacCvaCon Calico X-­‐ Inactivation, University of Miami 11 GeneCc disorders •  Why are recessive disorders more common among relaCvely inbred populaCons? •  Achondroplasia (dwarfism) –  is caused by a dominant allele •  If two parents are “lijle people” (or dogs), will all children also be affected? Explain. 12 6 3/4/13 Pedigree •  Family tree showing inheritance •  Useful in tracking phenotypic expression •  However: –  Requires mulC-­‐
generaCon data –  MulCple individuals per generaCon 13 Pedigree •  Allows us to infer carriers of different alleles •  Based on the expression in earlier and later generaCons 14 7 3/4/13 15 Aa x Aa A a A a Aa aa AA Aa Outcome: •  1 Homozygous dominant (not albino •  2 Heterozygous (not albion, but carriers) •  1 Homozygous recessive (albino) 16 8 3/4/13 17 Royal Families of Europe 18 9 3/4/13 Aneuploidy •  Having an extra copy of a chromosome 19 Aneuploidy (Trisomy 21) 20 10 3/4/13 Polyploidy •  More than two complete sets of chromosomes •  Triploid •  Tetraploid 21 Importance to Fish farming •  Triploid fish –  Low reproducCon rate –  Low success of ferClizaCon –  High growth rate 22 11 3/4/13 23 Aneuploidy and Cancer •  Aneuploidy can occur during mitosis –  Has less of an effect because cells can be eliminated (final check point of mitosis) •  However if it goes unchecked can lead to cancer forming cells –  Loss of cell cycle control 24 12 3/4/13 Chromosomal structural changes •  Physical changes can also lead to mutaCon –  By changing the geneCc informaCon stored in the chromosome. Dele=on Inversion Transloca=on Duplica=on 25 DeleCon •  Segment of DNA removed •  Chromosome is now missing some genes •  If passed along offspring will have only a single copy of deleted genes; express mutaCons 26 13 3/4/13 DeleCon – FainCng Goats •  Temporary Muscle Rigidity –  Missing gene causes muscles to temporarily lock when startled •  Congenital Myotonia •  Also found in humans, and other mammals 27 28 14 3/4/13 Inversion •  SecCon of a chromosome is taken out and flipped •  Can affect genes being turned on and off correctly 29 Williams Syndrome •  Impressive verbal & social skills •  Lack social inhibiCon •  “Elfin” Syndrome –  Because of resemblance to good natured elf/fairy characters in folklore –  Grin •  May suffer for a range of Developmental issues –  Severity varies with the size of the inversion 30 15 3/4/13 Balanced TranslocaCon •  Crossing-­‐over between non-­‐
homologus chromosomes •  ReorganizaCon of genes on chromosomes •  Responsible for some cancers 31 Unbalanced TranslocaCon •  When passed along to offspring •  Cause extra/
missing copies of genes •  Without causing Aneuploidy 32 16 3/4/13 DuplicaCon •  SecCons of the chromosome are copied –  Inserted next to the original •  Or into another chromosome (translocaCon) 33 Tandem Repeats •  Duplicated regions oren can keep duplicaCng •  Causing a build up of repeats •  Short repeats in order are called tandem repeats •  An increasing number of repeats within one gene (Runx-­‐2) create a longer snout •  Bull Terriers over 60 years 34 17 3/4/13 Tandem Repeats Lots of DuplicaCons Few DuplicaCons 35 Point MutaCons •  A Single NucleoCde Change –  InserCon/DeleCon –  Switch •  Can have a large effect on phenotype •  More in the next chapter… 36 18 3/4/13 QuesCons: •  What kind of traits are heritable? •  How can we tract heritable diseases within families? •  What are some ways chromosomal changes can cause mutaCons? 37 19