You will never change your life until you

“You will never change your life until you change something that you do daily” - John C. Maxwell “There is nothing in the caterpillar that tells you it I going to be a butterfly” - Buckminster Fuller Units of Heredity Chapter 12

Understanding Genetic Disorders �Down Syndrome is caused by an extra chromosome, but how does one pass on an extra chromosome? �Why �Are �Do are color-blindness and baldness typically found only in men? diseases dominant or recessive like other traits? sex chromosomes only code for the sex of the offspring or are their traits associated with each sex chromosome?

Discovery of Sex-Linked Traits �Thomas Morgan at Columbia University, 1908 �Fruit fly (Drosophila melanogaster) � Model organism �Discovered link between specific trait and ______ � X-linked trait �Discovered � Genetic crossing over recombination

Reciprocal Cross Reciprocal cross: experiment to test the role of _____ on the inheritance of a trait

X-Linked Inheritance � X-linked disorders: genetic disorders caused by genes found on the X chromosome � Ex: color blindness � _____ disorder: genetic disorder that does not exist in the presence of a functioning allele � Presence of a defective gene on one allele will result in the expression of the functional allele on the other chromosome � ______ recessive disorder: found on non sex chromosomes � X-linked recessive disorders: found on X chromosome

Spermatogenesis and the Sex of the Child �Half of the sperm produced have X chromosome and half have Y chromosome � 50% chance of having either a boy or a girl

X-linked Recessive Disorders: Color Blindness �Genes that code for red and green absorbing pigments are found close together on the X chromosome � Females have a back-up X chromosome, males do not

Check your Understanding X-linked recessive disorder Father’s genotype Hemophilia In this situation the mother does not suffer from hemophilia, but her father had hemophilia. The father does not suffer from hemophilia. Predict the chances of having a son with hemophilia. Mother’s genotype � Ex. X X X Y

Check you Understanding X-linked dominant disorder Father’s genotype Rett syndrome In this situation the mother’s father had Rett syndrome, while her mother did not. The father does not suffer from Rett syndrome. Predict the chances of having a daughter with Rett syndrome. Mother’s genotype � Ex. X X X Y

Linked vs. Sex Linked �Sex traits: genes that are located on the __________ linked or x-linked traits: genes that are located on the Xchromosome

Linked Traits �Almost always ________ during meiosis �Linked traits violate the principle of independent assortment

Crossing Over and Linked Traits �________ chromosomes: chromosomes with a combination of alleles that are different from that of the parent chromosomes �Due to _______

Linked Traits Genes that are located near each other on the chromosome have a tendency to be inherited together � Ex. Red hair and freckles

Autosomal Genetic Disorders �Genetic disorders associated with non-sex chromosomes or autosomes �Autosomal recessive disorder: a genetic disorder that occurs when ______ chromosomes in the pair contain a defective gene � Ex. Sickle cell anemia, Albinism �Autosomal dominant disorder: a genetic disorder that occurs when the offspring receives one defective allele from parent � Typically one of the parents has the disease

Genetic Disorders Type Name of Condition Effects X-linked recessive disorders Hemophilia Duchenne muscular dystrophy Red-green colorblindness Autosomal recessive disorders Albinism Sickle-cell anemia Cystic fibrosis Phenylketonuria Tay-Sachs disease Werner syndrome No pigmentation in skin Anemia, intense pain, infection Impaired lung function, lung infections Mental retardation Nervous system degradation in infants Premature aging Autosomal dominant disorders Huntington disease Marfan syndrome Polydactyly Brain tissue degradation Ruptured blood vessels Extra fingers and toes Aberrations in chromosome number Down syndrome Turner syndrome Klinefelter syndrome Mental retardation, shortened life span Sterility, short stature Dysfunctional testicles, feminized features Aberrations in chromosome structure Cri-du-chat syndrome Fragile-X syndrome Mental retardation, malformed larynx Mental retardation, facial deformities Faulty blood clotting Wasting of muscles Inability to distinguish shades of red from green

Autosomal Recessive Disorder _____: a person who does not suffer rom the recessive genetic disorder but who carries an allele for it that can be passed along to their offspring � Ex. Person heterozygous for albinism

Autosomal Recessive Disorder �Sickle-cell anemia: defective hemoglobin protein causes �Both mother and father must have at least one allele for sickle cell anemia � 25% chance that offspring will get the disease Sickle-cell anemia

Autosomal Dominant Disorder Ex: Huntington's disease is

Tracking Traits �______: conditions family history used to track genetic

Sample Problem A = Cystic fibrosis (cc) = Unaffected (CC or Cc) CC E B Cc F C G D

= Polydactyly (PP or Pp) = Unaffected (pp) Sample Problem ? F A ? B C D E

Polyploidy �Polyploidy: a condition in which one or more ______ of chromosomes have been added to the genome of a diploid organism

Aneuploidy �Aneuploidy: a condition in which an organism has _______ chromosomes than normally exist in the species full set �Possibly responsible for 30% of miscarriages � 30% of pregnancies end in miscarriage �Down Syndrome is the result of aneuploidy

Down Syndrome

Nondisjunction: failure in the ______ of homologous chromosomes (Meiosis 1) or sister chromatids (Meiosis II) during cell division

Genetic Disorders in Sex Chromosomes Genetic disorders associated with sex chromosomes are not inherited but are the result of ________ Turner Syndrome � Female with single X chromosome Klinefelter Syndrome � Male with extra X chromosome XYY Male � Male with extra Y chromosome XXX Female � Female with extra X chromosome

Turner Syndrome �Only one healthy X-chromosome � Other chromosome is missing or altered � Occurs in 1 of 2, 500 human females Characteristics � ______ between neck and shoulders � Short stature � Often sterile, underdeveloped ovaries

Klinefelter’s Syndrome �Extra x-chromosome in human males � Occurs in 1 of 1, 000 human males Characteristics � Underdeveloped testes � Development of some female features � ______ and taller than average � Lower testosterone, infertile

Aneuploidy and Cancer �Additional or fewer chromosomes in _____ cells � Occurs during mitosis �Not every cell in the body is affected, as in aneuploidy on sex cells �Almost all _____ are aneuploidy � Not sure if a cause of effect of cancer cells

Structural Aberrations in Chromosomes �_______: � Can deviation from the normal occur spontaneously, or as a result of exposure to radiation, viruses, or chemicals

Structural Aberrations in Chromosomes �Deletion: chromosome fragment breaks off and fails to reconnect with the chromosome � Ex: Cri-du-chat syndrome = deletion of section from chromosome 5 �______: chromosome fragment rejoins chromosome in an inverted fashion �Translocation: exchange of pieces from two __________ chromosomes �Duplication: � Can section of DNA is duplicated during crossing over have negative effect, but can also be beneficial

Cri-du-chat Syndrome: results from a deletion of chromosome 5 Characteristics �Mental retardation �Improperly developed ______ �Small head �Low-set ears Missing section of chromosome 5

Pre-implantation Genetic Diagnostics (PGD) Screening of genotype of potential embryos prior to in-vitro fertilization (IFV) 1. 2. 3. 4. Hormones stimulate egg maturation Egg collection Fertilization Removal of embryonic cell during 8 -cell stage �Couples with family history of genetic disorders �Parents can choose _____ of child

Methods of Fetal Testing �__________: cells obtained from amniotic fluid of 14 -18 week old fetus �Chorionic villus sampling (CVS): sample taken from placenta tissue at 8 -10 weeks of development