* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Genes and Medical Genetics
Polymorphism (biology) wikipedia , lookup
Neocentromere wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Y chromosome wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Saethre–Chotzen syndrome wikipedia , lookup
Behavioural genetics wikipedia , lookup
Gene therapy wikipedia , lookup
Human genetic variation wikipedia , lookup
Genomic imprinting wikipedia , lookup
Point mutation wikipedia , lookup
History of genetic engineering wikipedia , lookup
Genetic engineering wikipedia , lookup
Population genetics wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Genetic drift wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Gene expression programming wikipedia , lookup
Public health genomics wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Neuronal ceroid lipofuscinosis wikipedia , lookup
Medical genetics wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Epigenetics of neurodegenerative diseases wikipedia , lookup
X-inactivation wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Genome (book) wikipedia , lookup
Designer baby wikipedia , lookup
Genes and Medical Genetics Chapter 2 Genotype and Phenotype Genotype = all the genes that an individual has Phenotype = physical appearance of the individual Pictures of Jennifer Aniston Genotype (con’t) – Alleles can be dominant (capital letter) or recessive (lower case letter). – Alternate forms of a gene having the same position (locus) on a pair of matching chromosomes that control the same trait are called alleles – An individual has two alleles for each trait because a chromosome pair carries alleles for the same traits – How many alleles for each trait will be in the Example – in humans unattached earlobe is dominant over attached earlobes • Could use capital E to show dominant allele and lower case e to show recessive (nondominant) allele Note: it is customary to designate alleles by the same letter, with uppercase to Fig. 02-01 • When the two alleles are both dominant it is called a homozygous dominant genotype – The phenotype will be unattached earlobes • When the two alleles are both recessive it is called homozygous recessive – The phenotype will be attached earlobes • When the two alleles are different (one dominant, one recessive) it is called a heterozygous genotype – The phenotype will be ________________. Fig. 02-01 Forming gametes (gametogenesis) • Recall: gametes have ½ normal # of chromosomes • Happens when chromosome pair separates during meiosis • Since alleles are on chromosomes, they also separate during meiosis, thus gametes only carry one allele for each trait. – Ex. If individual was Ee, and produced four gametes, ½ would be E and ½ would be e. (Chromosomes already doubled) Fig. 02-02 Gametogenesis Genotypes WW or Ww ww EE or Ee ee SS or Ss ss Fig. 02-03 Common Inherited Character -istics in Humans Phenotypes Genetic Crosses (One-trait Crosses) • If know genotype of parents, can predict chances of having a child with certain genotypes (and thus certain phenotypes). – Ex. If one parent is homozygous dominant (EE) the chance of having a child with unattached earlobes is 100% because parent only has dominant allele (E) to pass on to baby. – But, if both parents are homozygous recessive (ee), the chance of having a child with attached earlobes is 100% because One-trait Crosses (con’t) • If both parents are heterozygous (Dad is Ee, and Mom is Ee), what are the chances that baby will have unattached or attached earlobes? • Determine using a Punnett Square • Each child will have a 75% chance of dominant phenotype (unattached), and 25% chance of having recessive phenotype (attached). Fig. 02-04 Heterozygous-byHeterozygous cross One-trait crosses (con’t) • What if one parent is Ee and the other is ee? • Each child will have a 50% chance of having unattached earlobes Fig. 02-05 Heterozygous By Homozygous cross Genetic Crosses (Two-trait Crosses) • What if want to look at two traits at the same time? – Ex. Widow’s peak (W) and short fingers (S) (both dominant traits). • If one parent is homozygous for widow’s peak and short fingers (WWSS) and other is homozygous for straight hairline and long fingers (wwss), what will – Children look like? – Grandchildren look like? Fig. 02-06 Dihybrid cross using Punnett Square • Expected phenotypic ratio for a dyhibrid cross is always 9:3:3:1 • Can use this expected ratio to predict chances of each child receiving a certain phenotype – Ex. Chance of getting two dominant phenotypes together is 9 out of 16 – Chance of getting two recessive phenotypes is 1 out of 16 Autosomal Dominant Disorders • Genetic disorders are caused by mutations • Mutations – permanent changes in genes (DNA) • If disorder is autosomal dominant mutation is a single allele, and heterozygotes will exhibit the disorder • If know genotype of parents, can determine chances of children having the disorder (see Table 2.2, p. 26) • Can provide genetic counseling to parents who can make decision about best courses of action (Chapter 4). Autosomal Dominant Disorders • Neurofibromatosis – Most common genetic disorders (1 in 3,500 newborns, all races and ethnicities) – Symptoms • Large tan spots on skin that get darker with age • Small, benign (?) tumors (neurofibromas) often occur in nerves • If severe case – Skeletal deformities (including a large head) – May develop eye and ear tumors become blind and deaf • Children with non-severe symptoms may still have learning disabilities and be hyperactive – Gene for neurofibromatosis has been located on chromosome 17 – Found that gene controls production of protein that usually blocks cell growth – If gene not working certain cells grow out of control =_______________ . Autosomal Dominant Disorders • Huntington Disease – Neurological (nervous system) disorder that causes progressive degeneration of brain cells. – Symptoms – – – – • Most patients appear normal until middle age (may already have children) • Severe muscle spasms • Personality disorders Treatment – none (patients die in 10 – 15 years after symptoms appear) Gene (mutated) located on chromosome 4 causes abnormal protein that clumps inside neurons (nerve cells) Test developed for presence but most people do not want to know Two minute paper: “Would you want to be tested for a fatal genetic disease? Why or why not?” Autosomal Recessive Disorders • Cystic Fibrosis (CF) – Most common lethal genetic disease among Caucasians in the US – 1 in 20 are a carrier, 1 in 2,500 newborns has it – Caused by defect in plasma membrane (gene on chromosome 7) – Symptoms • Thickened mucous in bronchial tubes (problems breathing) and pancreatic duct (problems digesting) – Treatment – mucous in lungs manually loosened and other treatments have raised Fig. 02-08 Treatment for CF Autosomal Recessive Disorders • Phenylketonuria (PKU) – Not so common as CF – Affects nervous system development • Caused by missing enzyme that normally allows metabolism of the amino acid phenylalanine • Causes abnormal breakdown product (phenylketone) in urine – Symptoms – severe mental retardation, black urine • PKU allele located on chromosome 12 prenatal DNA test can detect it (and elevated phenylalanine in blood) • If detect place newborn on diet low in phenylalanine until at least age 7 Autosomal Recessive Disorders • Tay-Sachs Disease – Usually occurs in Jewish people – Symptoms • Development slows at age 4 to 8 months • Neurological and Psychomotor impairment • Child gradually becomes blind and helpless, seizures, paralyzed, death by age 3 – 4 years old – Caused by gene on chromosome 15 caused buildup of nonfunctional lysosomes in neurons Autosomal Recessive Disorders • Albinism – Person unable to produce pigment melanin colors skin, hair, eyes – Symptoms • White hair, pink eyes, superwhite skin • Vision problems – Example of epistasis one gene affects the expression of other genes • In albino any gene for coloring cannot be expressed because mutated gene prevents them from producing melanin • Picture of Johnny Winter