Section 1 Vocabulary: • 1. Carrier: an individual that is heterozygous for a recessive disorder • 2. Pedigree: a diagram that traces the inheritance of a particular trait through several generations using symbols to illustrate the inheritance of the trait
Pedigree Charts Video • http://www.youtube.com/watch?v=PuWhstNgRpk&feature=youtube_gdata_player
PEDIGREE CHARTS • Pedigree charts show a record of the family of an individual. • It can be used to study the transmission of a hereditary condition. • It is particularly useful when there are large families and a good family record over several generations.
You cannot make humans of different types breed together so pedigree charts provide one of the few ethical ways of studying human genetics. • Today genetic engineering has new tools to offer doctors studying genetic diseases but a genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family.
In a marriage with five children, two daughters and three sons. The second son is affected by the condition
Organizing the pedigree chart • Below is a pedigree chart of a family showing four generations. A total of 20 individuals.
Generations are identified by Roman numerals. Individuals in each generation are identified by Arabic numerals numbered from the left. Therefore the affected individuals are II3, IV2 and IV3.
Inborn Errors of Metabolism - non-functional enzymes PHENYLKETONURIA - [PKU] pp 1/10,000 births disfunctional phenylalanine hydroxylase PHE --x--> PHE-pyruvate --> --> degraded & excreted accumulates - blood/brain barrier = mental retardation • ALKAPTONURIA aa A. Garrod in 1908 1/200,000 homogentisic acid oxidase --x--> ALKAPTON* [urine oxidizes black] 1st suggestion that effect of genes was to make proteins and disease is due to a defective enzyme/protein. • TAY SACHStt 1/300,000 births defective lysosomal (gangliosidase) enzyme = lysosomes swell burst -> death Ashkenazic Jewish ancestry show 1/ 3,600 births & 1 / 30 is Tt • SICKLE CELLs ss 1/6,000 births defective beta polypeptide of Hb improper folding of Hb --> clogs capillaries
Section 1 • 1. What is the genotype of a person who is a carrier for a disease? • heterozygous
Cystic Fibrosis • Cystic fibrosis happens most often in white people of northern European ancestry, occurring in about 1 out of 3,000 live births. • In cystic fibrosis, the lungs fill with thick mucus; a perfect breeding ground for bacteria and viruses. Most people with cystic fibrosis have almost constant infections in their lungs and sinuses.
In cystic fibrosis, a defective gene alters a protein that regulates the normal movement of salt (sodium chloride) in and out of cells. This results in thick, sticky secretions in the respiratory and digestive tracts, as well as in the reproductive system. It also causes increased salt in sweat.
2. What ions are to blame for the problem of mucus clogging the ducts in people with cystic fibrosis? chloride
Albinism • Albinism is an inherited condition that is present at birth. It is characterized by a lack of melanin, the pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may ultimately lead to skin cancer .
Tay Sachs • Tay-Sachs carriers are found most frequently among families of eastern European Jewish descent (Ashkenazi Jews). In the United States today, approximately one in every 27 Jews is a Tay-Sachs carrier.
What happens if you have Tay-Sachs? • Children with Tay-Sachs disease lack a vital enzyme, hexosaminidase A (Hex-A). Hex-A is needed for the body to break down a fatty waste substance found in brain cells. Without Hex-A, this substance accumulates abnormally and causes progressive damage until the nervous system can no longer sustain life. • In its most common variant, known as infantile Tay–Sachs disease, it causes a relentless deterioration of mental and physical abilities that commences around six months of age and usually results in death by the age of four
4. What is the effect of Tay-Sachs disease? • Build up of fats in the brain causing mental disfunctions
5. Why are there no cures for these diseases? • They are all recessive genetic disorders and occur due to defects in every cells DNA.
6. If all of the above genetic diseases are recessive, then what genotype is necessary to have the disorder? • 7. Are there any disorders that are dominant?_________ If so, Name 2 • 8. In a pedigree chart, what symbol represents a male? ___________ a female? __________ • 9. What is the purpose of a pedigree chart? • 10. Draw a pedigree of a boy with galactosemia if his father has it, his paternal grandparents are phenotypically normal and his mother and maternal grandparents are all phenotypically normal.
6. If all of the above genetic diseases are recessive, then what genotype is necessary to have the disorder? Homozygous recessive • 7. Are there any disorders that are dominant?_yes________ If so, Name 2 Huntingtons disease and Achondroplasia__ • 8. In a pedigree chart, what symbol represents a male? _a square _____ a female? A circle __________ • 9. What is the purpose of a pedigree chart? To trace the inheritance of a trait over the generations and to be able to predict the possibilities of the offspring inheriting the trait • 10. Draw a pedigree of a boy with galactosemia if his father has it, his paternal grandparents are phenotypically normal and his mother and maternal grandparents are all phenotypically normal.
Section 2 Vocabulary: • 1. Incomplete dominance • 2. Codominance • 3. Multiple alleles • 4. Epistasis • 5. Sex chromosome • 6. Autosome • 7. Sex-linked trait • 8. Polygenic trait
SC.912.L.16.2 Ch 8 • Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.
Advanced Genetics • http://www.youtube.com/watch?v=YoEgUqHOcbc&feature=youtube_gdata_player
1. Incomplete dominance , ( 302 ) • Define: (1 pt ) _when the heterozygous genotype results in an intermediate between the two parent’s homozygous phenotypes
Incomplete dominance • A mixture of the two phenotypes • Produces a new • Phenotype. • Red X White = Pink
Co dominance • 2. Codominance 302 • Define: (1 pt ) when both alleles are equally expressed in the heterozygous condition Both are expressed • Like a dog or cat with several colors fur
Blood groups A and B are co dominant! This is also an example of multiple alleles A, B and O
3. Multiple alleles, ( 304 ) • Define: (1 pt ) when a trait is determined by more than 2 alleles
Multiple alleles • More then two alleles for a trait. • Blood types A B O .
4. Epistasis , ( 305 ) • Define: (1 pt ) when one allele hides or alters the effects of another allele.
example: coat color in dogs 2 sets of alleles E determines if the fur is going to be dark. Ee no dark pigment, B determines how dar. EEbb Edbb will be chocolate brown eebb or eeBb will be yellow because e masks the effect of the dominant B allele!_
5. Sex chromosome , ( 305 ) • Define: (1 pt ) the one pair of chromosomes that determines the sex of the organism. In humans the X and the Y.
6. Autosome, ( 305 ) • Define: (1 pt ) All of the chromosomes that are not sex chromosomes. These contain the genes for everything necessary for life. 22 pair in humans
7. Sex-linked trait: , ( 307 ) • Define: (1 pt ) traits controlled by genes on the X chromosome. • Introduction--Sex Linked Inheritance (Video Clip)
Sex linked traits • The genes for these traits are on the X chromosome, because boys only receive one X chromosome they are more likely to inherit disorders passed to them from their mother who would be a carrier.
Coat color in cats is an X-linked gene, with alleles for black and orange-brown, so XBXB and XBY cats will have a black coat, while XOXO and XOY will have an orange-brown coat. Another possible combination for female cats would be XBXO. Both of the color alleles would be expressed, so the cat would end up being partially brown and partially black.
Q: Can a male cat ever be calico? • A: Yes, if he’s XXY, which would be abnormal. It turns out that abnormal numbers of X chromosomes aren’t as serious as other chromosome number abnormalities, because all but one X turn off, so an XXX individual would have two Barr bodies, an XXY individual would have one, etc.
Hemophylia (Video Clip) • Inherited human traits and patterned sex linked inheritance (Video Clip)
Organizing information about Sex Linked Inheritance in Pedigree charts (Video Clip)
8. Polygenic trait, ( 309 ) • Define: (1 pt ) traits controlled by many genes skin tone, height and eye color are examples.