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Genetics and Heredity Probability Probability The likelihood that a specific event will occur Probability = # of 1 times event occurs number of possible outcomes Example: What is the probability that a tossed coin will be heads? ½ or 50% Probability The First Law of Probability: the results of the first trial of a chance event do not affect the results of later trials of the same event. In other words, no matter how many times a flipped coin lands on tails, every flip still has a ½ chance of tails. Probability Second Law of Probability: The probability of two or more independent events occurring together is the product of their separate probabilities. What is the probability that a couple will have four boys? 50% (1/2 probability each time) ½ x ½ x ½ x ½ = 1/16 Inherited Traits Are these inherited traits? Your eye color Your hair color and texture Your height Are these inherited traits? Your personality Your musical, athletic, and artistic abilities Think about this…. “My parents have brown eyes, why are mine blue?” “My brother is tall. Why am I short?” “Why does my sister have blonde hair while mine is brown?” Gregor Mendel These are questions that Gregor Mendel tried to answer.. Born in 1822 in Austria 1843 – Studied Theology 1846-Studied Science at the University of Vienna Father of Genetics Johann Mendel was born in 1822 in Heinzendorf, Austria, to a peasant farming family. Austria Poland Italy Germany Czech Republic Austria During his early years, Johann did NOT like agriculture very much. He lay around in his bed “sick” for weeks, possibly to avoid farm chores. Do I LOOK like a farmer? When Johann was 16, his father had a debilitating farming accident and Johann was forced to provide for himself. When Johann was 18, he borrowed money from his younger sister’s dowry to pay for his education at the university for two years. When he was 21, one of Johann’s teachers took note of his exceptionally bright mind and persuaded him to join the Augustinian monks. St.Thomas Church, (now Brno, Czechoslovakia) After he arrived at St. Thomas, Johann Mendel changed his name to Brother Gregory. The monastery was a center of learning for young men who wanted to study theology and natural science. Brother Gregory also spent time teaching mathematics at a nearby school. After one year, in order to become a teacher, he took the teacher’s examinations at the University of Vienna . . . and failed. During his early years at the monastery, Mendel began studying and breeding mice. The bishop was not pleased. Brother Gregor settled on bees . . . and peas. University of Vienna While at the monastery, Gregor continued his studies at the University of Vienna for several years. He became a “reserve” teacher for an ailing professor, teaching science at a local college while studying physics at the University of Vienna. After many years at the university, Gregor retook the teacher’s exam, and failed for the second time. In spite of these failures, Mendel continued to conduct numerous experiments on plants. Mendel narrowed his focus to one particular garden pea, Pisum sativm. For 8 years, Mendel experimented with over 28,000 peas in the large gardens attached to the monastery. Rather than study every characteristic of the garden pea, Mendel narrowed his observations to 7 traits. Garden Pea Traits Observed Seed shape smooth Seed color yellow Pod shape inflated Pod color green Flower color Flower location Plant size purple axial tall wrinkled green constricted yellow white terminal short In 1866 when Mendel was 44, his experimental results were published . . . and ignored long after he died. In 1900, 3 scientists - Carl Correns, Hugo de Vries, and Erich von Tschermak - all independently rediscovered and verified Mendel's principles, marking the beginning of modern genetics. He is now considered the father of genetics. Mendel’s studies led to: Concepts in Inheritance Dominant (H) Homozygous (HH or hh) Genotype (HH, Hh or hh) Purebred (HH or hh) Recessive (h) Heterozygous (Hh) Phenotype (blonde, brown, red) Hybrid (Hh) Theory of Heredity Inherited allele for purple P HOMOZYGOUS purple flower PP Inherited allele for purple P Theory of Heredity Inherited allele for purple flower (P) HETEROZYGOUS purple flower (Pp) Inherited allele for pink flower (p) Theory of Heredity Inherited for pink flower (p) HOMOZYGOUS pink flower (pp) Inherited for pink flower (p) PREDICTING HEREDITY PUNNETT SQUARES A Punnett square is a tool used to help predict the probability of offspring of a couple. 1. Decide the genes that could be passed on to the offspring in the gametes from each parent. 2. Cross the different gene/gamete possibilities for each possible offspring combination. Monohybrid Cross Monohybrid Cross: a cross that shows the possible offspring for one trait Aa x Aa A: White fur a: Brown fur Parent Aa has what gentotype? Parent Aa can produce a gamete with either an “A” or with an “a” Monohybrid Cross Monohybrid Cross: a cross that shows the possible offspring for one trait A a Aa A: a: Aa x Aa A White fur Brown fur a produces gamete “A” or “a” • Separate the two genes (as though they were separating into different gametes) and place one outside the first row on the left and the other under it outside the second row. • Separate the other parent genes and place at the top, one above each column. Monohybrid Cross Monohybrid Cross: a cross that shows the possible offspring for one trait Aa x Aa A: White fur a: Brown fur • Cross over the genes to fill in the boxes of the square. A a A AA Aa a Aa aa Genotypic Ratios Genotypic Ratios compare the possible genotypes (gene combinations in the offspring. A a Aa x Aa A: White fur a: Brown fur A AA Aa a Aa aa Genotypic ratio: Number of offspring with homozygous dominant genes AA Number of offspring with heterozygous/hybrid genes Aa Number of offspring with homozygous recessive genes aa Sometimes abbreviated as: GR = #hom dom (AA) : #hyb (Aa) : hom rec (aa) GR = 1 : 2 : 1 Phenotypic Ratios Phenotypic Ratios compare the possible phenotypes (appearance of the offspring); how many show the dominant trait or recessive trait. A a Aa x Aa A: White fur a: Brown fur A AA Aa a Aa aa Phenotypic ratio: Number of offspring showing the dominant trait (AA & Aa) Number of offspring showing the recessive trait (aa) Sometimes abbreviated as: PR = #show dom (AA & Aa) : #show rec (aa) PR = 3 : 1 Practice! Cross a HOMOZYGOUS dominant female with a HETEROZYGOUS male using the same trait. What is the genotypic ratio? 2:2 or 50% A A A AA AA a Aa Aa What is the phenotypic ratio? 4 white fur Dihybrid Cross Dihybrid Cross: shows the possible offspring for two traits This shows a cross between parents hybrid for two traits: BbRr x BbRr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth BR BbRr x BbRr Br bR br BR BBRR BBRr BbRR BbRr Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr Dihybrid Crosses Phenotypic Ratio: # dom/dom : # dom/rec : # rec/dom : # rec/rec How many of the offspring would have BR Br bR br a black, rough coat? (#dom/dom) BBRr BbRR BbRr BR BBRR How many would have a black, Br BBRr BBrr BbRr Bbrr smooth coat? (#dom/rec) How many would bbRR bbRr bR BbRR BbRr have a white, rough coat? (#rec/dom) Bbrr bbRr bbrr br BbRr How many would have a white, smooth coat? Phenotypic Ratio: 9:3:3:1 (#rec/rec) 16 Dihybrid Crosses If mouse #1 were crossed with mouse #16, what would their offspring look like? 1 Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth #1 x #16 BBRR x bbrr #6 x #10 BBrr x BbRr #14 x #16 Bbrr x bbrr BR Br bR br BR BBRR BBRr BbRR BbRr Br BBrr BbRr Bbrr BBRr 16 bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr More Complex Patterns of Heredity Incomplete Dominance Codominance Multiple Alleles Sex-Linked Traits Incomplete Dominance R R R’ RR’ RR’ R’ RR’ RR’ Red (RR) X white (R’R’) make pink (RR’) Incomplete Dominance Red pigment is produced by the R allele the non-pigmented R’ allele codes for enzymes that do not function properly so it turns white Dilutes the effect of R causing only partial expression Problem: Incomplete Dominance Show the cross between a pink and a white flower. R R’ GENOTYPES: - RR’ (2); R’R’ (2) - ratio 1:1 R’ RR’ R’R’ PHENOTYPES: - pink (2); white (2) - ratio 1:1 R’ RR’ R’R’ Problem: Incomplete Dominance Show the cross between a pink (RW) and a white flower (WW). GENOTYPES: - RW (2); WW (2) - ratio 1:1 W RW WW PHENOTYPES: - pink (2); white (2) - ratio 1:1 W RW WW R W Polygenic Inheritance More than one gene controls a trait Ex. Skin color, height Eye color skin pigmentation Incomplete Dominance – two phenotypes create a third R’R’ WHITE Hybrid R’R RR PINK RED USE PRIMES FOR NON-PIGMENTED ORGASNISM (This is why you probably won’t see primes in codominance unless it tells you that it is codominant)!!! Codominance Codominance: two dominant alleles are expressed at the same time CRCR CWCW CRCW Codominance ** Example: When a red animal is crossed with a white animal, a roan animal is produced. The phenotypes are: RR = Red, WW = White, RW = Roan (red and white) Red (RR) White (WW) Roan (RW) Hybrid Occurs in cows too!!! Codominance – Both Alleles Expressed at the Same Time Both the pink and the white alleles are expressed May see P = Pink Allele, W = White Allele making pink and White PW BUT they will have to state that it is a codominant trait as primes are used in other types of inheritance ****Will probably see PW or IPIW, they show the same thing ! Codominance Sickle-Cell Anemia is another codominant trait. NA=Normal RBC NA National Institute of Health, http://www.cc.nih.gov/ccc/ccnews/nov99/ Photo attributed to Drs. Noguchi, Rodgers, and Schechter of NIDDK. NS=Sickle Cell RBC NA NS NSNA NSNA NA NANA NANA Codominance The heterozygous condition, both alleles are expressed equally Sickle Cell Anemia in Humans NN = normal cells SS = sickle cells NS = some of each Problem: Codominance Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (2) SS (2) - ratio 1:1 S NS SS PHENOTYPES: - carrier (2); sick (2) - ratio 1:1 S NS SS Multiple Alleles Gene for trait has more than two possible alleles Individual only inherits two alleles Multiple Alleles There are more than two alleles for a trait Blood type in humans Blood Types? Type A, Type B, Type AB, Type O Blood Alleles? IA, IB, i Blood Types Phenotype Genotype A AA or IAIA or IAi or AO B BB or IBIB or IBi or BO AB AB or IAIB O OO or ii **Type AB is codominant (both expressed) **O is recessive, must have BOTH alleles Rules for Blood Type A and B are codominant AA = Type A BB = Type B AB = Type AB A and B are dominant over O AO = type A BO = type B OO = type O Example of a punnett square of a Heterozygous Type A father and Type O mother. Let’s Make Some Punnett Squares – Cross the Following: A homozygous Type A female with a Type O male A Type AB male with an O female A heterozygous Type B male with a heterozygous A female A couple that are both type AB agglutinogen Type a produces anti-B antibodies against type B called agglutinins agglutinogen Type AB produce NO antibodies and can receive any blood type; attacks nothing agglutinogen no agglutinogen Type B produces anti-A antibodies against type A called agglutinins Type O Produces BOTH anti-A and anti-B antibodies and attacks both A and B so Type O folks can only receive Type O! http://highered.mcgrawhill.com/sites/0072556781/student_view0 /chapter33/animation_quiz_5.html Anti-A Anti-B Rh Type ** Agglutination (clumping) is a positive result ** No agglutination (clumping) is a negative result Multiple Alleles Multiple Alleles: traits with more than 2 alleles Blood type has 3 alleles: A, B, O A and B are codominant over O O is recessive Phenotype Genotype Can Receive From Can Donate To A I AI A, I Ai A, O A, AB B IBIB, IBi B, O B, AB AB I AI B A, B, AB,O AB O ii O A, B, AB, O Blood Types Blood Type Can Donate to: Can Receive A+ A+, AB+ A+, A-, O+, O- A- A+, A-, AB+, AB- A-, O- B+ B+, AB+ B+, B-, O+, O- B- B+, B-, AB+, AB- B-, O- AB+ AB+ A+, A-, B+, B-, AB+, AB-, O+, O- AB- AB+, AB- A-, B-, AB-, O- O+ A+, B+, AB+, O+ O+, O- O- A+, A-, B+, B-, AB+, AB-, O+, O- O- + can ONLY donate to other +’s…-’s can donate to + or – – Can ONLY receive from – …. + can receive from + or – How do you know if you carry deadly genes? Karyotypes Karyotypes are a “map” of all 46 (23 pair) of chromosomes. Karyotypes • During mitosis, Metaphase chromosomes are photographed, enlarged and arranged in pairs by a computer according to length and location of the centromere. Normal Karyotype How can I tell if I have a genetic disorder? Karyotypes are a “map” of all 46 (23 pair) of chromosomes. What’s wrong with this Karyotype? Is this a male or a female? Elbow Partner Take turns reading “Background Information” out loud to your elbow partner – switch every other sentence. One partner defines the odd numbered words; one partner defines the even numbered words Share definitions You have 9 minutes, 22 seconds. GO! Abnormal Number of Chromosomes What’s wrong with this Karyotype? Turner’s Syndrome What’s wrong with this Karyotype? Klinefelter’s Syndrome What’s wrong with this Karyotype? Down Syndrome Disorders due to Chromosomal Numbers Down’s Syndrome Trisomy 21 Trisomy 21 – Down Syndrome Minor to severe mental retardation; a characteristically large, thick tongue; shortened stature; and almond shaped eyes Trisomy 21 – Down Syndrome Trisomy 13 – Patau Syndrome Trisomy 13 - Patau Syndrome Symptoms: Cleft lip or palate Clenched hands (with outer fingers on top of the inner fingers) Decreased muscle tone Extra fingers or toes (polydactyl) Hernias Low-set ears Mental retardation, severe Seizures Abnormal Numbers of Sex Chromosomes Males are XY Females are XX Turner’s Syndrome XO-female Short and stocky Don’t develop adult female characteristics Sterile Beth at 13 (in middle) and at 31 Turner’s Syndrome - XO Monosomy -only 1 X chromosome Klinefelter’s Syndrome XXY- male Don’t develop adult male characteristics Low intelligence Sterile Klinefelter XXY • • • • Relatively high-pitched voices, feminine body contours and breast little facial and body hair sterile Diagnosing Disorders Amniocentesis Amniotic fluid removed by needle Karyotyped Chorionic Villus Sampling Sample of placenta removed karyotyped Karyotype Practice Look on back of Study Guide Follow Directions to complete table using the attached pictures Work individually; raise your hand if you have questions Tracing Family Traits A pedigree is a series of symbols that charts several generations of a families genetic history. Females are represented by circles and males by squares. A line connecting them is a marriage. This family has two children, one girl and one boy. If someone in the family has a certain disease, such as cystic fibrosis, the square will be colored in. Sometimes carriers are represented by a half colored in shape. Carries gene Has disease Other pedigree symbols: GENDER UNKNOWN ? MISCARIGE MULTIPLE INDIVIDUALS TWINS 6 GENERATIONS are represented by Roman numerals. The individuals are numbered in each generation. In the next slide, who is the mother of individual #4? DOMINANT GENETIC DISEASES I. 1 2 2 3 II. 1 4 III. 1 2 EXAMPLES: 1. HUNTINGTON’S DISEASE 2. POLYDACTYLY 3. DWARFISM RECESSIVE GENETIC DISEASE I. 1 2 4 5 II. 3 6 III. 7 8 RECESSIVE DISEASES: 1. CYSTIC FIBROSIS 2. PKU 3. TAY-SACHS 4. SICKLE CELL ANEMIA SEX-LINKED GENETIC DISEASE I. 1 2 2 3 II. 1 4 III. 1 2 SEX-LINKED DISEASES 1. HEMOPHILIA 2. COLOR BLINDNESS 3. DUCHENE MUSCULAR DISTROPHY 4. MALE PATTERN BALDNESS Sex-Linked Traits Sex-Linked Traits – Traits X or Y chromosome ** Y chromosome has between 70 and 200 genes, most code for what makes a dude a dude! ** X chromosome has between 900 and 1500 genes and contains more than just make me a gal genes ! What are Sex-Linked Traits? Traits that are located on one of the sex chromosomes (XY or XX) 1) Hemophilia: Failure of blood to clot Alix and Nicholas II 2) Muscular Dystrophy: wasting away of muscles Can I inherit a sex-linked disease? Fathers (XY) can only pass disorders to daughters (XX) Mothers (XX) can pass disorders to both sons (XY) and daughters (XX) Most disorders are carried on the X chromosome, so males are more likely to inherit them. Colorblindness Is Recessive and On the X Chromosome Pedigree for Colorblindness Pedigree of Tongue Rollers (Dominant) Rr rr Rr rr rr rr Rr Rr rr rr rr rr Rr rr rr Rr rr Rr rr Royal Hemophilia Pedigree http://www.sciencecases.org/hemo/hemo.asp