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1. Tongue rolling 2. Hair on second knuckle 3. Widow’s peak 4. Thumb crossing 5. Attached \ unattached ear lobes 6. Crooked finger A. Genetics is the study of heredity B. Heredity is the passing of traits from parents to offspring. C.―Father of Genetics‖- Gregor Mendel,an Austrian monk who studied garden pea plants in the 1800’s.☺ Why a pea plant? 1. True breeding 2. Reproduce quickly & in large numbers. 3. Easy to grow 4. Self-pollinating D. Mendel chose to cross pollinate Pollination-pollen is dispersed and makes its way to the female portion of a flower Fertilization is when the pollen unites with the ovule to form a zygote.☺ Pistil or (Carpel) is the female portion of the flower. It consists of: 1) Stigma 2) Style 3) Ovary-contains ovules (eggs) If fertilized, the ovules develop into seeds. The ovary develops into fruit. The male portion of the flower is called the stamen. The stamen is composed of: 1. Anther-where the pollen is produced. 2. Filament 1. 1st cross: true breeding tall plants (TT) with short plants(tt). (Called P1 or parental generation) 2. Offspring (called F1 or first generation) of this cross were all tall. 3. 2nd cross: 2 plants of the F1 generation and the 4. results were ¾ tall and ¼ short. This crossing of one trait is called a monohybrid cross.☺ A. Mendel thought that some ―factor‖ controlled the inheritance of traits B. one factor could mask or hide the expression of another. 1. Genes are segments of DNA on a chromosome that code for a trait. Each trait is coded for by two alleles. C. Mendel’s ―factors‖ are the alleles. Alleles are alternate forms of the same gene. Ex-color of flower is a trait The alleles for flower color in pea plants are purple or white☺ Some alleles are dominant (they are expressed over a recessive gene) Other alleles are recessive (they are not expressed when a dominant allele is present) a) Recessive alleles are ONLY expressed if the organism has 2 recessive alleles Capital letters are used for dominant alleles and lower case for recessive alleles. Ex- B means brown fur b means white fur☺ Genotype- Definition Phenotype- combo of physical alleles appearance BB Homozygous Brown fur dominant (pure) Bb Heterozygous Brown fur dominant (hybrid) bb Homozygous White fur recessive (pure) A. Organisms inherit one allele from each parent B. Each organism has 2 alleles per trait. C. The alleles can be the same or different D. During meiosis, the paired alleles for each trait separate and end up in different gametes Meiosis and the Separation of alleles Fertilization •What are the alleles for the flower? •What is the dominant allele? •What is the recessive allele? •What genes would be present in the gametes? •Are the parents heterozygous or homozygous? •How many alleles are donated to each gamete? •How many ways could the gametes combine? •How many offspring will be homozygous recessive? A. Patterns of only one trait are studied. B. One allele from the female gamete is combined with one allele from the male gamete. C. Pairs can be homozygous (pure) or D. Heterozygous (hybrid) E. Genotype is the gene combination – BB,Bb,bb F. Phenotype is physical appearance G. To determine if an organism is pure or hybrid, conduct a test cross with a homozygous recessive Laws of probability can be used to predict outcomes. Probability is the chance that a certain event will occur. A. Shows all possible genotypes B. Probability predicts what is most likely to occur C. But actual outcome may be different. D. Each outcome is NOT influenced by previous outcomes. The Punnett Square is a diagram showing all possible gene combinations for a genetic cross. Step 1: Assign letters for the traits B= brown b= white Step 2: Write the cross Brown Bb x White bb Step 3: Set up and work the Punnett square B b b b Step 4: State the genotype ratio and the phenotype ratio. 1. Probability is given as a ratio, fraction, or percentage. 2. Ratio-number of offspring that have a particular gene or trait versus the number of offspring that have another gene or trait. 3:1 3. Fraction-shows the predicted number of offspring having a particular trait over the total number of possible outcomes. ¾ tall to ¼ short 4. Percentage-calculated from fractions 75% tall to 25% short 1. What do the letters inside the square represent? 2. What does a correctly completed Punnett square tell you? 3. Does the probability predict the actual outcome? 4. Is the outcome of a cross affected by previous crosses? 5. Who was Gregor Mendel? 6. What is a monohybrid cross? 7. What are alleles? 8. What does it mean if an organism is heterozygous? 9. What is the only way a recessive trait will be expressed? A heterozygous tall pea plant is crossed with a homozygous short pea plant. A Punnett square predicts that the probability that the offspring of this cross will 50% tall and 50% short . In a classroom experiment, student tested this prediction with four seeds obtained from this cross . The first three offspring from this produced all tall plants. How is this possible? What is the probability that the fourth offspring will be tall? Step 1: Step2: Step3: Step 4: Two heterozygous tall pea plants are crossed. They produced 16 seeds. How many of those seeds will likely result in short plants? Step 1: Step2: Step3: Step 4: Phenylketonuria or PKU, is an inherited disease caused by a recessive allele. If baby has PKU and is untreated, a certain amino acid builds up in the tissues and causes severe mental retardation. If treated, the child can develop normally. A young couple has decided that they want to start their family. David is 28 years old and has been promised a promotion in his company that will gave him a better position and more benefits, as well as a larger salary. He has phenylketonuria, or PKU. His mother and one sister also have PKU. His wife Trevon is 25 years old and has an aunt with PKU. She also had two grandparents with phenylketonuria although neither of her parents had it. David and Trevon want to know what their chances are of having a child with PKU. David’s genotype:____ Trevon’s possible phenotypes: _____ or _____ What are the possible genotypes and phenotypes of their future children? Step 1: Step2: Step3: Step 4: What is the probability that their children will NOT have PKU? A. Often called blending. B. Neither allele is dominant over the other. C. Third phenotype is intermediate between the dominant and recessive ( Ex-four o’clock flowers white X red = pink) D. When making a Punnett Square for incomplete dominance, use 2 different capital letters (RR for red and WW for white, RW is pink) How to determine if there is incomplete dominance? Three different phenotypes, one of which is a blend. When homozygous dominant are crossed with a homozygous recessive, all F1 are intermediate, while the F2 have a 1:2:1 phenotypic ratio. A. Both alleles are expressed equally. B. Codominant alleles are designated with uppercase letters for each allele and a superscript may be used. Example = white chicken X black chicken = speckled chicken ( FWX FB = FWFB) This causes the 1. hemoglobin in the red blood cells to be the 2. wrong shape. Hemoglobin is the protein that carries the oxygen. People who are homozygous 3. recessive for the allele have very serious health problems. E. Roan color in cattle and horses-have both 1. red and white hairs mixed together or Blue 2. black & Roan white 1. A trait for snapdragon flower color is controlled by incomplete dominance. A snapdragon plant with red flowers is crossed with a snapdragon plant with white flowers. What percent of the offspring will have pink flowers? 2. If two snapdragon plants with pink flowers are crossed, what percent of offspring would you predict as also having pink flowers? 3. A pink snapdragon plant is crossed with a red snapdragon plant. What percent of the offspring can be predicted to have white flowers? 4. Cross a red horse crossed with a roan colored horse. List the possible genotypes and phenotypes. A. Traits controlled by more than 2 alleles. B. Only two alleles for each individual, but there are more than 2 alleles for the trait found in a general population. (in gene pool) C. Example ABO blood type in humans and D. coat color in rabbits There are three alleles for blood type 1. Type A ( IA) , 2. Type B (IB ) and 3. Type O (ii) 4. IA and IB are codominant to each other 5. Both IA and IB are dominant over i, which is recessive. 6. Blood typing is important because a person would die if the wrong type of blood was given. It is also used to determine who’s NOT ―Yo’ Daddy!‖ Pope Innocent VII- Infessura attempted the first blood transfusion. He drained the blood of three 10 yr old boys into the mouth of Pope Innocent VII. They all died. Dr. Jean Baptiste Denys-1667 1st successful transfusion – poured about 12 oz of sheep’s blood into a 15 yr old boy. The boy lived probably because so little blood actually made it into the boys blood stream It was not until the 4 basic blood types were identified that transfusions could be done safely. WWII blood trans- Fusion tool Sample problems: If a child has type AB blood and the mother has type A blood, could a man with type O blood be the father? A mother has type A blood and a father has type B blood. Can they have a child with type O blood? Why or why not? A woman with Type AB blood marries a man with homozygous Type O blood . What would the blood type of their children be? A woman with heterozygous Type A blood (IAI) marries a man with homozygous Type B blood (IBIB). What blood type could their children NOT have? A. Traits are inherited independently. B. Law is always true IF genes for traits are located on different chromosomes During meiosis, alleles for different traits assort independently from one another. c. For example, seed color has no effect on plant height. Each parent will donate half of their alleles to the offspring. FOIL – F the first letters of the genotype O the outside letters of each genotype I the inner letters of the genotype L the last letters of the genotype Example: mother is FfWW possible gametes – FW,FW,fW,fW Father is FfWw possible gametes – FW,Fw,fW,fw FW FW fW fW FW Fw fW fw A. IF genes for a trait are on the same chromosome, they may be linked. B. Inherited together C. Discovered by Thomas Hunt Morgan (early 1900’s) D. Studied Drosophila or the fruit fly • Early studies of crossing over were performed using the fruit fly Drosophila Wild type Variant (gray body, long (black body, short wings, red eyes) wings, cinnabar eyes) Figure 9.25 • Inheritance patterns of a sex-linked gene Female Male Female Male Female Male XRXR XrY XRXr XRY XRXr XrY All females inherit two X chromosomes, one from each parent. All males inherit Female Female one X chromosome, always from the R = red-eye allele mother. r = white-eye allele Male Male (a) Homozygous red-eyed female white- (b) Heterozygous female red- (c) Heterozygous female white- eyed male eyed male eyed male Figure 9.29 A. Humans have 23 pairs of chromosomes. 1. Autosomes are 22 matching chromosome pairs 2. Sex chromosomes make up the 23rd pair a. X and Y are the sex chromosomes b. XX is a female and XY is a male E. Traits found on the sex chromosomes 1. A male with a recessive trait on the X chromosome will always ―have it‖ because there is only one X. A. Hemophilia is an example of a sex-linked trait that is passed from mother to son, but not necessarily from father to daughter. B. X chromosomes are larger and carry more genes than Y chromosomes. C. Red-green colorblindness is another example 1. Organisms that have two identical alleles for the same trait are called— 2. Both hemophilia and red-green color blindness are examples of disorders that are— 3. A couple has two children, both girls. What is the chance that the parents’ next child will be a boy? 4. A Punnett square shows--- 5. Where are most the sex-linked genes located? 6. What is the genotype of a female? 7. The type of inheritance that produces roan color is called— 8. If the recessive trait is expressed as the phenotype, what would the genotype be? A. Pedigree is a diagram used to show genetic inheritance patterns. B. Male is represented by a square and a female is represented by a circle. C. Each horizontal row represents one generation labeled with Roman numerals. D. Line connecting male & female means they are a couple Figure 14-3 A Pedigree Section 14-1 A circle represents A square represents a female. a male. A vertical line and A horizontal line connecting a bracket connect a male and female the parents to their represents a marriage. children. A half-shaded circle or square A circle or indicates that a square that is person is a carrier not shaded of the trait. indicates that a person A completely neither shaded circle or expresses the square indicates trait nor is a that a person carrier of the expresses the trait. trait. Go to Section: Samples problems: In the pedigree above, determine the genotypes of the parents in the P1 generation. In the F1 generation, the one affected daughter has three children with an unaffected man. Their two sons are affected with color blindness. What is the chance of another son having the disorder? A. Type of Mutations 1. Gene Mutations-Changes in only one gene that codes for one protein a. Substitution-One nucleotide is substituted or replaced by another. 1) Point Mutation Normal: THE RAT HID AND THE CAT SAT AND GOT FAT. Substitution: THE PAT HID AND THE CAT SAT AND GOT FAT. This will change only one word or in this case one amino acid in the protein chain. b. Insertion-One nucleotide is added to the sequence. 1) Called a frame-shift mutation. Normal: THE RAT HID AND THE CAT SAT AND GOT FAT. Insertion: THE RAT HIX DAN DTH ECA TSA TAN DGO TRA T This throws off the whole message from the point of insertion on. This will more than likely change the amino acid sequence and the whole protein chain. c. Deletion-A nitrogen base is omitted. 1) Another type of frame-shift mutation. Normal: THE RAT HID AND THE CAT SAT AND GOT FAT. Deletion: The RAH IDA NDT HEC ATS ATA NDG OTF AT. The words or amino acid sequence is changed from the point of deletion. 2. Chromosomal mutation-structure or number of chromosome changes. Types a. Duplication-part of chromatid is duplicated b. Deletion-part of chromatid is missing c. Inversion-broken part reattaches backward d. Translocation-part of a chromatid attaches to a different chromosome duplication deletion inversion B. Karyotypes-pictures of chromosomes used to identify chromosomal mutations This is a method in which fragments of DNA are separated by electric charge and size on a gel with the smallest fragments traveling the greatest distance.
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