NAME : Block : Notes Page 6-1 SOL Objectives LS 12, Genetics By the end of this unit, the students should understand that organisms reproduce and transmit genetic information to new generations: a) the structure and role of DNA; b) the function of genes and chromosomes; c) genotypes and phenotypes; Unit Calendar: Subject to Change d) characteristics that can and cannot be inherited; e) genetic engineering and its applications; and f) historical contributions and significance of discoveries related to genetics.
Notes Page 6-2 1. Albino individuals lack all pigmentation so that their hair and skin are white. This family tree shows that albinism F is carried only by females in this family G is a recessive genetic trait H is a sex-linked gene J requires both parents to be albinos 2. In squash plants, yellow fruit (Y) is dominant to white fruit (y). If two plants heterozygous for yellow fruit are crossed, what are the possible genotypes of the offspring? F Yy only G YY, yy only H Yy, yy only J YY, Yy, yy only
Notes Page 6-3 Genes Alleles Phenotype Genotype Dominant Trait Recessive Trait Probability Meiosis Homozygous Heterozygous
Genes Alleles Phenotype A section of a chromosome that codes for a particular trait. Example: there is a gene for flower color in peas. Different forms of a single gene. Example: Peas may have a purple or white allele for flower color. An organisms inherited appearance (the way the DNA code is outwardly expressed). Genotype An organisms inherited alleles (actual DNA code) Dominant Trait The characteristic that is expressed if 2 different alleles are present Recessive Trait A characteristic that is masked whenever a dominant allele is present. Probability The likelihood, or chance, of something happening Meiosis Cell division that produces sex cells with 1 / 2 the required amount of DNA Homozygous Identical pairs of alleles for a trait. Ex. BB, bb Heterozygous Two different alleles for a trait. Ex. Bb
Notes Page 6-4 1. A rabbit that has the genotype Bb has a phenotype of brown because brown is the. 2. In this picture, the little girl has light hair. This characteristic is determined by the that the girl receives from her parents. 3. Your genetic makeup, or the genes that you have for each personal trait is known as your. 4. The outward appearance of the genetic traits that you have is your. 5. Jessica s mother has two different alleles for the handedness gene. This means that Jessica s mother is for handedness. 6. Gametes, or reproductive cells make sure that a new organism has the correct amount of chromosomes by undergoing before they combine to make an offspring. 7. The chance that something will occur is known as a. For example, if a brown hamster (BB) mates with a white hamster (bb), the probability that a baby will be white is 0% because the white (b) allele will be masked by the dominant brown (B) allele. 8. Bobby s father has identical alleles for the tongue rolling gene. This means that Bobby s father is for tongue rolling. 9. The trait that hides is the. 10. There are multiple different versions of genes. We receive one specific version from each of our parents. These differing forms of genes are known as.
Notes Page 6-5 Using the key, answer the questions for each trait. Corn Color 1. What is the genotype of this corn plant? Yellow corn is dominant over white corn. Y represents having a yellow corn allele y represents having a white corn allele Y y 2. What phenotype will the corn be? 3. What are Y and y? Chromosome 16 Sunflower height The tall sunflower allele is dominant over the short allele. T represents having a tall sunflower allele t represents having a short sunflower allele T T 4. What is the genotype of this sunflower plant? 5. What phenotype will the plant be? 6. Why do you think the letter T was chosen to represent this trait? Chromosome 2 Potato Color The red potato allele is dominant over the white allele. R represents having a red potato allele r represents having a white potato allele r Chromosome 7 r 7. What is the genotype of this potato plant? 8. What will the phenotype look like? 9. Why does this plant have 2 chromosome number 7s? Pea color 10. What is the genotype of this pea plant? Green peas are dominant over yellow peas. G represents having a green pea allele G g 11. What will the phenotype look like? g represents having a yellow pea allele Chromosome 11
Notes Page 6-6 DOMINANT RECESSIVE GENOTYPE PHENOTYPE
Mitosis makes my TOES! BOTH Mitosis and Meiosis Meiosis makes a NEW ME! Notes Page 6-7
Comparing mitosis and Meiosis Memory Maker Overall Goal Cells it Occurs in Number Of Cells Made Effect on DNA Type of Reproduction I will understand how cells divide... Mitosis Meiosis Comparing the Processes How are Mitosis and Meiosis Notes Page 6-8 I P M A T C Similar? Different?
Punnett Squares Notes Page 6-9 Scientists use a simple diagram to predict the possible combination of genes (genotypes) and the resulting physical characteristics (phenotypes) which can be produced in the offspring of certain parents. This diagram is called a Punnett square. Follow the steps in this example as you use a Punnett square to solve genetics problems. Problem: In pea plants, the gene which produces a tall plant is dominant over a gene which produces a short plant. A pure (homozygous) tall plant is crossed with a pure (homozygous) short plant. What are the phenotypes and genotypes expected from this cross? Step 1 Choose a letter to represent the genes for the trait. Usually, the first letter of the dominant trait is used. It is capitalized for the dominant trait, and the same letter is used in lower case to represent the recessive trait. Step 2 Write the genotypes of the parents that are being crossed. Step 3 Write the letters representing the two genes from one parent along the top of the square. Write the letters representing the second parent along the left side of the square. Step 4 Complete the Punnett square by filling each box with the gene from above and to the left side of that box. If there is a dominant gene, it is always written first. Each box now contains letter representing two genes, one from each parent. The letters in each of the boxes represent the possible genotypes of the offspring that the parents could produce. Step 5 Use the Punnett square to answer the questions below. What are the genotypes expected from this mating? What are the phenotypes expected from this mating?
Notes Page 6-10 DIRECTIONS: Using Punnett squares, you can work out the probabilities that children of the parents in each example will have particular phenotypes and genotypes 1. In humans, dimpled cheeks are a dominant trait, with a genotype of DD or Dd. Nondimpled cheeks are a recessive trait, with a genotype of dd. Imagine that Parent A, with a genotype of DD, has dimpled cheeks. Parent B has the genotype dd, and does not hace dimpled cheeks. The Punnett square below diagrams the cross between Parent A and Parent B. Please complete the Punnett square. 2. A Punnett square shows what genotypes are possible for the offspring of a certain cross. What genotypes are possible for the offspring of Parent A and Parent B? 3. Each of the four squares of a Punnett square represents a 25% probability that the offspring will have that particular genotype. What is the probability that the offspring of Parent A and Parent B will have dimpled cheeks? 4. Parent X, with genotype Dd, has dimpled cheeks. Parent Y also has the genotype Dd and has dimpled cheeks as well. To find out what their offspring might look like, complete the Punnett square below. 5. What is the probability that the offspring of Parent X and Parent Y will have each of the following genotypes? DD: Dd: dd:
Notes Page 6-11 6. What is the probability that the offspring of Parent X and Parent Y will have nondimpled cheeks? 7. What is the probability that the offspring of Parent X and Parent Y will have dimpled cheeks? (Remember that there are two genotypes that are able to produce dimpled cheeks). 8. One cat carries heterozygous, long-haired traits (Ss), and its mate carries homozygous shorthaired traits (ss). Use a Punnett square to determine the probability of one of their offspring having long hair and short hair. Probability that offspring will have long hair: Probability that offspring will have short hair: 9. One flower is homozygous red (RR) and it is crossed with a homozygous white (rr) plant. Use a Punnett square to determine the probability of one of their offspring having a red or a white color. Probability that offspring will have red color: Probability that offspring will have white color: 10. In a certain species of pine trees, short needles (S) are dominant to long needles (s). According to the Punnett square, what is the probability of an offspring having short needles? Long needles? Probability that offspring will have short needles: Probability that offspring will have long needles:
Notes Page 6-12 Sometimes mistakes happen when the DNA is being copied. These mistakes, or, change the order of the bases in DNA. There are three kinds of mutations that can occur in DNA: deletion, insertion, and substitution. A is a mutation when a base is accidentally left out of the DNA An is a mutation when an extra base is accidentally put into the DNA A is a mutation when one base is accidentally put in, in place of another. In the following DNA sequences, write what type of mutation happened and circle where it occurred. Original DNA sequence: C T C C T A A A C C T Mutated DNA sequence: C T C C T A A A A C T What type of mutation occurred? Original DNA sequence: C T A C C G T A A G A T Mutated DNA sequence: C T A C C G T A A A T What type of mutation occurred? Original DNA sequence: G T T A G C C T T A C T Mutated DNA sequence: G C T A G C C T T A C T What type of mutation occurred? Original DNA sequence: T A C C A T T A C C A T T Mutated DNA sequence: T A C C C A T T A C C A T T What type of mutation occurred? Mutations can do a lot of damage in the cell. Just imagine if a mutation happened in a sentence: Original sentence: AMY GOT THE RED HOT POT OFF THE LOG Mutated sentence: AMY GTT HER EDH OTP OTO FFR HEL OG What type of mutation occurred in this example? Describe how the mutation affected the sentence: Mutations do the same thing to the cells in our body.
Notes Page 6-13 Use charts, pictures, words, etc. to explain the importance of the following terms to the study of genetics. Karyotype Punnett Squares Dominant and Recessive Traits Genotype and Phenotype