Genetics

1. Genetics

2. Genetics 1. What is a chromosome? A threadlike structure of DNA and protein that contains genetic information. 2. Where are chromosomes located? In eukaryotes chromosomes are found in the nucleus; in prokaryotes, they are found in the cytoplasm Chromosomes

3. Genetics 3. What are genes? Special sequences of DNA that codes for a protein and thus determines a trait. 4. Where are genes found? Genes are found on chromosomes.

4. Genetics 5. What is genetics? Genetics is the scientific study of heredity. 6. Who is considered the father of genetics? Gregor Mendel, an Austrian monk Mendel’s paper on genetics 1865

5. Genetics 7. What kind of organism did Mendel study? Mendel studied pea plants 8. What are some of the traits that Mendel studied? Seed color and shape; Pod color and shape; Flower color and position

6. Genetics 9. What is an allele? An allele is one of a number of different forms of a gene. White flower allele Purple flower allele For example, the gene for flower color in peas has two alleles—purple (P) and white (p). And the gene for seed pod color has two alleles—Green (G) and yellow (g). Green Seed Pod allele Yellow Seed Pod allele

7. Genetics 10. What is meant by Mendelian Genetics? Locus for Flower Color Gene Any traits that are controlled by a single gene. For example, flower color is controlled by a single gene that has two alleles. 11. What is a locus? Locus for Pod Color Gene The specific location of a gene on a chromosome.

8. Genetics 12. What is a true breeding plant? Parents True breeding plants always make offspring identical to themselves. For example, white flower plants always produce white flower offspring. Offspring Parents And purple flower plants always produce purple flower offspring. Offspring

9. Genetics 13. What is the universal symbol for a male and female? Male Female 14. How many alleles for a single gene can an organism have? Parents Two. Offspring inherit one allele from the male parent and the other allele from the female parent. Alleles P P P P P P P P Offspring Click once for animation

10. Genetics 15. State Mendel’s Principle of Dominance? This principle states that some alleles are dominant and others are recessive. Dominant color (purple) For example, a plant that has a purple allele (P) and a white allele (p) will have purple flowers. This is because the purple allele is dominant over the white allele. P p Recessive allele (white) Dominant allele (purple)

11. Genetics 16. Define genotype? The genotype is the genetic makeup of an organism. For example, the possible genotypes for a purple flower could be PP or Pp. 17. Define phenotype? The phenotype is the physical characteristic of an organism. For example, the phenotype of the flower shown at right is white.

12. Genetics 18. Identify the genotype for each flower shown below? Genotypes = 19. What is the phenotype of each flower? Phenotypes = pp Pp PP White Purple Purple

13. Genetics 20. What is a hybrid? A hybrid is an organism that has two different alleles for a particular gene. 21. Which of the following is a hybrid? pp Pp PP Hybrid plant True breeding plants

14. Genetics 22. What does homozygous mean Homo- means “same” and -zygous means “pair.” Homozygous refers to the fact that two alleles for a gene are the same. For example PP or pp 23. What does heterozygous mean Hetero- means “different. Heterozygous refers to the fact that two alleles for a gene are different. For example, Pp.

15. Genetics 24. Match the flower genotypes on the left to the terms on the right. pp Pp PP Homozygous recessive Heterozygous Homozygous dominant

16. Genetics 25. How do the alleles get from parents to offspring? The chromosomes the alleles reside on are packaged in gametes (sex cells), like egg and sperm. Sperm Egg When egg and sperm meet, fertilization occurs, making a new cell called a zygote. Fertilization The zygote will divide by mitosis and develop into an embryo. Embryo

17. Genetics Pp x Pp 26. Draw a Punnett square for the following hybrid cross: a. Since this is a monohybrid cross, you should have drawn a 2 x 2 Punnettsquare.

18. Genetics Pp x Pp 26. Draw a Punnett square for the following hybrid cross: b. Next, you should have written the parent genotypes above the Punnett square.

19. Genetics Pp x Pp 26. Draw a Punnett square for the following hybrid cross: c. Then you should have placed the sex symbols on the Punnett square.

20. Genetics Pp x Pp 26. Draw a Punnett square for the following hybrid cross: P p d. After the sex symbols, you were to determine the alleles for the sperm and eggs. P p

21. Genetics Pp x Pp 26. Draw a Punnett square for the following hybrid cross: P p e. Finally, you should have combined the alleles of the gametes to form zygotes Pp PP P pp p Pp

22. Genetics Punnett Square Review Pp x Pp 27. Draw squares around the alleles of the parents P p 28. Draw ovals around those alleles found in sperm Pp PP P pp p Pp 29. Draw circles around those alleles found in eggs. 30. Draw diamonds around the alleles of the offspring.

23. Genetics Punnett Square Review Pp x Pp 31. Circle the homozygous dominant offspring. P p 32. Put squares around the heterozygous offspring. Pp PP P pp p Pp 33. Draw a diamond around the homozygous recessive offspring.

24. Genetics Punnett Square Review Pp x Pp 34. Circle the purebred offspring. P p 35. Put diamonds around the hybrid offspring. Pp PP P pp p Pp 36. Why is this called a monohybrid cross? Mono- means “one.” Hybrid refers to having different alleles for the same gene. Since the cross deals with only one character (mono-) and each parent is a hybrid, the cross is described as monohybrid.

25. Genetics Punnett Square Review Pp x Pp 37. What is the genotypic ratio of the offspring? P p PP : Pp : pp 1 : 2 : 1 Pp PP P pp p Pp 38. What is the phenotypic ratio of the offspring? Purple : White 3 : 1

26. Genetics 39. State Mendel’s Principle of Segregation. Allele pairs separate during gamete formation. Gametes Germ cell Meiosis

27. Genetics 40. State Mendel’s Principle of Independent Assortment. Allele pairs for different traits separate independently during gamete formation. Gametes Germ cell 1 Chromosome alignment A 2 Four different types of gametes or 3 Chromosome alignment B 4

28. Genetics 41. Study the table below for a pattern. What number do you think goes in the last space? (Assume genes are on separate chromosomes and sort independently) The formula for calculating the number of possible gametes is 2n, where 2 equals the number of different alleles and n is the number of genes. Possible number of unique gametes Genotype 1 gene 2 genes 3 genes 4 genes 5 genes Aa AaBb AaBbCc AaBbCcDd AaBbCcDdEe 2 4 8 16 32

29. Genetics 42. Humans have 23 sets of chromosomes. How many different ways could these chromosomes sort independently? Hint: You would use the same formula as was done for alleles and genes (2n). However, this time n represents the number of chromosome sets. 2n = 223 = 8,388,608 different combinations

30. Genetics 43. Draw a Punnett square for the following dihybrid cross: AaRr x AaRr ar aR Ar AR Since this is a dihybrid cross, you should have drawn a 4 x 4 Punnettsquare. Each parent will also be able to produce 4 different kinds of gametes. AaRr AaRr AARR AARr AR Ar AArr AaRr AARr AArr aR aaRr aaRR AaRR AaRr ar aarr aaRr AaRr Aarr

31. Genetics 44. What is the genotypic frequency of this dihybrid cross? AaRr x AaRr GenotypeFrequency ar aR Ar AR AARR AARr AArr AaRR AaRr Aarr aaRR aaRr aarr 1/16 2/16 2/16 1/16 5/16 1/16 1/16 2/16 1/16 AaRr AaRr AARR AARr AR Ar AArr AaRr AARr AArr aR aaRr aaRR AaRR AaRr ar aarr aaRr AaRr Aarr

32. Genetics 45. What is the phenotypic frequency of this dihybrid cross? A = Axial flowers A = Terminal flowers R = Round seeds r = Wrinkled seeds AaRr x AaRr Phenotype Frequency ar aR Ar AR Axial, Round Axial, Wrinkled Terminal, Round Terminal, Wrinkled 9/16 3/16 3/16 1/16 AaRr AaRr AARR AARr AR Ar AArr AaRr AARr AArr aR aaRr aaRR AaRR AaRr ar aarr aaRr AaRr Aarr