Category: 1st Semester

 

Report by Josh Jackson

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Section 11-1     Control of Gene Expression

 

1. Cells use ______________________ to build hundreds of different________________each with a unique ____________________________.

2. Are all proteins used by a cell at any one time? If not, how do cells control this?

3. Define gene expression.

4. When are proteins produced?

5. What is the genome?

6. What are the 2 steps of gene expression?

7. What 2 scientists determined how genes are expressed in prokaryotes?

8. What gene & in what organism did Jacob & Monod make their discoveries about gene expression?

9. Name the 3 regulatory elements on the DNA of the E. coli bacterium and tell the function of each.

10. What is an operon & what 3 things is it made up of?

11. What name did Jacob & Monod give their gene & why?

12. If lactose is not present, what attaches to the operator?

13. Define repressor protein and give its function.

14. Define repression.

15. What occurs if lactose is present in the E. coli in lactose metabolism?

16. What is an inducer?

17. What is an inducer for E. coli in lactose metabolism?

18. How does the genome of eukaryotes compare with that of prokaryotes?

19. Are operons found in eukaryotes?

20. Each eukaryotic cell contains a ___________________ set of genes, but only some genes

are ______________________ at a given time.

21. What controls much of the gene expression in eukaryotes?

22. What is euchromatin?

23. Some sections of chromatin always remain coiled preventing what process?

24. Name & define the 2 kinds of segments found behind the promoter in eukaryotes.

25. Where do the processes of transcription & translation take place in prokaryotes?

26. Where do these processes take place in eukaryotes?

27. Are introns and/or exons transcribed?

28. What is pre-mRNA and how is mRNA formed from this?

 

Section 11-2     Gene Expression and Development

 

29. Multicellular, sexually reproducing organisms begin life as a _____________________with all cells containing the same _______________________.

30. Genes may be turned ______________ and _____________as various ___________________ are needed by the cells.

31. What is cell differentiation?

32. Define morphogenesis.

33. What genes determine what anatomical structures an organism will develop during morphogenesis?

34. What is a tumor and what are the 2 main types?

35. Define benign tumor.

36. Are benign tumors dangerous? Explain.

37. What treatment do doctors use with benign tumors?

38. Define malignant tumor.

39. Malignant tumors are commonly known as ____________________________.

40. What is metastasis & what happens to the body when this occurs?

41. How are malignant tumors categorized?

42. Name & describe 4 types of malignant tumors.

43. Lung cancer & breast cancer are what type of tumors?

44. When do normal cells stop dividing? Do cancer cells respond the same way? Explain.

45. What trait of cancer cells facilitates the spread of cancer cells in the body?

46. What is a carcinogen & give 5 examples?

47. What causes most lung cancer?

48. What is the effect of mutagens on cells?

49. What are oncogenes?

50. Certain ____________________ can cause cancer in plants & animals.

 

Genetic Terminology:

• Trait – any characteristic that can be passed from parent to offspring
• Heredity – passing of traits from parent to offspring
• Genetics – study of heredity
• Alleles – two forms of a gene (dominant & recessive)
• Dominant – stronger of two genes expressed in the hybrid; represented by a capital letter (R)
• Recessive – gene that shows up less often in a cross; represented by a lower case letter (r)
• Genotype – gene combination for a trait (e.g. RR, Rr, rr)
• Phenotype – the physical feature resulting from a genotype (e.g. tall, short)
• Homozygous genotype – gene combination involving 2 dominant or 2 recessive genes (e.g. RR or Rr); also called pure 
• Heterozygous genotype – gene combination of one dominant & one recessive allele    (e.g. Rr); also called hybrid
• Monohybrid cross – cross involving a single trait
• Dihybrid cross – cross involving two traits
• Punnett Square – used to solve genetics problems

Blending Concept of Inheritance:

• Accepted before Mendel’s experiments
• Theory stated that offspring would have traits intermediate between those of its parents such as red & white flowers producing pink
• The appearance of red or white flowers again was consider instability in genetic material
• Blending theory was of no help to Charles Darwin’s theory of evolution 
• Blending theory did not account for variation and could not explain species diversity
• Particulate theory of Inheritance, proposed by Mendel, accounted for variation in a population generation after generation
• Mendel’s work was unrecognized until 1900

Gregor Mendel:

• Austrian monk
• Studied science & math at the University of Vienna
• Formulated the laws of heredity in the early 1860’s
• Did a statistical study of  traits in garden peas over an eight year period

Why peas, Pisum sativum?

• Can be grown in a small area
• Produce lots of offspring
• Produce pure plants when allowed to self-pollinate several generations
• Can be artificially cross-pollinate

GARDEN PEA

Mendel’s Experiments:

• Mendel studied simple traits from 22 varieties of  pea plants (seed color & shape, pod color & shape, etc.)
• Mendel traced the inheritance of individual traits & kept careful records of numbers of offspring
• He used his math principles of probability to interpret results
• Mendel studied pea traits, each of which had a dominant & a recessive form (alleles)
• The dominant (shows up most often) gene or allele is represented with a capital letter, & the recessive gene with a lower case of that same letter (e.g. B, b)
• Mendel’s traits included:

         a. Seed shape —  Round (R) or Wrinkled (r)
            b. Seed Color —- Yellow (Y) or  Green (y)
            c. Pod Shape — Smooth (S) or wrinkled (s)
            d. Pod Color —  Green (G) or Yellow (g)
            e. Seed Coat Color —  Gray (G) or White (g)
            f. Flower position — Axial (A) or Terminal (a)
            g. Plant Height — Tall (T) or Short (t)
            h. Flower color — Purple (P) or white (p)

•  Mendel produced pure strains by allowing the plants to self-pollinate for several generations
• These strains were called the Parental generation or P1 strain
• Mendel cross-pollinated two strains and tracked each trait through two
  generations (e.g. TT  x  tt )

   

  Trait – plant height
  Alleles – T tall, t short
  P1 cross    TT  x  tt				genotype      —    Tt
  	t	t		phenotype    —    Tall
  T	Tt	Tt		genotypic ratio –all alike
  T	Tt	Tt		phenotypic ratio- all alike

   

 

• The offspring of this cross were all hybrids showing only the dominant trait & were called the First Filial or F1 generation
• Mendel then crossed two of his F1 plants and tracked their traits; known as an F1 cross

 

• When 2 hybrids were crossed, 75% (3/4) of the offspring showed the dominant trait & 25% (1/4) showed the recessive trait; always a 3:1 ratio
• The offspring of this cross were called the F2 generation
• Mendel then crossed a pure & a hybrid from his F2 generation; known as an F2 or test cross

• 50% (1/2) of the offspring in a test cross showed the same genotype of one parent & the other 50% showed the genotype of the other parent; always a 1:1 ratio

Problems: Work the P1, F1, and both F2 crosses for all of the other pea plant traits & be sure to include genotypes, phenotypes, genotypic & phenotypic ratios.

• Mendel also crossed plants that differed in two characteristics (Dihybrid Crosses)
  such as seed shape & seed color
• In the P1 cross, RRYY  x  rryy, all of the F1 offspring showed only the dominant form for both traits; all hybrids, RrYy

• When Mendel crossed 2 hybrid plants (F1 cross), he got the following results

 

 

Problems: Choose two other pea plant traits and work the P1 and F1 dihybrid crosses. Be sure to show the trait, alleles, genotypes, phenotypes, and all ratios. 

Results of Mendel’s Experiments:

• Inheritable factors or genes are responsible for all heritable characteristics
• Phenotype is based on Genotype
• Each trait is based on two genes, one from the mother and the other from the father
• True-breeding individuals are homozygous ( both alleles) are the same
• Law of Dominance states that when different alleles for a characteristic are inherited (heterozygous), the trait of only one (the dominant one) will be expressed. The recessive trait’s phenotype only appears in true-breeding (homozygous) individuals

• Law of Segregation states that each genetic trait is produced by a pair of alleles which separate (segregate) during reproduction

• Law of Independent Assortment states that each factor (gene) is distributed (assorted) randomly and independently of one another in the formation of gametes

 

Other Patterns of Inheritance:

• Incomplete dominance occurs in the heterozygous or hybrid genotype where the 2 alleles blend to give a different phenotype
• Flower color in snapdragons shows incomplete dominance whenever a red flower is crossed with a white flower to produce pink flowers

• In some populations, multiple alleles (3 or more) may determine a trait such as in ABO Blood type
• Alleles A & B are dominant, while O is recessive

• Polygenic inheritance occurs whenever many variations in the resulting phenotypes such as in hair, skin, & eye color
• The expression of a gene is also influenced by environmental factors (example: seasonal change in fur color)