Dna Processes Content Guide

UNIT 4 DNA PROCESSES STUDY GUIDE Biology

CONTENT GUIDE (This includes the major concepts for which students will be responsible in this unit. Additional content as studied in the unit under these major concepts may be included. Examples would include information from labs, activities, diagrams, tables and charts. The student must also be able to use the basic content to make applications, analyze, synthesize and evaluate information.)

I. Cell Structure (p. 169-182, 241-243) A) Nucleus - contains the genetic material (DNA) of the cell B) Chromosomes - strands of DNA wrapped around proteins C) Ribosomes - site of protein synthesis D) Endoplasmic reticulum - after proteins are made the ER transports them to the Golgi body E) Golgi body - modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or secretion outside of the cell.

II. Nucleic Acid Structure and Function (pg. 291 – 294) A) Scientist in the History of DNA 1) Erwin Chargaff determines the amount of Guanine and Cytosine in the DNA (deoxyribonucleic acid) molecule is equal. The same is true of Adenine and Thymine. This became known as Chargaff’s rule. 2) Rosalind Franklin’s studies of the DNA molecule resulted in the image of an X, when x-rayed. 3) James Watson and Francis Crick, used clues from the work of Rosalind Franklin, built a structural model that explains how DNA carries information and how it can be copied. This became known as the Double Helix. N-b B) DNA contains the genetic information of the cell S 1) Is a long molecule made up of units called nucleotides - a phosphate group, a 5- carbon sugar (deoxyribose) with a nitrogenous base sticking out from the sugar. (a) The DNA molecule is arranged in a pattern resembling a twisted ladder called a P double helix. (b) Sides of the ladder are made up of the sugars and phosphates (c) The rungs of the ladder are made up of one of the four nitrogen bases, Adenine, Guanine, Cytosine, or Thymine joined by weak hydrogen bonds (d) Base paring rule - Adenine binds with Thymine, Guanine binds with Cytosine (e) The order (sequence) of the nucleotides accounts for the differences between organisms. C) The Genetic Code 1) The sequence of the nucleotides is responsible for specifying the traits of the organism. 2) A series of three nitrogen bases (N-base triplet) codes for a particular amino acid. 3) Amino acids are joined together to produce long chains of polypeptides which form proteins (structural molecules and enzymes). 4) The sequence of DNA that codes for a specific protein, determining the trait, is called a gene. 5) Universal Genetic Code - The amino acid/codon assignments of the genetic code are remarkably similar in all living organisms. 6) The Genetic Code Chart allows codons/triplets to be identified by the amino acid for which they code.

III. Protein Synthesis and Gene Regulation (pg. 300 – 312)) A) Protein Synthesis decodes the genetic message into the protein for which it codes. 1) Protein Synthesis is also called Gene Expression since genes are coded DNA instructions that control the production of proteins within the cell. 2) Protein Synthesis is a two-step process consisting of transcription and translation. This requires 3 forms of RNA (ribonucleic acid). (a) Transcription

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 1 (a) During transcription, the DNA separates and one strand is used as a template from which nucleotides are assembled into a single strand of messenger RNA (mRNA). (b) Base-pairing rules still apply, with Uracil substituting for Thymine (ie. Adenine – Uracil, Guanine – Cytosine) (c) The mRNA travels out of the nucleus and attaches to the ribosome (which contains ribosomal RNA or rRNA) (b) Translation (a) Translation begins when an mRNA moves through the ribosome. (b) As each set of 3 bases (a codon) moves through, the proper amino acid is brought into the ribosome by the transfer RNA (tRNA). This amino acid is attached to a growing chain of amino acids called polypeptide chain (protein). (c) The process continues until a stop codon is reached. The completed polypeptide chain (protein) is then released into the cell. (d) The amino acid for each codon may be determined by using the Genetic Code or Amino Acid Chart (pg. 303). B) Gene Expression 1) Each cell contains the complete genetic code for the organism. 2) Only a fraction of the genes in a cell are expressed at any given time. An expressed gene is a gene that is transcribed into mRNA. 3) Cell specialization requires genetic specialization. For proper function, only a very small number of the available genes needs to be expressed in the appropriate cell. 4) Cells undergo differentiation during embryonic development.

IV. Mutations (pg. 307 – 308) A) Mutations are changes in the genetic material. B) Point mutations involves changes in one or more of the nucleotide sequences. These changes may take the form of substitution, insertion, or deletion. 1) Substitution - one base is changed to another, usually affects Original DNA: AAG-TTT-GGC no more than a single amino acid, if any – least likely to cause Mutated DNA: AAG-ATT-TGG-C an effect on gene expression (formation of the protein) 2) Insertion - in which a base is inserted into the sequence, will Original DNA: AAG-TTT-GGC affect the amino acid with the insertion and all those following Mutated DNA: AAG-TTT-AGC in the sequence – causes a frame-shift that has a greater impact on gene expression 3) Deletion - in which a base is removed from the sequence, will Original DNA: AAG-TTT-GGC affect the amino acid with the deletion and each amino acid Mutated DNA: AAT-TTG-GC following in the sequence - causes a frame-shift that has a greater impact on gene expression C) Chromosomal mutations involve changes in the number or structure of chromosomes. D) Effect of Mutations 1) Many mutations are neutral, having little or no effect on the expression of genes. Generally, insertion and deletion which result in frame-shifts have the greater impact. Mutations in gametes or early in fetal development have greater impact than those in mature body cells. 2) Mutations are the source of genetic variability in a species. Some may be highly beneficial. 3) Harmful mutations may result in genetic disorders or cancer. E) Genetic Engineering - Some mutations are genetically engineered 1) to create new variations of an existing organism (seedless watermelons) 2) to replace or correct defective genes 3) to produce hybrids such as bacteria that can produce human insulin. F) Mutagens - Some environmental causes of mutations are UV rays, radiation, pollution, etc.

BIOLOGY OBJECTIVE AND TEKS Objective 7: NUCLEIC ACIDS Identify the structure & function of nucleic acids including their role in biodiversity. Subobjective:

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 2 a) Describe components of deoxyribonucleic acid (DNA), and illustrate how information for specifying the traits of an organism is carried in the DNA. b) Construct and analyze a model of DNA molecule. c) Explain protein synthesis (transcription, and translation) using models of DNA and ribonucleic acid (RNA). d) Relate the DNA sequence to an organism’s traits. e) Identify and illustrate how changes in DNA cause mutations and evaluate the significance of these changes. f) Recognize and apply biotechnology to the study of genetic variation in organisms including genetic engineering, electrophoresis (genetic fingerprinting), and the human genome project. g) Recognize macromolecules as the building blocks of living things; identify nucleic acids as containing genetic information (some used to make proteins), proteins as structural molecules and enzymes as regulators of activities TEKS: (3F) research and describe the history of biology and contributions of scientists. (6A) describe components of deoxyribonucleic acid (DNA), and illustrate how information for specifying the traits of an organism is carried in the DNA. (6B) explain replication, transcription, and translation using models of DNA and ribonucleic acid (RNA). (6C) identify and illustrate how changes in DNA cause mutations and evaluate the significance of these changes. (6D) compare genetic variations observed in plants and animals.

SAMPLE QUESTIONS (These are samples of the type of questions which might be on the test. Questions may require students to use the basic content to make applications, analyze, synthesize and evaluate information. Tests contain unit content questions as well as general scientific processing questions.)

DNA MUTATION REPAIR Figure 3

5' G T A _ _ _ A A 3' 3' C A T G C A T T 5'

1. This segment of DNA has undergone a mutation in which three nucleotides have been deleted. A repair enzyme would replace them with

A. CGT. B. GCA. C. CTG. D. GTA.

2. Mutations within a DNA sequence are

A. natural processes that produce genetic diversity. B. natural processes that always affect the phenotype. C. unnatural processes that always affect the phenotype. D. unnatural processes that are harmful to genetic diversity.

3. An inheritable mutation may occur if an organism has a change in its

A. appendages B. internal organs C. DNA structure D. ATP production rates

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 3 GENETIC CODE CHART Figure 2

4. Look at figure 2. A strand of mRNA containing the repeating sequence AAGAAGAAGAAG could code for which of the following amino acid sequences?

A. lys–arg–glu–lys B. ser–ser–glu–glu C. lys–arg–lys–arg D. lys–lys–lys–lys

5. Which of the following codons would signal a stop for the assembly of a protein?

A. CUA B. ACG C. GAC D. UAG

6. Chromosomal mutations occurring in gametes of humans can affect the appearance of offspring because

A. many traits are usually affected B. only one trait is usually affected C. these mutations usually speed up embryonic development D. these mutations usually result in sex-linked traits

7. The weakest bonds in a double-stranded molecule of deoxyribonucleic acid exist between the

A. deoxyribose sugars B. phosphate groups C. nitrogenous bases D. 5-carbon sugars

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 4 8. One similarity between DNA and messenger RNA molecules is that they both contain

A. the same sugar B. genetic codes based on sequences of bases C. a nitrogenous base known as uracil D. double-stranded polymers

9. The process of cloning involves making an identical copy of a cell’s

A. cytoplasm B. DNA C. ribosomes D. ATP

DNA and RNA Figure 10

10. Look at Figure 10. Which mRNA sequence complements the above section of DNA?

A. C U A G G A B. T C G A A G C. C T A G G C D. A G C U U C

11. Which of the following shows the three parts of an RNA nucleotide?

A. ribose, phosphate group, thymine B. ribose, phosphate group, uracil C. deoxyribose, phosphate group, uracil D. deoxyribose, phosphate group, cytosine

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 5 Comparing Fragments of DNA Table B

12. The shaded areas of Table B show the nucleotides that four fragments of DNA have in common. Which fragment is most different from the other three?

A. Q B. R C. S D. T

NUCLEIC ACID MOLECULE

13. The boxed structure is a/an:

A. DNA nucleotide B. RNA monomer C. amino acid D. codon

14. Which of these nucleic acids functions as a blueprint of the genetic code?

A. tRNA B. mRNA C. rRNA D. DNA

15. Which molecule carries attached amino acids?

A. tRNA B. mRNA C. rRNA D. DNA

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 6 Nucleotide Numbers in Plant Groups

Figure 3

16. The chart in Figure 3 shows the range of numbers of nucleotides among species of different groups of plants. Which of these groups has the largest range of nucleotide numbers among its species?

A. Bryophyta (mosses and liverworts) B. Lycopsida (club mosses) C. Gymnosperms (cedars and pines) D. Pteropsida (ferns)

17. Which of the following RNA types is/are involved in transcription?

A. transfer RNA only B. messenger RNA only C. ribosomal RNA and transfer RNA only D. messenger RNA, ribosomal RNA, and transfer RNA

18. Which of the statements best describes what happens during translation?

A. mRNA is made by copying the DNA code B. Proteins are produced at the ribosome. C. tRNA is made from mRNA’s code. D. DNA copies are produced.

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 7 19. How many nucleotides would it take to carry the code for a protein with 4 amino acids?

A. 4 B. 8 C. 12 D. 16

20. Genes contain instructions for assembling

A. DNA nucleotides B. carbohydrates C. nitrogen bases D. proteins

Answer Section

1. ANS: A OBJ: 7 STO: 6C 2. ANS: A OBJ: 7 STO: 6C 3. ANS: C OBJ: 7 STO: 6C 4. ANS: D OBJ: 7 STO: 6B 5. ANS: D OBJ: 7 STO: 6B 6. ANS: A OBJ: 7 STO: 6C 7. ANS: C OBJ: 7 STO: 6A 8. ANS: B OBJ: 7 STO: 6A 9. ANS: B OBJ: 7 STO: 6A 10. ANS: A OBJ: 7 STO: 6A 11. ANS: B OBJ: 7 STO: 6B 12. ANS: C OBJ: 1 STO: 2C 13. ANS: A OBJ: 7 STO: 6A 14. ANS: D OBJ: 7 STO: 6A 15. ANS: A OBJ: 7 STO: 6B 16. ANS: D OBJ: 1 STO: 2C 17. ANS: B OBJ: 7 STO: 6B 18. ANS: B OBJ: 7 STO: 6B 19. ANS: C OBJ: 7 STO: 6B 20. ANS: D OBJ: 7 STO: 6A

DNA Processes Study Guide –Biology Teacher - (Revised June 21, 2007) (printed 5/4/2018) p. 8