BIOL 110 Principles of Biology

BIOL 110  Principles of Biology

Worksheet 7, Week 7

1. What is the genetic material of organisms?

The genetic material of an organism refers are the materials found in the nucleus, mitochondria and cytoplasm, which play a major role in determining the structure and nature of cell substances, and capable of self-propagating and variation.

2. What are the requirements for DNA to be the genetic material?

It must be able to store information, stable so it can be replicated, and be able to undergo rare changes called mutations. BIOL 110 Principles of Biology

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3. Who can be credited with determining that DNA is the genetic material of living things?

Oswald Avery and his coinvestigators, Colin Macleod and Maclyn McCarty

4. What nucleotides are contained in DNA?

A is for adenine, G is for guanine, C is for cytosine, T is for thymine

5. What is the difference between pyrimidine and purine bases?

Pyrimidine has one ring and purine has two rings. Purine has a pyrimidine ring and an imidazole ring. Adenine and guanine are the purine derivative present in nucleic acids whereas cytosine, uracil and thymine are the pyrimidine derivatives present in the nucleic acids. Purines have more intermolecular interactions than pyrimidines BIOL 110 Principles of Biology. Melting points and boiling points of purines are much higher compared to pyrimidines.

6. State Chargaff’s rules.

In a DNA molecule, the ratio of pyrimidine to purine bases should be 1:1.

Specifically, the amount of guanine (G) should be equal to that of cytosine (C), and the amount of adenine (A) should be equal to thymine (T).

7. What is the estimate of the number of base pairs on each human chromosome?

An estimated 140 million base pairs

8. Describe the Watson-Crick model for DNA.

A three-dimensional model of the DNA molecule, consisting of two complementary polynucleotide strands wound in the form of a double helix and joined in a ladderlike fashion by hydrogen bonds between the purine and pyrimidine bases BIOL 110 Principles of Biology.

9. Explain the meaning of complementary base pairings.

The standard arrangement of bases in nucleotides in relation to their opposite pairing, such as thymine being paired with adenine and cytosine paired with guanine.

10. What enzyme is required for DNA replication?

DNA polymerase

11. What molecules form the backbone of a DNA molecule?

One phosphate group and deoxyribose sugars form the backbone.

12. What type of molecules does the genetic code in DNA produce?

DNA will code for amino acids in proteins and indicates the sequence of amino acids in a protein. The sequence of amino acids determines the structure of the protein and determines the function BIOL 110 Principles of Biology.

13. Identify three differences between DNA and RNA.

DNA is double-stranded. RNA is single stranded. In DNA base pairing, adenine links to thymine (A-T) and cytosine links to guanine (C-G). In RNA base pairing, adenine links to uracil (A-U) and cytosine links to guanine (C-G). DNA is found in the nucleus of a cell and in mitochondria. Depending on the type of RNA, this molecule is found in a cell’s nucleus, its cytoplasm, and its ribosome. BIOL 110 Principles of Biology.

14. What is the role of mRNA?

The role of mRNA is to transform the information stored in DNA into proteins. The mRNA carry the protein blueprint from a cell’s DNA to its ribosomes.

15. What is transcription?

DNA transcription involves transcribing genetic information from DNA to RNA. The RNA transcript is used to produce proteins and DNA is housed within the nucleus of our cells. Transcription controls cellular activity by coding for the production of proteins. BIOL 110 Principles of Biology.

16. What is translation?

When mRNA is transcribed and leaves the nucleus, it’s translated by a ribosome. The sequence of the mRNA tells the ribosome which amino acids to put in which places to make a protein.

17. What does it mean to say the genetic code is unambiguous?

It means that the genetic code is universal.

18. What role is performed by transfer RNA?

The tRNA carries an amino acid and an anti-codon to where a ribosome attaches and performs as an enzyme and as the codon joins attaches to the promoter, the amino acids link and form a protein strand. The anti-codons and tRNA latch off after the amino acid joins to the chain. BIOL 110 Principles of Biology.

19. If a DNA strand is represented by the bases: A-C-T-G-G-C what are the bases that will be included in the replicated strand?

A = T and G = C

20. If a DNA strand is A-C-T-G-G-C, what is the base representation that will be produced by transcription?

RNA = T G A C C G, mRNA = U G A C C G

21. If a messenger RNA molecule is U-C-A-A-C-G what will be the tRNA molecule?

tRNA = AGUUGC

22. What are the steps in translation?

They are initiation, elongation, termination and gene expression.

23. Where in the cell does transcription occur?

It is inside the nucleus of the cell where RNA polymerase binds to the DNA.

24. What three types of gene regulation that are present in the nucleus of eukaryotic cells?

Chromatin structure, Transcriptional control and Posttranscriptional control

25. In a prokaryotic cell what are the elements of an operon?

A regulator gene, a promoter, an operator and structural genes are the elements.

26. Define a gene mutation.

A gene mutation is any event that changes genetic structure; any alteration in the inherited nucleic acid sequence of the genotype of an organism

27. Identify two causes of gene mutations.

DNA can fail to copy accurately. When a cell divides, it makes a copy and sometimes the copy is not exact and the small difference from the original DNA sequence is a mutation. BIOL 110 Principles of Biology.

External influences and exposure to certain chemicals or radiation can also create mutations. These influences can cause the DNA to break down and when the cell repairs the DNA, it does not always do an exact job of the repair.

28. Explain the difference between a point mutation and a frameshift mutation.

Point mutations are gene mutations involving the substitution, addition, or deletion of a single nucleotide base and usually take place during DNA replication. Point mutations can have a range of effects, depending on the particular codon change. Point mutations are also referred as a base-pair substitution. Point mutations can be categorized into three types: silent mutation, missense mutation and nonsense mutation. Silent mutations create changes in the DNA sequence, this type of mutation does not change the protein that is to be produced. This is because multiple genetic codons can encode for the same amino acid. Missense mutations alter the nucleotide sequence so that a different amino acid is produced BIOL 110 Principles of Biology. This change alters the protein and may not have much effect, may be helpful or may be hazardous. Nonsense mutations alter the nucleotide sequence so that a stop codon is coded for in place of an amino acid. A stop codon signals the end of the translation process and stops protein production. If this process is ended too soon, the amino acid sequence is cut short and the resulting protein is most always nonfunctional.

A frameshift mutation, also called a framing error or a reading frame shift, is a genetic mutation caused by insertions or deletions of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame the grouping of the codons, resulting in a completely different translation from the original.

29. What are the three deadliest forms of cancer in the United States?

Lung, Colon, Breast

30. What is the relationship between tumor suppressor genes and oncogenes in the development of cancer?

They both code for transcriptions factors or proteins that control transcription factors. BIOL 110 Principles of Biology.