BIOL 2030 Lecture Notes - Lecture 5: The Sequence, Eukaryote, Chromosome

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5 Nov 2018

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Gene organization: collinearity between genes and protein: Continuous sequence of nucleotides encodes a continuous sequence of amino acids. Number of nucleotides in the gene is proportional to the number of amino acids in the protein. If there were 100 nucleotides in the dna, then there would be 100 nucleotides in the mrna that is produced, making however many polypeptides. The concept of collinearity is generally true for the genes that are found in bacterial cells and in viruses, as well as in certain eukaryotes. However, these genes would be slightly longer than what would be expected if the collinearity was strictly applied, as there are certain sequences contained in the mrna that do not specify amino acids: the discovery of split genes: At first, eukaryotic genes were also assumed to be collinear, but some experiments showed that not all genes are collinear.

Related Questions

1. Characters that show a continuous range of variation, such as height and eye color, usually are controlled:

a.	by a single gene with two alleles that are codominant.

b.	by many genes with an additive effect.

c.	by epistatic interactions between two genes.

d.	mainly by the environment, with only a small genetic component.

2. In humans, red-green colorblindness is inherited as a sex-linked recessive trait. In order for a woman to be red-green colorblind, which of the following statements must be true.

a.	Her mother must be red-green colorblind.

b.	All of her brothers must be red-green colorblind.

c.	Her father must be red-green colorblind.

d.	All of the above statements must be true if a woman is red-green colorblind.

3. The x-ray crystallography data collected by Rosalind Franklin suggested to Watson and Crick that the:

a.	structure of DNA is a double helix.

b.	two strands of the DNA molecule are joined by hydrogen bonds between the bases.

c.	four bases within DNA pair in a specific way.

d.	two strands of the DNA molecule are joined by covalent bonds between the bases.

4. In the genetic code, _________ one amino acid.

a.	one nucleotide specifies

b.	two nucleotides specify

c.	three nucleotides specify

d.	four nucleotides specify

5. During Meiosis I, a homologous pair of chromosomes may not separate, resulting in daughter cells that have extra chromosomes or are missing chromosomes. This can lead to genetic disorders, including Down Syndrome. This phenomenon is called:

a.	independent assortment.

b.	nondisjunction.

c.	segregation.

d.	crossing over.

6. You are a human geneticist studying the incidence of retinitis pigmentosa in the residents of Tristan de Cunha, a group of small islands in the middle of the southern Atlantic Ocean. The allele for retinitis pigmentosa, which causes a form of blindness, is inherited as an autosomal recessive. You have determined that the frequency of this allele (r) in the population is 0.4 (40%). Using the principles of the Hardy-Weinberg rule, you would estimate the frequency of individuals who are heterozygous for this allele (Rr) in the population to be:

a.	0.16 (16%)

b.	0.24 (24%)

c.	0.36 (36%)

d.	0.48 (48%)

7. Natural selection acts at the level of the:

a.	phenotype.

gene.

c.	population.

d.	nucleotide.

8. You are working with pea plants, trying to recreate the experiments that Mendel performed. You are doing a dihybrid cross with a plant that is heterozygous for both seed shape and seed color, with the genotype RrYy. Which allelic combinations would you expect to find in the gametes produced by this plant?

a.	This plant would produce only RY and ry gametes.

b.	This plant would produce only RrYy gametes.

c.	This plant would produce RY, Ry, rY, and ry gametes.

d.	You cannot determine which gametes this plant can produce without knowing the genotypes of its parents.

9. Biochemist Erwin Chargaff found that in DNA there is a special relationship between the four bases that we now call Chargaff's rule. His observation was that, in an organism's genome the:

a.	percentage of A nucleotides = the percentage of T nucleotides, and the percentage of C nucleotides = the percentage of G nucleotides.

b.	four bases all occur in an equal frequency (25%) within each organism.

c.	percentage of A nucleotides = the percentage of G nucleotides, and the percentage of C nucleotides = the percentage of T nucleotides.

d.	genetic material is composed of proteins, not DNA.

10. During DNA replication:

a.	each strand of the double helix acts as a template for the synthesis of a new strand.

b.	the enzyme DNA polymerase adds nucleotides to the strand being synthesized.

c.	the bases A,C,G and T are required.

d.	All of the above are true of DNA replication.

11. During translation, amino acids are joined by peptide bonds to make polypeptides. The formation of these peptide bonds is catalyzed by:

12. If an allele (R) at a gene with two alleles shows complete dominance, individuals with the genotypes ______ will have the same phenotype.

a.	RR and rr.

RR and Rr

Rr and rr

d.	Each of the three possible genotypes will have a different phenotype.

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QuestionGroup: #21 Gene expression 2

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The direct end result of gene expression is which of the following?

Amino acids

Translation

Proteins

Carbohydrates

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QuestionGroup: #22 Mutation

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Which of the following is the ways in which nucleotide mutations lead to altered proteins?

One nucleotide is substituted by another nucleotide, which can cause an early stop codon to be incorporated into the amino acid sequence resulting in a truncated protein.

One nucleotide is replaced by another nucleotide, which can change an amino acid in the protein sequence

Nucleotides are inserted into a nucleotide sequence causing a frameshift in the sequence.

All three choices may cause mutations.

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QuestionGroup: #23 Mutation 2

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Mutations are the result of which of the following?

Change in the normal nucleotide sequence in the DNA directly resulting in different carbohydrates

Change in the normal nucleotide sequence in the DNA directly resulting in different proteins

Change in the order of transfer RNA to messenger RNA so that the transfer RNA take over the role of Messenger RNA

Primarily an alteration in the sequence of nucleotides in the abnormal proteins

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QuestionGroup: #24 Cell division

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There are two major kinds of cell division. Which of the following plays a major role in promoting genetic diversity?

Meiosis since it causes the cells to make more daughter cells than mitosis

Mitosis since it causes the cells to duplicate and eventually have mutations

Meiosis since it causes the DNA sequences to be separated into new patterns in the daughter cells.

Mitosis since it essential for the ovaries in humans to separate and duplicate

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QuestionGroup: #25 Cancer

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Genes that slow down or stop the cell cycle are called...

Apoptotic genes

Oncogenes

Restriction genes

Tumor suppressor genes

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QuestionGroup: #26 Cancer2

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The common theme in the development of all cancers is...

Mutation

Evolution

Infection

Syncopation

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QuestionGroup: #27 Genetics

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Punnett's square is which of the following?

Example of all possible combinations of alleles

Example of all possible combinations of chromosomes

Example of only certain combination of alleles since some will not be expressed.

Example of all possible combinations of DNA

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QuestionGroup: #28 Embryo development

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Which of the following is the end of the cleavage phase?

A fetus

Formation of a blastocyst

Implantation to the lining of the uterus

Fewer number of cells

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QuestionGroup: #29 Development of organ system

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For organs to be differentiated, which of the following is the first step?

Stem cells trigger the development of differentiated cells

Tissues assemble into organ systems such as blood

Tissue specific genes in stem cells are triggered

Differentiated cells form tissues

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QuestionGroup: #30 Development and society

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Homework

A pregnant mother ingests a chemical which her mother said would be great for the baby. When the baby was born, it had a large head and flippers for arms. What caused this phenotype?

The chemicals were teratogens which influenced oxidative phosphorylation causing the changes in the phenotype.

The chemicals influenced the expression of different stem cells.

There is no way to assume the chemicals caused the phenotype since we have no data on other mothers who took this medicine. It could have been purely by chance.

The chemicals were teratogens which caused the baby to show early signs of evolution.

Part B

Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?

a) It could cause a frameshift nonsense or frameshift missense mutation because it would change the reading frame of the codon triplet.

b) It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.

c) It could cause a nonsense mutation because the sequence would no longer be the same, so the protein would be shorter and non-functional.

d) It could cause a silent mutation because A and T are complementary to each other so it is not really a substitution mutation.

Part C

Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?

a) A substitution missense mutation causes the protein to be shorter and thus non-functional.

b) A frameshift missense will cause the codons to be out of order, but a substitution missense does not change the order of the codons.

c) A frameshift missense mutation will cause an early Stop codon, but a substitution missense might be silent.

d) A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.

Part D

Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?

a) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAGAGUGA-3â

b) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACGUUGGAGUGA-3â

c) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAUCUGGAGUGA-3â

d) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUGUGACAUUGGAGUGA-3â

Part F

Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein?

5â-ATGCTAGCCTATCGTAAC-3â

a) The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.

b) The entire amino acid sequence would be altered due to the frameshift.

c) All of the amino acids after the deletion would be altered due to the frameshift.

d) All of the amino acids up to the deletion would be altered due to the frameshift.

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BIOL 2030 Lecture Notes - Lecture 5: The Sequence, Eukaryote, Chromosome

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