Latest Biological Science Reviewer 6 - LET EXAM - Questions & Answers

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Latest Biological Science Reviewer 6


1. A person with two copies of the C₁ allele has curly hair two copies of the C₂ allele produce straight hair. Heterozygotes, with the C₁ C₂ genotype have wavy hair. The inheritance of hair texture in humans is an example of ______________.

A. co-dominance
B. incomplete dominance
C. pleiotropy
D. polygenic inheritance

Ans: B. incomplete dominance
- When the heterozygous phenotype is intermediate between the two homozygous phenotype is intermediate between the two homozygous phenotype, the pattern of inheritance is known as incomplete dominance incomplete dominant alleles which are called and C₂.

2. A man with type A blood has a children with a woman who has type O blood. What is the chance that they have a child with type AB blood?

A. 100%
B. 50%
C. 2%%
D. 0%

Ans: D. 0%
-People with genotypes AA has only Type A glycoprotiens and have type A blood. Those with genotypes BB synthesis only Type B glycoprotiens and have Type B blood. Homozygous recessive individuals lack both types of glycoprotiens and have Type O blood. In people with type AB blood, both enzymes are present, so the plasma membranes of their red blood cells have both A and B glycoprotiens.

3. What is the manifestation of the iteraction between genotype and environment in Siamese cat. ?

A. Being fond of people
B. Presence of a long tail
C. Its pointed and elegant look
D. Appearance of dark fur nose, ears, paws and tail

Ans: D. Appearance of dark fur nose, ears, paws and tail
- An example of environmental effets on gene action happens in Siamese cats. All Siamese cats are born with pale fur but , within the first few weeks, the ears, nose, paws and tail turn dark. A Siamese cat actually has the genotype for dark fur all over its body. The gradual shading of the extremities is caused by a recessive gene with temperature-sensitive expression. After they are born, the ears, nose, paws, and tail become cooler than the rest of the body, and dark pigment is produced here.

4. What is usually being influenced by environment  in inheritance?

A. Genotype
B. Phenotype
C. Sex-linked traits
D. Sex-limited characteristics

Ans: B. Phenotype
- There are amny instances of environmental influence or gene expressions. However it is significant to keep in mind that there is a very complex interaction between genes and environmental that defines the phenotype.

5. What happens during DNA transcription?

A. Transfer RNA delivers the appropriate amino acids to the ribosomes
B. Ribosomal RNA combines with dozens of proteins to form a ribosome
C. The base sequence of mRNA encodes the amino acid sequence of protein
D. The information contained in the DNA of a specific gene is copied into messenger RNA.


Ans: D. The information contained in the DNA of a specific gene is copied into messenger RNA.
- Information in DNA is used to direct  the synthesis of proteins in two steps, called transcription and translation. Transcription is the initial step of gene expression in which a particular segment of DNA is copied into mRNA  by the enzyme RNA polymerase. Options B and C occur during translation.

6. What is the more recognizable term for condition Trisomy 21?

A. Down syndrome
B. Jacob syndrome
C. Klinefelter syndrome
D. Turner syndrome

Ans: A. Down syndrome
- If a baby is born with three number 21 chromosomes, rather than the usual pair, then the baby would be said to have “trisomy” 21. “trisomy” 21 is also known as Down syndrome. It is a genetic disorder that involves birth defects, intellectual disabilities, characters facial features like small mouth held partially open because it cannot accommodate the tongue.

7. A short female  was found to have premature ovarian failure have extra folds of skin on the neck, swollen hands and feet, kidney defects an hearing loss. What chromosomal condition does she suffer form?

A. Down syndrome
B. Jacob syndrome
C. Klinefelter syndrome
D. Turner syndrome

Ans: D. Turner syndrome
- Turner syndrome is a chromosomal condition that  affects development in females. The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. At puberty , hormone deficiencies prevent females form menstruating or developing secondary sexual characteristics. It is also known as 45 or XO because females suffering from this condition are partly or completely missing an X chromosomes. Hence, they display X-linked recessive disorders such as hemophilia and color blindness.

8. Which of the following cause Klinefelter syndrome?

A. Extra copy of chromosome 21
B. Only one X chromosomes for female
C. Two X chromosomes and Y chromosomes
D. Two Y chromosomes and one X chromosomes

Ans: C. Two X chromosomes and Y chromosomes
- A male with  two X chromosomes and one Y chromosomes is suffering from Klinefelter Syndrome (XXY). Most of these males go through life never realizing that they have an extra X chromosomes. However, at puberty some show mixed secondary sexual characteristics including partial breast development, broadening of the hips and small testes.

9. Some people [people from Hiroshima and Nagasaki, Japan were discovered to have cancer. To which may this be attributed?

A. Chemical in tobacco
B. Radioactive Fallout from Atomic Bomb
C. Ultraviolet radiation
D. X-rays

Ans: B. Radioactive Fallout from Atomic Bomb
- In august 1945, the United States dropped atomic bombs to the Japanese cities of Hiroshima and Nagaski. The ionizing radiation from the atomic bombs deposited molecular-bond-breaking energy to some survivors which damaged their DNA, thus altering genes.

10, Which type of mutation happens when nucleotides are added or deleted by a number other than multiple of three?

A. Deletion Mutation
B. Frameshift mutation
C. Insertion mutation
D. Substitution mutation

Ans: B. Frameshift mutation
- In a frameshift mutation, nucleotides are added or deleted by a number other than a multiple of three. Because triplets of DNA bases specify amino acids, such an addition or deletion disturbs the codon reading frame. It likely to alter the sequence of amino acids or cause premature stop codons.

11. The gene called Bt derived from bacterium bacillus damage the digestive tract of insect but not mammals. What is the genetically engineered trait of the crop possessing this gene?

A. Altered ripening
B. Resistance to disease
C. Resistnace to herbicide
D. Resistance to pest

Ans: D. Resistance to pest
- The insec resistance of many crops has been enhanced by giving them a gene known as Bt from Bacillus thuringiensis. When insect ingest toxin crytasls, their alkaline digestive tracts denature insoluble crystals, making them soluble and thus amenable to being cut with protease found in the insect gut, which liberate the toxin from the toxin the crystals.

12. Which of the following bioengineered crops whose oil was made healthier for human consumption?

A. Canola
B. Coconut
C. Corn
D. Cotton

Ans: A. Canola
- Canola (or rapseed), Brassica  napus, is an oilseed crop which is cultivated for its high quality edible oil ued in man foods such as margarines and cooking oil. By making it genetically modified, its oil can be made healthier for human consumption.

13. What is/are the objective/s of the Human Genome Project?

I. to determine what may genes can do
II. To have an enormous impact on medical practice
III. Appreciate our place in the evolution of life on Earth
IV. Help diagnose genetic disorder predisposition and to devise treatment in the future

A. I only
B. II and III only
C. I, II, and III only
D. I, II, III and IV

Ans: D. I, II, III and IV
- The Human Genome project was an international scientific research project with the goal of determining the sequence of nucleotides base pairs that make up human DNA. And identifying and mapping all of the genes of the human genome. The sequence of the human genome holds benefits for many fields, from molecular medicine to human evolution. All options are considered reasons for conducting the Human Genome Project

14. What disease is usually being diagnose by the Restriction Fragment Length Polymorphisms (RFLPs) analysis?

A. Albinism
B. Alzheimer disease
C. Congenital Heart Disease
D. Sickle-cell Anemia

Ans. D. Sickle-cell Anemia
- Restriction Fragment Length Polymorphism, or RFLPs is a technique that exploits variation in homologous DNA sequence. Analysis of RFLP variation in genomes was a vital tool in genome mapping and genetic disease analysis. It has become a standard technique for diagnosing sickle-cell anemia, even in a embryo. This is done by initially determining the chromosomal location of a particular disease gene. Then by analyzing the DNA of members of a family afflicted by the disease, and looking for RFLP alleles show a similar pattern of inheritance as that of the disease.
 
15. Which of the following is the BEST definition of evolutionary fitness?

A. The measure of the contribution of a genotype to the gene pool of the next generation
B. The relative health of each individual in the population
C. The ability to mutate an individual’s DNA
D. The ability to survive for a long time

Ans: A. The measure of the contribution of a genotype to the gene pool of the next generation
- Organism with highest evolutionary fitness are the one that have the greatest reproductive success.

16. Which type of natural selection is manifestated in the occurrence of large or small beak sizes among seed crackers in the absence of medium-sized beaks?

A. Directional
B. Disruptive
C. Stabilizing
D. Not enough information given

Ans: B. Disruptive
- Bird population with extreme break sizes only are examples of disruptive selections, two or more extreme phenotypes survive at the expenses of intermediate population. Stabilizing selection, an intermediate phenotypes has an advantage over individual with extreme phenotypes.

17. Which of the following may counter the effects of natural selection?

A. Gene flow
B. Genetic drift
C. Mutation
D. Sexual Dimorphism

And: A. Gene flow
- Gene Flow may counter the effects of natural selection by bringing in alleles to a population at a greater rate than selection removes them.

18. Ten thousand years ago, cheetahs were very common in many areas. Today, just two isolated population live in South and East Africa, numbering only a few thousands animals. What genetic drift is being experienced by cheetahs?

A. Artificial Selection
B. Bottleneck effect
C. Founder effect
D. Mutation

Ans: B. Bottleneck effect
-Genetic drift may result from a population bottleneck, which occurs when a population’s size drops rapidly over a short period of time. The founder effect, on the other hand, occurs when a small group of individual leaves its home population and establish a new isolated settlement.

19. Which evolutionary mechanism is a change in allele frequencies that occurs purely by chance and tends to eliminate alleles from a population?

A. Genetic drift
B. Hardy-Weinberg Equilibrium
C. Migration
D. Mutation

Ans: A. Genetic drift
- Genetic Drift is a change in allele frequencies that occurs purely by chance and tends to eliminate alleles from a population. At Hardy-Weinberg Equilibrium. Allele frequencies remain unchanged. Migration is the movement of individuals into or out of a population. Non-random mating is choosing mates based on location. Physical traits or other factors.

20. Which of the following are important water-soluble molecules and re very effective energy-yielding nutrients?

A. Carbohydrates
B. Lipids
C. Nucleic Acids
D. Proteins

Ans: A. Carbohydrates
- Carbohydrates, particularly mono-and disaccharides are water soluble. These carbohydrates are frequently mixed intofloods to give them a sweet taste. The role of carbohydrates is to provide energy, as they are the body’s main source of fuel, needed for physical activity brain function and operation of the organs

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