Genetics Remediation

The sequence of the nitrogenous bases in the DNA varies widely.

The sequence of the bases in the DNA is the most important for which of the following?

• Providing the instructions for the traits of an organism

• Preventing mutations from occurring during DNA replication

• Allowing the DNA to have the shape necessary for replication

• Helping form the sugar-phosphate backbone of the DNA molecules

  i

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The fact that a strain of yeast with a certain defective gene can use the human version of the gene to repair itself is evidence that yeast and humans –

• Depend on the same food supply

• Share a genetic code

• Both have eukaryotic cells

• Have identical genomes

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Answer explanation

ALL organisms (pro and eu) have the SAME 4 NITROGEN BASES (ATGC).

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E. coli has three genes that each code for different enzymes that break down lactose. Scientists conducted investigations about the production of these enzymes using samples of E. coli. Their results are shown in the table.

Which conclusion about the production of the enzymes can be determined by analyzing the scientists’ results?

• Gene expression for the enzymes was controlled by the temperature of lactose.

• The genes for the enzymes were expressed in equal amounts during both experiments.

• Gene expression for the enzymes was controlled by the presence of lactose.

• The genes for the enzymes were mutated before being expressed by the presence of lactose.

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Answer explanation

No mention of temperature or mutations--and definitely not expressed in equal amounts (one environment shows High enzyme concentration and the other shows low enzyme concentration)

A partial DNA strand is shown.

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

Which of the following accurately transcribes the DNA strand above?

• 5' T G T A C G T A C 3'

• 5' A G U A C G U A C 3'

• 5' A C U A G C U U C 3'

• 5' A G T A C G T A C 3'

An illustration of how a particular DNA mutation will most likely affect the polypeptide produced is shown. 

• Insertion

• Translocation

• Substitution

• Deletion

Answer explanation

Only ONE codon (amino acid) is changed as a result of the mutation. This is specifically a missense substitution.

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The survival of a species depends on its ability to adapt to changes in the environment. A species must be capable of surviving and reproducing despite changes to food sources, climate, or threats from predators. Which statement correctly describes a way that mutations increase the likelihood that a species will survive in a changing environment?

• Mutations are a source of variations in the species.

• Mutations are the cause of disease in the species

• Mutations are not harmful when they occur in somatic cells of the species

• Mutations are always passed on to subsequent generations of a species

  i

Answer explanation

Remember that not all mutations are bad--This question is asking for a GOOD thing about mutations (something about a mutation that might increase the survival rate of a species)--Only Answer Choice A gives an example of this--None of the other answers accurately address the question.

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Many organelles within the cell are involved in the production of proteins. Which of the following correctly identifies the organelles involved?

Select the 3 correct answers.

• Nucleus

• Lysosomes

• Ribosomes

• Golgi Apparatus

• Chloroplast

Answer explanation

Only Answer Choices C, D, and F have to do with proteins directly.

Nucleus: Has the instructions for making proteins (traits)

Ribosomes: Make protein (mRNA takes DNA instructions here)

Golgi Apparatus: Packages protein

Mitochondria: Powerhouse--Makes energy/ATP

Chloroplast: Uses energy from the sun to make glucose & oxygen in plant cells

Lysosomes: Breaks down wastes in animal cells

Scientists can determine relatedness among organisms by comparing partial amino acid sequences. The table shows four partial amino acid sequences from four organisms.

 

Organism 1: SER LEU VAL GLU

Organism 2: LEU SER ASN VAL

Organism 3: ALA LEU SER GLU

Organism 4: THR LEU SER GLU

 

Which organism is the LEAST related to the other three organisms?

• Organism 1

• Organism 2

• Organism 3

• Organism 4

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A Himalayan rabbit’s habitat has cold, snowy winters and mild summers. The body is typically covered in white fur except for the nose, feet, tail, and ears, which are covered in black fur.

 

A scientist shaved an area of white fur on the back of a Himalayan rabbit and placed an ice pack over the shaved area. The shaved area grew black fur.

 

Which of these best explains why the hair that grew back where the ice pack was placed was black and not white?

• The genes for black hair were activated by specific temperatures.

• The white hair mutated to black hair as the rabbit’s body temperature decreased.

• The coat color changed from white to black with the age of the rabbit.

• White hair only grows during certain times of the year

Answer explanation

We know that certain genes can be turned "on" (activated) or "off" (deactivated) due to internal factors or external factors (like temperature) and alter the traits of an organism.

This passage is clearly focusing on how a change in temperature (presence of an ice pack) affects the fur color in the rabbit. This is not an example of a mutation--Mutations are RANDOM changes in DNA. Also, there is no mention of the rabbit's age or the fur changing colors at different times of year.

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In the early 1980s scientist were able to produce two biomolecules by splicing a human gene into the bacterium E. coli to make recombinant human insulin and growth hormone.

Which statement best explains why this experiment was successful?

• Human cells are eukaryotic and E. coli cells are prokaryotic

• All living organisms share the same genome

• The genes for all organisms are composed of the same building blocks.

• The human body contains many types of bacteria, including E. coli

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Answer explanation

All living things have the SAME FOUR NITROGEN BASES (the same GENETIC CODE--A, T, C, G).

The genome is the unique DNA sequence a specific organism has.