6D gene expression and regulation

CRISPR-Cas9 is a genetic modification technique that edits parts of the genome of an organism. Using this technique scientists can add, remove, or modify sections of the DNA sequence. How can scientists use this technique to control gene expression?

• by activating or deactivating specific genes

• by calculating the number of genes different organisms produce

• by identifying how closely related one individual is to another

• by determining the number of chromosomes in an organism

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The 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 are 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

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The arctic fox inhabits northern areas of North America. The same arctic fox is shown in the drawing at different times of the year. What causes this change in fur color?

• the alleles for fur color change as the arctic fox grows older

• gene expression for fur color is regulated by latitude

• the arctic fox has two traits for fur color that are determined at birth

• gene expression for fur color is regulated by temperature

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Human bone, muscle, and nerve cells all contain the same number of chromosomes with the same complement of genes. What enables these cells to perform specialized activities?

• the ability of some cells to remove unnecessary DNA sequences

• the regulation of gene expression within each cell type

• the mutation of genes within each cell type

• the use of different methods of cell division

At birth Himalayan rabbits are usually white over their entire bodies. But when parts of their bodies reach temperatures below 35^oC, a pigment that causes these parts to turn black is produced. Which of the following is most likely the cause of this phenomenon?

• poor blood circulation

• infection caused by cold temperatures

• gene expression that is regulated by temperature

• a trait that is both sex-linked and hormone-dependent

In 1917 the biologist Thomas Hunt Morgan conducted studies in which he kept some caterpillars in the dark and placed some others under red, green, or blue lights. Exposure to red light produced butterflies with brightly colored wings. Exposure to green light resulted in dark-colored wings. Exposure to blue light or no light resulted in pale-colored wings. What was the most likely conclusion of Morgan's research?

• the pigment in butterfly wings absorbs light from the environment

• the phenotypic expression of wing shape depends on color pigmentation in butterflies

• the genes regulating wing color in butterflies are influenced by environmental factors

• caterpillars exposed to red and green light are healthier than caterpillars exposed to no light or blue light