Cell Membranes and Transport Across Them：練習問題

Which of the following components is found in a DNA mononucleotide but is not found in an RNA mononucleotide?

During DNA replication, the enzyme DNA polymerase plays a critical role. Which of the following correctly describes its function?

Cystic fibrosis is caused by a recessive allele \( (f) \). Two parents who are both carriers for cystic fibrosis \( (Ff) \) have a child who does not show symptoms of the disease. What is the probability that this child is a carrier of the recessive allele?

A segment of DNA has the base sequence 5'-ATGC-3'. What is the base sequence of the complementary DNA strand?

A plant cell is placed in a solution with a higher water potential than its cytoplasm. Which of the following correctly describes the movement of water and the resulting state of the cell?

Identify the type of chemical reaction and the specific bond formed when two amino acid monomers are joined together.

A specific segment of DNA contains the base sequence 5'-ATG CGA TTT-3' on the coding strand. Describe the sequence of bases on the antisense (template) strand and name the type of bond that holds the two strands together in the double helix.

Compare amniocentesis and chorionic villus sampling (CVS) as methods of prenatal genetic screening in terms of timing and risk.

The structure of the mammalian cell membrane is described by the fluid mosaic model. The membrane is composed of various molecules that allow it to be both flexible and functional.

(a) Explain how the amphipathic nature of phospholipids allows them to form a stable bilayer in an aqueous environment. (2 points)

(b) The fluidity of the membrane is essential for its function. Describe how the presence of cholesterol and the saturation of fatty acid tails within the phospholipids affect membrane fluidity. (3 points)

(c) Some proteins are embedded within the bilayer while others are attached to the surface. Distinguish between intrinsic (integral) and extrinsic (peripheral) proteins and suggest one role for each in the membrane. (2 points)

DNA replication and protein synthesis are highly regulated processes that ensure the correct genetic information is expressed as functional proteins.

(a) During transcription, an mRNA strand is synthesized from a DNA template. Describe the role of RNA polymerase and the principle of complementary base pairing in this process. (3 points)

(b) The genetic code is described as being degenerate and non-overlapping. Define these two terms and explain how a degenerate code can provide protection against the effects of certain mutations. (3 points)

(c) If the DNA template strand has the sequence 3'-TAC GGG CAT-5', determine the sequence of the mRNA codons and the corresponding tRNA anticodons. (2 points)