DNA and RNA

During which phase of the cell cycle does nuclear DNA replicate?

The first stage of DNA replication is [blank_start]unwinding[blank_end] of DNA, which is aided by the enzyme [blank_start]gyrase[blank_end]. Next, the two strands are [blank_start]unzipped[blank_end], thanks to an enzyme called DNA [blank_start]helicase[blank_end], which breaks the [blank_start]hydrogen[blank_end] bonds holding the bases together. Then, new strands of DNA are synthesised by an enzyme called [blank_start]DNA[blank_end] [blank_start]polymerase[blank_end]. In this stage, free nucleotides are joined to their complementary bases and each other by forming h[blank_start]ydrogen[blank_end] bonds and p[blank_start]hosphodiester[blank_end] bonds. They're added in the [blank_start]5[blank_end]' to [blank_start]3[blank_end]' direction.

DNA replication is said to be s[blank_start]emi[blank_end] c[blank_start]onservative[blank_end].

Which of the following statements is true about mutations?

The region of a molecule which is complementary to its substrate is called the [blank_start]active[blank_end] [blank_start]site[blank_end].

The sequence of nucleotide bases in DNA dictates the primary structure of proteins.

DNA is read three bases at a time, these are called [blank_start]triplets[blank_end]. DNA is found in nearly all living organisms, so it is [blank_start]universal[blank_end]. There are often several ways of coding for one amino acid, so DNA is [blank_start]degenerate[blank_end]. DNA bases are read one after the other, so it is [blank_start]non-overlapping[blank_end].

[blank_start]Transcription[blank_end] is the process of RNA being created according to a region of DNA (catalysed by [blank_start]RNA[blank_end] [blank_start]polymerase[blank_end]), whereas [blank_start]translation[blank_end] is the process of joining amino acids together according to the sequence of bases on a strand of RNA.

RNA is double-stranded.

rRNA stands for [blank_start]ribosomal[blank_end] RNA, while tRNA stands for [blank_start]transfer[blank_end] RNA. Both are formed in the [blank_start]nucleus[blank_end] and exit through nuclear [blank_start]pores[blank_end], but rRNA is s[blank_start]tructural[blank_end] and tRNA is f[blank_start]unctional[blank_end].

Label this tRNA molecule.

Three bases on an mRNA molecule require a specific [blank_start]amino acid[blank_end]. The [blank_start]anticodon[blank_end] on a tRNA molecule is matched to a [blank_start]triplet[blank_end] on an mRNA molecule. Also, tRNA molecules with a specific [blank_start]anticodon[blank_end] will have a specific [blank_start]amino acid attachment site[blank_end], and therefore binds a specific [blank_start]amino acid[blank_end].

The role of chaperone proteins is to...