Which statements about complementary base pairing are correct? 1 Purines and pyrimidines are different sizes. 2 Complementary base pairing occurs during translation. 3 The base pairs are of different lengths. 4 Uracil forms two hydrogen bonds with adenine.

1,2 and 3

1, 2 and 4

1, 3 and 4

2, 3 and 4

Biology

IGCSE&ALevel

CAIE

Exam No：9700_m24_qp_12 Year：2024 Question No：25

Answer:

Knowledge points:

6.1.1 describe the structure of nucleotides, including the phosphorylated nucleotide ATP (structural formulae are not expected)

6.1.2 state that the bases adenine and guanine are purines with a double ring structure, and that the bases cytosine, thymine and uracil are pyrimidines with a single ring structure (structural formulae for bases are not expected)

6.1.3.1 the importance of complementary base pairing between the 5' to 3' strand and the 3' to5' strand (antiparallel strands)

6.1.3.2 differences in hydrogen bonding between C–G and A–T base pairs

6.1.3.3 linking of nucleotides by phosphodiester bonds

6.1.4.1 the roles of DNA polymerase and DNA ligase (knowledge of other enzymes in DNA replication in cells and different types of DNA polymerase is not expected)

6.1.4.2 the differences between leading strand and lagging strand replication as a consequence of DNA polymerase adding nucleotides only in a 5 to 3 direction

6.1.5 describe the structure of an RNA molecule, using the example of messenger RNA (mRNA)

6.2.1 state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule

6.2.2 describe the principle of the universal genetic code in which different triplets of DNA bases either code for specific amino acids or correspond to start and stop codons

6.2.3.1 RNA polymerase

6.2.3.2 messenger RNA (mRNA)

6.2.3.3 codons

6.2.3.4 transfer RNA (tRNA)

6.2.3.5 anticodons

6.2.3.6 ribosomes

6.2.4 state that the strand of a DNA molecule that is used in transcription is called the transcribed or template strand and that the other strand is called the non-transcribed strand

6.2.5 explain that, in eukaryotes, the RNA molecule formed following transcription (primary transcript) is modified by the removal of non-coding sequences (introns) and the joining together of coding sequences (exons) to form mRNA

6.2.6 state that a gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

6.2.7 explain that a gene mutation is a result of substitution or deletion or insertion of nucleotides in DNA and outline how each of these types of mutation may affect the polypeptide produced

Which statements about complementary base pairing are correct? 1 Purines and pyrimidines are different sizes. 2 Complementary base pairing occurs during translation. 3 The base pairs are of different lengths. 4 Uracil forms two hydrogen bonds with adenine.

Answer:

Knowledge points:

Solution:

Related Question