a. 1 mark for correctly linking sugar, phosphate, and base to form at least one nucleotide

b. 1 mark for labeling deoxyribose, phosphate, and base/named base at least once

c. 1 mark for showing adenine paired with thymine and cytosine paired with guanine

d. 1 mark for drawing two antiparallel chains of nucleotides linked by hydrogen bonds, with all sugar-phosphate bonds in the correct position

$$\text{Sugar} - \text{Phosphate} - \text{Base}$$

1. A1 Translation occurs on ribosomes
2. A1 tRNA-activating enzymes attach amino acids to tRNAs
3. A1 Small and large ribosome units assemble on mRNA OR translation/polypeptide synthesis starts at a start codon
4. A1 Each tRNA arriving at the ribosome binds to the A site
5. A1 Anticodon «on tRNA» binds to codon «on mRNA»
6. A1 According to complementary base pairing/A with U and G with C
7. A1 Ribosome moves along the mRNA / mRNA moves over ribosome
8. A1 tRNA shifts from the A site to P site/from the P to the E site
9. A1 Peptide bond between amino acids «on tRNAs at A and P sites»
10. A1 tRNA released from ribosome at E site
11. A1 Cycle repeats with other tRNAs / polypeptide grows as tRNAs bring more amino acids
12. A1 Until stop codon on mRNA is reached
13. A1 Components are disassembled / polypeptide leaves the ribosome

a. 1 mark linear/not circular DNA molecule OR one chromosome is one molecule of DNA/one chromosome is two DNA molecules «after replication»

b. 1 mark associated with histone proteins/nucleosomes

c. 1 mark centromere joins sister chromatids «after DNA replication»

d. 1 mark telomeres at the end «of the chromosome/chromatid»

e. 1 mark carries a sequence of genes / each gene occupies a specific locus

f. 1 mark alternative alleles of genes / homologous chromosomes carry same sequence of genes

g. 1 mark chromosomes in pairs / two «homologous chromosomes» of each type «in a diploid cell»

h. 1 mark non-coding sequences/example of a non-coding sequence

i. 1 mark supercoiled/condensed «during mitosis/meiosis»

6