IB Biology HL DNA Structure & Replication Review

IB Biology HL: DNA Structure & Replication Review Key

-Phosphate NAME: -Nitrogen base 1. Draw a single nucleotide, labelling the phosphate, deoxyribose sugar and nitrogen base, in the box to the right: 2. Compare DNA and RNA. Nuckectiles -Deoxyribose suger DNA RNA Similarities, Nucleic acid polymers made upof nucleotides •Contain introgen bases Adenine, Cytosine, and Guanine Differences: Deoxyribose sugar Double-stranded (helix) Ribose sugar Thymine is fourth nitrogen Single-stranded (non-helix) buse Uracil is fourth base. 3. Draw and label a double stranded segment of DNA with four nucleotides (arranged in two base pairs): 3' ·Covalent bond Noctectide -phosphate -deoxyribose sugar 5 3' Nitrogen hydrogen bonds 4. The diagram shows a DNA double helix. How does a double helix form? What bonds hold it in position? DNA double helix is formed by two poly nucleotide strands running antiparallel to one another. Covalent bonds join nucleotides in sugar phosphate backbone. Hydrogen bonds join nitrogen base pairs. •core of 8 histone proteins. 5. Draw and label a nucleosome: DNA twice H1 6. What are the functions of nucleosomes? Nucleosomes allow packaging/supercoiling of DNA into chromosomes for easy Separation in mitosis/meiosis. When DNA is wrapped around nucleosomes it cannot be transcribed/translated so this allows genes to be turned "off." 7. Describe what is meant by "Highly-repetitive DNA sequences and list several functions of these sequences. Nucleotide sequences in DNA that do not code for production of proteins. also called Introns. Repeating base letter patterns are "5-300 Letters long (cx. ACACAC) and build of mutations quickly without affecting organism (since they don't code for traits) which makes them helpful for DNA fingerprinting. They also make up telomeres, produce tRNA and RNA, and help promote or silence gene expression.