Chapter 9 Molecular Biology
9.1: The Structure of DNA
- The building blocks of DNA are ________________________ which are made up of three parts:
- ___________________ a five-carbon sugar,
- _____________________________, and a
- The four types of nitrogenous bases in DNA are
- _____________ (A) and ______________(G) are double-ringed purines.
- _______________(C) and ______________ (T) are single-ringed pyrimidines.
- Check for understanding:
- T or F: Each nucleotide is named according to the nitrogenous base it contains?
- The DNA molecule is made up of two strands of nucleotides that are twisted around into a ____________ ______________.
- Base-pairing takes place between a _____________ and pyrimidine.
- An ____ binds with a T, and C binds with a ________.
- Chargaff’s rule states that: ______________________________________________________________________________________________________________________________________________________________________________________________________
- Adenine and thymine are connected by _____ hydrogen bonds, whereas C and G are connected by ________ hydrogen bonds.
- Check for understanding:
- T or F: The diameter of the DNA double helix is uniform throughout because a purine always base-pairs with a pyrimidine which makes the combined lengths equal.
- The Structure of RNA
- There is a second nucleic acid in all cells called __________ or ribonucleic acid.
- Like DNA each of the nucleotides in RNA is made up of a ________________ ________, a _________ - __________ sugar, and a _______________ group.
- How does the five-carbon sugar ribose differ from deoxyribose? See figure 9.5
- How DNA is Arranged in the Cell
- Stretched end-to-end, the DNA molecules in a single human cell would be ______________ _____________ long.
- Which cell has the larger genome? Human cell or a bacterial cell?
- Outline the packing strategy that eukaryotes utilize in organizing the DNA inside the nucleus. Use figure 9.7 as a guide
- At the most basic level: ______________________________________________________________________________________________________________________
- Nucleosomes stack compactly to form a ___________________________________________________________
- During which stage of mitosis are the chromosomes at their most compact.
9.2: DNA Replication
- DNA replication occurs during the _______ phase of interphase.
- The two strands of the DNA molecule are said to ___________________ to one another.
- The model that is used to explain the process of DNA replication is called the ___________________________ model. In this model each DNA molecule is a combination of one parental strand and one new daughter strand.
- Check for understanding: See figure 9.9 in the textbook
- T or F: When two DNA copies are formed, they have an identical sequence of nucleotide bases and are divided equally into two daughter cells.
- DNA replication in eukaryotes
- Specific nucleotide sequences called _______________ of _______________ at which replication begins.
- Certain proteins called ___________ unwind and open up the DNA helix.
- As the DNA helix opens Y-shaped structures called ________________ __________________ are formed.
- How many replication forks are formed at each origin of replication?
- T or F: There is only one origin of replication on the eukaryotic chromosome
- An enzyme called _____________________________ adds nucleotides to the ______’ end of the template.
- A ____________ sequence of complementary RNA nucleotides is added to provide the starting point for DNA replication. This primer is removed later with the RNA nucleotides replaced by DNA nucleotides.
- The strand that is complementary to the parental DNA strand is synthesized continuously toward the replication fork. This is called the ___________________ strand.
- The second new strand is synthesized in short pieces called ________________ ______________________. This strand is known as the __________________ strand.
- The enzyme that seals the gaps between the fragments is called _________________________.
- The ends of linear chromosomes are known as _______________, the enzyme that maintains the ends is called _________________.
- T or F: telomerase is not active in adult somatic cells. The shortening of telomeres in these cells is associated with aging.
- DNA Replication is Prokaryotes
- How does the prokaryotic chromosome differ from a eukaryotic chromosome?
- Fill in this table with the differences between prokaryotic and eukaryotic replications.
|Origin of replication|
|Rate of Replication|
|Structure of Chromosome|
- DNA Repair
- DNA polymerase-Proofreading during elongation of the DNA molecule.
- Mistakes such as wrong bases paired together are corrected by the ______________ ____________________ mechanism.
- In _______________ ____________________ ____________________ the incorrect bases are removed and replaced with the correct bases with the help of DNA polymerase. This type of repair is important in correcting thymine dimers.
- Mistakes in DNA replication that are not corrected may result in a ____________________
- The two functions of DNA are:
- _________________________________ and
- In transcription DNA is read or transcribed into a ______________ molecule.
- The Central Dogma: DNA Encodes RNA; RNA Encodes Protein
- Transcription: from DNA to mRNA
- The region of unwinding is called a ___________________ __________________
- The DNA sequence which initiates transcription is called a __________________________
- Transcription always proceeds along this DNA strand, the_________________________ strand
- The other DNA strand that is not involved in transcription is called the ________________________________ strand
- The enzyme involved in transcription is _____________________________________
- The end of transcription is called _____________________.
- In prokaryotes, upon termination, the process of transcription is (complete/incomplete).
- T or F: Only in prokaryotes can transcription and translation proceed together at the same time.
- What prevents simultaneous transcription and translation occurring in eukaryotic cells?
- Eukaryotic RNA Processing
- Eukaryotic genes are composed of protein coding sequences called ______________ and intervening, non-protein coding sequences called _________________.
- The removal of introns and reconnecting exons is called RNA __________________, which only occurs in the (nucleus/cytoplasm).
- The Protein Synthesis Machinery
- List the required inputs for translation.
- Ribosomes are in the ___________________ in prokaryotes and in the ___________ and endoplasmic reticulum of ________________________.
- Ribosomes are composed of two _________________, the large subunit binds ___________________ whereas the small subunit binds __________________.
- The Genetic Code
- Protein sequences consist of ___________ commonly occurring amino acids.
- Each amino acid is coded for a three-nucleotide sequence called the ________________
- The relationship between a codon and its corresponding amino acid is called the ________________________ ____________________.
- There is a total of __________ codons. Three of these codons are ___________ codons, they do not code for any amino acid. Therefore, __________ codons code for amino acids.
- Check for understanding: T or F: Many amino acids may be encoded by more than one codon?
- One codon _____________ is the start codon. Its code is for the amino acid _________________. This codon sets the reading frame for translation.
- Translation consists of the following three steps
- ________________________________________ which involves the small RNA subunit, the mRNA template, initiation factors and special initiator tRNA.
- ________________________________________ is the bringing of amino acids to be joined together to form a growing polypeptide.
- _________________________________________ occurs when a stop codon is reached.
9.5: How Genes are Regulated
- Prokaryotic vs Eukaryotic Gene Regulation
- In prokaryotes gene regulation occurs at the transcriptional level
- Lac Operon - _________________________________________________________________________________________________________________________________________________________________________________
- In eukaryotes gene regulation occurs at several levels:
- When DNA is uncoiled and loosened from nucleosomes to bind transcriptional factors:
- When the RNA is transcribed ___________________________
- When RNA is processed and then transported to the cytoplasm
- Or after the protein has been made: ______________________________________