Review Flashcards on Nucleic Acids, Replication, Transcription, Translation, and Cell Division

Flashcards to help review key concepts from lecture notes on Nucleic Acids: DNA and RNA Structure, Replication, Transcription, Translation, Gene Regulation, Cell Division, Substance Transport, CRISPR, Genetic Concepts, Prokaryotic Reproduction, Negative Feedback, Covalent Bonds, Fatty Acids, and Phospholipids.

What are the two types of nucleic acids?

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

What are the three components of a DNA nucleotide?

Deoxyribose (5-carbon sugar), Phosphate group, Nitrogenous base

Name the four nitrogenous bases in DNA and classify them as purines or pyrimidines.

Adenine (A) and guanine (G) are double-ringed purines; Cytosine (C) and thymine (T) are single-ringed pyrimidines.

What is the structure of DNA according to Watson and Crick?

Two strands in a right-handed double helix

List two functions of DNA.

Replication during cell division and Template for producing molecules (e.g., proteins)

Why must DNA be packaged?

To fit within a microscopic cell

Where is the single, circular chromosome located in prokaryotes?

In the nucleoid region of the cytoplasm

What are the three stages of eukaryotic DNA replication?

Initiation, elongation, and termination

What do histones form when bound to Eukaryotic DNA?

Nucleosomes

What happens during the initiation stage of DNA replication?

DNA is made accessible to replication proteins and enzymes.

What are origins of replication?

Specific nucleotide sequences where replication begins

What is the function of helicase in DNA replication?

Unwinds and opens the DNA helix.

What structures are formed as the DNA opens?

Y-shaped structures called replication forks.

How many replication forks are formed at each origin of replication?

Two

What is the role of DNA polymerase in elongation?

Adds DNA nucleotides to the 3' end of the template.

Why is a primer sequence of complementary RNA nucleotides added?

To provide a starting point because DNA polymerase can only add new nucleotides at the end of a backbone.

In what direction does DNA polymerase synthesize DNA?

5' to 3' direction

What are the short pieces synthesized on the lagging strand called?

Okazaki fragments

What is the function of DNA ligase?

Seals the gaps between Okazaki fragments.

Describe the semi-conservative method of DNA replication.

Each new DNA molecule has one parental strand and one new strand.

What is the role of primase in DNA replication?

Synthesizes an RNA primer to initiate synthesis by DNA polymerase.

How does the leading strand get synthesized?

Continuously toward the replication fork.

How does the lagging strand get synthesized?

In short stretches (Okazaki fragments) away from the replication fork.

What is the function of telomerase?

Extends the ends of eukaryotic chromosomes using an inbuilt RNA template.

What mechanisms do cells have for repairing damaged DNA?

Mismatch repair and nucleotide excision repair

Where does mRNA synthesis start in prokaryotes?

At the promoter sequence on the DNA template.

What modifications are made to eukaryotic mRNAs?

A cap and a poly-A tail are added.

What happens to eukaryotic mRNAs during splicing?

Introns are removed and exons are reconnected.

Describe the central dogma.

Genes to mRNA to proteins.

What is the genetic code?

The correspondence between the three-nucleotide mRNA codon and an amino acid.

How do tRNA molecules facilitate translation?

By associating a specific codon with a specific amino acid.

Why is the genetic code considered degenerate?

Because 64 triplet codons specify only 20 amino acids and three stop codons.

What is the initiating codon on the mRNA?

AUG

What happens when a stop codon is encountered during translation?

A release factor binds and dissociates the components, freeing the new protein.

Transcription and translation happen simultaneously in what type of cells?

Prokaryotic cells

Where transcription and translation happen separately?

Eukaryotic cells: Transcription occurs in the nucleus and is separate from translation in the cytoplasm.

How is gene expression regulated in prokaryotes?

Only at the transcriptional level

How is gene expression regulated in eukaryotic cells?

At the epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels.

What determines the sex of an individual in humans?

Sex chromosomes (one pair of non-homologous chromosomes)

Define codominance.

Both alleles for the same characteristic are simultaneously expressed in the heterozygote.

Define incomplete dominance.

One of the alleles appears in the phenotype in the heterozygote (but not to the exclusion of the other).

What are the key differences between mitosis and meiosis?

Mitosis is a single division resulting in two identical nuclei; meiosis is two divisions resulting in four genetically different nuclei.

What type of division is meiosis I?

A reduction division.

What is the result of Anaphase II?

Kinetochores divide and one sister chromatid is pulled to one pole, and the other sister chromatid is pulled to the other pole.

List the three types of passive transport.

Simple diffusion, Facilitated diffusion, Osmosis

How do particles move in simple diffusion?

From high concentration to low concentration—down their concentration gradient.

What is facilitated diffusion?

Passive transport that requires membrane proteins.

Who were awarded the Nobel Prize in Chemistry for developing CRISPR?

Charpentier and Jennifer Doudna

What is the function of the Cas9 enzyme?

Cuts the double-stranded DNA, which is then deleted or modified, depending on the goals of the gene editing process.

What occurs during crossing over?

Two homologous chromosomes exchange genetic material during prophase I.

How does reproduction occur in prokaryotes?

By binary fission, an asexual process that replicates DNA and distributes it to two daughter cells.

What is negative feedback?

The product of a reaction slows the production of more product.

What is a nonpolar covalent bond?

Electron sharing between two atoms of the same element or between different elements that share the electrons equally.

How do electrons spend time in polar covalent bonds?

Electrons shared by the atoms spend more time closer to one nucleus than the other nucleus.

What is a saturated fatty acid?

In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated.

What type of fatty acid is liquid at room temperature?

Most unsaturated fats

What type of fat helps to improve blood cholesterol levels?

Unsaturated fats

What is the major constituent of the plasma membrane?

Phospholipids

What regions do phospholipids have?

Hydrophobic and hydrophilic regions