bio test

What are the components of the DNA backbone?

Sugar (deoxyribose) and phosphate

What type of sugar is found in DNA?

Deoxyribose

How do nitrogen bases pair in DNA?

Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C)

Which nitrogen bases are purines?

Adenine (A) and Guanine (G) (they have two rings)

Which nitrogen bases are pyrimidines?

Thymine (T) and Cytosine (C) (they have one ring)

Why are the two DNA strands considered complementary?

Each base on one strand pairs specifically with a base on the other strand

DNA Replication

the biological process where a cell creates an exact copy of its DNA, ensuring each daughter cell receives a complete set of genetic information during cell division

What does "semi-conservative" mean in DNA replication?

Each new DNA molecule has one original strand and one new strand

What enzyme unwinds and unzips DNA?

DNA helicase

What enzyme adds complementary bases during replication?

DNA polymerase

What is the difference between the leading and lagging strands?

The leading strand is synthesized continuously (5' to 3'), while the lagging strand is synthesized in fragments (Okazaki fragments)

What are Okazaki fragments?

Short DNA fragments synthesized on the lagging strand

What enzyme proofreads the new DNA strands?

DNA polymerase

Prokaryotic vs. Eukaryotic Replication

share the same fundamental process of creating two identical DNA strands from one, but differ in location, DNA structure, replication machinery, and rate

How many origins of replication do prokaryotic cells have?

One

How is replication different in eukaryotic cells compared to prokaryotic cells?

Eukaryotic cells have multiple origins of replication, while prokaryotic cells have only one

Central Dogma

describes the flow of genetic information in cells, stating that DNA is transcribed into RNA, which is then translated into proteins.

What is the process of converting DNA into RNA called?

Transcription

What is the process of converting RNA into a polypeptide called?

Translation

What are the three types of RNA and their functions?

mRNA (messenger RNA): Carries genetic code from DNA to ribosome; tRNA (transfer RNA): Brings amino acids to ribosome; rRNA (ribosomal RNA): Forms part of the ribosome and helps in protein synthesis

Transcription

the process of making an RNA copy of a gene's DNA sequence

Where does transcription occur?

In the nucleus

What enzyme is responsible for transcription?

RNA polymerase

What sequence signals RNA polymerase to start transcription?

Promoter (TATA box)

What sequence signals RNA polymerase to stop transcription?

Terminator sequence

What modifications occur to mRNA before it leaves the nucleus?

Splicing (removal of introns), addition of a 5' cap, and a poly-A tail

Translation

the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis

Where does translation take place?

In the ribosome

What type of RNA carries amino acids to the ribosome?

tRNA

What are the three sites in the ribosome where translation occurs?

A-site: Amino acid site (where new tRNA binds); P-site: Peptide bond site (where growing protein is held); E-site: Exit site (where tRNA leaves)

What is the start codon, and what amino acid does it code for?

AUG; Methionine

What signals the end of translation?

Stop codons (UAA, UGA, UAG)

Genetic Code

the set of rules used by living cells to translate information encoded within genetic material into proteins

Why is the genetic code considered "degenerate"?

Most amino acids have more than one codon

Why is the genetic code considered "universal"?

It is the same in almost all living organisms

How many possible codon combinations exist?

64

Gene Mutations

a permanent change in the DNA sequence that makes up a gene

What is a point mutation?

A change in a single nucleotide

What are the three types of point mutations?

Silent Mutation: No change in amino acid; Missense Mutation: Changes one amino acid; Nonsense Mutation: Creates a stop codon, leading to an incomplete protein

What is a frameshift mutation?

Insertion or deletion of a nucleotide, shifting the reading frame

How does an insertion or deletion mutation affect the reading frame?

It alters all codons after the mutation, changing the entire protein

Gene Regulation

the mechanisms by which cells control which genes are expressed (turned on) and which are not, allowing them to respond to environmental changes and perform specific functions

What is an operon?

A cluster of genes controlled by a single promoter

What is the function of the promoter in gene regulation?

It is the binding site for RNA polymerase

What is the function of the operator in gene regulation?

It is the binding site for the repressor protein

How does an inducible operon work?

It is normally off but turns on when an inducer binds to the repressor (e.g., lac operon)

How does a repressible operon work?

It is normally on but turns off when a corepressor binds to the repressor (e.g., trp operon)

What is the corepressor in the trp operon?

Tryptophan

Eukaryotic Gene Regulation

a complex process that controls which genes are expressed and when, involving mechanisms at epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels, ensuring proper cell function and development

What are the four levels of gene regulation in eukaryotic cells?

Transcriptional Control: Regulates how much mRNA is produced; Post-Transcriptional Control: Affects mRNA processing and transport; Translational Control: Regulates mRNA lifespan and initiation of translation; Post-Translational Control: Modifies and regulates protein activity

What is euchromatin, and how does it affect transcription?

Loosely packed DNA that allows transcription

What is heterochromatin, and how does it affect transcription?

Tightly packed DNA that prevents transcription

Biotechnology

a field that uses biological processes, organisms, cells, or cellular components to develop new technologies and products

What is recombinant DNA?

DNA that contains genes from two or more sources

What is the purpose of a plasmid in genetic engineering?

It acts as a vector to transfer foreign genes into cells

What enzyme is used to cut DNA for cloning?

Restriction enzyme

What enzyme is used to seal DNA fragments together?

DNA ligase

What is PCR used for?

Amplifying DNA sequences

What is CRISPR used for?

Gene editing

How does DNA fingerprinting work?

It analyzes unique DNA patterns to identify individuals

What is the difference between ex vivo and in vivo gene therapy?

Ex vivo: Cells are modified outside the body and reinserted; In vivo: Genes are modified directly inside the body

How can bacteria be genetically modified to produce useful proteins?

By inserting human genes into bacterial plasmids to produce substances like insulin