Bio103 Exam3 (pt 2)

What is DNA polymerase?

An enzyme that builds new DNA strands during DNA replication and proofreads for mistakes.

What is RNA polymerase?

An enzyme that makes RNA from a DNA template during transcription.

What is the difference between DNA polymerase and RNA polymerase?

DNA polymerase makes DNA; RNA polymerase makes RNA.

What does 5′ → 3′ indicate?

The direction in which a new DNA or RNA strand is synthesized.

In what direction does DNA polymerase build DNA?

5′ → 3′.

In what direction does RNA polymerase build mRNA?

5′ → 3′.

In what direction does RNA polymerase read the DNA template strand?

3′ → 5′.

What does complementary DNA strand mean?

A DNA strand whose bases pair with another strand using A-T and C-G base-pairing rules.

What does antiparallel mean?

The two DNA strands run in opposite directions (one 5′ → 3′ and the other 3′ → 5′).

What are the DNA base-pairing rules?

A pairs with T; C pairs with G.

What are the RNA base-pairing rules?

A pairs with U; C pairs with G.

If given the DNA template strand, how do you make mRNA?

Use complementary base pairing: A → U, T → A, C → G, G → C.

What is gene expression?

The process of using information in a gene to make a functional product, usually a protein.

What does it mean when a gene is expressed?

The gene is turned on and its instructions are being used.

Are all genes expressed all the time?

No. Different genes are turned on or off depending on the cell's needs.

What happens when a protein-coding gene is expressed?

DNA is transcribed into mRNA, and the mRNA is translated into a protein.

What is mRNA processing?

The steps that prepare pre-mRNA for translation.

Where does mRNA processing occur?

In the nucleus of eukaryotic cells.

When does mRNA processing occur?

After transcription and before mRNA leaves the nucleus.

What are the three main steps of mRNA processing?

Adding a 5′ cap, adding a poly-A tail, and splicing.

What is the function of the 5′ cap?

Protects the beginning of mRNA and helps with ribosome attachment.

What is the function of the poly-A tail?

Protects mRNA, increases stability, and helps it leave the nucleus.

What are introns?

Sections of pre-mRNA that are removed during processing.

What are exons?

Sections of RNA that remain in mature mRNA and are joined together.

What are spliceosomes?

Complexes made of RNA and proteins that remove introns and connect exons.

What is mature mRNA?

Processed mRNA that is ready to leave the nucleus and be translated.

What is transcription?

The process of making mRNA from a DNA template.

Where does transcription occur in eukaryotic cells?

In the nucleus.

What happens during transcription initiation?

RNA polymerase attaches to the promoter region of DNA and begins separating the strands.

What happens during transcription elongation?

RNA polymerase reads the DNA template and adds complementary RNA nucleotides to build mRNA.

What happens during transcription termination?

RNA polymerase reaches a termination signal, stops transcription, and releases the RNA transcript.

What is translation?

The process of using mRNA instructions to build a protein.

Where does translation occur?

At ribosomes in the cytoplasm or on the rough endoplasmic reticulum.

What happens during translation initiation?

The ribosome attaches to mRNA, recognizes the start codon (AUG), and the first tRNA brings methionine.

What happens during translation elongation?

tRNAs bring amino acids to the ribosome, which joins them together with peptide bonds.

What happens during translation termination?

The ribosome reaches a stop codon, and the completed protein is released.

What is the central dogma of molecular biology?

DNA → RNA → Protein.

What is the difference between transcription and translation?

Transcription makes RNA from DNA; translation makes protein from mRNA.

What is p53?

A tumor-suppressor protein that helps prevent cells from becoming cancerous.

What is the function of the p53 protein?

Checks for DNA damage, stops the cell cycle for repair, and can trigger apoptosis if damage cannot be repaired.

Why is p53 called the guardian of the genome?

It protects cells by preventing damaged DNA from being passed on through cell division.

What can happen if the p53 gene is mutated?

Damaged cells may continue dividing uncontrollably, contributing to cancer.

What is biotechnology?

Using living organisms, cells, or biological processes to create useful products or solve problems.

What is genetic engineering?

Directly changing an organism's DNA by adding, removing, or modifying genes.

What are GMOs?

Genetically modified organisms whose genetic material has been changed.

What is a transgenic organism?

An organism that contains a gene from another species.

What is cloning?

Producing genetically identical copies of DNA, cells, or organisms.

What was Dolly the sheep?

The first mammal cloned from an adult somatic cell.

What is recombinant DNA?

DNA created by combining genetic material from two or more different sources.

What are restriction enzymes?

Enzymes that cut DNA at specific sequences; they act like molecular scissors.

What is the function of restriction enzymes in genetic engineering?

They cut DNA so scientists can insert desired genes into other DNA molecules.

What is a plasmid?

A small, circular piece of bacterial DNA often used to carry genes in genetic engineering.

What is the function of DNA ligase in recombinant DNA?

Joins DNA fragments together.

How can bacteria be used to produce human insulin?

Scientists insert the human insulin gene into a bacterial plasmid, and bacteria use the gene to produce insulin.

What is PCR (Polymerase Chain Reaction)?

A technique used to make millions or billions of copies of a specific DNA segment.

What are the three steps of PCR?

Denaturation, annealing, and extension.

What happens during PCR denaturation?

Heat separates the two DNA strands.

What happens during PCR annealing?

Primers attach to the DNA strands.

What happens during PCR extension?

DNA polymerase builds new DNA strands.

What is gel electrophoresis?

A technique used to separate DNA fragments based on size.

How does gel electrophoresis work?

An electrical current moves negatively charged DNA through a gel toward the positive end.

Which DNA fragments travel farther during gel electrophoresis?

Smaller DNA fragments.

What is DNA fingerprinting?

A technique used to identify individuals by comparing patterns in their DNA.

What are STRs?

Short tandem repeats, which are repeating DNA sequences used in DNA profiling.

What are three uses of DNA fingerprinting?

Crime investigations, paternity testing, and identifying human remains.

What is proteomics?

The study of all proteins produced by a cell, tissue, or organism.

What is DNA barcoding?

Using a short, standardized DNA sequence to identify a species.

What is metagenomics?

Studying genetic material collected directly from an environmental sample to examine entire communities of organisms.

What is bioinformatics?

Using computers and technology to store, organize, analyze, and interpret biological information.

What is the P generation?

The original parental organisms used in a genetic cross.

What is the F1 generation?

The first generation of offspring produced from crossing the P generation.

What is the F2 generation?

The second generation of offspring produced by crossing or self-fertilizing F1 individuals.

What are gametes?

Reproductive cells (sperm and egg) that contain half the normal chromosome number.

What are offspring?

The children or new organisms produced by parents.

What are alleles?

Different versions of the same gene.

What is genotype?

The genetic makeup or combination of alleles an organism has (TT, Tt, or tt).

What is phenotype?

The observable physical traits of an organism (tall, short, blue eyes, etc.).

What is a Punnett square?

A diagram used to predict possible genetic combinations and probabilities of offspring.

What does TT represent?

Homozygous dominant.

What does Tt represent?

Heterozygous.

What does tt represent?

Homozygous recessive.

What does homozygous mean?

Having two identical alleles for a gene.

What does homozygous dominant mean?

Having two dominant alleles (TT).

What does homozygous recessive mean?

Having two recessive alleles (tt).

What does heterozygous mean?

Having two different alleles for a gene (Tt).

What is a dominant trait?

A trait expressed when at least one dominant allele is present.

What is a recessive trait?

A trait expressed only when two recessive alleles are present in simple dominant/recessive inheritance.

How are dominant alleles represented?

With capital letters (T).

How are recessive alleles represented?

With lowercase letters (t).

What is the phenotype of TT or Tt if T represents tall?

Tall.

What is the phenotype of tt if t represents short?

Short.

Does dominant mean better or more common?

No. It only means one copy of the allele is enough for the trait to be expressed.

What is incomplete dominance?

Neither allele is completely dominant, resulting in a blended phenotype.

What is an example of incomplete dominance?

Red flower + white flower = pink flower.

What is codominance?

Both alleles are fully expressed in the heterozygous offspring.

What is an example of codominance?

Roan cattle have both red and white hairs.

What is another example of codominance in humans?

AB blood type, where both A and B antigens are expressed.

What is the difference between incomplete dominance and codominance?

Incomplete dominance blends traits; codominance shows both traits fully.

What are the typical female sex chromosomes?

XX.

What are the typical male sex chromosomes?

XY.