Unit 5

What contains the genetic instructions for building proteins?

DNA

Where is DNA located in eukaryotic cells?

In the nucleus.

What do almost every cell in the body have in common?

They have the same DNA.

Why are cells different from each other?

They express different genes.

How many base pairs does the human genome have?

About 3.5 billion.

What is the basic building block of DNA?

Nucleotide.

What are the parts of a nucleotide?

Phosphate group, deoxyribose sugar, nitrogenous base.

What sugar is found in DNA?

Deoxyribose sugar.

What sugar is found in RNA?

Ribose sugar.

What carries genetic information in DNA or RNA?

Nitrogenous base.

What are pyrimidines?

Single-ring bases: Cytosine and Thymine (or Uracil in RNA).

What are purines?

Double-ring bases: Adenine and Guanine.

What is the shape of DNA called?

Double Helix.

What makes up the DNA backbone?

Alternating sugar and phosphate groups.

What holds nitrogen bases together?

Hydrogen Bonds.

What does antiparallel refer to in DNA structure?

The two DNA strands run in opposite directions.

What is at the 5’ end of a DNA strand?

The phosphate group.

What is at the 3’ end of a DNA strand?

The sugar group.

What does Chargaff’s Rule state?

A pairs with T, and G pairs with C.

Which base does Adenine (A) pair with in DNA?

Thymine (T).

Which base does Thymine (T) pair with?

Adenine (A).

Which base does Cytosine (C) pair with?

Guanine (G).

Which base does Guanine (G) pair with?

Cytosine (C).

What is DNA replication?

The process of copying DNA before cell division.

What is the first step in DNA replication?

Unwinding of the DNA double helix.

What happens in the second step of DNA replication?

Unzipping when hydrogen bonds break apart.

What does DNA Polymerase do during replication?

Adds matching nucleotides.

What happens in step four of DNA replication?

Replication stops at the end of the strand.

What occurs in step five of DNA replication?

New DNA strands rewind into double helices.

What is the role of DNA Polymerase?

Enzyme that adds complementary nucleotides during replication.

What is semi-conservative replication?

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

What is chromatin?

Loose, unwound DNA used during normal cell activities.

What are chromosomes?

Tightly coiled DNA visible during cell division.

How many chromosomes do human somatic cells contain?

46 chromosomes.

What is a gene?

A section of DNA that codes for a protein.

What are sister chromatids?

Two identical copies of a chromosome.

What is the centromere?

The area holding sister chromatids together.

What is the cell cycle?

The series of events a cell goes through to grow and divide.

What is interphase?

The longest phase of the cell cycle where the cell grows and copies DNA.

What happens in the G1 phase?

The cell grows and performs normal functions.

What occurs during the S phase?

DNA replication.

What happens during the G2 phase?

The cell prepares for division.

What is the G0 phase?

Resting phase where the cell stops dividing.

What is mitosis?

The process where the nucleus divides.

What happens in prophase?

Chromosomes condense and nuclear membrane disappears.

What occurs during metaphase?

Chromosomes line up in the middle of the cell.

What happens in anaphase?

Sister chromatids separate to opposite sides.

What occurs during telophase?

New nuclei form around chromosomes.

What is cytokinesis?

Cytoplasm divides into two separate cells.

What is the difference between DNA and RNA?

DNA is double stranded while RNA is single stranded.

What type of sugar does DNA use?

Deoxyribose sugar.

What does RNA use instead of thymine?

Uracil.

What does messenger RNA (mRNA) do?

Carries genetic instructions from DNA to ribosomes.

What is the function of transfer RNA (tRNA)?

Brings amino acids to the ribosome.

What is ribosomal RNA (rRNA)?

Makes up the structure of ribosomes.

What is the process of transcription?

Making mRNA from DNA.

Where does transcription occur?

In the nucleus.

What replaces thymine in RNA?

Uracil (U).

What is translation?

The process of building proteins from mRNA instructions.

Where does translation take place?

At ribosomes in the cytoplasm.

What is a codon?

A group of 3 mRNA bases coding for one amino acid.

What is a peptide bond?

Bond connecting amino acids together.

What is the start codon and what does it signal?

AUG; it signals the start of translation and codes for Methionine.

What are stop codons?

UAA, UAG, and UGA; they signal the ribosome to stop translation.

What is a mutation?

A change in the DNA sequence.

What can cause mutations?

Random replication errors or environmental factors like radiation and chemicals.

What is a benefit of mutations?

They create genetic variation for evolution.

What is a potential harm of mutations?

Can cause diseases or cancer.

What is a substitution mutation?

One base is replaced with another base.

What effect does a substitution mutation usually have?

Usually changes only one codon.

What is a nonsense mutation?

A substitution mutation creating an early stop codon.

What is an insertion mutation?

An extra base is added into the DNA sequence.

What effect does an insertion mutation have?

Causes a frameshift that changes all following codons.

What is a deletion mutation?

A base is removed from the DNA sequence.

What effect does a deletion mutation have?

Causes a frameshift changing all following amino acids.

What is a frameshift mutation?

A mutation that shifts the reading frame of codons.

What is cancer?

Disease caused by uncontrolled cell division.

What is a tumor?

A mass of abnormal cells.

What is a benign tumor?

A tumor that does not spread.

What is a malignant tumor?

A cancerous tumor that spreads uncontrollably.

What are carcinogens?

Substances or factors that increase cancer risk.

What are some examples of carcinogens?

Alcohol, smoke, UV rays, radon.

What characterizes healthy cells?

They have controlled replication and normal DNA.

What characterizes cancer cells?

They replicate uncontrollably and contain mutated DNA.

What do both healthy and cancer cells contain?

DNA and organelles and they undergo mitosis.

What is an example of normal DNA sequence?

ACG → mRNA UGC → Protein Cysteine.

What is an example of a substitution mutation?

ACT → mRNA UGA → STOP codon.

What is an example of an insertion mutation?

Adding a base shifts all codons after it.

What is mRNA?

Single-stranded RNA carrying genetic instructions.

What is a protein?

A chain of amino acids folded into a functional molecule.

What is an amino acid?

Building block of proteins.

What is a ribosome?

Organelle where proteins are made.

What is protein synthesis?

Process of making proteins using transcription and translation.

What is the Central Dogma?

DNA → RNA → Protein.

What are complementary base pairing rules?

Rules determining how bases match during replication/transcription.

What is cysteine?

An amino acid coded by UGC.

What is methionine?

Amino acid coded by the start codon AUG.

What is phenylalanine?

Amino acid from codon UUU.

What is tyrosine?

Amino acid from codon UAU.

What is alanine?

Amino acid from codon GCA.