STUDY GUIDE MASTER DECK

What enzyme can stop Type R Streptococcus pneumoniae from transforming to Type S?

DNase (deoxyribonuclease)

How did Rosalind Franklin contribute to the discovery of DNA structure?

Generated critical X-ray diffraction images (such as Photo 51) that revealed the helical dimensions of DNA

How did James Watson and Francis Crick contribute to the discovery of DNA structure?

Used Franklin's X-ray data and chemical rules to build the physical double-helix model of DNA

What are the components of a DNA molecule?

One phosphate group, one molecule of the 5-carbon sugar deoxyribose, and one nitrogenous base (Adenine, Guanine, Cytosine, or Thymine)

What is the DNA backbone made of?

Alternating sugar (deoxyribose) and phosphate groups

What are nucleotides?

Monomer subunits that join together into strands of DNA

What type of bond holds the DNA structure together between nitrogenous bases?

Hydrogen bonds

Which base pairs with Adenine (A) in DNA, and via how many hydrogen bonds?

Thymine (T) via 2 hydrogen bonds

Which base pairs with Guanine (G) in DNA, and via how many hydrogen bonds?

Cytosine (C) via 3 hydrogen bonds

How does the number of hydrogen bonds affect base pair stability?

More hydrogen bonds increase the structural stability of the base pairs

Which base is only found in RNA?

Uracil (U)

Who does Uracil (U) bind with?

Adenine (A)

How are strands in DNA oriented relative to each other?

Antiparallel strands oriented in opposite directions with 5' and 3' ends

How do you transcribe a strand of DNA to RNA?

Match complementary bases (A-U, T-A, C-G, G-C)

What is a genome?

An organism's complete set of genetic instructions (all its DNA)

What is a gene?

A small region of a chromosome whose sequence encodes a specific protein

What is a chromosome?

A thread-like structure consisting of a long DNA molecule wrapped around histone proteins

What is chromatin?

The diffuse, relaxed state of DNA and histone proteins inside the nucleus when the cell is not dividing

What is a chromatid?

One of the two identical, replicated halves of a duplicated chromosome joined at the centromere

How does the sugar in RNA differ from DNA?

RNA has ribose; DNA has deoxyribose

How do the nitrogenous bases in RNA differ from DNA?

RNA contains Uracil (U) instead of Thymine (T)

How does the form of RNA differ from DNA?

RNA is generally single-stranded; DNA is a double-stranded helix

How do the functions of RNA and DNA differ?

RNA carries protein-encoding information, helps make proteins, and catalyzes reactions; DNA stores RNA- and protein-encoding information

Where does DNA transcription occur in eukaryotes?

In the nucleus

Where is RNA translated into proteins in the cell?

In the cytoplasm (at ribosomes)

What is the function of messenger RNA (mRNA)?

Brings the information

What is the function of ribosomal RNA (rRNA)?

Makes up the ribosome

What is the function of transfer RNA (tRNA)?

Brings the amino acids

What are the 3 main steps of transcription?

Initiation, Elongation, Termination

What enzyme is involved in transcription?

RNA polymerase

Is a transcription factor a protein or DNA?

Protein

What is the function of introns in RNA processing?

Non-coding sequences removed from mRNA

What is the function of exons in RNA processing?

Sequences that specify amino acids

What is the function of the 5' cap added during RNA processing?

Added to the 5' end to protect mRNA from degradation

What is the function of the poly A tail added during RNA processing?

Added to the 3' end to protect mRNA from degradation

What are the two components of RNA splicing?

Intron removal / alternative splicing

How many nucleotides does each codon include?

3

What is the total number of possible codons (4x4x4)?

64

What is the start codon?

AUG

What part of tRNA pairs with codons?

Anticodon

What is a mutation?

A change in a cell’s DNA sequence

What are the possible effects of mutations?

Good, bad, and creating genetic variation

What is a silent mutation in terms of amino acids?

A mutation where the changed nucleotide codon still encodes the exact same amino acid, resulting in no change to the protein sequence

What are the effects of a point mutation?

Alters one or a few base pairs, changing a single codon and amino acid

Frameshift mutations cannot be multiples of what number?

3

What is an operon?

A group of genes in prokaryotes that are always transcribed together

How does the Lac operon save energy for E. coli?

By only producing lactose-digesting enzymes when lactose is present (when absent, a repressor protein binds to the operator to block transcription)

What is the overall pathway of genetic information described by the central dogma?

DNA is transcribed to RNA, which is then translated into proteins

What are the complementary base pairing rules for building a complementary DNA strand?

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

How do you determine the amino acid sequence if given a DNA sequence?

Transcribe the DNA template to mRNA (read 5' to 3'), then use the genetic code table

DNA wraps around what proteins in a eukaryotic chromosome?

Histone proteins (forming nucleosomes).

What is the term for programmed cell death

Apoptosis.

Main function of apoptosis: eliminates excess cells

Carving out structures.

Main function of apoptosis: weeds out cells

Weeds out aging or defective cells.

Why must all DNA be replicated before mitosis?

So that each daughter cell receives an identical copy of the entire genome.

Chromosomes in a human somatic cell in the G_2 phase

46 chromosomes (note: while DNA has replicated into 92 sister chromatids, chromosomes are counted by centromere number).

A fish egg has 7 chromosomes. What is its ploidy?

Haploid gamete (n = 7).

A fish has 7 chromosomes in its egg. What is its mitotic somatic cell ploidy?

Diploid (2n = 14).

A fish has 7 chromosomes in its egg. How many chromosomes does its somatic cell have in the G_2 phase?

14 chromosomes (each duplicated into sister chromatids).

Do daughter cells have the same number of chromosomes as their original parent cell in mitosis?

Yes, daughter cells have the same number of chromosomes as the original parent cell (diploid to diploid).

Do daughter cells have the same number of chromosomes as their original parent cell in meiosis?

No, daughter cells have half the number of chromosomes as the original parent cell (diploid 2n parent cells produce haploid n gametes).

What template is needed for DNA replication?

Double-stranded DNA template.

What building blocks are needed for DNA replication?

Complementary nucleotides.

What primers are needed for DNA replication?

RNA primers.

What enzymes/proteins are needed for DNA replication?

Replication proteins/enzymes (helicase, single-strand binding proteins, primase, DNA polymerase, and ligase).

Definition of sister chromatids

Two identical copies of a single replicated chromosome joined together at the centromere, formed during the S phase of interphase.

When are sister chromatids found?

In both mitotic and meiotic cells prior to anaphase (or anaphase II).

Definition of homologous chromosomes

A pair of matching chromosomes—one inherited from the mother and one from the father—that share the same length, centromere position, and gene loci, but may have different versions (alleles) of those genes.

Where are homologous chromosomes found?

Somatic/mitotic cells contain homologous pairs, and homologous chromosomes pair up and separate during meiosis I.

What are the 2 major phases of the cell cycle?

Interphase and Cell Division (Mitosis and Cytokinesis).

What happens in the G_1 phase of interphase?

Normal cell function, cell growth, and protein synthesis.

What happens in the S phase of interphase?

DNA replication (every chromosome is replicated).

What happens in the G_2 phase of interphase?

Additional growth and preparation for division, producing necessary mitotic proteins.

What happens in the G_0 phase?

Nondividing state where the cell continues to function without replicating DNA or dividing.

What are the four checkpoints of the cell cycle?

G_1 checkpoint, S phase checkpoint, G_2 checkpoint, and Metaphase checkpoint.

Where do spindle fibers connect on chromosomes?

Spindle fibers attach to kinetochores on chromosomes.

What happens during prophase of mitosis?

Chromosomes condense and become visible; spindle forms as centrosomes move to opposite poles.

What happens during prometaphase of mitosis?

Nuclear envelope breaks up; spindle fibers attach to kinetochores.

What happens during metaphase of mitosis?

Chromosomes line up along the equator of the cell.

What happens during anaphase of mitosis?

Centromeres split as sister chromatids separate and move to opposite poles.

What happens during telophase of mitosis?

Nuclear envelope and nucleolus form at each pole; chromosomes decondense; spindle disappears.

What is the correct order of mitosis phases?

Prophase -> Prometaphase -> Metaphase -> Anaphase -> Telophase.

What happens during cytokinesis?

Division of the cytoplasm/cell itself.

How does cytokinesis differ in animal cells?

Animal cells use a cleavage furrow formed by a contracting protein ring.

How does cytokinesis differ in plant cells?

Plant cells form a cell plate composed of vesicles that builds a new cell wall between daughter cells.

What is a telomere?

Repetitive, non-coding nucleotide sequences found at the ends of eukaryotic chromosomes that protect vital genetic information from being lost during cell division.

What happens to telomeres in normal cells during division?

Telomeres shorten progressively with each round of cell division because DNA polymerase cannot fully replicate the very ends of the lagging strand.

What is the role of telomeres in cell death and aging?

Once telomeres shorten beyond a critical threshold, they trigger a cellular response that halts division (senescence) or induces programmed cell death (apoptosis).

Definition of a benign tumor

An abnormal mass of tissue contained within a capsule of connective tissue that does not spread.

Definition of a malignant tumor

An abnormal mass of tissue that lacks a containment capsule and can invade surrounding tissues or spread ("seed" new tumors).

Which type of tumor metastasizes?

Malignant tumors.

What do proto-oncogenes do when mutated or overly active into oncogenes?

Produce proteins that hyper-accelerate the cell cycle and stimulate excessive, uncontrolled cell division.

What happens when tumor suppressor genes are mutated or silenced?

Their protective proteins become absent or inactive, failing to block cancer development or repair damaged DNA.

How do cancer cells differ from normal cells in specialization?

They lose specialization (dedifferentiation).

How do cancer cells differ from normal cells regarding lifespan?

They are "immortal" (can divide endlessly and override cell cycle checkpoints).

How do cancer cells handle their telomeres?

They can regenerate their telomeres.

How do cancer cells differ physically and physiologically?

They exhibit altered physical and physiological characteristics compared to normal body cells.

What is the main advantage of sexual reproduction?

Produces genetic diversity among offspring, which increases the chance that some offspring will survive in changing environments.

What are body cells called?

Somatic cells (and germ cells)