Bacterial and Eukaryotic Genetics Lecture Review

Comprehensive vocabulary flashcards covering linked genes, bacterial genetic transfer, transcription, translation, mutations, DNA repair, and genetic testing based on the provided lecture notes.

Linked genes

Genes located close together on the same chromosome that tend to be inherited together.

Unlinked genes

Genes located far apart on a chromosome or on different chromosomes that assort independently.

Parental/noncrossover genes

Allele combinations that match the original parental chromosome because no crossover occurred between them.

Recombinant/crossover genes

Allele combinations that differ from the parental arrangement because a crossover occurred between the loci.

Single crossover

One crossover event occurring between two linked genes during meiosis.

Double crossover

Two crossover events occurring between two linked genes, which can restore the parental allele arrangement.

Recombination Frequency (RF)

The probability of crossing over occurring between two genes, calculated as: $RF = (\frac{\text{number of recombinant offspring}}{\text{total offspring}}) \times 100\%$

Map Unit (cM)

A unit of distance on a genetic map where $1\%\ \text{recombination frequency} = 1\ \text{map unit}$ (also called 1 centiMorgan).

Physical map

A map showing the actual physical distance between genes on a chromosome, usually measured in base pairs ($bp$) based on DNA sequence data.

Genetic (linkage) map

A map showing the relative distance between genes based on recombination frequency ($map\ units/cM$).

Conjugation

Direct transfer of DNA between bacterial cells through a physical connection called a pilus.

Transformation

The uptake of free DNA from the environment by a bacterial cell.

Transduction

The transfer of bacterial DNA from one cell to another via a bacteriophage.

Cotransformation

The simultaneous uptake and incorporation of two or more genes during transformation, indicating they are close together.

Cotransduction

The simultaneous transfer of two or more genes by a single phage particle, indicating they are close together.

Vertical gene transfer

The transmission of genetic material from parent to offspring.

Horizontal gene transfer

The transmission of genetic material between organisms that are not parent and offspring.

Bacteriophage

A virus that infects bacteria.

F+ cell

A bacterial cell that contains the F (fertility) plasmid and can act as a DNA donor in conjugation.

F- cell

A bacterial cell that lacks the F plasmid and acts as a DNA recipient in conjugation.

Hfr cell

\"High frequency of recombination\" cell, in which the F plasmid has integrated into the bacterial chromosome, allowing efficient transfer of chromosomal genes.

F’ plasmid

An F plasmid that has excised from the chromosome carrying adjacent bacterial genes with it.

Partial diploid

A bacterial cell that carries two copies of some genes, one on the chromosome and one on a plasmid (such as an F').

Prototroph

A \"wild type\" bacterium for a specific gene that can synthesize everything it needs and grows on minimal media.

Auxotroph

A bacterium that has a mutation in a gene needed to make a specific nutrient and cannot grow on minimal media without that nutrient added (e.g., $leu^-$).

Lytic cycle

A fast, destructive phage life cycle where the phage takes over the host, assembles new particles, and lyses (bursts) the cell.

Lysogenic cycle

A phage cycle where the DNA integrates into the host chromosome as a prophage and is copied silently along with the host DNA for generations.

Template strand

The DNA strand that is read by RNA polymerase and used as the basis for RNA synthesis; also known as the non-coding strand.

Non-template strand

The DNA strand not used as the template, which matches the RNA transcript sequence (with T instead of U); also known as the coding strand.

RNA polymerase

The enzyme that synthesizes RNA from a DNA template.

Holoenzyme

The complete bacterial RNA polymerase complex, consisting of the core enzyme and a sigma factor.

Transcription factors

Proteins that help regulate the binding of RNA polymerase and the initiation of transcription.

Promoter

A DNA sequence located near the start of a gene that directs RNA polymerase where to begin transcription.

Upstream

The direction on DNA opposite to the direction of transcription, toward the $5'$ end of the coding strand.

Downstream

The direction on DNA in the direction of transcription, toward the $3'$ end of the coding strand.

TATA box

A eukaryotic promoter consensus sequence ($TATAAA$) that helps position RNA polymerase II for transcription initiation.

-10 consensus sequence

A bacterial promoter element located about $10\ bp$ upstream of the transcription start site ($TATAAT$).

-35 consensus sequence

A bacterial promoter element located about $35\ bp$ upstream of the transcription start site ($TTGACA$).

Introns

Noncoding sequences within a gene that are removed from the pre-mRNA during splicing.

Exons

Coding sequences within a gene that are retained in the mature mRNA after splicing.

Splicing

The process of removing introns and joining exons together to form mature mRNA.

RNA processing

The modifications (capping, splicing, polyadenylation) that convert pre-mRNA into mature mRNA in eukaryotes.

5’ cap

A modified guanine nucleotide added to the $5'$ end of pre-mRNA to protect it from degradation and help the ribosome bind.

Poly-A tail

A long string of adenine nucleotides added to the $3'$ end of mRNA that protects it from degradation and aids in nuclear export.

snRNAs

Small nuclear RNAs that form spliceosome components to catalyze splicing.

snRNP

A small nuclear ribonucleoprotein complex (snRNA + proteins) that is a component of the spliceosome.

Codon

A three-nucleotide sequence in mRNA that specifies a particular amino acid or a stop signal.

Anticodon

A three-nucleotide sequence on tRNA that base-pairs with a complementary codon on mRNA.

Start codon

The codon ($AUG$) that signals the beginning of translation and codes for methionine.

Stop codon

A codon that signals the end of translation ($UAA$, $UAG$, or $UGA$).

Reading frame

The way an mRNA sequence is divided into consecutive, non-overlapping codons during translation.

Aminoacyl-tRNA synthetase

The enzyme that attaches a specific amino acid to its corresponding tRNA.

Shine-Dalgarno sequence

A bacterial ribosome-binding sequence ($AGGAGG$) located upstream of the start codon.

Kozak sequence

A eukaryotic consensus sequence ($GCCRCCAUGG$, where $R = purine$) that promotes efficient translation initiation.

Spontaneous mutation

A mutation that arises naturally, without exposure to an external mutagenic agent.

Induced mutation

A mutation caused by exposure to an external mutagen such as chemicals or radiation.

Mutagen

An agent that increases the rate of mutation.

Base-substitution mutation

A mutation in which one nucleotide base is replaced by another.

Frameshift mutation

A mutation caused by insertion or deletion of nucleotides that shifts the reading frame of the gene.

Thymine dimer

A DNA lesion where two adjacent thymine bases become covalently linked, often due to UV light exposure.

Depurination

A spontaneous mutation where a purine base ($A$ or $G$) is chemically removed from the sugar-phosphate backbone.

Deamination

The removal of an amino group from a base, such as converting cytosine into uracil.

Intercalating agents

Flat molecules that wedge between base pairs, distorting the DNA helix and causing frameshift mutations.

Transposable elements

DNA sequences (\"jumping genes\") that can move to different locations in the genome, potentially disrupting gene function.

Mismatch repair

A post-replication repair mechanism where proteins scan DNA for mismatched bases and resynthesize the incorrect section.

Photoreactive repair

A repair mechanism using photolyase and light energy to break apart thymine dimers.

Base excision repair

A mechanism where an enzyme removes a single damaged base and DNA polymerase fills in the correct one.

Nucleotide excision repair

A mechanism that removes a bulky DNA distortion (like a thymine dimer) by cutting out a section of nucleotides and resynthesizing it.

Nonhomologous end joining

An error-prone repair pathway that fixes double-strand breaks by directly gluing the two broken ends back together without a template.

BRCA1 and BRCA2

Tumor suppressor genes that normally produce proteins involved in repairing double-strand DNA breaks via homologous recombination repair.