Genetics Flashcards

Review flashcards for genetics exam.

DNA

Antiparallel strands, complementary base pairing, has A, C, G, T nucleotides (deoxyribose sugar, phosphate group, nitrogenous base), runs 5’ to 3’

RNA

Antiparallel strands, complementary base pairing, has A, C, G, U nucleotides (ribose sugar, phosphate group, nitrogenous base), usually shorter than DNA, runs 5’ to 3’

Gene

The fundamental unit of inheritance, a specific sequence of DNA that carries instructions for building proteins or influencing other genetic processes.

Allele

The different versions of a gene, each with its own specific DNA sequence inherited from each parent.

Mutant Allele

Often results in a protein that is either produced in an incorrect amount or may not function normally, the opposite of a wild-type allele

Trait

A characteristic that an organism displays

Gene Expression

How the information in gene sequences are used to synthesize functional proteins that affect cellular characteristics

Position Effect

The change in gene expression that can happen when a gene is moved from its original location on a chromosome.

Euchromatin

Relaxed state of chromatin in eukaryotic chromosomes.

Heterochromatin

Condensed state of chromatin in eukaryotic chromosomes.

Transposable Elements (TEs)

DNA transposons and retrotransposons, with the latter using an RNA intermediate for transposition.

Simple Transposition

Requires the enzyme transposase, which cuts out the transposon from its original location and facilitates the insertion of the transposon somewhere else within the genome.

Locus

Physical place of a gene on a chromosome

Translocation

A segment of a chromosome is moved to a new location, which can lead to gene fusion or disruption.

Inversions

A segment of DNA is reversed within the chromosome, which can affect gene regulation and expression.

Paracentric Inversion

Involves a segment that does not include the centromere, affecting the structure but not the chromosome number.

Pericentric Inversion

Involves a segment that includes the centromere, which can lead to changes in chromosome length and gene dosage.

Mitotic Recombination

Genetic recombination that occurs in somatic cells during mitosis, primarily used to repair DNA damage or double-strand breaks (DSBs).

Mosaicism

Patches of cells with different genotypes can occur with mitotic recombination.

Heterogametic

The human male is considered the heterogametic sex, as it has X and Y chromosomes.

Haploid

One copy of each chromosome (n) as occurs in gametes (sperm and egg).

Diploid

Normal body cells, somatic cells, are diploid, meaning they have two copies of each chromosome.

Leptotene

Replicated chromosomes begin to condense during prophase I of meiosis.

Zygotene

Synapsis occurs, where homologous chromosomes recognize each other and begin to align themselves length wise during prophase I of meiosis.

Pachytene

Crossing over (also known as recombination) occurs during prophase I in meiosis.

Diplotene

The synaptonemal complex starts to dissociate during prophase I in meiosis.

Diakinesis

The synaptonemal complex completely disappears and the nuclear envelope starts to break apart during prophase I in meiosis.

Mitotic Nondisjunction

When chromosomes fail to separate during cell division in mitosis, results in daughter cells with an abnormal number of chromosomes (aneuploidy).

Dominant Allele

Will show its trait even if only one copy is present.

Recessive Allele

Trait will only be expressed if two copies are present.

Incomplete Dominance

A heterozygous individual expresses an intermediate phenotype between the two homozygous phenotypes, resulting from a blend of the alleles.

Law of Segregation

Alleles of a gene separate during gamete formation, ensuring each gamete receives only one allele for a trait.

Law of Independent Assortment

During gamete formation, the alleles for different traits are distributed independently of each other.

Epistasis

Occurs when the alleles of one gene mask the effects of alleles from another gene at a different locus.

Maternal Effect

The influence of the mother's genotype on the phenotype of her offspring, regardless of the offspring's genotype.

Genomic Imprinting

Only one copy of a gene is active, either from the mother or the father, while the other copy is silenced.

Genetic Linkage

The tendency of genes located close together on a chromosome to be inherited together.

Dosage Compensation

How organisms balance gene expression from sex chromosomes to prevent imbalances in gene dosage.

X-Chromosome Inactivation (XCI)

A process in female mammals where one X chromosome is randomly inactivated (barr body), leading to dosage compensation.

Cytoplasmic Inheritance

Involves genes located in organelles like mitochondria, inherited maternally.

Mendelian Inheritance

Follows the principles established by Gregor Mendel, including dominant and recessive traits.

Paternal Inheritance

Traits inherited from the father, often seen in certain mitochondrial diseases due to paternal leakage.

Sex-Linked Inheritance

Traits associated with genes located on sex chromosomes, leading to different expression patterns in males and females.

Genetic Variation

The differences in DNA sequences among individuals within a species, which can arise from chromosomal variations.

Copy Number Variation

Variation in the number of copies of a particular gene, which can influence phenotypic diversity.

Endopolyploidy

A condition where certain cells undergo multiple rounds of DNA replication without cell division, leading to increased ploidy levels.

Aneuploidy

The presence of an abnormal number of chromosomes in a cell, often resulting from nondisjunction during meiosis.

Mutations

Changes in DNA sequence that can lead to variations in traits, including single-base mutations that alter phenotypes.

Epigenetic Inheritance

Heritable changes in gene expression that do not involve changes to the underlying DNA sequence.

Okazaki Fragments

Short DNA fragments synthesized on the lagging strand during DNA replication.

Helicase

An enzyme that unwinds the DNA double helix, essential for replication to occur.

Single-Strand Binding Proteins

Proteins that stabilize unwound DNA strands during replication to prevent re-annealing (snapping back together).

DNA Polymerase III

The enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand.

DNA Ligase

An enzyme that joins Okazaki fragments together, completing the DNA strand.

RNA Polymerase

Essential for transcription in eukaryotic cells and can be affected by various transcription factors (TFs).

Translation

Initiation in eukaryotes requires 5' capping of mRNA, which protects the mRNA and aids in ribosome binding.

Riboswitches

RNA molecules that can exist in 2 different conformations (e.g., “on” and “off”), usually facilitated by binding of a small molecule.

Non-coding RNAs (ncRNAs)

RNA molecules that do not encode proteins but play crucial roles in cellular functions.

Operons

A cluster of genes under the control of a single promoter, allowing coordinated expression in prokaryotes.

Corepressors

Molecules that bind to repressors to inhibit gene expression, as seen in the trp operon with tryptophan.

Operator

Regulatory sequence that can be bound by repressor proteins.

Plasmids

Small circular DNA molecules that can replicate independently of chromosomal DNA in bacteria.

Horizontal Gene Transfer (HGT)

The process by which genetic material is exchanged between organisms that are not related by parent and offspring.

Conjugation

Direct transfer of DNA between two bacteria through physical contact, often mediated by a sex pilus.

Reverse Transcriptase

An enzyme used by retroviruses like HIV to convert RNA into DNA during their reproductive cycle.

Depurination

The most common spontaneous mutation, involving the loss of a purine base (adenine or guanine).

Natural Selection

A process where environmental factors favor certain phenotypes over others, leading to evolutionary changes.