Genetics Terminology Quiz

Locus

• A locus is a specific location on a genome.
• The plural is loci.
• Each chromosome has two copies, so the term locus typically refers to both copies of a gene.

Polymorphism

• Variations in DNA sequences.
• Can be single nucleotide differences (SNPs) or larger segments.
• Occur across individuals and chromosomes.
• Polymorphisms can exist with or without phenotypic effects.

Allele

• A specific variant of a polymorphism found within a gene.
• For example, a gene might have a C or T allele.
• Different combinations of alleles result in different genotypes.

Variant

• Any difference in DNA sequence.

Mutation

• A change in a DNA sequence, often associated with diseases or phenotypic changes.

Copy Number

• The number of copies of a specific gene or region of DNA.

Genotype

• The individual's complete genetic makeup.

Phenotype

• Observable physical and biochemical characteristics.
• Influenced by both genotype and environment.

Homozygous

• Having two identical alleles for a gene.

Heterozygous

• Having two different alleles for a gene.

Marker

• A gene or DNA sequence used in genetic mapping studies.

Linkage

• Genetic linkage between loci.

Recombination

• Exchange of genetic material during meiosis.

Contig

• A set of overlapping DNA fragments.

Phase

• Arrangement of alleles within a haplotype.

Haplotype

• A group of genes or alleles inherited together.

De novo

• New mutations not present in parents.

Inherited

• Mutations or variations passed down from parents through generations.

Polymorphism vs Mutation

• Polymorphisms can be ancient and prevalent across generations with or without phenotypic effects.
• Mutations often show genetic variation and are frequently associated with specific diseases or phenotypic effects.

Rare Variants

• Variants occurring less than 1-2% in a population.
• Can be de novo (new mutations).

Human Variation

• Roughly 0.1% sequence difference exists between individuals, equating to about 6 million differences.

Types of Polymorphic DNA Sequences

• SNPs: Single-nucleotide polymorphisms.
• Microsatellites (STRs/SSRs): Short tandem repeats (2-7 base pairs).
• Minisatellites (VNTRs): Variable number tandem repeats (8- >50 base pairs).
• CNVs: Copy number variants (0, 1, 3, or more copies in large sequences, >1000 bp to Mb).

Microsatellites vs Minisatellites

Applications of Polymorphisms

• Forensic science, assessing biodiversity, food quality control, ancestry and archaeology, human genome sequencing, mapping disease genes, and RFLPs.

Restriction Fragment Length Polymorphisms (RFLPs)

• An older technique for DNA profiling, utilizing restriction enzymes.
• Restriction enzymes are bacterial enzymes that cut specific DNA sequences.
• The sizes of fragments are altered by changes in or between enzyme recognition sites, reflecting differences in DNA sequences.

DNA Fingerprinting Techniques

• Polymorphisms are used for DNA fingerprinting in forensics, paternity testing, and disaster victim identification.
• Developed by Alec Jeffreys in 1985.
• Currently PCR methods are used over RFLP.

SGM+ Markers in Forensics

• Specific markers used in the UK for genetic profiling (examples include FGA, TH01, VWA, D2S1338, etc.).

Determining Biological Sex through AMEL Gene

• The AMEL gene locus (AMELX on X chromosome, AMELY on Y chromosome) is used to distinguish biological sex.
• AMELX and AMELY indicate male (XY), while only AMELX indicates female (XX).

Polymorphisms and Ancestry

• Polymorphisms reflect genetic origins and diversity across populations.

Food Quality and Genetic Integrity

• DNA polymorphisms produce genetic fingerprints for breeds, used to verify labels (organic, region-specific), identify species, and assess genetic diversity.

Other DNA Features

• Repetitive DNA: Multiple copies of sequences (often considered "junk DNA").
• Highly Repetitive DNA (Satellite DNA): Found at telomeres and centromeres, exhibiting long tandem repeats.
• Middle Repetitive DNA (Mobile DNA Elements): Includes transposons (DNA-based LINES, SINES, ALUs) and retrotransposons (RNA-based LTRs). They can move within a genome.

Test your knowledge on key genetic terms such as locus, polymorphism, allele, and mutation. This quiz covers essential concepts that are fundamental to understanding genetics and molecular biology. Dive into the world of DNA and discover how these terms relate to genetics and phenotype.