Genes and Chromosomes Vocabulary

Vocabulary flashcards defining key genetics concepts, chromosomal structures, and genetic abnormalities covered in Section 7A.

Gene

A section of DNA that carries the code to make a protein and acts as the basic biological unit responsible for inheritance.

Deoxyribonucleic acid (DNA)

A double-stranded nucleic acid chain made up of nucleotides that carries the instructions for proteins required for cell and organism survival.

Nucleic acid

The class of macromolecules that includes DNA and RNA, which are polymers made out of nucleotide monomers.

Nucleotide

The monomer unit of nucleic acids, consisting of a nitrogen-containing base, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group.

Genome

The complete set of DNA contained within an organism's chromosomes.

Allele

Alternate forms of a gene with small differences in their base sequence.

Locus

The fixed position on a chromosome where a particular gene is located.

Inheritance

The genetic transmission of traits from parent to offspring.

Phenotype

The observable trait of an individual.

Haploid

Describes a single set of chromosomes ($n$).

Histone protein

Highly basic proteins that associate with DNA inside the nucleus and help it condense into a chromosome allowing it to fit inside the nucleus.

Chromosome

The structure made of protein and nucleic acids that carries genetic information.

Somatic cell

Any cell that is not a reproductive cell; somatic cells are diploid ($2n$), meaning they contain two sets of chromosomes.

Chromatid

One half of a replicated chromosome.

Telomeres

A region of repetitive base sequences found at the end of every chromosome that protects the ends of chromosomes from fusing with other nearby chromosomes.

Centromere

A specialised sequence of DNA that holds together two chromatids.

Sister chromatids

The identical daughter strands of a replicated chromosome.

Short arm

Also known as the 'p arm', this is the section of the chromosome that is shorter in length.

Long arm

Also known as the 'q arm', this is the section of the chromosome that is longer in length.

Homologous chromosomes

A pair of chromosomes of similar length, gene position, and centromere location, where one is inherited from the mother and the other from the father.

Homologue

A homologous chromosome.

Karyotype

A visual representation of an individual's entire genome organised into homologous pairs.

Autosome

Any chromosome (1–22 in humans) that is not a sex chromosome.

Sex chromosome

A chromosome responsible for determining the biological sex of an organism, such as an X or Y chromosome in humans.

Aneuploidy

A chromosomal abnormality in which a cell or organism varies in the usual number of chromosomes in its genome by the addition or loss of a chromosome.

Polyploidy

A chromosomal abnormality where an organism contains additional sets of chromosomes in its genome.

Monosomy

A genetic abnormality where an organism has one missing chromosome ($2n-1$).

Trisomy

A genetic abnormality where an organism has one extra chromosome ($2n+1$).

Tetrasomy

A genetic abnormality where an organism has two extra chromosomes ($2n+2$).

Turner syndrome

A monosomy chromosomal abnormality characterized by a single X chromosome (XO), with symptoms including infertility, short stature, and a fused neck and head.

Down syndrome

A trisomy genetic abnormality (trisomy 21) caused by an extra copy of chromosome 21, resulting in symptoms like delayed physical growth and intellectual disability.

Klinefelter syndrome

A trisomy genetic abnormality in males characterized by an extra X chromosome (XXY), leading to accelerated growth, small testes, and reduced testosterone levels.

Tetrasomy X

A tetrasomy genetic abnormality (XXXX) caused by having two extra copies of the X chromosome.

Short tandem repeats (STRs)

Specific sections of noncoding DNA where unit bases, typically two to five bases long, are repeated multiple times at a given gene locus.