7A - 8A Biology Unit 2 AOS 1

Deoxyribonucleic acid (DNA)

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

Gene

A sequence of DNA that codes for a protein product.

Genome

The complete set of DNA contained within an organism's haploid (n) set of chromosomes.

Allele

A gene with an alternate sequence of nucleotides, representing a variation of that gene.

Chromosome

A structure made of proteins and nucleic acids that carries genetic information.

Homologous Chromosomes

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

Karyotype

An image of a set of chromosomes from a cell that has been sorted by size, length, centromere position, and gene position.

Autosomal Chromosome

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. In humans, sex chromosomes can be either an X or Y chromosome

Aneuploidy

A variation in the usual number of chromosomes in a genome due to the addition or loss of a chromosome.

Polyploidy

The presence of additional sets of chromosomes in an organism's genome.

Haploid (n)

A cell with a single set of chromosomes; in humans, the haploid number is 23.

Diploid (2n)

A cell with two sets of chromosomes; in humans, the diploid number is 46.

Meiosis

A specialized form of cell division used to produce gametes in sexually reproducing organisms.

Non Disjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to an unequal distribution of chromosomes in daughter cells.

Germline Cell

Cells involved in the generation of gametes in eukaryotes.

Gonads

The organs that produce gametes from germline cells.

Gametes

Reproductive cells that arise from germline cells and contain half the genetic material (n) of a somatic cell.

Sperm

A haploid male gamete produced through spermatogenesis in the testes.

Egg Cell

A haploid female gamete produced through oogenesis in the ovaries

Zygote

The diploid cell formed by the combination of two haploid gamete cells.

Genotype

The genetic composition of an organism at a particular gene locus, represented using letter symbols.

Phenotype

The physical or biochemical characteristics of an organism resulting from gene expression and the environment.

Homozygous

Having identical alleles for the same gene on homologous chromosomes.

Heterozygous

Having different alleles for the same gene on homologous chromosomes.

Dominant

The variant of a gene that masks the effect of a recessive allele of the same gene on a homologous chromosome.

Recessive

The variant of a gene that is masked by a dominant allele on a homologous chromosome.

Complete Dominance

A pattern of dominance where only the dominant allele from the genotype of a heterozygous individual is expressed in the phenotype.

Co-dominance

A pattern of dominance where both alleles from the genotype of a heterozygous individual are expressed in the phenotype.

Incomplete Dominance

A pattern of dominance where neither allele from the genotype of a heterozygous individual is dominant, resulting in an intermediate phenotype.

Epigenetics

Changes to an organism’s phenotype resulting from modifications to gene expression.

Methylation

The process by which methyl (CH3) groups are added to particular nucleotides in a DNA segment, modifying gene expression.

Histone Modification

An epigenetic process where chemical groups attach to histone proteins, altering how DNA wraps around the histones.

Gene Expression

The process of reading the information stored within a gene to create a functional product, typically a protein.

Transcription

The process whereby a sequence of DNA is used to produce a complementary sequence of mRNA.

Translation

The process whereby an mRNA sequence is used to produce a protein.

Monohybrid Cross

A cross showing the inheritance of one trait or characteristic.

Autosomal Monohybrid Inheritance

The inheritance of one trait controlled by a gene located on an autosome.

Genetic Cross

A method used to determine the likelihood of offspring inheriting a particular trait.

Punnett Square

A diagram used to determine the possible genetic outcomes of a genetic cross.

Genotypic Ratio

The ratio of different genotypes expected among offspring from a genetic cross.

Phenotypic Ratio

The ratio of different phenotypes expected among offspring from a genetic cross.

Sex-linked Inheritance

The inheritance of a trait controlled by a gene located on a sex chromosome.

Sex-linked Gene

A gene located on a sex chromosome.