Biology SAC 1 Unit 2 AOS1

Allele

A different form of the same gene that determines a specific trait or characteristic.

Autosome

A chromosome that is not involved in determining an individual's sex (22 pairs of autosomes)

Beneficence

An ethical concept that maximises the benefits and minimises the risks involved in taking a particular course of action.

Carrier

An individual who carries a recessive gene for a particular trait or disorder but does not express the symptoms of the gene.

Centromere

A constricted region of a chromosome that links a pair of sister chromatids together and plays a crucial role in cell division.

Chromatid

One of the two identical copies of a chromosome. During cell division, each ____ separates and becomes an individual chromosome.

Chromosome

A thread-like structure made up of DNA and proteins found in the nucleus of a cell that carries genetic information in the form of genes (23 pairs of chromosomes)

Co-dominance

Two alleles of the same gene are expressed separately to express different traits in an individual (C^B C^W = speckled black and white)

Complete dominance

When an allele is fully dominant over the other, canceling out the recessive allele’s effect once present in a heterozygous condition (Aa)

Dominant

The individual only needs one of these genes to show a trait

Epigenetics

The study of how your behaviour’s and environment can cause changes that affect the way your genes are expressed.

F1 Generation

Stands for ‘first filial’ and is the hybrid offspring of the P generation

F2 Generation

Stands for ‘second filial’ and is the offspring from the F1 hybrid

Gamete

A gamete is a haploid (half the number of chromosomes) reproductive cell that fuses with another gamete during sexual reproduction to form a zygote (sperm, egg or ovum)

Gene

A segment of DNA that act as a set of instructions to make molecules called proteins. Genes are responsible for the inherited traits and characteristics of living organisms.

Gene linkage

The tendency of genes located close to each other on the same chromosome to be inherited together. This is because the genes are physically linked and tend to stay together during the process of meiosis.

Genetic testing

A type of medical test that identifies changes in genes, chromosomes or proteins.

Genotype

An organism’s set of alleles for a gene

Hemizygous

The presence of only one copy of a particular gene in an organism's genome instead of the usual two copies. X-linked and Y-linked genes in a male are hemizygous as they only have one X and one Y chromosome.

Heterozygous

An individual having two different alleles for a particular gene (one dominant allele and one recessive allele).

Homozygous

An individual having two identical alleles for a particular gene.

Incomplete dominance

Both alleles of a gene at a locus are partially expressed, often resulting in an intermediate/different phenotype (red x white = pink)

Independent assortment

Refers to when alleles on different chromosomes are inherited independently of one another (these genes are said to be un-linked)

Inheritance

Describes how genetic material is passed on from parent to offspring

Integrity

Acting with honesty, fairness and decency (the commitment to searching for knowledge and understanding as well as the honest reporting of all sources of information and communication of results, contributing to public knowledge and understanding).

Justice

a moral obligation to ensure the fair distribution of benefits and burdens to individuals, with fair consideration of competing claims.

Karyotype

An individuals complete set of chromosomes (a full set of 46 chromosomes - 22 pairs of autosomes and 2 sex chromosomes)

Locus

A term used to tell us where on a chromosome a particular gene is located

Meiosis

A cell division for the production of gametes, only occurring in the ovaries and testes. The cell divides to produce four new daughter cells and each new cell has one chromosome from each homologous pair in the parent cell. The gamete is haploid (half the no. of chromosomes. haploid number for humans is 23). The new cells created are not genetically identical to the original cell.

Monosomy

The condition in which only one chromosome from a pair is present in cells, rather than the two copies usually found in diploid cells (when a person is missing a chromosome such as Turner’s Syndrome).

Non-Maleficence

Refers to avoiding the influence of harm and injuries on others.

P Generation

The parental generation - the original pair of parents at the start of a genetic cross experiment

Pedigree

A chart much like a family tree that is used to analyse the pattern of inheritance of a particular trait throughout a family. They show the presence of a particular trait as it relates to the relationship among parents, offspring and siblings.

Phenotype

The characteristics of an organism (physical, chemical, physiological, behavioural) Environment + genotype = phenotype

Punnet Square

A square grid used to calculate the frequencies of genotypes and phenotypes among offspring

Recessive

A gene that can be masked by a dominant trait and needs to of the same allele to receive the trait

Respect

Involves the consideration and respect to the intrinsic dignity of all other individuals.

Somatic cell

Are all the other cells in the body except for the sperm and egg cells (reproductive cells). They are diploid (meaning they contain two sets of chromosomes one from each parent) and are responsible for the growth and development of an organism.

Trisomy

A medical term used to refer to an individual who has an extra copy of a chromosome (downs syndrome is referred to as Trisomy 21)

True breeding

A kind of breeding where the offspring have the same phenotype as the parents, indicating the organism is homozygous for every gene.