VCE Biology Unit 2

Anaphase

The third stage of cell division, where the chromosomes move away from one another to opposite poles.

Binary fission

a kind of asexual reproduction, where the fully grown parent cell splits into two halves, producing new cells.

Cell cycle

The series of events that take place in a cell leading to its division and replication of DNA.

Centrioles

Each of a pair of organelles near the nucleus, that is involved in the development of spindle fibres in cell division.

Centromere

What holds the sister chromatids together.

Chromatid

Each of the two thread-like strands into which a chromosome divides long ways during cell division.

Cytokinesis

The cytoplasmic division of a cell at the end of mitosis/meiosis, separating the cell into two daughter cells.

Interphase

The phase in the life cycle of a cell where the cell grows in size, replicates its DNA and prepares for division.

Checkpoints

Several points in the cell cycle in which the progression of a cell to the next stage in the cycle can be stopped until conditions are favourable.

Mitosis

Responsible for growth and repair, occurs in somatic cells, one division, produces two identical daughter cells

Prophase

the stage of cell division, where the chromosomes become visible as paired chromatids and the nuclear envelope disappears.

Spindle fibres

A network of filaments that are responsible for moving and segregating the chromosomes during nuclear division.

Telophase

The stage of the cell cycle in which the separated chromosomes reach opposite poles of the cell and the nuclei of the daughter cells reforms arounds the two sets of chromosomes.

Asexual reproduction

a type of reproduction by which offspring occur from a single organism, and inherit only the genes of that parent, making them genetically identical.

Animals v plant cell (mitosis)

In plants a cell plate forms in telophase, ensures the cell wall forms when the cell splits.

Cloning

The process of producing similar populations of genetically identical individuals.

Enucleated cell

A cell whose nucleus has been removed.

Parthenogenesis

a type of asexual reproduction where fertilisation doesn't occur

Genetic variation

Diversity in gene distribution.

Totipotent

can turn into any type of cells, found in zygote + in the blastocyst before the germ layers form.

Chromosomes

A thread-like structure in all living cells that consist of a single molecule of DNA bonded to various proteins and contains genetic information.

Crossing over

Chromosomes swap over in prophase 1 of mitosis

Diploid number

Full set of DNA

Haploid number

Half set of DNA

Gametes

sex cells, formed through meiosis (haploid).

Germ cells

found in the gonads, site where gametes are formed.

Homologous

An organ, system or body part that shares a common ancestry in multiple organisms.

Meiosis

produces gametes in germ cells in the gonads. Second division is reduction division, involves two divisions, produces four unidentical, haploid gametes.

Non-disjunction

Chromosomes don't seperate properly in the second division of mitosis. Can lead to genetic disorders.

Recombination

The process of forming new allele combinations in offspring by exchanging genetic materials.

Reduction division

the first cell division in meiosis, where the number is reduced from diploid to haploid.

Sexual reproduction

the production of new living organisms by combining genetic information from two individuals of different types.

Somatic cell

Body cell, (diploid)

Stem cell

undifferentiated cell

Blastocyst

a structure formed in the early development of mammals, which possesses an inner cell mass which subsequently forms the embryo.

Cell based therapy

Therapy in which cellular material is injected into a patient.

Differentiation

the normal process by which a less specialised cell develops or matures to become more distinct is form and function.

Ectoderm

one of the three primary layers in the very early embryo, the ectoderm is the most exterior layer.

Embyro

From the first mitotic division to week 8/9, organ systems are starting to develop.

Endoderm

The inner most layer of the very early embryo.

Fetus

week 8/9 to birth (growth occurs).

Germ layer

made up of inner cells of the blastocyst.

Mesoderm

the middle layer of cells of an embryo.

Metastasis

The development of secondary malignant growths at a distance from a primary site of cancer.

Multipotent

can only turn into cells of the same family e.g.. blood cells

Mutagen

a physical or chemical agent that changes the genetic material, usually DNA, of an organism.

Oligiopotent

can only change into a few types of cells.

Zygote

After fertilisation (cell becomes diploid), until the first mitotic division.

Pluripotent

can turn into most cell types, found in the germ layers + bone marrow.

Unipotent

can only turn into one type of cell, are terminal cells eg. muscle + liver cells.

Sexual v asexual reproduction

"in sexual reproduction, the offspring are genetically different to the parent.

in asexual reproduction, the offspring are identical to the parent, 'CLONES'"

Internal v external fertilisation

"internal fertilisation occurs inside the female reproductive tract.

External fertilisation occurs outside the reproductive system, gametes are released into the environment. "

Gastrulation

where the inner cells of the blastocyst migrate to form the 3 germ layers.

Therapeutic cloning

"Stems cells, embryonic cells umbilical cord, bone marrow.

Using your own cells for treatment reduces the risk of rejection, is used in the treatment of degenerative diseases."

Allele

Different forms of a gene.

Base pair

Adenine—Thymine

Guanine—Cytosine

Base sequence

the order of nucleotide bases in a DNA molecule.

DNA

the carrier of genetic information.

Dihybrid cross

a mating experiment between two organisms that are identically hybrid for two traits

Dominant

an allele that is expressed in an organisms phenotype, that overrides a recessive allele when present

Gene

a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Genome

the haploid set of chromosomes in a gamete or microorganism

Human Genome Project

a global, long-term research effort to identify the estimated 30,000 genes in human DNA and to figure out the sequences of the chemical bases that makes up human DNA.

Hybridisation

the process of mating organisms of different species to create a hybrid.

Monohybrid

A genetic cross between parents that differ in the alleles they possess for one particular gene, one parent having two dominant alleles and the other two recessives.

Nucleotide

one of the building blocks of DNA.

Recessive

an allele on which the effect is overridden by a dominant allele. the recessive trait can only be expressed when 2 recessive alleles are present.

Autosome

any chromosome that is not a sex chromosome

Test Cross

the breeding of an individual with a recessive individual in order to determine the genotype.

Down syndrome

a genetic disorder, caused by the presence of an extra chromosome on the 21st set.

Environmental sex determination

Environmental factors experienced during embryonic development that determines the sex of the offspring.

Karyotype

the number and visual appearance of the chromosomes in the cell nuclei of an organism.

Monosomy

when a diploid organism has only one copy of one of its chromosomes instead of two.

Sex chromosomes

A type of chromosome in the genome that is involved in the determination of the sex of an organism.

Autosomal gene

A gene located on a numbered chromosome and usually affects males and females.

Carrier

a person or other organism that has inherited a recessive allele for a genetic trait, but does not have the trait.

Co-dominance

Both dominant alleles are expressed together.

Genotype

The set of genes in our DNA which is responsible for a particular trait.

Epigenetics

The study of the mechanisms of temporal and spatial control of gene activity during the development of complex organism.

Hemizygous

1 allele needed for the trait to be expressed, and only occurs for genes located on the sex chromosomes.

Heterozygous

A pair of alleles where one is dominant and one is recessive.

Homozygous

Two of the same allele.

Monogenic

A kind of inheritance where a trait is determined by the expression of a single allele.

Phenotype

The physical appearance of an organism as a result.

Polygenic

A trait affected by multiple genes.

Genetic screening

An experimental technique used to identify and select for individuals who possess a phenotype.

Crossing Over

A process where homologous chromosomes pair up with each other and exchange different segments to form recombinant chromosomes.

Genetic testing

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

Linked genes

Genes that are inherited together with the other genes as they are located on the same chromosome.

Locus

The location of a gene on a given chromosome

Pedigree

An ancestral line or chart showing the inheritance of a trait or disease through a family.