Biology Module 5: Heredity

Mitosis

The division of the nucleus

Cytokinesis

The division of the cytoplasm; The 5th phase of mitosis where the centre of the cell contracts, pinching the cell into 2 daughter cells

Chromatin

The form in which genetic material is in when not dividing, DNA coiled around proteins

Histones

Proteins that DNA is coiled around, when not dividing

Chromosomes

Tightly-coiled structures of DNA that contain genetic instructions

Sister chromatids

2 identical strands that form after DNA duplication

Centromere

The structure in a chromosome to which chromatids are joined at during cell division

Karyotype

An individual’s complete set of chromosomes

Homologous pair

A non-identical pair of chromosomes that are the same size but different alleles

Prophase

The 1st phase of mitosis where chromatin condenses, chromosomes become visible and nuclear envelope breaks down

Metaphase

The 2nd phase of mitosis where chromosomes align along the centre of the cell, attached to spindle fibres by a centromere

Anaphase

The 3rd phase of mitosis where sister chromatids split at the centremere and move to opposite poles

Telophase

The 4th phase of mitosis where new nuclear membrane forms and chromosomes decondense

Apoptosis

Programmed cell death

Genes

The basic units of heredity made of DNA

Somatic cells

Cells of the body

Diploid

Containing 2 copies of each chromosome, one from each parent

Meiosis

A type of cell division that produces gametes

Gametes

Sex cells

Haploid

Containing only 1 copy of each chromosome

Zygote

A cell that arises during fertilisation when the sperm cell fuses with the egg cell

Synapsis

Process that takes place during prophase where chromosomes come together and become homologous pairs

Crossing over

A process in prophase one resulting in the swapping of genetic material between maternally and paternally derived chromosomes

Chiasmata

Sites of contact where crossing over occurs

Independent assortment

The process in metaphase where homologous pairs line up independent of other pairs

Linked genes

Genes on the same chromosome

Alleles

Alternative forms of a particular gene

Random segregation

The random separation of maternal and paternal chromsomes into gametes during metaphase

DNA

Deoxyribonucleic acid, a large molecule containing many genes

Watson and Crick model

The model of DNA that describes the double helix structure with twisted ladder

Nucleotide

The basic unit of the DNA molecule that consists of 1 phosphate, 1 sugar and 1 base

Complementary

Bases that pair together

Locus

The position of a gene on a particular chromosome

Semi-conservative

A process of DNA replication where one old strand and one new strand results

Helicase

An enzyme responsible for unwinding the double helix into a ladder

Replication fork

The point where the 2 DNA strands separate

Primase

An enzyme that produces an RNA primer to initiate the synthesis of new DNA strands

Polymerase

An enzyme that link together new nucleotides to strands

Leading strand

One of the 2 DNA strands that is synthesised continuously

Lagging strand

One of the 2 DNA strands that is synthesised in chunks

Okazaki fragments

Short segments of DNA synthesised on the lagging strand

Ligase

An enzyme that ensures that fragments are joined on the lagging strand

Mutation

A change to the nucleotide base sequence of an organism’s DNA

Mutagen

A physical or chemical agent that permanently changes an organism's genetic material, usually DNA, leading to an increase in the frequency of mutations

Reproduction

The successful production of offspring

Fertilisation

The fusing of two gametes

Sperm

The male gamete

Ovum/ova

The female gamete

Internal fertilisation

Sexual reproduction where the fertilisation occurs inside the female body

Copulation

Sex

Flagellum

Feature of sperm cells that enables mobility/swimming

Viviparous development

The development of offspring occurs inside the mother

Oviparous development

The development of the offspring occurs externally

External fertilisation

Sexual reproduction where the fertilisation occurs outside the female body

Asexual reproduction

A form of reproduction that involves a single parent producing offspring that are genetically identical clones of the parent

Sexual reproduction

The process of creating new organisms by combining genetic information from two parents through the fusion of gametes

Stamen

The male part of the flower

Anther

Male organ where the pollen grains are formed

Filament

Stalk on which the anther is held

Carpel

Female part of the flower

Stigma

Sticky top surface of the female part to which the pollen grains adhere

Style

Female part that joins the stigma to the ovaries

Ovary (plant)

Female organ where the ovules are formed and where fertilisation occurs

Ovule

Smaller structure inside the ovary that contains the ova and becomes a seed after fertilisation

Self-pollination

Male gametes are transferred from anthers of one flower to the stigma of a flower on the same plant

Cross-pollination

Male gametes are transferred from anthers of one flower to the stigma of a flower on a different plant (of same species)

Pollination

The transfer of pollen from a flower's male part, the anther, to the female part, the stigma

Vector

Any agent that moves pollen from the male part of a flower (anther) to the female part (stigma) to fertilize it

Seed

Ovule containing the embryo

Fruit

Grown from surrounding ovary

Germination

The process where an organism, like a plant, grows from a seed or spore after a period of dormancy

Vegetative propagation

Another name for asexual reproduction in plants

Perennating organs

Storage organs (specialised organ) in certain plants

Fragmentation

A form of asexual reproduction where an organism breaks into multiple fragments, and each fragment grows into a new, genetically identical individual

Runners

Modified overground stems that grow along the surface of the soil

Rhizomes

Modified underground stems which can generate new shoots along each node

Bulbs

Modified leaves that store food and can grow into new plants

Tubers

Modified stems which serve as underground food stores

Budding

A process of asexual reproduction where a new organism develops from an outgrowth or bud on the parent

Spores

A reproductive cell capable of developing into a new individual without fusion with another reproductive cell

Sporangia

A structure in certain plants that is charged with making and storing a large number of spores

Hyphae

Fine filaments which absorb nutrients made by multicellular fungi

Mycelium

Large masses of widely branched threats formed by hyphae

Zygospore

Diploid, thick-walled, and resistant spore that is formed by the fusion of two haploid cells

Binary fission 

An asexual reproduction process where a single organism splits into two identical daughter cells

Protists

Unicellular eukaryotes that use binary fission

External budding

Small daughter cell grows and then separates from the surface of the mother cell

Internal budding

Process in which the mother cell produces buds internally and is destroyed in the process

Cell cleavage

The point at which the cell splits apart in binary fission

Hormone

A chemical messenger that acts as messenger in the body and control the function of processes

Pituitary gland

The main gland (in the brain) that releases many hormones for reproduction

Androgens

Male hormones which control the growth and functioning of male reproductive organs and characteristics

Testosterone

The primary male sex hormone that develop the male reproductive organs

Oestrogen

Main group of female hormones which control the growth and functioning of female reproductive organs and characteristics

Progestogens

A second group of female hormones which plays an important role in pregnancy

Progesterone

A sex hormone that plays an important role in pregnancy

Follicular phase

First phase of the menstrual cycle where the pituitary gland releases FSH

Ovulation

The release of a mature ovum from the ovary

LH (Luteinising Hormone)

A hormone produced by the pituitary gland that triggers ovulation and regulates the menstrual cycle

Luteal phase

The second half of the menstrual cycle that thickens uterine lining for pregnancy OR sheds it during menstruation