topic 2

anther

the part of a flower which contains pollen grains

diploid

cells with two copies of each chromosome

double fertilisation

the fertilisation event occurring in seed plants where one sperm cell fertilises the egg cell to produce a diploid zygote and the other fuses with the two polar nuclei to form a triploid endosperm

embryo sac

a sac which contains the female ovule of a flowering plant

endosperm

a mass of tissue formed from the fusion of a sperm cell with the two polar nuclei which provides energy and nutrition for the growing seed

generative nucleus

the haploid nucleus found in the pollen grains of flowering plants which divides by mitosis to form the two sperm nuclei

haploid

cells with only one copy of each chromosome

micropyle

a small opening in the ovule which the pollen tube grows towards. it allows for the entry of sperm nuclei into the ovule

pollen

grains produced by flowers which contain the male gametes from the plant

pollen tube digestive enzymes

enzymes found in the tip of the pollen tube which break down the style to create a path for tube growth from the pollen grain to the embryo sac

pollen tube

the tube used to transport the sperm nuclei from the pollen grain to the micropyle on the embryo sac for fertilisation of the ovule

triploid

cells with three copies of each chromosome

tube nucleus

the nucleus found in the pollen grains of flowering plants which controls the growth of the pollen tube

acrosome

the head portion of a sperm cell which contains digestive enzymes to break down the outer membrane of an egg cell during fertilisation

blastocyst

a fluid filled mass of cells which contains the inner cell mass which later becomes an embryo

blastomere

the cells which result from the immediate divisions of a fertilised ovum

capacitation

maturation of sperm cells which happens after ejaculation and allows them to fertilise the oocyte

cortical reaction

the reaction that occurs in a fertilised oocyte to harden the zona pellucida and prevent polyspermy

fertilisation

the fusion of a sperm cell nucleus and an egg cell nucleus to form a diploid zygote

gametes

mature haploid sex cells which can fuse during fertilisation to create a diploid zygote

germ cells

diploid cells which give rise to gametes through meisosis

oogenesis

the formation of a mature haploid ovum from the differentiation of immature diploid oogonium

polyspermy

the fertilisation of an oocyte by multiple sperm

somatic cells

all diploid body cells except gametes

spermatogenesis

the formation of mature haploid sperm cells from diploid germ cells

zona pellucida

the outer layer surrounding oocytes made of glycoproteins

zygote

a diploid fertilised egg cell formed from the fusion of a sperm and ovum

anaphase

the third stage of mitosis where the chromosomes are pulled apart to the poles of the cell by the spindle fibres

asexual reproduction

the production of genetically identical offspring from one parent through the process of mitosis

cell cycle

the series of stages preparing the cell for division consisting of three main phases (interphase, mitosis, cytokinesis)

chromosome non-disjunction

failure of homologous chromosome separation during meiosis which leads to daughter cells which have an abnormal amount of chromosomes

chromosome translocation

a mutation which is caused when part pf a chromosome breaks off and then rejoins to a different chromosome

crossing over

the exchange of genetic material between two chromosomes in a bivalent

diploid

cells with two copies of each chromosome

down's syndrome

a genetic condition which causes intellectual disability and physical birth defects and is caused by the presence of a third copy of chromosome 21

G1 phase

the first growth phase in interphase where the cell synthesises proteins and RNA, duplicates its organelles, and increases in size before DNA replication in S phase

G2 phase

the second growth phase of interphase where the cell continues to increase in size and synthesize biomolecules

haploid

cells with only one copy of each chromosome

homologous chromosomes

two chromosomes with similar gene loci but different alleles, one inherited from each parent

independent assortment

a source of variation in meiosis where the bivalent chromosomes can line up either way around on the metaphase plate

interphase

the largest part of the cell cycle where cells spend most of their time growing, synthesising biomolecules and preparing for mitosis

meiosis

a type of cell division used to produce gametes that produces four genetically different haploid daughter cells from one parent cell

metaphase

the second stage of mitosis where the chromosomes attach to the spindle fibres and align in the centre of the cell along the metaphase plate

mitosis

the division of a cell to produce two genetically identical daughter cells

monsomy

a condition where an organism only has one copy of a chromosome

polysomy

a condition where an organism has at least one extra chromosome than normal

prophase

the first stage in mitosis where the nuclear envelope breaks down, the centromeres move to opposite poles of the cell, the mitotic spindle begins to form, and the chromosomes condense

recombinant chromosomes

the chromosomes produced by crossing over and exchange of genes during metaphase 1

S phase

the second phase in the cell cycle where the DNA in the cell is replicated

telophase

the final stage of mitosis where new nuclear envelopes begin to form around the separated sets of chromosomes

turner's syndrome

a genetic condition where the second X chromosome in females is either partially or fully missing

AIDS

a condition caused by HIV which is characterised by a large decrease in proper immune function

antivirals

a class of drugs which work to inhibit viral replication to stop or suppress the infection caused by a virus

ebola virus

an RNA virus which causes major internal bleeding and is spread through contact with bodily fluids of an infected person

epidemic

an infectious disease which has spread to many individuals within a community or region concurrently

HIV

an RNA retrovirus which is transmitted through certain bodily fluids like blood or semen and attacks the immune system which can lead to the development of AIDS

lambda phage virus

a type of DNA virus which infects the bacterium E. coli

latency

the amount of time between exposure to a pathogen and the presentation of symptoms caused by the pathogen

lytic cycle

the replication of a virus within a host cell which ultimately leads to the rupture and death of host cell

pandemic

an epidemic which has spread over a wider geographical area (typically international)

tobacco mosaic virus

a type of single stranded RNA virus which infects plant cells and causes discolouration of the leaves in a mosaic-like pattern and hinders their growth

cell theory

a concept that defines cells as a fundamental unit of structure, function, and organisation in all living organisms

cell wall

a tough outer layer which surrounds some cell types and is made of peptidoglycan in bacteria and cellulose in plants

centrioles

structures found in the cytoplasm made of microtubules that produce the spindle fibres during mitosis

chloroplasts

organelles found in plants and algae which are the site of photosynthesis

differential staining

using multiple different stains to distinguish different parts of a specimen

eukaryotic cell

a type of cell that contains a nucleus along with membrane bound organelles

golgi apparatus

an organelle that is found in eukaryotic cells that is involved in the modification and packaging of proteins

gram-negative bacteria

a type of bacteria with an outer membrane and a thin inner peptidoglycan cell wall which does not retain the crystal violet stain during gram staining

gram-positive bacteria

a type of bacteria with thick peptidogylcan cell walls which retain the crystal violet stain during gram staining

light microscope

a type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen

lysosomes

membrane-bound vesicles found in the cytoplasm that contain a hydrolytic enzyme called lysozyme

magnification

how much bigger an image appears compared to the original object

mitochondria

the organelles found in eukaryotic cells which are the sites of aerobic respiration

nucleoid

the area in prokaryotic cells where the chromosomes are found

nucleolus

a dense region found inside the nucleus that contains proteins and RNA and is involved in synthesizing new ribosomes

nucelus

an organelle found in eukaryotic cells that stores the genetic information of the cells as chromosomes and is surrounded by a membrane called the nuclear envelope

organ

a group of specialised tissues working together to carry out a specific function

organ system

a group of specialised organs working together to carry out a specific function

permanent vacuole

a membrane bound structure found in plant and fungal cells that contain cell sap

plasmids

circular loops of DNA found in the cytoplasm of prokaryotic cells separate from the nucleoid

prokaryotic cell

a type of cell that does not contain any membrane bound organelles or a nucleus

resolution

the ability to distinguish two different nearby points in a specimen

ribosomes

organelles which are the site of protein production in the process of translation

rough endoplasmic reticulum

a membrane-bound organelle that is involved in the synthesis and packaging of proteins

scanning electron microscope

a type of electron microscope that passes a beam of electrons over the surface of a specimen to produce an image

smooth endoplasmic reticulum

a membrane-bound organelle that is involved in lipid synthesis

tissue

a group of specialised cells working together to carry out a specific function

tonoplast

the membrane which surrounds the permanent vacuole

transmission electron microscope

a type of electron microscope that passes a beam of electrons through a sample to produce an image

what is cell theory?

• cells are the smallest unit of all living organisms

• new cells are only formed by division

• cells contain inherited information

what does unicellular mean?

composed of a single cell

what does multicellular mean?

composed of many cells. these cells usually differentiate to become tissues, organs, and organisms.

what is a eukaryote?

a cell with a nucleus.

what does a plant cell have that an animal cell doesn't?

• permanent vacuole

• cellulose cell wall

• chloroplasts

what is a prokaryote?

a cell without a nucleus, e.g. bacteria.
usually have a loop of DNA, plasmids, slime capsule, and a flagella and are usually smaller than eukaryotes.

give some information about prokaryotes

• probably first form of life

• DNA not enclosed in nuclear membrane

• no membrane bound organelles

• always 5 structures in a prokaryote = cell wall, plasma membrane, cytoplasm, ribosome, and circular DNA

• cell wall is made of peptidoglycan

• absence of true nucleus only occurs in 2 groups = bacteria and cyanobacteria

give some information about the nucleus

• in all eukaryotes apart from red blood cells

• within the cytoplasm

• contains DNA (usually 46 chromosomes apart from gametes which have 23)

• double membrane = outer and inner

what is the nuclear envelope?

controls entry and exit of materials

what are the nuclear pores?

control passage of large molecules out of nucleus