SACE STAGE 2 : BIOLOGY

Gene

A certain sequence of nucleotides in DNA/RNA that is located on a chromosome

Genetic information

The hereditary information about DNA sequences contained in chromosomal DNA/RNA

Chromosomes

Consists of single molecule DNA bonded to proteins

Sister chromatids

The identical copies (chromotids) former by the DNA replication of a chromosome

Cytosol

The fluid in which organelles of the cell reside

Nucleotide

An organic molecule that is the building block of DNA/RNA

Nucleotide region

Is where cytosol and DNA is located

Double helix

The structure formed by double stranded molecules of nucleic acid

Nucleus

A large membrane bounded organelle that contains the genetic material in the form of many linear DNA molecules, controls all cell activity and regulates transcription of genes

Complementary base pairing

The pairing of the two complementary base nucletides.

In DNA, A pairs with T and C pairs with G

In RNA, A pairs with U and C pairs with G

Adenine

Thymine

Cytosine

Guanine

Uracil

Eukaryotic cells

Complex and have multiple linear chromosomes eg. plants, animals and fungi

Prokaryotic cell

Simple and have singular circular chromosomes eg, bacteria

DNA replication (semi-conservative)

1: Helix bonds broken by enzyme

2: DNA polymerase enzyme assists as a catalyst

3: Results in two DNA molecules, contain 1 old and 1 newly synthesised strand

DNA

Deoxyribonucleic acid, it stores and transmits information, is self replicating and is made from sugar, phosphate and base

Chromotin

A mass of genetic material composed of DNA and histones that are the condensed into chromosomes

Enzymes

Organic catalysts which speeds up a biochemical reaction in a cell without being changed

Catalyst

Substance that speeds up the rate of a chemical reaction

Specificity

Unique binding of one molecule to another. one substrate to one enzyme

Active site

Region on an enzymes surface where the substrate binds in a complementary fashion

Induced fit model

Model where the substrate induces a fit into the active site where it did not initially fit

Activation energy

Amount of energy necessary for a chemical reaction to occur

Metabolism

All of the biochemical reactions occurring within an organism

Metabolic pathway

A series of biochemical reactions occurring in cells, each catalysed by a specific enzyme

Competitive inhibitor

An inhibitor whose structure is so similar to the structure of the substrate that it binds to the active site of enzyme and prevents substrate from binding

Non-competitive inhibitor

A chemical which combines with an enzyme, but not at the active site, but changes the shape of the active site, preventing the substrate from binding

RNA

Ribose nucleic acid

Cytoplasm

Contents of an eukaryotic cell, excluding the nucleus and other organelles

Exons

Intronoding segment of DNA which carries bases which are transcribed (expressed)

Intron

Section of non-coding DNA which carries non-coding bases, segments are spliced out of RNA

rRNA (ribosomal RNA)

Ribosomal RNA; type of RNA that makes up part of the ribosome

mRNA (messenger RNA)

Messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

tRNA (transfer RNA)

Transfer RNA; type of RNA that carries amino acids to the ribosome

Polypeptide

Long chain of amino acids held together by peptide bonds

Template strand

Coding strand in DNA helix and contains genes that are transcribed into mRNA

Complementary strand

A strand of DNA that is one of the strands of the double helix and complements the coding of template strand

DNA base triplet

Three nucleotides bases code for one amino acid

Codon

A three base sequence on mRNA molecule that provides codes for a particular amino acid

Anticodon

A three-base sequence on the tRNA that is complementary to the mRNA codon

Amino acids

A molecule consisting of an amino and acid part which is joined by peptide bonds in long chains to form polypeptides and proteins

Ribosome

An organelle in the cytoplasm which has a vital role in translation

Transcription

Process which occurs in the first part of protein synthesis in the nucleus of a cell in which DNA make a copy of mRNA

Translation

Second stage of protein synthesis that occurs in ribosomes in which the base sequence in ,mRNA is used to make an amino acid sequence in a polypeptide

RNA splicing

Process in which mRNA bases are produced as a result of transcription, introns are removed and the remaining mRNA bases (exons) are joined together

Antibody

A protein made by a plasma cell in the blood as a response to the presence of a specific antigen

Antigen

A non-self marker protein or carbohydrate, that stimulates production of an antibody

Peptide bond

Chemical bonds that link amino acids in a polypeptide chain or protein molecule

Alpha helix

Secondary structure of polypeptides with a coiled, helical shape

Beta pleated sheet

Secondary structure of polypeptides with a folded sheet shape

Enzyme

Organic catalyst which is able to speed up a biochemical reaction in a cell without being changed itself

Hormones

Chemical released from endocrine gland and carried in blood.

bind to surface receptor in the cell membrane and bring about specific functions

Receptor

An organelle which is able to detect a stimulus and send a message through sensory neurons to the central nervous system

Repressor protein

A protein that switches off genes by making them inaccessible for transcription

Activator protein

Protein that switches on genes by making them more accessible for transcription

Gene expression

Process that results in information stored in DNA being used to make a gene-product, usually a polypeptide or RNA molecule

Promoter

Specific base sequence near the start of a gene, which RNA polymerase binds too, to start transcription

Transcription factors

A variety of proteins involved in the process of converting, or transcribing, DNA into RNA

Phenotype

The appearance of an organism which is determined by its genotype and the effect of the environment

Cell differentiation

The process by which cells become different in structure and function

RNA polymerase

The enzyme that catalyses the production of mRNA in transcription

Chromatin

Granular material found in the nucleus of a cell during interphase, consists of unwound chromosomes and DNA molecules

Histones

Small proteins around which DNA is wrapped to form chromosomes in eukaryotic cells

Zygote

A cell which is formed in result of the fertilisation of a male and female gamete (sperm and ovum)

Stem cell

A type of unspecialised cells that is able to divide and produce different types of cells

may be pluripotent or multipotent.

Methylation

Attachment of methyl groups to section of DNA that may interfere with gene expression

One of several factors involved in epigenetic.

Epigenetics

Inheritance if traits caused by modification of gene expression rather than simple transmission of genetic information

Cancer

General name of cells which grow uncontrollably and are malignant and will invade and kill other tissues in the body

Auto-immune system

A complex organization within the body that is designed normally to "seek and destroy" invaders of the body, including infectious agents.

Mutation

A random and permanent change in the sequence of bases in the DNA which may be expressed as a change in the amino acid sequence of a polypeptide.

Not all mutations are bad and can lead to improving chance of survival and consequently increase population

Point mutation

A type of mutation in which only one base in a gene in substituted

Frameshift mutation

A type of mutation in which DNA bases are inserted or deleted therefore causing DNA triplets to be read in a different sequence after the change

Base substitution

A mutation where one base is replaced by another.

Base insertion

A mutation where a base is added

Base deletion

A mutation where a base is removed.

Mutagen

Any chemical, radiation or other agent which increases the rate of mutation in an organism.

Germline cell mutation

A mutation in a sperm or ovum cell which may be included in the zygote and therefore in all cells of the resultant organism.

Somatic cell mutation

A type of mutation which occurs in normal body cells, may sometimes give rise to a cancer.

Genetic engineering

Deliberate manipulation of genetic material in order to change some of characteristics or produce useful products

Gene probe

Artificially prepared DNA or RNA sequence used to located particular base sequence or gene.

Restriction enzymes

An enzyme used to cut DNA into different segments over 1000 known and each one cuts DNA at a specific restriction site.

DNA ligase

Enzyme that can be used to join one fragment of DNA to another

Recombinant DNA

A DNA molecule formed by joined segments of DNA from different species

PCR

Polymerase chain reaction, reaction in which millions of copies of the DNA can be made in a short period of time

DNA primer

Short sequence of DNA bases used to control PCR

DNA polymerase

Enzyme that catalyses the production of new DNA strand during replication

Gel electrophoresis

A technique used to separate large molecules using an electric field, based on size and charge

DNA profiling

Technique that compares DNA from different sources by cutting it into fragments with restriction enzymes and then separating these fragment into visible bands using gel electrophoresis.

Microinjection

A technique using micro-pipette to transfer genes between species.

Virus vector

A virus that is used to transfer genes from species to another

CRISPR

Clustered Regularly Interspaced Short Palindromic Repeats, gene editing technology that permits the genes of an organisms to be permanently altered

Cas-9

Enzyme that recognizes guide RNA and binds here and cuts the DNA

Binary fission

Division process of prokaryotic cells

Heterotroph

Organisms that consume other organisms for chemical energy.

Vacuole

Single membrane-bound sac which stores food/nutrients to be broken down in animal cells and is a support structure of plant cells that holds water and salt

Vesicle

Transports substances in/out of cell by endo/exocytosis

Mitochondria

Site of aerobic respiration, making ATP molecules that stores energy for cell to use

Golgi Body

Stack of flattened membrane-bound sacs that are not linked to each other

involved in the processing and packaging of molecules into vesicles for movement out of the cell by exocytosis

Ribsomes

Made up of proteins and RNA, free or attached to the rough ER, site of protein synthesis

Rough ER

Rough Endoplasmic Reticulum.

Flattened membrane sacs with ribosomes attached to surfaces

Intra-cellular transport, site of protein synthesis of ribosomes

Meiosis (def)

Sexual cell reproduction that produced 4 daughter gametes

Chloroplast

Stacks of internal membrane structures called grana (contains chlorohpyll)

site of photosynthesis, usually in the cells of the leaves of a plant