My lesson

Protein

A biological molecule made of amino acids and produced by ribosomes according to genetic instructions

Eukaryotic organism

An organism whose cells have a nucleus and membrane-bound organelles

Cytosol

The aqueous part of the cytoplasm of a cell; the cytoplasm excluding organelles

Prokaryotic organism

A single-celled organism whose nucleic acid is not contained in a membrane-bound nucleus

DNA

Deoxyribonucleic Acid (DNA) is a thread-like chain of nucleotides carrying the genetic instructions of an organism in a double helix of antiparallel strands

Nucleotides

Organic molecules that are the building blocks of DNA; made of a sugar-phosphate backbone and nitrogenous bases

Double helix

A pair of helices wound around a central axis; the shape of a DNA molecule

Nitrogenous base

Nitrogen-containing molecule that forms part of the structure of a nucleotide

Leading strand

The exposed strand of an unwound DNA molecule that runs in a 5' to 3' direction towards the replication fork

Lagging strand

The exposed strand of an unwound DNA molecule that runs in a 5' to 3' direction away from the replication fork

Daughter Cells

The two cells produced after a parent cell undergoes cell division

DNA Helicase

The enzyme responsible for breaking hydrogen bonds between nitrogenous bases to unwind the DNA double helix into separate strands

DNA polymerase

The enzyme responsible for matching and binding free-floating nucleotides to exposed nucleotides on unwound DNA strands

Free-floating nucleotides

Nucleotides floating in the nucleoplasm or cytosol

Semi-conservative replication

Replication of DNA resulting in two copies that each contain one of the original strands and one new strand

Sister chromatids

The original and replicated chromosome joined by a centromere after DNA replication

Three-prime (3') end

End of a nucleotide or DNA strand with the third carbon atom of the sugar molecule and a free hydroxyl group

Five-prime (5') end

The end of a nucleotide or DNA strand with the fifth carbon atom of the sugar molecule and a free phosphate group

Replication fork

The point of a DNA molecule where the helicase enzyme breaks hydrogen bonds between nitrogenous bases and exposes the two strands of DNA

Mitosis

The process by which cells replicate during growth in multicellular organisms and reproduction in unicellular organisms

Gametes

Reproductive cells in sexually reproducing organisms (e.g. sperm and egg)

Alleles

Different forms of a gene found at the same locus in the genome of a species

Haploid cell

A cell containing one of each chromosome required for the development of a new individual through sexual reproduction

Meiosis

The process by which haploid sperm and egg cells are made from a diploid parent cell

Diploid cell

A cell in which there are two of each chromosome present in the nucleous

Parent cell

A cell that undergoes replication and division to produce identical daughter cells in mitosis or haploid gametes in meiosis

Crossing over

The transfer of genes between homologous chromosomes during meiosis

Cytokinesis

The division of a parent cell into two daughter cells as part of meiotic division

Seminiferous Tubules

Tubules located in the male testes, the site of spermatogenesis

Spermatogonium

A diploid parent cell that produces haploid sperm cells through meiosis

Spermatogenesis

The process of haploid sperm cell production in males

Spermatocytes

Diploid daughter cells produced from spermatogonia through mitotic division in the first stage of meiosis

Spermatid

Immature haploid sperm cells

Spermatozoa

Mature, motile sperm cells capable of fertilising an ovum

Oogonia

Diploid parent cells that produce haploid egg cells through meiosis

Oogenesis

The process of haploid egg cell production in females

Primary oocyte

Diploid daughter cells produced from oogonia through meiotic division in the first stage of meiosis

Secondary oocyte

Immature haploid egg cells

Polar body

Cells produced during meiotic division in females that don't develop into gametes

Ovulation

The release of a mature egg from the ovaries in preparation for fertilisation by a sperm cell

Gene Expression

The process of producing a functional protein from the DNA code of a gene

Genes

Sections of DNA that code for proteins; inherited from parent to offspring

Codon

Series of three bases on an mRNA strand that will match with the anticodons on a tRNA molecule to determine amino acid selection

Amino acid

The molecular building blocks of proteins

Translation

Reading of an mRNA strand by a ribosome to form a polypeptide chain from amino acids

Noncoding DNA

A section of DNA that doesn't code for a protein

RNA

(ribonucleic acid); a single-stranded molecule of genetic information essential for protein synthesis

Transcription

The production of an mRNA molecule from an unwound DNA double helix to be used for protein synthesis

mRNA

(Messenger RNA); single stranded copy of one strand of DNA; carries the code required by a ribosome to build a polypeptide chain from amino acids

Initiation

The process where DNA helicase breaks the hydrogen bonds between nitrogenous bases and the replication fork is formed

Elongation

The process where RNA polymerase moves along the exposed DNA strand, using it as a template to build an mRNA strand from free-floating nucleotides

Termination

The process of completing and releasing an mRNA molecule triggered by the ribosome reading a stop codon

Transcription Bubble

A region of unwound DNA approximately 12-14 base pairs in length, produced by DNA helicase breaking hydrogen bonds between base pairs

Polypeptide chains

A string of amino acids produced by a ribosome according to the genetic code provided by mRNA

Ribosomal Subunit

One large and one small subunit molecule are required to assemble a functional ribosome for translation

tRNA

(transfer RNA); A molecule that brings amino acids to a ribosome for translation and polypeptide production

Anticodon

A sequence of three bases on a tRNA codon that correspond to an attached amino acid and matched an mRNA codon

Ribosome

The organelle responsible for translation of the mRNA code into a polypeptide chain during protein synthesis

Condensation polymerisation reaction

The reaction between amino acids joining them by a peptide link while releasing a water molecule

Cytoplasm

Cell contents not including the nucleus

Epigenome

A range of chemical compounds that alter genetic function while leaving the genetic sequence unaltered

Germ line

Cells that form gametes and pass on genetic information from parent to offspring

Non-disjunction

The failure of chromatids to separate during meiosis, causing aneuploidy in a gamete

Spindle fibres

Long tubular structures produced by centrioles to attach to centromeres of chromosomes for separation in mitosis and meiosis

Aneuploidy

The condition of a gamete that has an abnormal number of chromosomes

Karyotype

An image of every chromosome of an organism, arranged to allow for comparison between chromosomes

Chromosome

A structure of the cell nucleus containing DNA wound around histone proteins

Homologous pairs

Corresponding chromosomes of the same shape in an individual produced through sexual reproduction; one of the chromosomes in the pair is inherited from the organism's father and the other from the organism's mother

Centromere

The location on a chromosome where sister chromatids adjoin and spindle fibres attach to separate chromatids during cell division

Dominant Allele

An allele that will be expressed phenotypically when paired with a recessive allele or another dominant allele

Recessive allele

An allele that will be suppressed when paired with a dominant allele and will be expressed phenotypically when paired with another recessive allele

Genotype

The combination of alleles for a particular trait present in an organism that determines its phenotype for that trait

Phenotype

The trait expressed in an organism determined by its genotype

Punnett square

A diagram used to predict likely percentages of genotype and phenotype of offspring based on the genotype of each parent

Autosomes

Any chromosome that is not a sex chromosome

Autosomal dominance

Dominance exhibited by any chromosome other than a sex chromosome causing traits or conditions to be expressed in the phenotype of an organism

Multiple Alleles

Phenotypic traits controlled by more than two alleles

Recombinant DNA

A DNA strand containing a genetic sequence artificially inserted in a laboratory

Target gene

The gene that codes for the desired protein to be transferred between organisms

Donor organism

The organism a target gene is removed from

Vector organism

The organism that received the target gene into its genome to be expressed as a protein

Restriction enzyme

An enzyme that breaks hydrogen bonds between nitrogenous bases at a particular sequence, leaving sticky ends

Recognition site

The sequence of bases recognised by a restriction enzyme as the location to break hydrogen bonds and expose sticky ends

Sticky end

The bases of a DNA molecule exposed when a restriction enzyme breaks hydrogen bonds between bases at a recognition site

Plasmid

A circular molecule of DNA found in the cytoplasm of bacteria

PCR

(Polymerase chain reaction); a technique that amplifies a short sequence of DNA

Gel electrophoresis

A method of separating DNA or other biological molecules according to their molecular size

Evolution

Changes in the phenotype of a species in response to selection pressures

Microevolution

Changes in allele frequency across a population of a species

Macroevolution

The accumulation of microevolutionary changes leading to long-term changes to a species, potentially leading to the emergence of one or more new species

Allele Frequency

The number of times an allele appears in a population when compared with all other possible alleles for a trait

Bipedalism

The ability of an animal to walk upright on two legs

Cranial capacity

The volume of the skull; used as an indicator of brain size

Random mutations

A change in the DNA sequence of an individual caused by random errors that occur during the DNA replication process

Homozygote

An organism carrying two of the same allele for a trait, whether they be dominant or recessive

Heterozygote

An organism carrying a combination of a dominant and a recessive allele for a trait, with the dominant phenotype expressed