Biology

Gene

DNA sequence coding for a protein. Nucleotide sequence (DNA, RNA) which determines the amino acid of a protein or RNA (coding sequence) or controls where and when a protein or RNA molecule is to be produced (regulatory sequence)

Coding region

Nucleotides coding for the amino acid sequence of a protein

Non-coding region

Regulatory sites, sites binding RNA-polymerase, sites binding transcription factors, introns

Chromatin

A complex of DNA and proteins (RNA) packaging DNA in the eukaryotic nucleus

Nucleosome

Basic, repetitive, unit of chromatin

Centromere

The strongest and thinnest region of the chromosome. It holds the two sister chromatids.

Functions in:

- sister chromatid replication

- kinetochore formation

- pairing of homologous chromosomes

Kinetochore

A protein structure on the centromere that links the chromosome to the microtubules of the mitotic and meiotic spindle

Telomere

A region of highly repetitive DNA at the end of linear chromosomes; every time a cell divides, telomeres shorten; aging; telomeras

Metacentric

Both arms are equal in length

Submetacentric

Arms length are unequal, long arm “q” and short arm “p”

Acrocentric

The “p” arm is so short that it shard to observe, but still present

Telocentric

The centromere is located at the terminal end of the chromosome

Constitutive heterochromatin

Highly condensed and functionally inactive, contains tandemly repeated DNA sequence blocked genes which are not transcribed, localised at centromeres and near telomeres

Facultative heterochromatin

Temporarily inactivated euchromatin, contains temporarily repressed genes, regulates gene activity

Karyotype

The quantitative and qualitative characteristic of the chromosomal set of a eukaryotic species

Autosome

A non-sex chromosome. It is an ordinarily paired type of chromosome that is the same in both sexes of a species

Sex-chromosomes

Non-autosomal chromosomes

Dark bands

Heterochromatin, replicates late, rich in A-T bp

Light bands

Euchromatin, replicates early, rich in G-C bp

Heterochromatinization

Inactivation of one of the X chromosome copies in the interphase of somatic cells of female mammals and transforming it into a barr body

Barr body

Is the inactive X chromosome in a female somatic cell

Aneuploidy

The condition of having an abnormal no of chromosomes in a haploid set

Trisomy

A condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities

Monosomy

Condition of having a diploid chromosome complement in which one chromosome lacks its homologous partner

In vitro

Outside a living organism

In vivo

Inside a living organism

Cell cycle

Cell reproduces by carrying out an orderly sequence of events in which it duplicates its contents and then divides in two

G1 phase

Intermediate phase between the end of cell division in mitosis and the beginning of DNA replication during S phase

S phase

Phase which DNA is replicated, between G1 and G2 phase

G2 phase

Period of rapid cell growth and protein synthesis during which the cell prepares itself for mitosis

M phase

The cell divides its copied DNA and cytoplasm to make two new cells

Asexual reproduction

Involves a single cell dividing to make two new identical daughter cells (Mitosis + binary fission)

Sexual reproduction

Involves two new cells (egg + sperm) joining to make a new cell (zygote) that is not identical to the original cells (Meiosis)

Karyogenesis

Division of nuclear material in cell division

Cytokinesis

Physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells

Centrosome

An organelle, principle microtubule- organising centre in animal cells. Duplicates same time as DNA replication, aka centrosome cycle

Kinetochore

Structure that specifies the attachments between the chromosomes and microtubules of the spindle, is essential for accurate chromosome segregation

Leptotene

The chromosomes become visible under the light microscope

Zygotene

Homologous chromosomes are paired into synapsis; synaptonemal complex – involved in the process of genetic recombination

Pachytene

Bivalents are formed; crossing-over – recombination between homologous chromosomes

Diplotene

The bivalents begin to separate and appear cross-shaped structure – chiasmata

Diakinesis

Maximal condensation

Synaptonemal complex

Hold the bivalent together and align the homologs so that the strand exchange can readily occur between the non-sister chromatids

Chiasma

Structure that corresponds to a crossover between non-sister chromatids

Synapsis

A process in which the paired homologous chromosomes become associated with one another

Nondisjunction

Mistakes in separation of chromosome or chromatids

Acrosomal reaction

The cap of the acrosome breaks down and releases hydrolytic enzymes – hyaluronidase, acrosin

Nucleoside

Nitrogenous base + pentose

Nucleotide

Nitrogenous base + pentose + phosphate

DNA polymerase

Synthesis DNA using a parental strand as a template

Base-pairing

Determines which of the four nucleotides will be selected

Discontinuously

Separate, in small pieces – DNA pol. moving backward

DNA topoisomerase

Relieve the tension that builds up in front of a replication fork

Telomerase

Replicates the ends of eukaryotic chromosomes

Telomeres

Long, repetitive nucleotide sequences which form structures that mark the true ends of a chromosome

Cockayne syndrome

Is a rare autosomal recessive genetic disorder:

- poor growth, microcephaly, progeria (premature aging), sensitivity to sunlight, moderate to profound developmental

Xeroderma pigmentosum

Is a rare, autosomal recessive disorder:

- an impairment of the skin's ability to repair damage from ultraviolet (UV) light

- photosensitivity, skin changes + a high incidence of skin cancer at very young age

Transcription

The process by which genetic information from DNA is enzymatically transferred (copied) into a complementary RNA molecule

mRNA

Serves as a template for protein synthesis (translation)

rRNA

Builds ribosomes

tRNA

Transports amino acids (translation)

Exon

Any region of DNA within a gene that is transcribed to the final mRNA molecule

Intron

Non-coding sections of DNA, which are spliced out in mature mRNA

Replication

Both DNA strands are copied

Transcription

Only one strand is copied into mRNA

Structural gene

Single stranded DNA sequence transcribed into a single molecule of rRNA or tRNA or in several mRNA molecules.

Terminator

A regulatory DNA-seq. at the end of the operon. When transcribed, it signals the end of transcription

Genetic code

The set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins (amino acid sequences) by living cells. defines how sequences of nucleotide triplets, codons, specify which AA will be added next during protein synthesis the alphabet, the rules by which the genetic information is coded and decoded.

Actinomycin D

Antibiotic that inserts into complementary bases in the DNA-template

Tetracyclins

Antibiotic that blocks the binding of АА-tRNA to ribosomal A-site

Streptomycin,neomycin

Antibiotic that inhibits the binding of mRNA to the ribosome

Erythromycin

Antibiotic that blocks translocase

Amopen,Cephalex

Antibiotic that inhibits peptidyltransferase

Ciprofloxacin

Antibiotic that inhibits replication and translation

Toxin amantidin (mushrooms)

Antibiotic that inhibits RNA-polymerase ІІ and ІІІ

Reading frame

A codon is defined by the initial nucleotide from which translation starts and sets the frame for a run of uninterrupted triplets, known as open reading frame

Start/stop codons

The actual frame from which a protein sequence is translated is defined by a start codon = initiation codon (first AUG codon in mRNA). The three stop codons = termination codons  are: UAG, UGA and UAA

Degeneracy

The redundancy of the genetic code. It has redundancy but no ambiguity - although codons GAA and GAG both specify glutamic acid (redundancy), neither of them specifies any other AA (no ambiguity). Errors in the third position of the triplet codon cause only a silent mutation

Apoptosis

Programmed = cell death in cell

Autophagy

Controlled by a cascade of proteins and protein complexes, each regulating a distinct stage of autophagosome initiation and formation

Transition

If a purine is replaced by another purine or a pyramidine replaced by another pyramidine

Transversion

If a purine is replaced by pyramidine or vice-versa

Open reading frame

A continuous stretch of codons that begins with a start codon (usually AUG) and ends at a stop codon

Multiple reading frames

Lead to the possibility of overlapping genes; in viral, prokaryote, and mitochondrial genome

Cystic fibrosis

Deletion of three nucleotides in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that results in the loss of the amino acid phenylalanine and causes an incorrectly folded protein.

Frameshift mutations

Indels of a single nucleotide in a codon shift the reading frame so that the same sequence of nucleotides encodes a different AA

Duplications

Doubling of a section of the genome during crossing over between sister chromatids that are out of alignment can produce one chromatid with a duplicated gene and the other with the two genes with deletions

Inversions

Break in two sites of the chromosome, rotation at 1800 and inverted arrangement of a chromosomal segment

Translocation

Transfer of a piece of one chromosome to a nonhomologous chromosome

Hybridisation probe

A fragment of DNA or RNA of variable length (usually 100–1000 bases long) which can be used in DNA or RNA samples to detect the presence of nucleotide sequences (the target) that are complementary to the sequence in the probe

Southern blotting

Detection of a specific DNA sequence in DNA samples. Combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization

Northern blotting

Detect specific RNA molecules among a mixture of RNA. Used to analyse a sample of RNA from a tissue or cell type in order to measure the RNA expression of particular genes

DNA sequencing

The process of determining the precise order of nucleotides within a DNA molecule

Tumour

An abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues; uncontrolled and progressive growth

Autonomy

Uncontrolled proliferatio

Adaptivity

Plasticity

Atypism

Immunological, biochemical, genetic etc

Aggressiveness

Invasion and metastasis

Oncogenes

Mutated normal genes which upon hyperactivation transform a normal cell into a tumor cell. Their normal, nonmutated analogue is the protooncogene