Class notes
definitions, terminology, effective
- Course
- Life Sciences
- Institution
- 12th Grade
these notes provide clear definitions/ terminology for bio helpful for biological terms
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Isabelle BolesPaper 1
Genetics:
Genetics: branch of biology that studies hereditary and variation in organisms.
Chromatin Network: visible as thread like structures in the nucleus of an inactive
cell.
Chromosome: a structure made up of two chromatids joined by a centromere that
carries the hereditary characteristics within the DNA.
Chromatid: one half of a chromosome consisting of a protein core surrounded by
DNA that carries the hereditary characteristics. Two chromatids are joined by a
centromere to form a chromosome.
Gene: the unit of heredity transmitted in the chromosome which controls the
development of the characteristics.
Chromosome mapping: plotting of the relative positions of certain genes with
respect to the positions of the other genes in the same linkage group.
Nucleotide: the building block of nucleic acids RNA and DNA, consisting of a
pentose sugar, a phosphate group and a purine or pyrimidine nitrogenous base.
Nitrogenous bases: a nitrogen containing molecule which has the properties of a
base. E.g. purines and pyrimidines which forms the main part of the nucleotide.
DNA (deoxyribonucleic acid): located on the chromosome in the nuclei of all living
cells and carries the hereditary information of the organism.
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, Isabelle Boles
Messenger RNA (mRNA): responsible for carrying the genetic code transcribed
from the DNA to specialised sites on the ribosomes where the information is
translated for protein synthesis.
Transfer RNA (tRNA): carries specific amino acids to the mRNA codon in the
production of proteins.
Ribosomal RNA (rRNA): from the ribosomes and produce the proteins based on the
information from the tRNA.
Base pairing: purines pair with pyrimidines – adenine (A) always bonds to thymine
(T) and guanine (G) always bonds with cytosine in DNA. In RNA, however, uracil (U)
replaces thymine (T).
Codon: the corresponding three-base sequence on the mRNA required to specify
one amino acid in a protein chain on the DNA template.
Anticodon: a set of three-base sequence on the tRNA that corresponds with the
codon on the mRNA.
DNA Replication: takes place to produce two identical DNA molecules (DNA
unspirals, weak hydrogen bonds break, each separate strand of DNA attracts a new
complementary nucleotide partner, resulting in DNA containing half the original
molecule and a new complimentary half and is an exact copy of the original DNA) –
process occurs during mitosis.
Semi-conservative replication: the formation of new DNA that consists of a strand
of old DNA and one strand of new DNA.
Transcription: the enzyme-controlled process where the base sequence of
chromosomal DNA is transferred to mRNA to form a complimentary copy.
Translation: the process where the code on a piece of mRNA results in a specific
sequence of amino acids, to form a specific protein.
Protein: macro-molecules that contain the elements carbon, hydrogen, oxygen and
nitrogen and some may contain sulphur and phosphorus. Amino acids are the
building blocks of protein, these amino acids are joint by peptide bonds to form
peptide chains which then join to form a protein through the process of
polymerisation.
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, Isabelle Boles
Protein synthesis: a process which provides the sequence of the amino acids
combination that are unique to each individual. All cells, hormones (except sex
hormones), antibodies, blood and enzymes consist of proteins.
Mutation: any change that will result in the protein losing its ability to function or may
cause a mutation.
Mutagen: a factor that increases the chance of a mutation occurring.
Gene mutation: a change of one or more bases in the nuclear DNA of an organism
Point mutation: one base pair is incorrectly translated / transcribed.
Sense mutation: codon still codes for the same amino acid in a particular place.
Mis-sense mutation: new codon results in one wrong amino acid in a particular
place.
Nonsense mutation: mutation results in the transcription of a stop codon and hence
terminates the polypeptide chain early.
Chromosomal mutation: there is a mutation in the chromosome, affecting large
sections of the chromosome, and this usually occurs during cell division.
Beneficial mutation: change in phenotype to adapt to an environment. Will
contribute to the long-term survival of the organism.
Locus: this is the exact position or location of a gene on a chromosome.
Alleles: a pair of genes that are located at the same point on each of the two
homologous chromosomes and represent a specific trait – one from the father
(paternal) and one from the mother (maternal).
Homozygous: (homo: same, zygous: zygote). When two alleles of a pair of genes
are the same for a trait, e.g. both alleles are for red flowers, the cross will result in a
pure breed for red.
Heterozygous: (hetero: different, zygous: zygote). When two alleles of a pair of
genes are different for a trait, e.g. one of the alleles is for red flowers and one if for
white flowers, the cross will result in a hybrid.
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