All information on Genetics needed to be covered according to SAGS. Includes simplistic explanations of complex topics and diagrams to aid learning. Makes the learning of genetics (which is sometimes difficult) a lot easier. Over 50 pages of in depth explanation- ensuring work is covered thoroughly.
Genetics: Life at Molecular, Cellular and tissue level
Summary of Genetics Definitions: (35)
● DNA: Deoxyribonucleic Acid which is responsible for replication of material
(chromosomes) present in organisms. Carrier of genetic information.
● RNA: Ribonucleic Acid which acts as a messenger and carries instructions from DNA for
protein synthesis.
● Chromatin: chromosomal material made up of DNA, RNA and histone proteins found in a
non-dividing cell.
● Replication: the process of making a new DNA molecule from an existing DNA molecule
that is identical to the original molecule
● Transcription: DNA makes and codes for mRNA
● Codon: assortment of 3 nucleotides forming a genetic code which codes for amino acid
● Stop-Codon: 3 nucleotides which do NOT code for amino acid
● Mutation: any alteration in genetic makeup of organism
● Mutagen: physical or chemical agent speeding up mutation
● Gene Mutation: a small localised change in structure of DNA strand
● Point Mutation: change in single nucleotide
● Substitution: one nucleotide exchanged for another in DNA molecule
● Insertion: one or an extra nucleotide is inserted into DNA molecule
● Deletion: a nucleotide is removed from DNA molecule
● DNA profile: an individual's unique DNA fragments separated by electrophoresis
● Chromosome: a long, thread-like structure that makes up the chromatid network in nuclei
of cell. Are made up of strand of DNA wound around proteins called histones.
● Sex Cell: 46 chromoyyyyyfffgsomes (23 and 23)
● Somatic Cell: body cell (diploid) 23
● Diploid: 2 sets of chromosomes
● Haploid: 1 set of chromosomes (1 in each daughter cell, when gametes fuse = 2)
● Meiosis: cell division takes place in reproductive organs of both plants and animals to
produce gametes in animals and spores in plants.
● Crossing over: mutual exchange of parts of chromosome where maternal and paternal
information is shared.
● Chiasmata (breaking of parts of chromatin)
● Bivalent formed via synapsis (when chromosomes meet)
● Chromosomal nondisjunction: chromosomes fail to separate properly
● Aneuploidy: extra or missing chromosome (e.g: down syndrome = extra chromosome
21, trisomy)
● Karyotype = set of chromosomes in cell
● Autosomes = non-sex chromosomes (human)
● Sex chromosome = gonosome
, ● Genetics: the study of heredity and genetic variation
● Alleles: genes responsible for different variations of a trait found in the same locus on
homologous chromosomes.
● Gene: section of DNA that controls a hereditary characteristics and codes for a specific
function
● Father of genetics = gregor mendel
● Gene Pool: set of genes in sexually reproductive organisms
● Genotype: gene of an organism that carries chromosomes which is inherited by parents.
● Phenotype: physical appearance. Programmed by genes in genotype and outside
factors.
● Genome: complete set of genetic instructions necessary to create an organism
● Harmful: chromosomal mutation
● Beneficial: change in phenotype (adaption)
● Neutral: doesn’t affect organism
DNA: Structure and coding (SAGS Breakdown:)
➔ How the work done by many scientists allowed Watson and Crick to unravel the
genetic code (1953) and, in the 1960s the mechanism of protein synthesis and
DNA replication.
➔ The structure and location of DNA and RNA (mRNA, tRNA) in a cell
➔ Simple structure of nucleotides, including names of the four nitrogenous bases of
DNA (adenine = A, thymine = T, cytosine = C, guanine = G) and that uracil replaces
thymine in RNA and which bases are complementary
➔ Mitochondrial DNA also exists and remains unaltered from mother to child. That
this is used to determine relatedness.
Background (Understand):
● Nucleic acids = molecules of life
● They have the capacity to store information that controls cellular activity and
development of entire organism
● They do this by controlling the synthesis of proteins
● Proteins: make up structure of body + control chemical processes inside cells (enzymes
are proteins)
● Proteins ultimately control structure + functioning of all living organisms
● Two nucleic acids:
- Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
Who Discovered the Structure of DNA (SAGS):
, ● King’s College, London (early 1950s): Maurice Wilkins and Rosalind Franklin were trying
to work out structure of DNA
● Took experimental approach: looked at X-ray crystallography (diffraction images of DNA)
● At same time at Cavendish Institute (Cambridge University) graduate students Francis
Crick and research fellow James Watson also became interested in determining the
structure of DNA
● They analysed the x-ray data collected by Rosalind Franklin and others
● They built a model out of brass plates and clamps and other bits of laboratory equipment
and realised that nucleic acids are arranged like a twisted ladder (with 2 runners made of
phosphates and sugars and a series of rungs made of pairs of organic compounds
known as bases)
Genetic Replication (unravelling of genetic code) (SAGS):
● Watson and Crick developed ideas about genetic replication in a second article in
Nature, published May 30th 1953
● Pairing of bases (A with T and C with G) showed that ---> given a sequence of bases in
one strand, the other strand was automatically determined
● This meant that when two strands separated, each served as a template for a
complimentary new chain (thus each strand could replicate)
● After ‘double helix’ model, there were still Q’s about how DNA directs the synthesis of
proteins
● 1961: Francis Crick and Sydney Brenner provided genetic proof that a Triplet code was
used in reading genetic material in DNA and transferring the information from nucleus to
cytoplasm via RNA to where proteins are made
● The two showed that in DNA- form is function: double-stranded molecule could both
produce exact copies of itself (replicate) and carry genetic instructions
● Thus the sequence of bases in DNA forms a code by which genetic information can be
stored and transmitted
Who Won The Nobel Prize (understand):
● Rosalind Franklin: only researcher with a degree in chemistry
● Worked alone and suspected (through her x-ray diffractions) that all DNA molecules
were helical in structure but she was reluctant to announce this finding until she had
sufficient evidence
● She died of cancer at 37, before expressing her views
● 1962: Watson, Crick and Wilkins won nobel prize for physiology/medicine (Franklin was
dead)
● Nobel prize only goes to living recipients and can only be shared among 3 winners
● Would she have received the prize if she were alive though? (women in era, oppressed
and not recognised)
, DNA:
The Location of DNA (SAGS):
● Found mainly in the nucleus of a cell where it forms an important part of chromosomes
that make up chromatin network
● Chromatin: chromosomal material made up of DNA, RNA and histone proteins found in
a non-dividing cell
● DNA molecule, coiled so that these long structures can fit inside nucleus (2m of DNA in
every cell)
Extracellular DNA (understand):
● Small amounts of DNA found outside the nucleus in: mitochondria in plants and
animals as well as in chloroplasts in plants
The Structure of DNA (SAGS):
● Shape: long, twisted ladder. Two strands twist to form stable, 3-dimensional double
helix.
What Units Make Up DNA (SAGS):
● DNA molecule: long chain (polymer) made of small units (monomers) i.e: building blocks
called nucleotides. Each nucleotide is made up of a:
❏ Deoxyribose (sugar molecule)
❏ Phosphate molecule (P)
❏ Nitrogenous base which may be:
- Adenine (A)
- Thymine (T)
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