The document contains specification points separated by synoptic themes of the entire A Level biology course. Each specification point is expanded on to provide a comprehensive guide for exams.
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GENETICS Definition Example
2.6 Transcription:
Protein RNA polymerase binds to a section of the
synthesis DNA at a certain locii.
DNA unzipped by breaking the hydrogen
bonds
Complementary bases attached to make
the antisense strand of the mRNA.
Start codons and stop codons indicate
where the transcription begin and end.
Leaves via nucleaic pores to the
ribosomes
Start and stop codons indicate where
Translation:
tRNA attaches complementary anti
codons to the codons.
Have amino acids attached to a binding
site which makes the polypeptide chain
Folded into the primary structure of the
protein.
2.7 The Non-overlapping genetic code:
Nature of the transcribed in threes
Genetic Code Degenerate: multiple codons can code for
the same amino acid.
2.8 gene Gene: is a sequence of bases on a DNA Patterns of inheritance can be in
2.13 molecule that codes for a through punnet squares and
sequence of amino acids in a polypeptide pedigree charts
chain
Allele: different version of a gene
Genotype: combination of alleles for a
characteristic
Phenotype: physical characteristic
expressed from genotype
Dominant: alelle that is favoured in
inheritance. Only requires one to be
expressed
Recessive: alelle that is not favoured in
inheritance therefore two must be present
, in order for this characteristic to be
expressed.
Incomplete dominant?
Homozygote: same two alelles
Hetereozygote: 2 different (recessive and
dominant) alleles.
2.11 DNA Semi-conservative replication: one strand
replication is from the original DNA.
IMPORTANCE: Genetic continuity. Cells are
also replicated often in body for growth
and repair therefore it is necessary
remaining the same.
Ocurs during the S-phase of interphase
when number of DNA molecules doubles
before mitosis
DNA helicase unwinds the DNA by
breaking the hydrogen bonds so two anti-
paralell polynucleotide strands make two
single polynucleotide strands.
Both strands are a template for new
strand to form as DNA polymerase joins
complementary bases.
DNA POLYMERASE:
Nucleoside triphosphates found in
nucleaus which are free floating bases
with three phosphate groups. This allows
them to become activated for DNA
replication
These bases align with the
complementary base on the template
strand
The enzyme catalyses reactions between
the deozyribose and phosphate group
making phosphodiester bond which forms
the sugar phosphate backbone. The
energy needed for this is provided by the
releasing of the two phosphate groups on
the activated nucleotide.
Hydrogen bonding forms between C-bases
to make a new DNA strand.
Mendor and Stahl experimental vidence
, for DNA replication involves the use of
generations of N15 AND N14 nitrogenous
bases in bacteria.
One N14 makes light band
Second genration, adding N15, found that
strand was medium- if conservative
replication ocurred would have been two
bands present.
Second generation of n15 showed tjeir to
be one strand of medium and one strand
of light disporoving fragmentation theory.
2.12 Errors in the genetic code give rise to
Mutations mutations (randomly)
Example would be mutation for the CFTR
protein meaning it is unable to allow
chloride ions to be pumped through.
3.8 Loci and Location of a gene on a chromosome People with red hair are likely
sex linkage Linkage: Two genes found on the same green eyes due to the genes bei
chromosome will be inherited together. on the same chromosome
During meiosis, crossing over ocurs where
sections of the chrosome are cut from the
ends and swapped with the non-sister
chromatid.
Inheritance of a gene therefore
dependent on locii and distance from one
another.
Sex linkage: Certain genes found on the X
chromsome and not the Y chromosome
meaning men more likely to inherit
recessive disorders.
chiasmata
3.9 Meiosis 2 divisions and produces 4 genetically
different haploid daughter cells.
Independent assortment: the process by
which the chromosome are randomly
arranged and inherited.
Crossing over: chiasma, process whereby
small sections of the chromosomes are
cut and exchanged with the non-sister
chromatid.
, 3.10 Mitosis Produces 2 genetically identical daughter Plants have stem cells in meris
diploid cells. present for whole life.
Used in asexual reproduction
Growth and repair
Interphase: Ocurs in 3 stages where
organelles double.
Prophase: chromsome condenses, spindle
fibres start to form and organelles double.
Metaphase: chromosomes line at the
equator of the cell
Anaphase: chromosomes pulled across via
spindle fibres to poles of the cell
Telophase: Nuclear membrane begins to
reform and chromatin uncondenses.
Cytokinesis:
3.12 Process by which genes are switched Fibrodysplasia Ossificans Pro
Differential on/off and therefore expressed. (FOP)
Gene In prokaryotes: Repressor molecule Growth of bone in odd places lik
Expression often binds to gene. An external cue will or connective tissue. Gene not sw
bind to this repressor molecule and allow in white blood cell so when
the RNA polymerase to bind to the DNA damaged, the white blood cells m
strand and transcribe the gene to make produces the protein diffusing to
the corresponding proteins cells. This causes the muscle cell
Lac Operon: expressing other genes that turn t
Escherichia Coli which are bacteria that bone cells.
only produce Beta-galactosidase to break
down lactose. When lactose not present,
repressor molecule binds to operator so
Beta galactosidase not produced. When
lactose is present, It binds to the
repressor molecule so the MRNA coding
for the enzyme is transcribed and
translated.
Eukaryotes: RNA polymerase must
attach to the promoter region for the
transcription of a gene to ocur. It also
requires the binding of a regulator
protein. Repressor proteins can prevent
the transcription of such genes.
3.14 Arises from interaction between
Phenotype environment and genotype
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