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higher biology - unit 1
Terms in this set (201)
strands of DNA are made up of repeating units called __________
nucleotide is made up of:
four types of bases:
what links the phosphate and sugar, and isn't easily broken and joins nucleotides into a permanent strand ?
strong chemical bonds
deoxyribose sugar diagram
antiparallel DNA strands diagram
bases are held together by?
weak hydrogen bonds
what are prokaryotes?
organisms that lack true membrane bound nucleus
where is the DNA found in prokaryotes?
example of prokaryote
what are eukaryotes?
organisms that have a membrane bound nucleus that stores their genetic information
example of eukaryotes
fungi, animals and plants
organisation of chromosomal DNA in prokaryotes?
organisation of chromosomal DNA in eukaryotes?
linear and circular ( in mitochondria and chloroplasts)
plasmids are found in one type of eukaryote
linear chromosome diagram
circular chromosome diagram
(found in chloroplast and mitochondria)
DNA is wrapped around ___________ ___________
packaging proteins or histones
DNA can reproduce itself and this is called ____________
DNA replication stages
1) DNA double helix unwinds
2) weak hydrogen bonds break causing 2 strands to separate (unzipped)
3) free DNA nucleotide joins complimentary pair on open strand
4) weak hydrogen bonds reform between base pairs
5)strong chemical bond forms between both nucleotides
6)newly formed daughter DNA (identical to original) begins to wind into double helix
what enzyme controls stage 5 of DNA replication?
what does DNA polymerase need to be present before it can start replicating DNA?
DNA replication can only happen from __ to __ because DNA polymerase enzymes can only add nucleotides towards the 3' end
5' to 3'
DNA replication diagram
this strand is replicated continuously
this strand is replicated in fragments
fragments on lagging strand are joined then together using the enzyme DNA _______
DNA unwinding occurs at multiple locations along a DNA molecule at ___________ ______
what is Polymerase chain reaction used for?
to amplify DNA fragments in vitro and so creates many identical copies of the fragments
what does vitro mean?
outside the cell
initial requirements for PCR
-heat tolerant (Taq) polymerase
example of DNA template for PCR
what are complimentary primers needed for in PCR
to target specific DNA
what is a thermal cycling
a cycle consisting of three steps carried out at different temperatures
five uses of practical applications of PCR
-diagnosis of genetic disorders
example of use of PCR for DNA fingerprinting
semen, blood, tissue from crime scene/ tissue typing / paternal testing
example use of PCR for diagnosis of genetic disorders
embryonic cell DNA for paternal testing
example use of PCR for investigating evolution
example use of PCR for research
cancer cell research and viruses
example use of PCR for archeological studies
studying remains of extinct species
stages of PCR
2) annealing of primers
3) DNA extension
what happens during denaturation of PCR?
the mixture is heated to 95 degrees to break hydrogen bond between bases (Taq polymerase does not denature) and separate DNA strands (denatures DNA)
what happens during annealing of primers in PCR?
cooled down to 55 degrees, this allows complimentary primers to anneal (form hydrogen bond) to target sequences on single stranded DNA
what happens during DNA extension in PCR?
mixture heated to 72 degrees, the optimum temperature for the Taq polymerase to extend the complimentary strand in a 5' to 3' direction
temperature for stage 1 of PCR
temperature for stage 2 of PCR
temperature for stage 3 of PCR
72 degrees (optimum temp for Taq polymerase)
how are specific primers chosen for PCR?
the primer is complimentary the specific target sequences at the 2 ends of the region to be amplified
what is the role of Taq DNA polymerase in PCR?
produces replicate of DNA strand of the target DNA
an organisms __________ is determined by the sequence of bases in its genes- genetic code
an organisms ___________ is determined by the protein synthesised when the genes are expressed
3 steps to ones phenotype
1) DNA base sequence determines genotype
2) proteins synthesised when genes expressed
3) proteins determines phenotype
the genetic code used in ___________ ___ ____________ is found in all forms of life
transcription and translation
proteins produced are affected by ______ ___ ______ cellular environmental signs
intra and extra
mRNA is transcribed from DNA in the NUCLEUS and translated into proteins by ribosomes in the ______________
proteins have a large variety of structure and shapes resulting in a wide range of _____________
amino acids are linked by __________ _____ to form proteins. polypeptide chains fold the 3D shape of a protein, held together by hydrogen bonds and other interactions between amino acids.
gene expression diagram
where does translation of DNA happen ?
the sugar present in RNA nucleotide
number of strands of RNA
complimentary base pair of adenine in RNA
three types of RNA
mRNA, rRNA, tRNA
what does mRNA (messenger) do?
carry a copy of the DNA code from the nucleus to the ribosome
what does rRNA (ribosomal) do?
rRNA and proteins form the ribosome
what does tRNA (transfer) do?
carry a specific amino acid to the ribosome to be inserted into a protein
what is genetic code?
the information that DNA contains that takes the form of a code
codons are the ________ _____ for the genetic code
how many bases makes up a codon ?
3 (giving 64 different combos)
what does RNA polymerase do in transcription?
moves along DNA unwinding and unzipping the double helix and synthesising a primary transcript of RNA from RNA nucleotides by complementary base pairing
the primary transcript mRNA is made up of ______ ____ ______
introns and exons
what are introns?
non-coding sequence of DNA (non-coding regions)
what are exons?
sequence of DNA that codes for proteins (coding regions)
what is a mature transcript?
after introns are cut out and removed from the primary transcript and then exons are spliced together forming the mature transcript
alternative RNA splicing diagram
what is alternative RNA splicing?
a primary transcript can form different mRNA molecules depending on which exons are included in the mature mRNA
how does the mRNA leave the nucleus?
through a nuclear pore into the cytoplasm
the tRNA has triplet bases called ___________
each tRNA carries a specific ___________ _____
the triplet codons on the mRNA are recognised by the anticodons on tRNA which ___________ the genetic code into a sequence of amino acids
an ________ within the ribosome is responsible for joining adjacent amino acids with peptide bond
the mRNA codon AUG (tRNA=UAC)
the mRNA codons UAA, UAG, UGA
where does translation happen?
mRNA is translated into ________
the message of mRNA is made up of _____ ________ called codons
post translational modifiction
this process makes changes to the chemical structure of the polypeptide chain by:
-cutting and combining polypeptide chains
-adding phosphate or carbohydrate groups
therapeutic value of stem cells?
you can use stem cells to repair or replace damaged or diseased tissue
examples of use of stem cells
-bone marrow transplants to treat cancer
-potential to treat diabetes, alzheimer's disease, parkinson disease
what can stem cells be used as for research?
they can be used as models of real tissue for drug testing, understanding disease progression, induced pluripotent stem cells (IPS)
what is differentiation?
the process in which unspecialised cells become specialised for a particular function
all body (somatic) cells contain ___ of the genetic information to produce every cell in the body during differentiation
in differentiation many genes remain switched __
in differentiation some genes that control ________________ features of specialised cell are switched on
in differentiation unnecessary genes are switched ___
are the only site of mitosis in plants and the point of plant growth
two types of meristem
- apical, in the roots and shoots
-lateral, in stems that increase
embryonic stem cells
they have the potential to become different types of cells and undergo mitosis indefinitely (under the correct conditions). They are described as PLURIPOTENT
adult stem cells
they maintain the growth and repair of the body, there are many types of adult stem cells which have a narrower differentiation potential because their genes are already switched off. they are MULTIPOTENT
model answer on how stem cells can be used treat a disease
disease: diabetes, alzheimer's, parkinson
the stem cells are directed to differentiate into specific cell types to replace damaged/ diseased tissue
reasons FOR the use of embryonic stem cells of research
- have the potential to benefit humanity
-can be used in research and help patients with medical problems
-at 14 days or less an embryo is not sentient (does not have a brain, nervous system, consciousness)
-stem cell uses embryos that were from IVF but were not used so they would be destroyed anyway
reasons AGAINST use of embryonic stem cells
-a human life begins when a sperm cell fuses with an egg cell and it is inviolable (sacred and must not be harmed)
- a unique version of DNA is created at conception
-violates the sanctity of life
solutions to the ethical problems of stem cell research
-induced pluripotent stem cells (IPS)
is an organisms entire hereditary information encoded in DNA
only __ of the genome is made up of genes, the other 98% have other functions
the 98% of the genome which is not made up of genes have what two functions
-regulation of transcription
-transcription of non-translated RNA
transcription of non- translated RNA
these types are transcribed but not translated into proteins, tRNA and rRNA
regulation of transcription
RNA polymerase is unable to start transcription on its own. it needs transcription factors, these can take the form of activators (help and start) and repressors (prevent)
single gene mutation
involves the alteration of a DNA nucleotide sequence
single gene mutations impact ___________ nucleotides and can be a SUBSTITUTION, DELETION, INSERTION
single gene mutation can either be _______ or ____________ mutation
occur at a single point i.e. SUBSTITUTION
(generally not too harmful as only one amino acid is affected so the protein will probably be functional)
frame shift mutation
this changes the open reading frame by moving it one base pair forward or backward i.e. DELETION OR INSERTION
(generally more harmful since all the amino acids in the primary structure of the protein will have changed from the mutation onwards, protein likely to be non-functional)
substitutions can have three different impacts
a single amino acid is changed
inserts a STOP codon, produces a truncated protein
this does not change the protein sequence
mutations in non-protein coding sequences can also impact protein expression in two ways
-splice site mutations (can alter post-transcriptional mRNA processing)
-regulatory sequence mutations (can alter gene expression)
naturally occurring mutations occur ____________ and _______________
randomly and spontaneously
example of mutagenic agents
gamma rays, x-rays and UV light
some mutagens are also _____________ (cancer causing mutations)
mutations are considered to be the raw material of ___________ as it gives rise to better genes and alternative genes which natural selection can act upon
four types of chromosome mutations
section is deleted
section is duplicated
section is flipped
section of two different chromosomes switch places
organisms that contain more than 2 sets of chromosomes e.g. triploid, tetraploid
polyploidy occurs due to errors during _____________ of chromosomes during cell division (total nondisjunction of spindle fibres)
polyploidy is common is ________ species
polyploidy plants tend to be ________ (increased yield)
closely related plants species can be crossed to form polyploids, the plants show HYBRID VIGOUR, resulting in HIGHER yield, disease RESISTANCE and drought RESISTANCE
importance of polyploidy in evolution
-provides additional material upon which natural selection can work on
-they are more vigorous/disease resistant/ grow faster
the changes in organisms over generations as a result of genomic variation
evolution of species involves 4 main categories of change
-selection (natural, sexual)
DNA can be transferred in two ways
vertical transfer occurs through _______ and _________ reproduction
in prokaryotes DNA can be passed in two ways
-vertical (asexual reproduction)
-horizontal (where DNA is passed within the same generation)
how can horizontal transfer of DNA happen in prokaryotes
-direct DNA transfer
some prokaryotes can also transfer DNA to ______________
1) temporary bridge forms between two bacterial cells that differ in genome
2) transfer of plasmid happens
3) the donor cell is unchanged, the recipient cell now has a copy of the plasmid
is the NON-RANDOM increase in the frequency of DNA sequences that increase survival and the NON-RANDOM decrease in DELETERIOUS sequences
stages of natural selections
1)more offspring are produced than the environment will support and a large number die before reaching reproductive age
2)as members of a species are not all identical (show variation) some will be more suited to the environment than others
3)these individuals whose phenotype are more favourable survive and pass on their genes to the next generation, while those less suited die and do not pass on their genes
4)over many generations, the best phenotypes are selected
natural selection of characteristics that increase reproductive success
sexual selection is NON-RANDOM and operates in two ways
-male-male competition (for access to mates and territory)
example of male-male competition
example of female choice
some individuals have better ___________ success than others and these traits are selected for
any any characteristic that shows ____________ ________ (e.g. height, mass) can be affected by selection
selection pressure goes against extreme variants and favours the intermediate versions of a trait. Leads to a reduction in genetic diversity
common during period of environmental change. selection favours a version which was initially less common
selection pressure selects extreme versions of a trait at the expense of the intermediate version, can result in the population being split into two distinct groups. driving force behind SPECIATION
example of stabilising selection
natural human birth mass, babies of very low body mass are more susceptible to fatal diseases and those of a very high birth mass encounter difficulties passing the mothers pelvis
example of directional selection
european black bears, increased average body size during the ice age, since a larger body losses less heat, a larger body is of survival value int he cold climates
example of disruptive selection
plant and animal breeding involving artificial selection of extremely large and small varieties e.g. dogs
is the RANDOM increase or decrease in frequency of genetic sequences, it differs from natural selection which is non-random
evolution due to genetic drift is not influenced by __________ or __________________ pressures
genetic drift has the greatest influence in ________ populations
genetic drift occurs due to 2 things
these change the DNA but not the proteins structure, they cannot influence natural selection but can alter genetic drift
a small part of a large population is removed, that population will continue to diverge from the initial population through random changes
a group of organisms that can interbreed to produce fertile offspring
Is the formation of new biological species by evolutionary changes
2 types of speciation that can occur
gene flow between 2 populations is prevented by a GEOGRAPHICAL BARRIER
example of allopatric speciation
darwin finches, separated by sea
2 or more populations live in close proximity to one another in the same environment yet they become genetically isolated, gene flow is prevented by BEHAVIOURAL or ECOLOGICAL BARRIERS or by the occurrence of POLYPLOIDY in plants.
sympatric speciation is promoted by ________________ selection
example of sympatric speciation
form where the ranges of two closely related species overlap. Within the zone members of the two species interbreed.
if one disappears, breaking the chain, then they may become ___________ ____________
what can genomic sequencing be used for?
to determine the order of nucleotide bases for genes or even entire genomes
what was the first sequencing method ever used
what are the more modern techniques for genomic sequencing?
using fluorescent labelling of modified nucleotides and bioinformatics to determine base sequencing
the use or development of statistical analysis and computers (software tools) to understand/ produce biological data
what other genomes have been sequenced apart from the human genome?
-disease causing organisms (e.g. viruses and bacteria)
-pest species (mosquitos)
-model organisms used in research (mouse of fruit fly)
this involves the comparison of genome sequences:
-from different species
-from members of the same species
-from cancerous cells and normal cells
highly conserved genes
these genes are very similar across species, and are often involved in basic cellular processes
study of genome comparison can be used to understand ______________ changes
is the study of evolutionary relatedness between organisms
sequence of evolutionary events can be determined using:
-genome sequencing comparisons
-fossil evidence (using half life)
-the quantity of molecular differences between 2 groups is a measure of how long ago they shared a common ancestor
major events in evolution
-evolution of life on earth
-evolution of cells resembling prokaryotes
-evolution of last universal ancestor (prokaryote)
-evolution of cyanobacteria (prokaryote able to photosynthesise)
-evolution of eukaryotes
-evolution of multicellular organisms
-evolution of animals
-evolution of vertebrates
-evolution of land plants
three domains of life
_______________ RNA (rRNA) nucleotide sequences have been studies because they are shared by all living things
sequencing a persons DNA is becoming ________ and ___________
the probability of getting a disease is predicted, if an individual is at high risk, preventative measures can be taken
personalisation of drug doses based on genetic information of drug metabolising pathways
ethical issues with personal genomics
GENETIC DISCRIMINATION may occur - insurance companies, banks and others may decline service or increase premium as a result of finding less desirable traits e.g. degenerative diseases
set up to check the experimental method. i.e. if new fertiliser was being tested in a field trial a positive control would be plots with existing fertiliser
set up to be sure that the variable under investigation is causing the result. i.e. if new fertiliser was being tested in a field trial then plot with no fertiliser would act as negative control
explain why cells need to carry out DNA replication
so new cells have the same genetic material as the original cell or to maintain the number of chromosomes in new cells
effect of mutation of regulatory sequences
alters the way in which genes are expresses in the phenotype
effect of splice site mutations
can cause introns to be left in the mature mRNA, leading to altered protein
How are hybrid zones maintained?
-the hybrid offspring are less fit or sterile and are eliminated by natural selection
-members of each species recolonise the hybrid zone and undergo further hybridisation to repopulate the zone
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