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202 Cards in this Set

  • Front
  • Back

Advantage to having small cells

Larger sa:v allowing rapid absorption of substances/secretion of waste


The smaller the cell the shorter the diffusion pathway across the membrane and around the whole cell

Why do epidermal transfer cells in broad beans/endothelium cells in the gut/arbuscles in plants have proliferations?

Provide larger sa:v to allow substances to be absorbed quickly into the blood system/seed

Reasons for compartmentation in cells

Maintain different environments to allow incompatible processes to occur simultaneously


Keeps enzymes, toxic substances etc in separate locations


Destruction of substances and organelles


Cells secrete and internalise proteins in ER/Golgi

Examples of prokaryotes

Bacteria and Archaea

Examples of eukaryotes

Plants, protists, fungi and animals

Prokaryotes / eukaryotes which is unicellular /multicellular?

Prokaryotes unicellular


Eukaryotes multicellular

Genetic organisations in eukaryotes /prokaryotes

Eukaryotes - linear, associates with Justine proteins to form chromatin =chromosomes


Prokaryotes - circular and free without proteins in cytoplasm

Which type of cell has a cytoskeleton -eukaryotes or prokaryotes?

Eukaryotes

What are the cell walls in eukaryotes /prokaryotes made of?

Prokaryotes -Peptidoglycan =sugars and peptides Eukaryotes -cellulose or chitin

Which type of cells is flagellum present and what is it made of?

Prokaryotes and eukaryotes


Flagellin in prokaryotes


Tubulin in eukaryotes

Method of cell division and what type of reproduction in eukaryotes /prokaryotes

Asexual binary fission in prokaryotes using pilus


Dominantly sexual mitosis /meiosis in eukaryotes

What is a capsule, its function and what type of cells is it found on?

Polysaccharide layer coating prokaryotes hiding antigens used for sticking cells together and preventing phagocytosis

Function of glycosome and what type of cells is it found in?

Lysosome/peroxisome involved in glycogen storage found in animal cells

Where is rRNA synthesised?

Nucleolus

What does compartmentation of the genome from the cytoplasm allow?

Gene expression to be regulated

How do small particles get transported across the nucleus?

tRNA, signalling molecules etc use nuclear pores to diffuse passively

3 types of protein filaments consisting the cytoskeleton

Actin - 2 intertwined helical strands


Microtubules - long hollow cylinders made of tubulin which form the mitotic spindle that segregates chromosomes during mitosis


Intermediates- rope like fibres coiled with keratin

Function of the cytoskeleton

Anchorage for organelles, mechanical support providing rigidity holding the cell's shape, which is useful for animal cells since they lack cell walls


Act as track ways to directly transport substances across the cell

Where is the cytoskeleton commonly found?

Next to the RER where the necessary proteins are synthesised

Function of motor proteins, the different types and what direction they move in

Allow vesicles etc to walk along the cytoskeleton to their destination


Kinesin travels away from the nucleus (+)


Dynein travels towards the nucleus (-)

Function of melanophores and how they work

Pigments which allow crustaceans etc to change colour


Motor proteins transport pigments in melanosomes across the cytoskeleton to the cell's centre (appears light) or dispersed (appears dark)

What processes so proteins undergo to enhance stability before secretion from the ER?

Glycosylation -adding a carbohydrate


Disulphide bond formation


How do proteins enter the ER and what is the function?

Recognised by a translocator pore on the ER surface using signal proteins


Makes sure that proteins are folded properly

How do vesicles transport themselves and what ensures that they reach the correct target membrane?


Walk along microtubules in cytoskeleton


Have a protruding protein that is specific to shape of target membrane

Function of protein bodies in animals and plants

Animals - growth and development


Plants - stored in vacuole to provide sulfur, carbon and nitrogen foe growth

Function of chaperone proteins

Assist correct intracellular folding of polypeptides in ER

Autophagy

Lysis and recycling of misfolded proteins


Originates in cytoplasm

Functions of vacuole

Storage of carbohydrates, respiratory organic ions


Homeostatic devise ensuring hydrostatic pressure and cell turgidity is maintained


Anti-herbivory using cyaogenic glucosides e.g. ricin

Why does the majority of mtDNA come from the mother?

Egg cell is larger than sperm cell and so contains more genetic information

Nucleotide

Nitrogenous base


Deoxyribose sugar


Inorganic phosphate group

5' end

Phosphate group end of DNA

3' end

Hydroxy group end in DNA


-OH

What forms DNA backbone?

Neighbouring phosphate and sugar bonded together (covalent)


Anti parallel held by hydrogen bonds

Purines

Adenine and guanine


2 organic (carbon) rings

Pyrimidines

Cytosine and thymine


1 organic (carbon) ring

Chargraff's rules

Number of Adenine and Thymine bases equal


Number if Cytosine and Guanine bases equal


Base composition varies from species to species in relative base amounts

Semi-conservative replication

Parent molecule with 2 complementary strands unwind


Complementary strands separate


Each daughter strand consists of one parental strand and one new strand

What sites does replication begin and how many are there in eukaryotes / prokaryotes?

Origins of replication


Where 2 DNA strands separate opening a replication bubble where replication occurs simultaneously in both directions


Eukaryotes - many


Prokaryotes - one

What is found at the end of a replication bubble?

Replication fork where new DNA strands are being unwound

Topoisomerases

Enzyme used in replication which corrects overwinding helping to relieve strain ahead of replication forks by breaking, swivelling and rejoining DNA

Helicase

Breaks H bonds untwisting the double helix at the replication fork

Binding proteins

Used in replication to stabilise single-stranded DNA preventing them from sticking back together again as they are being copied

DNA polymerase

Catalyses the synthesis of a new DNA at a replication fork


Requires a primer and a DNA template strand

Adding a nucleotide to a DNA strand

Nucleoside triphosphates (dATP,dTTP etc ) add onto the free 3' end


DNA replication occurs in the opposite direction to anti parallel helix so DNA strand inky elongates in 5'-3'

Lagging vs leading strand

Leading strand =parental


Lagging = new strand complementary to leading strand synthesised as a series of segments called Okazaki fragments

Okazaki fragments

Segments of the lagging strand joined together by ligase which bonds together the sugar-phosphate backbone

Nucleosome and where is it found?

DNA wound twice around 4 pairs of histone proteins supercoiled into the nucleoid

Looped domains

Thick chromatin fibre formed by histone tail and linker DNA of nucleosomes

Difference between RNA and DNA

Uses ribose sugar


No thymine, uracil instead


Single stranded

What is the difference in the way translation /transcription occurs in prokaryotes?

DNA not segregated from ribosomes so translation can occur before transcription has finished

Triplet of nucleotide bases is called a

Codon

Degeneracy

More than one coin may specify a particular amino acid but no codon specifies more than one amino acid

What can be produced due to the universal nature of the genetic code

Transgenic animals

Transcription unit

Stretch of DNA that is transcribed into an RNA molecule

Terminator

Sequence that signals the end of transcription

TATA box

Promoter sequence which defines direction of transcription and indicates the DNA strand to be read


Transcription factors recognise the box and bind to it before RNA polymerase 2 does to form the transcription initiation complex

Initiation of transcription at a eukaryotic promoter

Transcriptional factor recognises TATA box and binds to the DNA.


RNA polymerase 2 then binds too to form the transcription initiation complex

3 steps in transcription

Initiation


Elongation


Termination

Termination step in transcription in eukaryotes

RNA polymerase 2 transcribes the polyadenylation signal sequence in the pre-mRNA

Polyadenylation

Used in termination of transcription


Adds multiple adenine bases


3' end gets a poly-A tail

Untranslated regions

Parts of mRNA that will not be translated into a protein

RNA splicing

Removes introns and joins exons creating an mRNA molecule with a continuous coding sequence using a spliceosome

Spliceosome

Excises pre -mRNA releasing the introns for degradation and splices the exons together

Alternative splicing and what this means

Genes can encode more than one kind of polypeptide depending on which segments are treated as exons during splicing


The number of different proteins that can be produced is grater than the number of genes

Which is junk DNA that is spliced out -introns or exons?

Introns

Elongation step in transcription in eukaryotes

Helicase untwists the double helix


Nucleotide are added to the 3' end if the growing RNA molecule


A gene can be transcribed simultaneously by several RNA polymerases, increasing the mRNA transcribed. This allows the encoded protein to be made in large amounts quickly in stressful situations

How is initiation in transcription different for bacteria

RNA polymerase itself recognises and binds to the promoter


No TATA box required

How is termination in transcription different in bacteria

Polymerase stops transcription at the terminator RNA sequence

In which direction does both translation and transcription occur

5'-3'

tRNA

Used in translation


80 nucleotides held in place by hydrogen bonds into a clover shape


Contains anticodons


Recycled


Picks up the designated amino acid in the cytosol and deposits it at the ribosome

Each amino acid is joined to the correct tRNA by

Aminoacyl -tRNA synthetase


(works as an enzyme and so is an active process)


Each synthetase (20 kinds) has an active site specific for a particular amino acid


Results in an aminoacyl tRNA

Wobble

Flexible base pairing


Anticodons of some tRNAs recognise more than one codon

Wobble

Flexible base pairing


Anticodons of some tRNAs recognise more than one codon

Ribosome structure

Large and small subunit made of rRNA


P site on ribosome

Peptidyl -tRNA


Holds the tRNA that carries the growing polypeptide chain

A site on ribosome

Aminoacyl tRNA site


Space for enzyme to bind


Holds the tRNA that carries the next amino acid to be added

E site in ribosome

Exit site

3 stages of translation

Initiation


Elongation


Termination

What can be produced due to the universal nature of the genetic code

Transgenic animals

Promoter region

Where RNA polymerase attaches to along with a primer in order to initiate transcription

Terminator

Sequence that signals the end of transcription

Initiation of translation in eukaryotes

Small ribosomal subunit carrying methionine binds to 5' cap of mRNA moving downstream until it reaches the complementary codon AUG


Attachment of large ribosomal subunit using energy (GTP) forms translation initiation complex

Where is the initiator tRNA held

P site of ribosome

Initiation of translation in bacteria

Smal ribosomal subunit carrying methionine binds to mRNA at a specific RNA sequence just upstream of the start codon

Elongation of translation

Amino acids are added involving elongation factor proteins


1. Codon recognition


2. Peptide bond formation


3. Translocation

Termination of translation

When stop codon reached the A site of the ribosome a releasing factor binds to the stop codon causing hydrolysis of the hond between


the polypeptide and its tRNA in the P site


Polypeptide exits via exit tunnel


Translation initiation complex dissassembles requiring GTP

Polyribosomes

Used in translation to tail along the same mRNA to make many copies of a polypeptide simultaneously

Targeting polypeptides to specific locations

Polypeptide has a signal peptide bound


Signal recognition particle binds to this momentarily stopping translation


Signal recognition particle leaves for ER and


translation resumes


Signal leaving enzyme cuts off signal peptide

If activator is degraded/represser binds to operator then transcription of lac operon is

Blocked

Prokaryotic gene regulation when lactose is present

Lactose binds to repressor causing a configuration change so that the repressor cannot hind to operator and so lac operon can be translated to produce lactase

What reduces lactose levels and makes the repressor change to its original shape


What is this an example of?

B galactosidase


Negative feedback - as lactose levels decrease, b galactosidase levels imcrease

DNA isolation for microbes

Heat or alkaline lysis

DNA isolation for higher organisms

Salt, buffer and detergent to break open cell membranes

3 steps in PCR and their

Denauration 94-98


Annealing = complementary primers to GOI (variable)


Extension 72 = taq polymerase 5'-3'

PCR contents

Template DNA


Primers


dNTPs


Buffer


Taq polymerase

Restriction enzymes

Cuts palindromic sequences producing blunt/sticky ends

DNA ligation

Enzyme which catalyses phosphodiester bonds between nucleotides using ATP

Cloning vectors

provide the extra sequences required by the cloned genes to be replicated and expressed

Transformation of bacteria

GOI put into cloning vector with ligation mixture and then heated onto a solid media allowing them to grow with selection


OR


Electroporation

Bacterial antibiotic selection

If plasmid with resistance present then bacterium can multiply to form a colony

Nucleosome

DNA wound round 8 histones resembling beads on a string


Histone tails and linker DNA interact to form a fibre

Heterochromatin

Condensed form of chromatin inaccessible to machinery responsible for transcription

Euchromatin

Dispersed form of chromatin due to neutralised histone tails which drift apart


Accessible to transcription machinery so contains genes to be transcribed

Gene regulation in transcription of eukaryotic cells


Inactive


Paused/stalled


Elongation/active

Inactive - RNA polymerase 2 not bound to promoter


Paused- phosphorylated serine 5,RNA polymerase bound to TATA so transcription factors come into place


Active - phorphorylated serine 5 and 2

What is the advantage of double stranded hairpin small RNAs

More stable

Which small RNA is used for repression of Gene translation

miRNA

Which small RNA is used for promoting mRNA degradation

miRNA

Which small RNA is used for repression of Gene transcription via chromatin remodeling and DNA methylation

siRNA

Ubiquitin mediation degradation and what is used to do this

Small RNAs = microRNA and siRNA


Attach to protein to be degraded


Recognised by a proteasome which unfolds the protein and sequestered it within a central cavity


Enzymes in proteasome cut protein into small peptides to be degraded by other enzymes into cytosol

Functions of 5' end and poly-A-tail of mRNA ends

Facilitates export of mature mRNA from nucleus after transcription


Protects mRNA from degradation


Helps ribosomes attach to 5' end to begin translation

Reporter construct

Promoter region of gene fuses to visual marker to see whether GOI is switched on

3 types of reporter constructs

GUS


Fluorescent proteins


Luciferase

GUS

Reporter construct


GOI binds to b glucronidase


Blue stain shows enzyme activity seen by light microscope

Fluorescent proteins

Reporter construct


Jellyfish gene shown under UV


Allows you to see no. of chromosomes

Luciferase

Firefly gene binds to promoter


Dark box and sensitive camera needed to detect chemiluminescence

2 ways of synthesis of insulin

Bacteria - chains a and b produces from two plasmids whereby disulfide bonds form


Eukaryote - proinsulin formed in yeast, disulfide bonds form then progressed used to purify it


What do black regions on a chromosome represent?

Condensed heterochromatin

Cloning a genome

Fragmented using REs


Packaged into bacterial artificial chromosomes which can then be amplified

Finding the GOI

Nucleic hybridisation based on complementary base pairing

Sickle cell anaemia

Single nucleotide polymorphism mutation creates a polar, hydrophilic protein instead of a non polar, hydrophobic one creating a rigid discoid shape which melts as O2 is taken up


Feedback inhibition

Final product can repress expression of the genes needed for all the enzymes needed for the pathway (long term)


Enzyme can inhibit the activity of the first enzyme in the pathway (short term)

Tight junctions

Holds plasma membranes in close proximity together


Maintains polarity


Restricts movement of ions and molecules

Physical communication between plant cells

Plasmodesmata

Lipid bilateral membrane structure

Phospholipid made up of non polar hydrophobic tail and polar hydrophilic head

Passive transport

Molecule following concentration gradient, no energy required

Active transport

Transport of molecule against concentration gradient requiring energy

Ion channel

Ions pass down their electrochemical gradient without input if metabolic energy

Aquaporins

Membrane channel for transport of water, glycerol, CO2


Allows osmosis

2 forms of ATP driven membrane transport

P-type pump transports specific ions


ABC transporters found everywhere on membrane transports lots of different substabces

Human chromosome

23 pairs


Diploid

Polyploidy

Multiple sets


More than two complete chromosome sets

Aneuploidy

Incomplete number of chromosomes


One or more chromosome has an extra copy or is deficient

Karyotype

Display of the chromosome pairs of a cell arranged by size and shape

Chromosome translocation

Non homologous fusion

Chromosome deletion

Part missing

Chromosome inversion

Chromosome fragment in wrong direction /orientation

Dispermy

Greater than 2 sets of chromosomes

3 forms of aneuploidy

Nullisomy = both members of a chromosome pair missing


Monosomy = one member of a pair is missing


Trisomy = one extra chromosome

2 forms of chromosome inversion

Paracentric - centromere excluded


Pericentric - centromere included

Substitution mutation

Code for same amino acid =silent/synonymous


Code for different amino acid =replacement/nonsynonymous

Consequence of insertion/deletion mutation

Shift in reading frame

Coding region mutations

Substitutions


Insertions


Deletions

SNP

Non coding region mutation


Single Nucleotide Polymorphisms


Satellite DNA

Very variable non coding DNA nearly always harmless sit used as a genetic marker i. e parent tests

Why garden pea (pisum sativum) is a model organism

Readily available


Short generation time


Large number of progeny


Easy to manipulate via cross pollination

Observation from Mendelian Genetics

Alternative versions of a gene (allele) cause variation


An organism inherits one allele from each parent


Alleles can be dominant or recessive


Alleles segregate during gamete production at random

Principle of segregation

Two members of a gene pair segregate during meiosis at random.


Half of the gametes carry one member of the pair and the other carry the other half

What would the blending hypothesis result in?

Clones - genetically uniform

Independent assortment and what is the exception

Alleles of different genes segregate from each other at random


Recombination -crossing over


When two genes are physically proximate on the same chromosome

If a disease only involves one gene it is known as

Mendelian/monogenic

If a disease involves more than one gene it is known as

Multifactorial

Which chromosome pairs are autosomal

1-22

Characteristics of autosomal dominant disease


Affected person's parental genotype


Sex of affected


Transmitted by which sex

At least one affected parent


Affects either sex


Transmitted by either sex

Characteristics of autosomal recessive disease


Phenotype of affected's parents


Affects which sex


Increased incidence of

Carriers/unaffected


Affects either sex


Inbreeding

Characteristics of X-linked recessive


Affects which sex


Carriers are which sex

Affects mainly males


Females only affected if father is affected and mother is a carrier


Males cannot be carriers, can only be affected due to only having 1 X chromosome

Characteristics of X - linked dominant


Affects which sex


All female children of affected male are


All male children of affected male are

Both sexes


Affected


Unaffected

Characteristics of Y - linked disorder


Affects which sex


All sons of affected man are

Only males


Affected

Recombination occurs in what stage

Meiosis prophase 1

Recombination processes required

Recombination enzyme to cut


Ligase to anneal nicked ends into new combinations


Recombination fraction


Units


Equation


Meaning

Measure of distance between two genes


Units = cM (centiMorgans)


Number of recombinants/(no. of recombinant + non-recombinant)


Higher recombination fraction means a higher frequency of recombinants/recombination that occurs

Evolutionary significance of recombination

Produce potentially be fitter genotypes


Speeds up rate of evolution in sexual organisms (asexual organisms so not recombine)

Double recombination evidence

All offspring appear to be recombinant

Barr body

Females inactive one of their X chromosomes in each cell to match the dosage found in men


Inactive X chromosome condenses along the inside of the nuclear envelope

Why is recombination fraction never more than 50%

Only 2 of the 4 chromatids recombine

Locus

Physical position of a gene along a chromosome

Hardy weinburg assumption and requirements

Gene frequency stays same in future generations


Random mating


No natural selection


Large population size


No migration


No mutation

Selection coefficient

Difference between the standard relative fitness (1.0) and fitness of genotype in question

When an allele increases in frequency it is said to be under what kind of selection?

Positive

Balancing selection

Form of natural selection where heterozygotes are fitter than homozygotes

What kind of populations have a lower chance of survival

Small genetically homogeneous

In what kind of populations is inbreeding more likely to occur

Small

Wright's inbreeding coefficient (f)

Measure of degree of inbreeding in individuals


Higher f = more inbred

Consequences of inbred populations

High frequencies of homozygotes meaning that dangerous recessive alleles are easily revealed and thus less likely to be benefitted from (heterozygote advantage )


Less fit = inbreeding depression

Linked genes

Genes on the same chromosome


Normally close in proximity so that they are inherited together

2 models explaining human population genetics

Multi regional


Out of Africa

Multi regional model

Homo erectus left Africa and dispersed over several continents


(All humans derive from Homo erectus )


Gene flow between many populations - high genetic density

Out of Africa model

Homo sapiens migrated out of Africa replacing all populations descending from Homo erectus without interbreeding


African populations should have the greatest diversity

Evidence for Out of Africa model

Negative relationship between genetic diversity and their geographical distance from Africa


African populations are more polymorphic


-> as first population moved this acted as a succession of genetic bottlenecks as they travelled further


Humans emerged in Africa 120-140KYA, humans spread from Africa 30-80KYA

Our closest living relative and how we figured this out

Chimpanzees


Time to most common ancestor (TMRCA)

What is the best way to achieve accurate TMRCA

Test non-recombining molecules e.g. mtDNA and Y chromosome

As humans migrated out of Africa how did they face the new climate


Eumalanin - black/brown pigments


Phaemelanin - red/yellow pigments

Skin colour



How do we know that humans and Neanderthals inhabited the same geographical regions

Shared headlice

Effects of UV

Sunburn


Cancer


Nutrient photodegradation


Synthesis of vitamin D

Downside of having dark skin in bright environment

Little vitamin D produced so high vitamin D diet is needed

Genome

Complete set of genes in an organism

Difference between intergenic DNA and introns

Both non coding DNA


Introns = non - translatable


Intergenic = non - transcribed

Pseudogenes

Former genes that have accumulated mutations and are nonfunctional

Discontinuous phenotypic variation

Discrete classes, no intermediates


Not influenced by environment so Mendelian ratios observed

Continuous phenotypic variation

No classes, intermediates present


Influenced by environment so Mendelian ratios observed

Percentages of standard deviations from mean

1 sd = 68%


2 sd = 95%

Threshold variation

Appears discontinuous but is caused by a multi factorial continuous distribution


Distribution called liability


Phenotype depends on threshold

Quantitative trait locus

Area of DNA containing genes (close together) for a phenotype due to continuous variation

Heritability

Total variation within a population for a phenotype


Add genetic variance and environmental variance (so long as the effects are independent )

Broad sense heritability

Proportion of phenotypic variation due to genotypic differences


Genetic variance /(genetic variance and environmental variance)

How do inbreeding influence the heritability value

More inbred =lower heritability

Vp equation with genotype-environment interaction

Vp =Vg + Ve + Ve x g

Norm of reaction

Curve indicating contribution of environmental variation to phenotypic variation

Difference between broad sense and narrow sense heritability

Broad is specific to the population and environment in which it is measured


Narrow is proportion of variation passed on to offspring

Multi niche polymorphism

Different phenotypes for each niche within a species

Signs that natural selection is acting on a trait

Heritable variation in trait


Competition for resources


Differences in fitness that depend on trait

Narrow sense heritability

Predicts how trait will respond to selection


Response to selection (change in mean per generation )/ difference between mean and selected group

Effect of selection of quantitative traits on genetic variance


Directional


Stabilising


Disruptive

Directional - same


Stabilising - decrease


Disruptive - increase