unit 4: reproducing life FOR FINAL EXAM

key concepts: 

• Genome = All the genetic material of a cell 

In Eukaryotes (complex cells): 

• Cell genome packaged as chromosomes 

• Chromosome = one DNA molecule + proteins 

• Chromatin = proteins of many chromosomes + DNA molecules 

• DNA carries genes which specify characteristics 

• Proteins control gene activity & chromosome structure 

Human chromosomes (somatic cells) 

• 46 chromosomes, 23 from each parent (2n = 46) 

• 22 pairs homologous chromosomes + Sex chromosomes 

• Nuclear DNA is linear 

• Circular DNA is in mitochondria 

Plant chromosomes eg Strawberry (cultivated) 

• Nuclear DNA= Octoploid 2n = 8x = 56 

• Circular DNA is in chloroplasts 

chromosomes and genes 

• Chromosomes carry genes 

Genes specify characteristics 

• Eg blood type, type B has only B proteins on outside of blood 

• AB can receive any blood type 

• O can give to any blood type. Can only receive O 

DNA fingerprinting 

• Each person has a specific DNA sequence 

• Collect a sample, extract the DNA 

• Make copies of 13 different STR regions of DNA (Short Tandem Repeat regions) e.g. GATA GATA GATA GATA 

• Count the repeats & look for a match 

• Some regions don't code for anything important, but can act as signature for where it came from 

DNA fingerprinting at a crime scene 

• Looking for presences of genes STR#2 and STR#1 in suspects 

• Count the Short Tandem Repeats & look for a match 

• Match tells if person was there, cannot account for twins 

Fingerprints 

• Develop before you are born 

• fully formed at about 19 weeks of pregnancy 

• Can be shaped by environmental factors, not only genetic (eg twins can have different fingerprints) 

shape caused by higher blood pressure, Shows that environment influeces development

Cell division and DNA 

cells replicate genome before they divide 

• Most cell divisions create indentical daughter cells 

• Cell division in unicellular organism = reproduction 

• e.g. prokaryotes & unicellular eukaryotes 

Cell division (Mitosis) in multi-cellular eukaryote  

• = fertilised egg development to multicellular organism 

• = mechanism for cell replacement/repair 

cell division 

1. Chromatin condenses and duplicates 

2. Once duplicated, chromosome consist of 2 sister chromatids connected along entire length by sister chromatid cohesion.  

• Each chromotid contains copy of DNA molecule 

• Called chromatids when stuck together, chromosomes when seperated. 

3. Sister chromatids are separated by molecular and mechanical processes into two chromosomes & distributed to different daughter cells 

Mitotic spindles 

Allows chromosomes to move apart for cell division 

• Made up of microtubules  

• Extend from nearest centrosomeand overlap and metaphase plate 

In animal cells: 

• Spindle forms from centrosomes & includes spindle microtubules + asters 

• Some spindle microtubules attach to kinetochores 

• Period where chromosomes sperate called metaphase 

Meiosis basics

cell division unique to eukaryotes = Eukaryotic cell division to produce eggs/sperm (gametes) 

Steps: 

• Genome is doubled (replicated) 

• Homologous chromosomes align 

• Halving of genetic material (Meiosis 1) 

• Halving of genetic material again (Meiosis 2) 

• Gamete formation - eggs, sperm have half as many chromosomes as parent somatic cells 

cell cycle

Begins at G1 --> S phase --> G2 phase --> mitosis --> cytokinesis 

Interphase (growth): 

G1 

• Metabolic activity and growth 

S  

• DNA synthesis (and metabloic activity and growth) 

G2 

• Metabloic activity, growth, DNA synthesisand preparation for cell division 

Mitosis (M) phase: 

Mitosis 

• Distribution of chromosomes into two daughter cells 

Cytokinesis 

• Division of cytoplasm to produce two daughter cells 

• Each daughter cell starts a new cell cycle 

Distribution of chromosomes in mitosis

Prophase 

1. Chromosome condenses and becomes visible 

2. Spindle fibres emerge from centrosomes 

3. Nuclear envelope breaks down 

4. Nucleolus disappears 

Prometaphase 

1. Chromosomes continues to condense 

2. Kinetochores appear and centrosomes 

3. Mitotic spindle microtubules attach to kinetochores 

4. Centrosomes move towards opposite planes 

Metaphase

1. Mitotic spindle is fully developed, centrosomes at opposite poles of cell 

2. Chromosomes are lined up at each metaphase plate 

Anaphase 

1. Cohesion proteins binding siter chromatid together break down 

2. Sister chromatids (now chromosomes) are pulled towards opposite poles 

3. Non-kinetochore spindles lengthen, elongating the cell 

Telophase 

1. Chromosomes arrive at opposite cells and begin to condense 

2. Nuclear envelope material surrounds each set of chromosomes 

3. Mitotic spindle breaks down 

Cytokinesis 

• Animal cells: 

• Cleavage furrow separates daughter cells 

• Plant cells: 

• Cell plate separates daughter cells 

prophase

1. Chromosome condenses and becomes visible 

2. Spindle fibres emerge from centrosomes 

3. Nuclear envelope breaks down 

4. Nucleolus disappears 

Prometaphase 

1. Chromosomes continues to condense 

2. Kinetochores appear and centrosomes 

3. Mitotic spindle microtubules attach to kinetochores 

4. Centrosomes move towards opposite planes 

metaphase

1. Mitotic spindle is fully developed, centrosomes at opposite poles of cell 

2. Chromosomes are lined up at each metaphase plate

anaphase

1. Cohesion proteins binding siter chromatid together break down 

2. Sister chromatids (now chromosomes) are pulled towards opposite poles 

3. Non-kinetochore spindles lengthen, elongating the cell 

telophase

1. Chromosomes arrive at opposite cells and begin to condense 

2. Nuclear envelope material surrounds each set of chromosomes 

3. Mitotic spindle breaks down

cytokinesis

Animal cells: 

• Cleavage furrow separates daughter cells 

Plant cells: 

• Cell plate separates daughter cells 

DNA during interphase and mitosis

Interphase  

• G1, S, G2 

• DNA is loosely packed 

• Chromatin 

• DNA is replicated in S-phase 

During M-phase  

• DNA is condensed 

• “Move” chromosomes into daughter cells 

nuclear membrane during the cell cycle

Interphase  

• Nuclear membrane present 

During M-phase  

• Nuclear membrane is broken down 

• Spindle fills whole cell 

• Can’t see organelles in cytoplasm (too small) but they are still there and they move with the cytoplasm into the daughter cells 

• Nuclear membrane re-forms at telophase around nucleus of each daughter cell 

Parthenogenesis vs mitosis vs meiosis 

• Mitosis in humans = body cells 

• Meiosis in humans = produce eggs/sperm 

• Parthenogenesis – aphids, bees, some plants 

• Different mechanisms 

• Adaptations of mitosis or meiosis 

cell cycle control

Cyclin proteins:  

• Only produced at certain times in cycle, broken down when no longer needed  

CdK (Cyclin-dependent kinase proteins):  

• high levels in cell at all times 

role of CdK and cyclin 

• Cdk’s are inactive 

• Cdk’s activated when a cyclin binds to them 

• Cyclin-Cdk complex is active and phosphorylates other proteins 

• e.g. nuclear membrane 

activation of cyclin-dependent kinase (CdK)

• Cyclin binds to Cdk to form active Cyclin-Cdk complex 

• Active Cyclin- Cdk complex binds to other proteins 

cell cycle: late S phase/G2 phase 

Late S phase/G2 phase: M-cyclin produced + binds to CdK 

MPF = Maturation-Promoting Factor (M-Phase- Promoting Factor) = M-Cyclin-Cdk complex M-cyclin degraded at metaphase/anaphase transition

key concepts for cell cycle 

• Cell division is part of the cell cycle 

• Cell grows throughout interphase (G1, S, G2) 

• DNA replicated in S-phase 

• M-phase = Mitosis + Cytokinesis (for most organisms) 

 

• Cell cycle regulated by C-Cdk complexes (Cyclins bound to Cyclin-dependent kinases) 

• Cyclin only present at c

Cell cycle checkpoints 

needed so dont end up with abnormal number of chromosomes 

• G1 --> S-phase 

• G2 --> M-phase 

Within M-phase: 

• Metaphase --> Anaphase 

bacteria daughter cells/reproduction 

one becomes two 

• bacteria produce daughter cells by binary fission (“division in half”) 

• Single circular DNA chromosome + proteins for DNA packaging in nucleoid region 

• Bidirectional replication of genomic DNA beginning at origin  

FtsZ proteins divide cell 

• FtsZ proteins= filamenting temperature-sensitive mutant Z 

FtsZ proteins divide bacteria cell

1. Replication of the circular prokayotic chromosomes begins at the origin of replication and continues at both directions at once 

2. Cell begins to elongate. FtsZ proteins migrate toward the midpoint of the cell 

3. The duplicated chromosomes seperate and continue to move away from each other toward opposite ends of the cel. FtsZ proteins form a ring around teh periphery of the midpoint between chromosomes 

4. FtsZ ring directs teh formation of a septum taht divides the cell. Plasma membrane and cell wall material accumulates 

5. After the septum is complete the cell pinches in two, forming two daughter cells. FtsZ is dispersed throught the cytoplasm of the new cells 

Dinoflagellate reproduction

• Linear chromosomes attach to nuclear envelope  

• Nuclear envelope remains intact during division  

• Microtubules pass through nucelus inside cytoplasmic tunnels  

• Nucleus divides 

diatom and most yeasts reproduction

• Linear chromosomes attach to nuclear envelope 

• Nuclear envelope remains intact during division 

• Microtubules form a spindle within the nucleus 

• Nucleus divides 

Eukaryotes: plants and animals daughter cells/reproduction 

• Spindle forms outside nucleus 

• Nuclear envelope breaks down during mitosis 

• Microtubules separate chromosomes 

• Two nuclear envelopes form

Mitotic spindle again

• In animal cells, centrosome replicates (at interphase), one moves to each end of cell (at prometaphase) 

• Centriole pair at the centre of each centrosome,  

• centriole presence not required for spindle formation 

Made up of microtubules 

• in animal cells: 

• Spindle forms from centrosomes & includes spindle microtubules + asters (at prometaphase) 

• Some spindle microtubules attach to kinetochores 

how does spindle pull chromosomes apart? 

• Theory 1: reeling in/fishing 

• theory 2: pacman: removing sections of spindle to make shorter to pull chromosome closer to centrosome 

Experiment: 

• Labelled microtubules with dye 

• Marked region between spindle and chromosomes (no dye) 

• If microtuble segments on kinetochore got shorter=pacman model 

• If microtubule segments on spindle pole got shorter=fishing model 

Found in pig kidney cells: 

• During anaphase a chromosome is walked along a microtubule as the microtubules depolymerises at kinetochore end 

• Evidence of pacman model 

Meiosis: 

Cell division unique to eukaryotes, eukaryotic cell division to produce eggs/sperm (gametes) 

• Genome is doubled (replicated) 

•  Homozygous chromosomes align CHECK IF HOMOZYGOUS 

• Halving of genetic material (Meiosis 1)  

• Halving of genetic material again (Meiosis 2) Gamete formation - eggs, sperm have half as many chromosomes as parent somatic cells 

chromosome vs chromatid 

Autosome=non-sex chromosomes 

• Chromosome replicates DNA to form Sister chromatids 

• When the Sister chromatids separate, each one is now called a Chromosome 

Lining up and separation of chromosomes 

• Chromosomes line up along the metaphase plate differently in mitosis vs meiosis 

• The Sister chromatids separate at different times in mitosis vs meiosis 

division of chromosomes in meiosis

• Same chromosome types (eg 1a and 1b and 2a and 2b) line up and cross over to exchange dna.  

• Cell divide to create two diploid daughter cells 

• Cell divide again without dna replication to create 4 haploid daughter cells 

• Chromosomes line up along metaphase plate and seperate 

Meiosis 1 

Increases genetic variation via: 

• Prophase I: 

• Crossing over of non-sister chromatids 

• Metaphase I: 

• Independent assortment of homologs 

• Random fertilisation of gametes 

Meiosis 2

Separate sister chromatids to produce 4 haploid daughter cells 

Meiosis, Prophase 1: Variation from Crossing over 

• DNA has been duplicated. 

•  Homologous chromosomes are paired and stuck together in a synaptonemal complex by cohesin protein 

• Double-stranded DNA of non-sister chromatids broken at specific points  

• DNA joins seal up (Synapsis) 

• Crossover point = chiasma (plural = chiasmata) 

• Need at least one chiasma per complex 

• Recombinant chromatids can be formed 

Tentacle theory, chiasma, recombinant chromatids 

Tentacle theory: 

• One strand of the DNA flaps around like a tentacle until it finds a homologous non-sister chromatid to which it joins (e.g. paternal chromatid joined to maternal chromatid) 

• Synapsis: DNA breaks sealed up 

• Crossing over: Recombinant chromatids formed 

• Metaphase I: Independent assortment of homologs 

humans 

Human multicellular diploid adult  

• Only haploid cells = gametes (eggs/sperm) are produced by meiosis  

•  Egg fertilised by sperm  

• Diploid zygote grows by mitosis into adult 

Animals: 

Multicellular diploid adult 

• Only haploid cells = gametes (eggs/sperm) are produced by meiosis 

• Egg fertilised by sperm 

• Diploid zygote grows by mitosis into adult 

plants and some algae 

• Diploid multicellular organism = sporophyte (spore producer) produces haploid spores by meiosis  

•  Haploid spore grows into multicellular haploid gametophyte (gamete producer)  

• Haploid gametophytes produce haploid gametes (mitosis) 

 

• Two haploid gametes fuse to form diploid zygote  

• Diploid zygote grows by mitosis to form diploid sporophyte (Sporophyte makes spores) 

Most fungi & protists 

• Haploid unicellular or haploid multicellular organism produces haploid gametes by mitosis 

• Two haploid gametes fuse to form diploid zygote 

• Mostly live unicellular, but can introduce genetic variation via meiosis 

 

• Diploid zygote DOES NOT grow by mitosis into adult, instead produces haploid cells by meiosis  

• haploid cells grow into haploid multicellular adult OR haploid unicellular offspring (mitosis) 

Theories: Evolution of Meiosis & Mitosis 

Living Eukaryotes share a set of genes specifically associated with meiosis (e.g. cohesin genes) 

Theory:  

• Meiosis only evolved once before the last common ancestor for Eukaryotes 

• Everything since has meiosis since descended from common ancestor 

Meiosis – 4 novel steps 

• Pairing of homologous chromosomes 

• Recombination between non-sister chromatids 

• Suppression of separation of sister- chromatids during the first meiotic division 

• No chromosome replication during the second meiotic division 

Theory:  

• Pairing of homologous chromosomes came first 

Evolution of Meiosis & Mitosis theories 

Prokaryotes lived on earth more than a million years before Eukaryotes 

Therefore … 

•  More likely Meiosis evolved from Mitosis  

• Can’t test the hypothesis 

• Unlikely to find the progenitor 

• Different variants of Meiosis in different organisms – more yet to be discovered! 

lecture 4 vocab

Gene: 

• a unit of hereditary information encoded by a specific DNA sequence (or RNA in viruses) 

Chromosome:  

• One DNA molecule + associated proteins  

• Prokaryote, usually single, circular  

• Eukaryote, many linear chromosomes 

Allele:  

• an alternate version of a gene 

Mendel: genotype vs phenotype 

Alternative versions of genes account for variations in inherited characters 

•  For each character an organism inherits two versions (alleles) of a gene, one from each parent 

Phenotype:  

• the physical traits of an organism that are determined by its genetic makeup 

Genotype:  

• genetic makeup (set of alleles) of an organism 

Mendels laws: 

Law of segregation:  

• Two alleles in a pair segregate(separate) into different gametes during meiosis  

Law of independent assortment: 

•  Each pair of alleles segregates (assorts) independently when gametes form … 

if looking at more than one gene, these genes need to be on different chromosomes or far apart on the same chromosome for the alleles to assort independently 

Meiosis, prophase 1: crossing over 

• Need at least one chiasma per complex  

• Recombinant chromatids can be formed 

• If genes/alleles are close together, chances are genes will often cross over and appear together 

• If genes/alleles are on opposite ends on the chromosome, less likely to cross of together and be concurrent 

SPO-11 gene codes for a protein that makes each of the DNA strands break in double strand 

Minimum distance between each chiasma 

Genetic linkage and chiasmata  

Linked genes:  

• genes located close to each other on same chromosome, tend to be inherited together, less chance of chiasmata separating them 

• Genes that generally get inherited together because they sit close together 

• Genes far apart, more likely to be sorted independently (more chance of chiasmata forming between genes) 

Linkage map:  

• relative locations of genes along a chromosome  

Independent assortment 

• if looking at more than one gene, these genes need to be on different chromosomes or far apart on the same chromosome for the alleles to assort independently 

• If crossing over occurs in homozygous alleles, not much will happen 

Alleles and phenotypes 

Dominant:  

• An allele that is fully expressed in a heterozygous phenotype  

Recessive:  

• An allele that not expressed in a heterozygous phenotype 

Incomplete dominance: 

•  Heterozygous phenotype midway between two homozygous phenotypes  

Codominance:  

• Both phenotypes expressed in heterozygote (e.g. blood types AB) 

Dominant vs Recessive 

Wild type: dominant over every other gene, denoted with + and capitla letter (eg C+C+) 

• C+C+ = Wild type. Brown fur, dominate over other coat colours  

• cch cch = Chinchilla. White fur with black tips Incompletely dominant over Himalayan 

• ch ch = Himalayan. White fur, black paws, black nose, black tail  

• Incompletely dominant over Chinchilla 

• Dominant over Albino 

• cc = Albino. White fur (no pigment) 

More complicated inheritance (pleiotropy, polygenic, epistasis)

Pleiotropy (Greek pleion = more):  

• One genehas many phenotypic effects (e.g. cystic fibrosis, mutation in chloride channel protein,excess mucus, 1/25 Caucasians are carriers) 

Polygenic:  

• quantitative variation (e.g. height700 variations, >180 genes) 

• Many genes contribute, also influenced by environmental factors like starvation etc) 

Epistasis (Greek – standing upon):  

• Phenotypic expression of one gene alters phenotypic expression of another inherited gene 

Epistasis (in Labrador dogs) 

• BB or Bb = “black” as B is dominant,  

• bb = “chocolate” 

• EE or Ee = colour is placed in hair follicles  

• ee = no colour is placed in hair follicles (no matter what B or b gene is there) 

so if Eee, no colour=golden lab

Sex chromosomes and sex determination 

Humans system:  

• XX or XY 

X-O system:  

• One X or two XX (grasshopper and cockroaches) 

Z-W Systems:  

• Female sex chromosomes determine sex 

Haploid/diploid system (bees, ants)  

• No sex chromosomes 

X-linked inheritance - Colour blindness (in humans) 

Allele carried ONLY on the X chromosome 

No allele on Y chromosome 

• e.g. Red-green colour blindness 

N = Dominant 

• Allele for normal colour vision 

n = Recessive 

• Allele for red-green colour blindness 

Abnormal chromosome number 

Non-disjunction 

• Incorrect splitting of chromosomes 

Meiosis I: 

• Homologous chromosomes 

• Leads to every single gamete having unusual chromosome number 

Meiosis II: 

• Sister chromatids 

• Leads to only some gametes having wrong number of chromosomes 

• Happens if microtubule not properly or unevenly connected to kinetochore 

Deletion: 

• Fragment lost

Duplication:  

• fragment attaches to sister/non- sister chromatid 

Inversion: 

•  Inverted segment within a chromosome

Translocation:  

• Fragment joins non-homologous chromosome 

imprinting 

Genomic imprinting:  

• Expression of an allele in offspring depends on parent it was inherited from, offspring express ONE allele of the gene 

• Turn expression of one allele OFF by adding methyl group (-CH3) to cytosine nucleotide of one allele 

• Most imprinted (“silenced/activated”) genes are located on autosomes 

• Occurs during gamete formation, imprinted differently in male parent/female parent  

• The old “imprint” is erased when the offspring produce their own gametes 

DNA 

• Right-handed 

• Anti-parallel 

• Semi-conservative replication 

• Replicates in a 5’ to 3’ direction 

• New nucleotides of daughter strand added to 3’ end 

• Covalent phosphodiester linkages in the backbone 

• Strands held together by hydrogen bonds between the bases

Bonds within DNA 

5' end: 

• Phosphate attached to 5' carbon of sugar 

Phosphodiester linkages: 

• Covalent sugar- phosphate bonds involving the 5' and 3' carbons. Each phosphate has a negative charge 

3' end: 

• Hydroxyl group attached to 3' carbon of the sugar 

How does DNA transmit genetic information 

DNA replication allows genetic information to be inherited from:  

• Parent cell to daughter cell by mitosis 

• Generation to generation by meiosis 

Semi-conservative replication 

Replicate new strand of DNA using template parental strand to assemble a complementary strand 

How is DNA packaged in eukaryotes 

• DNA wrapped around histone proteins to form nucleosomes.  

• Nucleosome = 200 base pairs of “linker DNA” + DNA wrapped around a histone core  

• Nucleosomes loop and coil to form chromatin fibres  

• chromatin fibres loop and coil and form tightly packed chromosomes  

• 1.8 meters of DNA in each cell  

• 10 trillion cells in our bodies 

Chromatin (DNA + proteins bound to it) 

Heterochromatin 

• Condensed/closed 

Euchromatin 

• Accessible/open 

DNA replication 

• Chromatin must be in accessible/open euchromatin arrangement 

• Replicates in a 5’ to 3’ direction 

• Semi-conservative 

• Parental strands act as templates for daughter strands (copy = parental & daughter strand) 

During S-phase of interphase

• DNA less compacted during interphase =mixture of heterochromatin and euchromatin

Cell moves into G2 after DNA replication and prepares for M-phase  

• DNA tightly wound during M phase (chromosomes visible) = heterochromatin 

•  Each chromosome is made up of two chromatids which will separate at anaphase and will then be called chromosomes.  

• At end of M- phase/cytokinesis have 2 daughter cells. 

• Process of replication for prokaryotic and eukaryotic DNA is similar 

• More is known about prokaryotic DNA replication 

Replicating circular DNA (bacteria) 

Begins at a single origin  

• Parental strands: 

• separate to form replication bubble with two forks 

• are templates for new daughter strands 

• Replication proceeds in both directions until the forks meet 

Replicating linear DNA (during S-phase) 

Begins at many sites 

• Parental strands: 

• separate to form replication bubbles, each with two forks 

• are templates for new daughter strands 

• Replication proceeds in both directions until the bubbles fuse 

DNA replication step 1: access and unwind DNA 

Chromatin must be in accessible/open euchromatin arrangement 

Helicase: 

•  Untwists parental DNA  at replication forks (very rapid – as fast as a jet engine!) 

• Replication bubbles form (2 forks/bubble) 

Topoisomerase: 

•  breaks, swivels, rejoins the parental DNA, ahead of the replication fork, to relieve strain cause by unwinding 

Stabilise unwound single DNA strands 

• Single-strand binding proteins:  

• stabilize unwound parental strands

RNA primer 

• DNA polymerase cannot initiate synthesis of a polynucleotide, they can only add nucleotides to an existing chain base-paired to the template strand. 

•  RNA primase synthesises RNA primers 

RNA primer: 

• 5-10 nucleotide-long RNA chain based-paired to the parental strand 

Replicate DNA: step 2

DNA pol III adds nucleotides to the 3’ end of the RNA primer.  

• DNA strand only added to in 5’ to 3’ direction  

DNA pol I removes RNA nucleotides from primer at 5’ end and replaces with DNA added to 3’ end of adjacent fragment 

Join DNA Okazaki fragments, leading strand : DNA replication step 3

DNA ligase: 

Leading strand:  

• Joins 3’ end of DNA that replaces primer to the rest of the leading strand 

Lagging strand:  

• Replication fork opens and leading strand grows at 3’ end. Joins Okazaki fragments on lagging strand

  
  

• Prokaryotic chromosomes are circular 

• A single ligase is needed for the leading strand to form a circle of DNA. Many ligase molecules needed to connect all the Okazaki fragments for the lagging strand to complete a circle of DNA. 

Leading daughter strand synthesis (5’ to 3’ strand) 

• RNA primase synthesises RNA primer at site where replication begins (middle of bubble) 

• DNA polymerase III adds nucleotides to the 3’ end 

• Only one RNA primer is needed 

• Bubbles join 

• Strands joined by DNA ligase 

• Leading strand is completed 

• Replicate new strand of DNA using template parental strand to make a complementary strand 

• RNA primer added to 5’ end, grows in 3’ direction (bases added on in 3’ direction) 

Lagging daughter strand (3’ to 5’ strand) 

• Each Okazaki fragment must be primed separately 

• RNA primase synthesises RNA primer at sites where replication begins 

• DNA polymerase III adds nucleotides to the 3’ end 

• DNA polymerase I replaces the RNA nucleotides of the adjacent primer with DNA nucleotides 

• Okazaki fragments joined by DNA ligase 

• Lagging strand is completed 

• The lagging daughter strand is made in “sections” of DNA called Okazaki fragments 

• RNA primer added to 5’ end, grows in 3’ direction (bases added on in 3’ direction) 

Why have linear chromosomes? 

• It is thought that the more ‘primitive’ state for DNA is the one seen in Prokaryotes (circular DNA) – also seen in DNA of mitochondria and chloroplasts  

• Linear chromosomes allow for: 

• Crossing over, formation of chiasmata and exchange of genetic material during DNA replication 

• More genetic variability can therefore be found in offspring – potentially a huge advantage in a changing environment 

Pillars of bio-ethics: 

focus on individual rights 

• Autonomy (individual choice) 

• Beneficience (do good) 

• Justice (available to all, fair/just) 

• Non-maleficence (do no harm) 

Māori ethical framework 

Goes beyond individual rights, to iwi and wider care 

• Whakapapa (relationships) 

• Eg testing blood tells about whakapapa, not just yourself 

• Tika (research design) 

• Who is consulted, how is research designed,  

• Manaakitanga (cultural and social responsibility) 

• Mana (justice and equity) 

Core concepts of māori ethical framework

TAPU 

• RESTRICTED 

kia tūpato 

• Careful consideration 

Āta – whakairo 

• Precise analysis 

Āta – korero 

• Robust discussion 

Āta - whiriwhiri 

• Determine these conditions 

Āta – haere 

• Proceed with understanding 

NOA 

• UNRESTRICTED 

te tiriti: All research in New Zealand is of interest to Māori, and research which includes Māori is of paramount importance to Māori.

Best practise 

Best practice level of ‘relationship’ empowers Māori to take a kaitiaki role within the research project with a view to ensuring that tangible outcomes are realised within Māori communities. 

A relationship displaying transparency, good faith, fairness and truthfulness is captured in the concept of whakapono (hope) and the whakatauki (proverb): “kia u ki te whakapono, kia aroha tetahi ki tetahi” (Hold strong to your beliefs and care for one another) 

Heel prick testing 

• Within 24 hours after birth 

• Blood (up to 4 spots) from heel prick 

Why more than one spot? 

• Re-test, medical or forensic use, research, police 

Release samples? Parent/caregiver or police request 

Info noted: 

• Baby’s name, gender, NHI number, date of birth 

• Mother’s name, NHI number, date of birth 

• Breast milk or formula 

• Midwife/Doctor name & contact details 

What do genetic and metabolic screenings screen for: 

• Amino acid disorders 

• Fatty acid oxidation disorders 

• Congenital hypothyroidism  

• Congenital adrenal hyperplasia  

• Galactosaemia 

• Biotinidase deficiency  

• Severe combined immunodeficiency  

• cystic fibrosis (the only DNA test) 

Lily and Milton’s stories 

Congenital hypothyroidism (CH): 

• Thyroid hormone (thyroxine) essential for: 

• normal brain development in first two years of life 

• regulating growth & development 

case study on bio-ethics: demanding blood samples

• Report by the Privacy Commissioner (2003) into the collection, retention, use and release of newborn metabolic screening test samples  

• High Court in Auckland 

• Judge ask to produce the blood sample of a child 

• Wanted to test DNA in blood sample for declaration of paternity 

• Mother did not consent, child was below age of consent 

Issues raised by the Privacy Commissioner  

Approx. 60,000 births/year In 2003 1.9 million samples = DNA database. must know: 

• How long will samples be kept for? 

• (France destroy post-testing, W. Australia 2 years)

• What information is given to mothers? 

• What can the samples be used for/who has third party access? 

• How will this be enforced by the legislation?