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1. NAGE and Genetics
2. So whats first year all about?! First years all about having a good time, you dont need to study till a week before!
3. Pictures are welcome!
4. NAGE - The Basics! A, G, C, T present in DNA, U only present in RNA.
DNA & RNA are both nucleic acids linear polymers of nucleotides.
Difference between sugars in DNA & RNA deoxyribose lacks O on 2 carbon.
A, G, C, T present in DNA, U only present in RNA.
DNA & RNA are both nucleic acids linear polymers of nucleotides.
Difference between sugars in DNA & RNA deoxyribose lacks O on 2 carbon.
5. NAGE - DNA Phosphodiester bonds phosphate is always on 5C linked to OH on 3.
Bases encode genetic info point inwards and held together by H bonds A T 2H bonds and C G 3H bonds Note T is replaced by U in RNA.
Specificity of base pairing is critical to ensure production of correct protein Hybridisation in mixture of different strands complementary strands will find each other.
Melt strand heat or low salt and to reanneal cool or high salt.
Sugar phosphate backbone plays a structural role and makes up backbone of DNA negative charges on outside see next slide for more info.
Phosphodiester bonds phosphate is always on 5C linked to OH on 3.
Bases encode genetic info point inwards and held together by H bonds A T 2H bonds and C G 3H bonds Note T is replaced by U in RNA.
Specificity of base pairing is critical to ensure production of correct protein Hybridisation in mixture of different strands complementary strands will find each other.
Melt strand heat or low salt and to reanneal cool or high salt.
Sugar phosphate backbone plays a structural role and makes up backbone of DNA negative charges on outside see next slide for more info.
6. NAGE - Packaging of DNA Chromatin: a complex of DNA and proteins
Eukaryotic DNA is tightly packaged into chromatin
Nucleosome: DNA wrapped around histone proteins
The nucleosome is the lowest level of packaging: it causes ~7-fold condensation of DNA (~10 nm)
30 nm fibre: the chain of nucleosomes is further packed to generate a more compact structure (40-fold condensation)
The nucleosome includes: ~200 bp of DNA (linker DNA + core DNA)
Nucleosomes form a chain which pack into a helical array
Histones: positively charged proteins which interact with the negatively charged sugar-phosphate backbone of DNA
Core DNA: ~150 bp of DNA is wound around the histone octamer in a left-handed superhelix
Histone octamer: composed of histones H2A, H2B, H3 and H4 (2 copies of each histone)
Beads on a string is a form of chromatin which is made of several histones
Chromatin packed together to form 30nm fibers
30nm fibers make up a chromosome
Net result DNA molecule has been packaged into a mitotic chromosome that is 10 000 fold shorter than its extended length. Chromatin: a complex of DNA and proteins
Eukaryotic DNA is tightly packaged into chromatin
Nucleosome: DNA wrapped around histone proteins
The nucleosome is the lowest level of packaging: it causes ~7-fold condensation of DNA (~10 nm)
30 nm fibre: the chain of nucleosomes is further packed to generate a more compact structure (40-fold condensation)
The nucleosome includes: ~200 bp of DNA (linker DNA + core DNA)
Nucleosomes form a chain which pack into a helical array
Histones: positively charged proteins which interact with the negatively charged sugar-phosphate backbone of DNA
Core DNA: ~150 bp of DNA is wound around the histone octamer in a left-handed superhelix
Histone octamer: composed of histones H2A, H2B, H3 and H4 (2 copies of each histone)
Beads on a string is a form of chromatin which is made of several histones
Chromatin packed together to form 30nm fibers
30nm fibers make up a chromosome
Net result DNA molecule has been packaged into a mitotic chromosome that is 10 000 fold shorter than its extended length.
7. NAGE DNA replication DNA Helicase uses ATP to break the H bonds between bases more energy required to break C G than A T.
DNA Polymerase adds to 3 prime end it cannot syntheise a new chain from scratch.
Energy released by hydrolysis of OH group free 3 hydroxyl group is required nucleoside analogue.
Nucleoside analogues act as chain terminators ? No free 3 OH group this prevents further DNA replication cliinical useful in treatment of HIV Zalcitabine, ziduovine. DNA Helicase uses ATP to break the H bonds between bases more energy required to break C G than A T.
DNA Polymerase adds to 3 prime end it cannot syntheise a new chain from scratch.
Energy released by hydrolysis of OH group free 3 hydroxyl group is required nucleoside analogue.
Nucleoside analogues act as chain terminators ? No free 3 OH group this prevents further DNA replication cliinical useful in treatment of HIV Zalcitabine, ziduovine.
8. NAGE - Replication Because DNA is asymmetrical there are 2 template strand for the daughter cell the leading strand and the lagging strand they have opposite orientations.
Leading strand is synthesised continuously in a 5 ? 3 direction.
Lagging strannd synthesised in short pieces known as okazaki fragments. Because DNA is asymmetrical there are 2 template strand for the daughter cell the leading strand and the lagging strand they have opposite orientations.
Leading strand is synthesised continuously in a 5 ? 3 direction.
Lagging strannd synthesised in short pieces known as okazaki fragments.
9. NAGE 2 - transcription RNA primes the synthesis of new DNA:
Primase: an RNA polymerase which synthesises a short RNA primer (~5 nucleotides long)
RNA primer: required to start synthesis of the leading strand at a replication origin
The RNA primer is transient; it is removed later during replication
Synthesis of the lagging strand:
Primase synthesises a new RNA primer
DNA polymerase adds dNTPs to the RNA primer: this forms an Okazaki fragment
DNA polymerase completes the Okazaki fragment
A ribonuclease primer removes the RNA primer using 5 ? 3 exonuclease activity
DNA polymerase synthesises DNA through the RNA primer region
DNA ligase joins the new Okazaki fragment to the growing DNA chain using ATP: this makes the DNA strand continuous
Incorrect bases removed by 3 ? 5 exonuclease activity of DNA polymerase hydrolyses the phosphodiester bond & new correct nucleotide added.
RNA primes the synthesis of new DNA:
Primase: an RNA polymerase which synthesises a short RNA primer (~5 nucleotides long)
RNA primer: required to start synthesis of the leading strand at a replication origin
The RNA primer is transient; it is removed later during replication
Synthesis of the lagging strand:
Primase synthesises a new RNA primer
DNA polymerase adds dNTPs to the RNA primer: this forms an Okazaki fragment
DNA polymerase completes the Okazaki fragment
A ribonuclease primer removes the RNA primer using 5 ? 3 exonuclease activity
DNA polymerase synthesises DNA through the RNA primer region
DNA ligase joins the new Okazaki fragment to the growing DNA chain using ATP: this makes the DNA strand continuous
Incorrect bases removed by 3 ? 5 exonuclease activity of DNA polymerase hydrolyses the phosphodiester bond & new correct nucleotide added.
10. NAGE replication fork Replication fork proteins: a group of proteins that work together with DNA polymerase and primase to form a multi-enzyme complex which performs DNA replication
The replication complex: most of the enzymes involved in DNA replication are held together as a large multi-enzyme complex
Both daughter strands are synthesised continuously since the lagging strand template is loopedReplication fork proteins: a group of proteins that work together with DNA polymerase and primase to form a multi-enzyme complex which performs DNA replication
The replication complex: most of the enzymes involved in DNA replication are held together as a large multi-enzyme complex
Both daughter strands are synthesised continuously since the lagging strand template is looped
11. NAGE Gene Expression Genes ? units of DNA which encode info for synthesis of proteins & functional RNA.
Majority of genes are housekeeping genes only 25% specific function.
Gene expression occurs in nucleus of cells. RNA is ALWAYS the product of initial gene expression.
Transcription DNA nucleotide sequence info copied into RNA.
DNA unwinds ? RNA base pairs with DNA bases on ANTISENSE STRAND
Requires RNA Polymerase and transcription factors.
RNA polymerase ? enzyme which carries out gene transcription.
Eukaryotic cells possess 3 types:
RNA polymerase I transcribes rRNA
RNA polymerase II transcribes genes encoding proteins into mRNA
RNA polymerase III transcribes tRNA and 5S RNA.
RNA polymerase ? enzyme which carries out gene transcription.
Eukaryotic cells possess 3 types:
RNA polymerase I transcribes rRNA
RNA polymerase II transcribes genes encoding proteins into mRNA
RNA polymerase III transcribes tRNA and 5S RNA.
12. NAGE Basal transcription complex Gene promoter: DNA sequence where initiation complex assembles.
Transcription factor binding sites: Control rate of transcription via transcription binding.
TATA box: Specifies initiation for transcription by RNA pol II
Transcription factors: proteins which regulate level of transcription ? activators & repressors.
TF IID ? contains TATA binding proteins (TBP) & TBP accessory factors (TAFs) this allows for asymmetrical unwinding ? allows for unidirectional transcription.
TF IIB ? able to bind to TF IID & RNA Pol II.
TF IIH ? promotes further unwinding which facilitates RNA synthesis by RNA Pol II.
BASAL transcription complex for BASAL low level of transcription. Can have additional TFs which can change the level of transcription (increase or decrease)
TFs can recruit enzymes that modify histones acetylation opens histone tails loosening the tie of DNA to histones therefore, hyperacetylation correlates with gene expression and hypoacetylation correlates with genre repression. Gene promoter: DNA sequence where initiation complex assembles.
Transcription factor binding sites: Control rate of transcription via transcription binding.
TATA box: Specifies initiation for transcription by RNA pol II
Transcription factors: proteins which regulate level of transcription ? activators & repressors.
TF IID ? contains TATA binding proteins (TBP) & TBP accessory factors (TAFs) this allows for asymmetrical unwinding ? allows for unidirectional transcription.
TF IIB ? able to bind to TF IID & RNA Pol II.
TF IIH ? promotes further unwinding which facilitates RNA synthesis by RNA Pol II.
BASAL transcription complex for BASAL low level of transcription. Can have additional TFs which can change the level of transcription (increase or decrease)
TFs can recruit enzymes that modify histones acetylation opens histone tails loosening the tie of DNA to histones therefore, hyperacetylation correlates with gene expression and hypoacetylation correlates with genre repression.
13. NAGE TFs in action Initiators of inflammation stimulate breakdown of ikB therefore NFkB stimulates transcription of cytokine genes in nucleus to produce cytokines.
Aspirin inhibits breakdown of IkB ? NFkB cannot stimulate transcription of cytokine gene.
**mention tamoxifen use in breast cancer treatment- anti oestrogen (50% breast cancer over-expresses oestrogen receptor)Initiators of inflammation stimulate breakdown of ikB therefore NFkB stimulates transcription of cytokine genes in nucleus to produce cytokines.
Aspirin inhibits breakdown of IkB ? NFkB cannot stimulate transcription of cytokine gene.
**mention tamoxifen use in breast cancer treatment- anti oestrogen (50% breast cancer over-expresses oestrogen receptor)
14. NAGE mRNA processing Overview of RNA processing: Introns are spliced out and the exons are joined together to form mature mRNA this is modified further by the poly A tail and the cap. Overview of RNA processing: Introns are spliced out and the exons are joined together to form mature mRNA this is modified further by the poly A tail and the cap.
15. NAGE - mRNA splicing Splice donor site 5 end AGGU
Splice acceptor site 3 end (Pyr)15 NCAG
snRNPs u1,2,4,5,6 ? U1 binds to donor site whereas U5 binds to the acceptor site the rest bind to the complex to form the SPLICESOME
Spliceosome: a large RNA-protein complex that catalyses splicing
It is composed of 5 small ribonuclear proteins (snRNPs): U1, U2, U4, U5 and U6
Splice donor sequence is cleaved (AG/GU)
A phosphodiester bond is formed between the 5 phosphate of the G at the 5 end of the intron and the 2 OH of the branchpoint A (adenylate)
The phosphodiester bond between the G at the 3 end of the intron and next exon is cleaved
The intron is removed as a lariat structure
The exposed, adjacent exons are ligated
7 methyl guanalyate CAP structure added to 5 end protects & greatly enhances translation of mRNA. Polio and cap.Splice donor site 5 end AGGU
Splice acceptor site 3 end (Pyr)15 NCAG
snRNPs u1,2,4,5,6 ? U1 binds to donor site whereas U5 binds to the acceptor site the rest bind to the complex to form the SPLICESOME
Spliceosome: a large RNA-protein complex that catalyses splicing
It is composed of 5 small ribonuclear proteins (snRNPs): U1, U2, U4, U5 and U6
Splice donor sequence is cleaved (AG/GU)
A phosphodiester bond is formed between the 5 phosphate of the G at the 5 end of the intron and the 2 OH of the branchpoint A (adenylate)
The phosphodiester bond between the G at the 3 end of the intron and next exon is cleaved
The intron is removed as a lariat structure
The exposed, adjacent exons are ligated
7 methyl guanalyate CAP structure added to 5 end protects & greatly enhances translation of mRNA. Polio and cap.
16. NAGE post transcriptional modification of mRNA RNA Capping
The terminal 5 triphosphate of mRNA is hydrolysed to a diphosphate (i.e. a phosphate is removed)
The terminal 5 diphosphate reacts with the a-phosphate of GTP to form a 5-5 phosphate linkage: this forms a cap at the 5 end of mRNA
The cap is modified: guanine is methylated at the N7 position in the purine ring to form a 7-methylguanylate cap
5 cap Polio: virus ? cap less recognised in translation ? reduced translation ? paralysis
Thalassaemia: a genetic, haematological disease in which there is an imbalance in the relative amount of a- and -globin chains which make up haemoglobin
Symptoms: severe anaemia by 12 months of age; extramedullary haematopoiesis; hepatomegaly or hepatosplenomegaly
-Thalassaemia: there is a relative deficiency of -globin chains RNA Capping
The terminal 5 triphosphate of mRNA is hydrolysed to a diphosphate (i.e. a phosphate is removed)
The terminal 5 diphosphate reacts with the a-phosphate of GTP to form a 5-5 phosphate linkage: this forms a cap at the 5 end of mRNA
The cap is modified: guanine is methylated at the N7 position in the purine ring to form a 7-methylguanylate cap
5 cap Polio: virus ? cap less recognised in translation ? reduced translation ? paralysis
Thalassaemia: a genetic, haematological disease in which there is an imbalance in the relative amount of a- and -globin chains which make up haemoglobin
Symptoms: severe anaemia by 12 months of age; extramedullary haematopoiesis; hepatomegaly or hepatosplenomegaly
-Thalassaemia: there is a relative deficiency of -globin chains
17. NAGE Genetic code
Wobble position non standard base pairing may occur between 3rd (3) base in mRNA codon & 1st base (5) in tRNA.
Wobble position non standard base pairing may occur between 3rd (3) base in mRNA codon & 1st base (5) in tRNA.
18. NAGE Aminoacyl tRNA synthetase Amino acid + ATP + Enzyme ? Enzyme AMP Amino acid + Ppi
Enzyme AMP Amino acid = tRNA ? Aminoacyl tRNA + AMP + EnzymeAmino acid + ATP + Enzyme ? Enzyme AMP Amino acid + Ppi
Enzyme AMP Amino acid = tRNA ? Aminoacyl tRNA + AMP + Enzyme
19. NAGE Translation initiation Translation occurs in cytoplasm or rough ER.
Differences in eukaryotic and prokaryotic ribsomoes clinically useful as antibiotics can selectively inhibit protein translation in prokaryotes.
Only initiator Met tRNA can bind to 40S subunit alone.
Met tRNA then binds to AUG once mRNA is bound to pre-initiation complex.
Hydrolysis of GTP ensures correct base pairing, Translation occurs in cytoplasm or rough ER.
Differences in eukaryotic and prokaryotic ribsomoes clinically useful as antibiotics can selectively inhibit protein translation in prokaryotes.
Only initiator Met tRNA can bind to 40S subunit alone.
Met tRNA then binds to AUG once mRNA is bound to pre-initiation complex.
Hydrolysis of GTP ensures correct base pairing,
20. NAGE Translation elongation Remember A site aminoacyl i.e. binds an aminoacyl tRNA
P site peptidyl site i.e. binds a peptidyl tRNA
E site exit site binds a free tRNA prior to its exit
1.A new aminoacyl tRNA, carrying a 2nd amino acid, binds to the A (aminoacyl) site:
Initiator Met-tRNA occupies the P (peptidyl) site
The aminoacyl tRNA binds to the A site in frame with the initiator Met-tRNA using eIF2 and GTP
2. Peptidyl transferase catalyses the formation of a peptide bond between the 2 amino acids on the 60S subunit
tRNA is translocated to the P site and the 1st tRNA molecule moves to the E site before it dissociates:
3. The ribosome moves along mRNA by 1 codon
Elongation factors (EFs) promote movement of the ribosome along mRNA using GTP
The 1st tRNA molecule dissociates
Steps 1-3 are repeated and the cycle continues with a new aminoacyl tRNA
N.B. EFs use energy from GTP to enhance the efficiency and the accuracy of translation by providing pauses which allow incorrect base pairs to dissociate
Termination: stop codon, RFs and peptidyl transferase transfers peptide chain to water
Antibiotics exploit difference between prokaryotic and eukaryotic transcription mechanismsRemember A site aminoacyl i.e. binds an aminoacyl tRNA
P site peptidyl site i.e. binds a peptidyl tRNA
E site exit site binds a free tRNA prior to its exit
1.A new aminoacyl tRNA, carrying a 2nd amino acid, binds to the A (aminoacyl) site:
Initiator Met-tRNA occupies the P (peptidyl) site
The aminoacyl tRNA binds to the A site in frame with the initiator Met-tRNA using eIF2 and GTP
2. Peptidyl transferase catalyses the formation of a peptide bond between the 2 amino acids on the 60S subunit
tRNA is translocated to the P site and the 1st tRNA molecule moves to the E site before it dissociates:
3. The ribosome moves along mRNA by 1 codon
Elongation factors (EFs) promote movement of the ribosome along mRNA using GTP
The 1st tRNA molecule dissociates
Steps 1-3 are repeated and the cycle continues with a new aminoacyl tRNA
N.B. EFs use energy from GTP to enhance the efficiency and the accuracy of translation by providing pauses which allow incorrect base pairs to dissociate
Termination: stop codon, RFs and peptidyl transferase transfers peptide chain to water
Antibiotics exploit difference between prokaryotic and eukaryotic transcription mechanisms
21. NAGE Translation termination Stop codon recognised by release factors which then bind to empty A site
Release of polypeptide chain peptidyl transferase catalyses transfer of completed chain to water
Release factors and ribosomes dissociate
There is no tRNA for a stop codon and they do not specify an amino acid instead it is recognised by release factors.
Binding of release factors to the A site alters the activity of the peptidyl transferase, causing it to catalyse the addition of a water molecule instead of an amino acid to the peptidyl- tRNA.
This reaction frees the carboxyl end of the polypeptide from its attachement to the tRNA because this is the only attachment holding the polypeptide to the ribosome, the completed chain is immediately released into the cytosol.
There is no tRNA for a stop codon and they do not specify an amino acid instead it is recognised by release factors.
Binding of release factors to the A site alters the activity of the peptidyl transferase, causing it to catalyse the addition of a water molecule instead of an amino acid to the peptidyl- tRNA.
This reaction frees the carboxyl end of the polypeptide from its attachement to the tRNA because this is the only attachment holding the polypeptide to the ribosome, the completed chain is immediately released into the cytosol.
22. NAGE Secretory and transmembrane proteins Protein synthesis takes place in the cytoplasm, but most cellular compartments are bounded by a membrane so a mechanism is required to transport secretory and transmembrane proteins across the bilayer.
Binding of SRP to signal sequence doesnt actually stop translation slows down ribosome. Alberts page 508
Secretory proteins then packaged into vesicles and transported to correct site.
Transmembrane proteins have 2 signal sequences when it reaches the second one the protein channel discharges the proteins sideways and cleaves off first signal sequence. The second sequence remains anchored in the membrane and protein synthesis continues on the cytosolic side. Protein synthesis takes place in the cytoplasm, but most cellular compartments are bounded by a membrane so a mechanism is required to transport secretory and transmembrane proteins across the bilayer.
Binding of SRP to signal sequence doesnt actually stop translation slows down ribosome. Alberts page 508
Secretory proteins then packaged into vesicles and transported to correct site.
Transmembrane proteins have 2 signal sequences when it reaches the second one the protein channel discharges the proteins sideways and cleaves off first signal sequence. The second sequence remains anchored in the membrane and protein synthesis continues on the cytosolic side.
23. NAGE 6 analysis of nucleic acids Type II restriction endonucleases only cleaves unmethylated DNA
Electrophoresis- DNA moves towards the anode
Hybridisation- labelled probe and homologous target, on a solid supportType II restriction endonucleases only cleaves unmethylated DNA
Electrophoresis- DNA moves towards the anode
Hybridisation- labelled probe and homologous target, on a solid support
24. Meiosis and recombination The karyotype
The processes of miosis and mitosis and the differences between them
Recombination
Linkage
25. Pedigrees
Modes of inheritance
Polymorphism and mutation
Markers and linkage The inheritance of variation
26. Recombination
28. This can be clinically useful (linkage)
29. What if the disease gene and marker are far apart?
31. Using this diagram of a family tree, state which of the following statements is TRUE
A is a carrier of the disease.
A and B have two daughters and one son.
Any children C and F have will be carriers of the disease.
B is male.
This is an example of an autosomal recessive disorder.
32. What is meant by Polymorphism?
a) A variant present in the population at a frequency of more than 1%
b) A variant present in the population at a frequency of less than 1%
c) When there are many mutations in one gene
d) When there are many phenotypical effects
e) When several genes experience mutations simultaneously
Answer= a
33. Linkage is the association of any known marker with another marker more often than by chance. (>50%). Log of Odds (LOD) score establishes linkage between a trait and a marker or two markers. Which of these statements is true?
a) LOD > 3 indicates linkage and LOD = -2 indicates no linkage
b) LOD > 4 indicates linkage and LOD = -2 indicates no linkage
c) LOD < 3 indicates linkage and LOD = -1 indicates no linkage
d) LOD < 3 indicates linkage and LOD = 0 indicates no linkage
e)LOD > 3 indicates linkage and LOD = 0 indicates no linkage
Answer= a
34. Aneuploidy and other chromosome aberrations Human chromosome banding
Translocations
What is aneuploidy
Downs Syndrome
Turners syndrome
Kleinefelters Syndrome
XYY Males
Sex determination
37. Sex determination
38. The Y chromosome carries very few genes. What is the main gene carried by the Y chromosome?
a) XY gene
b) XX gene
c) SRYY gene
d) SRX gene
e) SRY gene
Answer: e
39. Prenatal Diagnosis Indications for prenatal diagnosis
Ante-natal screening for Downs Syndrome
Prenatal testing
Cytogenetic Techniques
Management options
40. Testing for Downs Syndrome: Trisomy 21
Increased maternal age
Nuchal translucency
Serum screening
Nasal bones absent in ~74% of aneuploid fetuses
41. Prenatal testing: USS guided Amniocentesis at >15wks
(better in mid-trimester than earlier)
Chorionic Villus Sampling at >11 wks
(was thought to be associated with limb bud defects)
Issues: increased miscarriage risk, Rh sensitisation, culture failure
Blood sampling > 18wks under USS guidance to intra-hepatic vein
(mainly for anaemia)
42. Genetic diseases in Childhood: Disorders of amino acid metabolism
Disorders of carbohydrate metabolism
Disorders of steroid metabolism
Disorders of lipid storage
Disorders of urea cycle
Classification of congenital abnormalities
44. Congenital Adrenal Hyperplasia
45. Population Genetics Why study it?
Some basic definitions- population, gene pool, polymorphisms
Concept of the Hardy Weinberg equilibrium
Using the Hardy Weinberg Equation in calculations
46. DNA mutations and Genetic Diseases Consequences of somatic and germline mutations
Cystic Fibrosis
Huntingdons Disease
Duchennes Muscular Dystrophy
The concept of X-inactivation
Genetics in diagnosing and treating disease
47. Cystic Fibrosis (7q31 mutation)
48. The result Pancreatic insufficiency
Chronic lung infections
Male infertility (no vas deferens)
Perinatal gut obstruction
Severity depends on degree of malfunction (only 10% transporter function needed)
49. Mutations causing cystic fibrosis: Mainly point mutations:
Non-sense (stop codon included)
b) Missense (wrong amino acid). E.g. deltaF508 ? protein made doesnt get transported from the ER to the cell membrane.
c) Frameshift
123 123 123 123 123 123 123 123 123 123
121 231 231 231 231 231
50. Cancer
52. QUESTIONS 1) A woman's brother has Duchenne muscular dystrophy, but her father and mother are not affected. What is the probability that the woman is a carrier?
53. The Genetics of Complex Traits The difference between monogenic disease and complex traits
Disease susceptibility genes
How do we know a disease has a genetic component?
Autoimmune disease
54. More MCQs
55. A person with two X chromosomes and one Y chromosome (plus normal autosomes) is phenotypically female
F
56. 1 in 25 of the population are carriers of cystic fibrosis (CF). A carrier and a random member of the population (both unaffected) wish to have children. The probability that their child will be affected is 0.01
T
57. If there is a genetic component to a complex human disease, the disease should show lower concordance in monozygotic than dizygotic twins.
F
58. Conclusion Well done on making it so far
Work EVERY DAY starting now
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