Pedigree Charts

Essential idea: The inheritance of genes follows patterns.

The patterns that genes and the phenotypes they generate can be mapped using pedigree charts. The image show a small section of a pedigree chart that maps the inheritance of hair colour in an extended family over several generations. Analysis of pedigree charts enables us to the nature of the inheritance; controlled by dominant or recessive alleles? linked to the sex chromosomes? controlled by multiple genes or a single gene?

By Chris Paine http://www.bioknowledgy.info/ http://www.indiana.edu/~oso/lessons/Genetics/RealColors.html Understandings

Statement Guidance 3.4.U1 Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. 3.4.U2 Gametes are haploid so contain only one allele of each gene. 3.4.U3 The two alleles of each gene separate into different haploid daughter nuclei during meiosis. 3.4.U4 Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles. 3.4.U5 Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects. 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. 3.4.U7 Some genetic diseases are sex-linked. The pattern of Alleles carried on X chromosomes should be inheritance is different with sex-linked genes due to shown as superscript letters on an upper case X, their location on sex chromosomes. such as Xh. 3.4.U8 Many genetic diseases have been identified in humans but most are very rare. 3.4.U9 Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer. Applications and Skills

Statement Guidance 3.4.A1 Inheritance of ABO blood groups. The expected notation for ABO blood group alleles: O = i, A=IA, B = IB. 3.4.A2 Red-green colour blindness and hemophilia as examples of sex-linked inheritance. 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. 3.4.A4 Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl. 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses. 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. 3.4.S3 Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases. 3.4.U1 Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. Johann Gregor Mendel Mendel’s principles of inheritance (1822-1884) Learn about Mendel and his work by using the weblinks

Gregor Mendel: Great Minds by SciShow Because of his work with pea plants Mendel is considered the father of modern genetics.

He planted 1000s of seeds per trial and https://youtu.be/GTiOETaZg4w?list=PLC31B0C382 carried out many trials Biologica: Mendel’s Peas F9585D6 to be sure of his results.

Gregor Mendel and pea plants His published work (1865) is now considered important, but at the time was ignored for 30 years. http://biologica.concord.org/webtest1/ https://www.dnalc.org/view/16002-Gregor- web_labs_mendels_peas.htm Mendel-and-pea-plants.html https://upload.wikimedia.org/wikipedia/commons/3/3d/Gregor_Mendel_oval.jpg Nature of science: Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. (3.2) To use statistical tests correctly and reach valid conclusions samples of quantitative data has to be sufficiently large Larger samples give smaller First to develop theory scientists must make standard deviation*, this in deductions and test hypotheses: both processes turn makes it easier to find a rely on quantitative data. statistically significant result at Secondly It is not enough to just have numerical a higher confidence level data, the sample size must be sufficiently large to be judged reliable. In smaller samples anomalous values are more likely to skew the calculated mean The sample size required and standard varies: deviation • The larger the natural variation the larger the sample • Depends on the type *The standard deviation of the population is constant: (small) samples of statistical test used have a higher standard deviation than the population the sample comes from. http://www.conceptstew.co.uk/PAGES/nsamplesize.html Nature of science: Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. (3.2) To use statistical tests correctly and reach valid conclusions samples of quantitative data has to be sufficiently large Larger samples give smaller First to develop theory scientists must make standard deviation*, this in deductions and test hypotheses: both processes turn makes it easier to find a rely on quantitative data. statistically significant result at Secondly It is not enough to just have numerical a higher confidence level data, the sample size must be sufficiently large to be judged reliable. In smaller samples anomalous values are more likely to skew the calculated mean The sample size required and standard depends on: deviation • The larger the natural variation the larger the sample • Type of statistical test *The standard deviation of the population is not affected, remember used that (small) samples have a higher standard deviation than the population the sample comes from. http://www.conceptstew.co.uk/PAGES/nsamplesize.html This image shows a pair of homologous chromosomes. Definitions Name and annotate the labeled features. This image shows a pair of homologous chromosomes. Definitions Name and annotate the labeled features. Genotype The combination of alleles Homozygous dominant of a gene carried by an organism Having two copies of the same dominant allele Phenotype The expression of alleles Homozygous recessive of a gene carried by an organism Having two copies of the same recessive allele. Recessive alleles are Centromere only expressed when homozygous. Joins chromatids in cell division Codominant Alleles Pairs of alleles which are both Different versions of a gene expressed when present. Dominant alleles = capital letter Recessive alleles = lower-case letter Heterozygous Having two different alleles. The dominant allele is expressed.

Carrier Gene loci Heterozygous carrier of a Specific positions of genes on a recessive disease-causing allele chromosome Review: 3.3.U2 The halving of the chromosome number allows a sexual life cycle with fusion of gametes.

Many eukaryotes reproduce by sexual reproduction. Even organisms capable of asexual reproduction will reproduce sexually as well. Sexual reproduction involves fertilisation, the fusion of gametes (sex cells), one from each parent.

Because fertilisation involves the fusion of gametes the number of chromosomes in the next generation is doubled. To compensate for the chromosome doubling during fertilisation gametes To prevent a doubling of undergo meiosis, chromosomes in each which halves the generation a halving chromosomes mechanism is needed present in gametes during the life cycle. compared to the parent.

http://www.biologycorner.com/resources/diploid_life_cycle.gif 3.4.U3 The two alleles of each gene separate into different haploid daughter nuclei during meiosis. AND 3.4.U2 Gametes are haploid so contain only one allele of each gene. AND 3.4.U4 Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles.

Because fertilisation involves the fusion of gametes the number of chromosomes is doubled. The diploid organism also now contains two alleles for each gene locus. Meiosis, along with halving the chromosomes present in gametes The alleles present at also reduces the a gene locus maybe number of alleles similar or different. of each gene locus from two to one.

http://www.biologycorner.com/resources/diploid_life_cycle.gif 3.4.A1 Inheritance of ABO blood groups.

The ABO blood type classification system uses the presence or absence of certain antigen on red blood cells to categorize blood into four types. Distinct molecules called agglutinogens (a type of antigen) are attached to the surface of red blood cells. There are two different types of agglutinogens, type "A" and type "B”.

http://www.ib.bioninja.com.au/_Media/abo_blood_groups_med.jpeg http://www.anatomybox.com/tag/erythrocytes/ 3.4.A1 Inheritance of ABO blood groups. More about blood typing A Nobel breakthrough in medicine. Antibodies (immunoglobulins) are specific to antigens. The immune system recognises 'foreign' antigens and produces antibodies in response - so if you are given the wrong blood type your body might react fatally as the antibodies cause the blood to clot.

Blood type O is known as the universal donor, as it has no antigens against which the recipient immune system can react. Type AB is the universal recipient, as the blood has no antibodies which will react to AB antigens.

Blood typing game from Nobel.org: Images and more information from: http://nobelprize.org/educational/medicine/landsteiner/readmore.html http://learn.genetics.utah.edu/content/begin/traits/blood/ 3.4.A1 Inheritance of ABO blood groups.

The ABO blood type is controlled by a single gene, the ABO gene. This gene has three different alleles:

i O allele (no anitgen is produced) Allele variant IA A allele (type “A” anitgen is produced) A IB B allele (type “B” anitgen is produced) I Gene (lower case for ‘recessive’ alleles)

Diploid cells possess two alleles therefore the possible genotype and phenotype combinations are:

Genotype Antigen production Phenotype (allele combination) (characteristic expressed)

ii No antigen produced Blood type O IAIA and IAi Type “A” anitgen produced Blood type A IBIB and IBi Type “B” anitgen produced Blood type B IAIB Both type “A” and “B” anitgens produced Blood type AB

http://www.anatomybox.com/tag/erythrocytes/ 3.4.U5 Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.

Dominant alleles have the same effect on Type “A” allele present and blood the phenotype whether it is present in the type is A therefore the type “A” homozygous or heterozygous state allele is dominant to type “O” IAi Recessive alleles only have an effect on the Type “O” allele present and blood phenotype when present in the homozygous type is not O therefore the type “O” state allele is recessive to type “A”

Codominant alleles are pairs of different Type “A” and “B” alleles are alleles that both affect the phenotype when A B present and blood type is AB I I therefore type “A”and “B” alleles present in a heterozygote are codominant

http://www.anatomybox.com/tag/erythrocytes/ 3.4.U5 Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.

http://www.anatomybox.com/tag/erythrocytes/ 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

Mendel crossed some yellow peas with some yellow Explain this peas. Most offspring were yellow but some were green!

Mendel from: http://history.nih.gov/exhibits/nirenberg/popup_htm/01_mendel.htm 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

“alleles of each gene separate into different Segregation gametes when the individual produces gametes”

The yellow parent peas must Mendel did not know about be heterozygous. The yellow DNA, chromosomes or meiosis. phenotype is expressed. Through his experiments he did Through meiosis and work out that ‘heritable factors’ fertilisation, some offspring (genes) were passed on and peas are homozygous that these could have different recessive – they express a versions (alleles). green colour.

Mendel from: http://history.nih.gov/exhibits/nirenberg/popup_htm/01_mendel.htm 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

“alleles of each gene separate into different Segregation gametes when the individual produces gametes”

Key to alleles: F0 Y = yellow y = green Genotype: Y y Y y Alleles segregate during meiosis (anaphase I) and end up in different haploid gametes. Gametes: Y or y Y or y

Punnet Grid: gametes

Simplified notation of using upper case for dominant and lower case for Genotypes: recessive is acceptable in F the case of two alleles 1 Phenotypes: without co-dominance.

Phenotype ratio: Mendel from: http://history.nih.gov/exhibits/nirenberg/popup_htm/01_mendel.htm 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses. Monohybrid Cross Crossing a single trait.

A punnet grid can be used to deduce the potential outcomes of the cross and to calculate the expected ratio of phenotypes in

the next generation (F1). F Genotypes: 1 Phenotypes:

Key to alleles: F0 Y = yellow y = green Genotype: Y y Y y Alleles segregate during meiosis (anaphase I) and end up in different haploid gametes. Gametes: Y or y Y or y Fertilisation results in diploid Punnet Grid: gametes Y y zygotes. A punnet grid can be used to Y YY Yy deduce the potential outcomes of the cross and to calculate the y Yy yy expected ratio of phenotypes in the next generation (F1). F Genotypes: 1 Phenotypes:

Genotypes: YY Yy Yy yy Ratios are written in the F simplest mathematical form. 1 Phenotypes:

Phenotype ratio: Mendel from: 3 : 1 http://history.nih.gov/exhibits/nirenberg/popup_htm/01_mendel.htm 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype:

Homozygous recessive Homozygous recessive

Punnet Grid: gametes

F Genotypes: 1 Phenotypes:

Phenotype ratio: 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype: y y y y Homozygous recessive Homozygous recessive

Punnet Grid: gametes y y y yy yy y yy yy F Genotypes: yy yy yy yy 1 Phenotypes: Phenotype ratio: All green 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype:

Homozygous recessive Heterozygous

Punnet Grid: gametes

F Genotypes: 1 Phenotypes:

Phenotype ratio: 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype: y y Y y Homozygous recessive Heterozygous

Punnet Grid: gametes Y y y Yy yy y Yy yy F Genotypes: Yy Yy yy yy 1 Phenotypes: Phenotype ratio: 1 : 1 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype:

Homozygous dominant Heterozygous

Punnet Grid: gametes

F Genotypes: 1 Phenotypes:

Phenotype ratio: 3.4.S1 Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

What is the expected ratio of phenotypes Monohybrid Cross in this monohybrid cross?

Key to alleles: F0 Phenotype: Y = yellow y = green Genotype: Y Y Y y Homozygous dominant Heterozygous

Punnet Grid: gametes Y y Y YY Yy Y YY Yy F Genotypes: YY YY Yy Yy 1 Phenotypes: Phenotype ratio: All yellow 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. Cat genetics – collecting real world data Do the inherited traits match what we know about cat genes?

http://www.g3journal.org/content/4/10/1881/F4.large.jpg 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. Cat genetics – collecting real world data

Locus Phenotype and genotypes guide Cats surveyed 1 2 … 12 1. Sex Male (XY) / Female (XX) record genotype 2. Hair length short (ll) / long (LL, Ll) record phenotype 3. Dominant white completely white (WW, Ww) / some colour (ww) record phenotype - stop here if white is recorded 4. Piebald No white (ss) / Some White (Ss) / Mostly White (SS) record genotype, some is < 50%, more is > 50% 5. Pigment density dense - black, brown or orange (DD, Dd) / diffuse - gray, light brown or cream (dd) record phenotype 5. Orange orange or cream (XOXO, XOY) / orange and black or cream and grey (XOXo) / black or grey (XoXo, XoY) record genotype appropriate for the sex

Cat images: https://www.petfinder.com/ Source: http://udel.edu/~mcdonald/mythintro.html 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. Cat genetics – collecting real world data

1. Use the slide (previously) or first hand data collected from a family of cats 2. Survey the cats by completing the table (on the prior slide) – make sure you indicate which cats are the parents and which are the offspring It is important you do not create results, if you cannot determine a characteristic learn the box empty or write unknown 3. From the parental background on the genetic traits construct an expected frequency table 4. Test the expected frequencies against those observed using the Chi-Squared test (see the following slides

n.b. especially with small sample sizes it is not always the case that observed data will support theory. Outcomes are individual events and independent of the collective probability, but the larger the sample the more likely the general outcome will follow the theoretical expectation.

How well does the piebald frequency in the offspring match the predictions made from our knowledge of the genes? Key to alleles: F0 Phenotype: Some white No white S = White s = no white Genotype: S s s s Key to genotypes: ss = no white Punnet Grid: gametes s s Ss = some white SS = mostly white S Ss Ss s ss ss F Genotypes: Ss Ss ss ss 1 Phenotypes: Some white No white Expected ratios Phenotype ratio: 1 : 1 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. Cat genetics – collecting real world data

How well does the piebald frequency in the offspring match the predictions made from our knowledge of the genes? df critical values genotype observed expected at 5% 1 3.84 SS 0 0 2 5.99 (mostly white) 3 7.82 Ss 3 2 (some white) 4 9.49 ss 5 11.07 1 2 (no white)

N = number of classes Degrees of freedom (df) = N – 1 Chi-squared value = = 3 – 1 = 2 = (0 – 0)2 + (3 – 2)2 + (1 – 2)2 0 2 2 Chi-squared value < critical value therefore we support the hypothesis of piebald coat colour = 1 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data. Chi-squared Test and genetics

More help and examples using the Chi-squared test:

http://www.slideshare.net/gurustip/the-chisquared-test 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data.

Used to determine the genotype of an unknown individual. Test Cross The unknown is crossed with a known homozygous recessive.

Key to alleles: F0 Phenotype: R = Red flower r = white Genotype: R ? r r unknown Homozygous recessive Possible outcomes:

F1 Phenotypes: Unknown parent = RR Unknown parent = Rr

gametes gametes 3.4.S2 Comparison of predicted and actual outcomes of genetic crosses using real data.

Used to determine the genotype of an unknown individual. Test Cross The unknown is crossed with a known homozygous recessive.

Key to alleles: F0 Phenotype: R = Red flower r = white Genotype: R ? r r unknown Homozygous recessive Possible outcomes:

F1 Phenotypes: All red Some white, some red Unknown parent = RR Unknown parent = Rr

gametes r r gametes r r R Rr Rr R Rr Rr R Rr Rr r rr rr 3.4.U8 Many genetic diseases have been identified in humans but most are very rare.

3,358 genes with a phenotype-causing mutation (OMIM, March 19, 2015) Estimated total of 20,000-25,000 genes that are expressed as proteins (International Human Genome Sequencing Consortium, 2004). Although it is impossible to give a single value estimate we can say that genetic diseases are very rare.

The number of genes present in the human genome along with the fact that most conditions are autosomal recessive: it is unlikely that one parent will have a mutation on a disease related gene, but the probability that both parents have a mutation on the same gene is very small. http://learn.genetics.utah.edu/content/history/geneticrisk/ For example: Phenylketonuria (PKU) is a rare metabolic disorder that can be destructive to the nervous system, causing intellectual disability. About 1 out of every 15,000 babies is born with PKU. (Source: http://learn.genetics.utah.edu/content/disorders/singlegene/pku/) 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Career-related Case Study “According to the US Bureau of Labor Statistics, the graduate of today will change career four to six times in a lifetime. By one estimate, 65 per cent of the jobs that will be available upon college graduation for students now entering high school (that's eight years from now) do not yet exist. Consider the new interdisciplinary field of genetic counselling, which combines biological science with social work and ethics - it was ranked as one of the "top 10" career choices of 2010 because it offered far more openings than could be filled by qualified applicants.” From the Times Higher Education Supplement – “So Last Century” http://www.timeshighereducation.co.uk/story.asp?sectioncode=26&storycode=415941&c=2

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Career-related Case Study “According to the US Bureau of Labor Statistics, the graduate of today will change career four to six times in a lifetime. By one estimate, 65 per cent of the jobs that will be available upon college graduation for students now entering high school (that's eight years from now) do not yet exist. Consider the new interdisciplinary field of genetic counselling, which combines biological science with social work and ethics - it was ranked as one of the "top 10" career choices of 2010 because it offered far more openings than could be filled by qualified applicants.” From the Times Higher Education Supplement – “So Last Century” http://www.timeshighereducation.co.uk/story.asp?sectioncode=26&storycode=415941&c=2 You are a genetic counselor. A couple walk into your clinic and are concerned about their pregnancy. They each have one parent who is affected by cystic fibrosis (CF) and one parent who has no family history. Explain CF and its inheritance to them. Deduce the chance of having a child with CF and how it can be tested and treated.

Use the following tools in your explanations: • Pedigree chart • Punnet grid • Diagrams

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. AND 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. Cystic Fibrosis (CF) Clinical example. Pedigree charts can be used to trace family histories and deduce genotypes and risk in the case of inherited gene-related disorders. Here is a pedigree chart for this family history.

key female male I affected

Not II Affected A B deceased III ? Is CF dominant or recessive? How do you know? • •

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. AND 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. Cystic Fibrosis (CF) Clinical example. Pedigree charts can be used to trace family histories and deduce genotypes and risk in the case of inherited gene-related disorders. Here is a pedigree chart for this family history.

key female male I affected

Not II Affected A B deceased III ? Is PKU dominant or recessive? How do you know? • Recessive • Unaffected mother in Gen I has produced affected II A. Mother must have been a carrier.

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. AND 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. Cystic Fibrosis (CF) Clinical example. A mutation in the CFTR gene causes secretions (e.g. mucus, sweat and digestive juices) which are usually thin instead become thick.

Instead of acting as a lubricant, the secretions block tubes, ducts and passageways, especially in the lungs and pancreas. Despite therapeutic care lung problems in most CF sufferers leads to a early death (life expectancy is between 35 and 50 years).

Diagnosis- blood test taken at 6-7 days after birth http://www.flickr.com/photos/ozewiezewozewiezewallakristallix/263 2833781/ https://youtu.be/-a-WHZoTX0E

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. AND 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. Cystic Fibrosis (CF) Clinical example. What is the probability of two parents who are both carriers of the recessive allele producing children affected by CF? Key to alleles: F0 Phenotype: carrier carrier T = Normal allele t = mutated allele Genotype: T t T t

Punnet Grid: gametes T t T t F Genotypes: 1 Phenotypes: Phenotype ratio: Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. AND 3.4.A3 Inheritance of cystic fibrosis and Huntington’s disease. Cystic Fibrosis (CF) Clinical example. What is the probability of two parents who are both carriers of the recessive allele producing children affected by CF? Key to alleles: F0 Phenotype: carrier carrier T = Normal allele t = mutated allele Genotype: T t T t

Punnet Grid: gametes T t T TT Tt t Tt tt F Genotypes: TT Tt Tt tt 1 Phenotypes: Normal CF Therefore 25% chance Phenotype ratio: 3 : 1 of a child with CF Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.S3 Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

Key to alleles: Pedigree Charts T = Normal allele Pedigree charts can be used to trace family histories and deduce t = mutated allele genotypes and risk in the case of inherited gene-related disorders. Here is a pedigree chart for this family history. Key: female male

affected

Not Affected

deceased

Looks like

Deduce the genotypes of these individuals: A & B C D Genotype

Reason

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.S3 Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

affected

Not Affected

deceased

Looks like

Deduce the genotypes of these individuals: A & B C D Genotype Both Tt tt Tt To have produced affected Trait is recessive, as both Recessive traits only child H, D must have inherited are normal, yet have produced expressed when Reason a recessive allele from either A an affected child (C) homozygous. or B Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.S3 Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

Key to alleles: Pedigree Charts T = Normal allele Individuals D and $ are planning to have another child. t = mutated allele Calculate the chances of the child having CF. Key: female male

affected

Not $ Affected

deceased

Looks like

Genotypes: D = Gametes Phenotype ratio

$ = Therefore

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics 3.4.S3 Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

Key to alleles: Pedigree Charts T= Has enzyme Individuals D and $ are planning to have another child. t = no enzyme Calculate the chances of the child having CF. Key: female male

affected

Not $ Affected

deceased

Looks like

Genotypes: D = Tt (carrier) Gametes T t Phenotype ratio t Tt tt 1 : 1 Normal : CF $ = tt (affected) Therefore 50% chance of a t Tt tt child with CF

Edited from: http://www.slideshare.net/gurustip/theoretical-genetics Review: 3.1.A1 The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. Review: 3.1.A1 The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin.

https://youtu.be/1fN7rOwDyMQ 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Sickle Cell Another example of codominance. Remember the notation used: superscripts represent codominant alleles. In codominance, heterozygous individuals have a mixed phenotype.

The mixed phenotype gives protection against malaria, but does not exhibit full-blown sickle cell anemia.

Complete the table for these individuals:

Genotype

Description Homozygous HbA Heterozygous Homozygous HbS

Phenotype

Malaria protection? 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Sickle Cell Another example of codominance. Remember the notation used: superscripts represent codominant alleles. In codominance, heterozygous individuals have a mixed phenotype.

The mixed phenotype gives protection against malaria, but does not exhibit full-blown sickle cell anemia.

Complete the table for these individuals:

Genotype HbA HbA HbA HbS HbS HbS

Description Homozygous HbA Heterozygous Homozygous HbS

Phenotype normal carrier Sickle cell disease

Malaria No Yes Yes protection? 3.4.U6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles.