Copyright © 2010 Pearson Education, Inc. Chapter 7  DNA Detective  Complex Patterns of Inheritance and DNA Fingerprinting

Copyright © 2010 Pearson Education, Inc. Chapter 7 Section 1 – Forensic Science Section 2 – Dihybrid Crosses

Copyright © 2010 Pearson Education, Inc. DNA Detective  1918: the Romanovs and four servants were murdered by Communists  1991: shallow grave containing bones of at least nine people dug up  Were any of these the Romanovs? If so, which ones?

Copyright © 2010 Pearson Education, Inc. 7.1 Forensic Science Forensic Science The study of evidence discovered at a crime scene and used in a court of law.  Bones seemed to belong to six adults and three children  Sexing was inconclusive, due to decomposition of pelvises  Skeletons might be the Romanovs.  Could resemblance among relatives be useful?

Copyright © 2010 Pearson Education, Inc. 7.2 Dihybrid Crosses Dihybrid crosses = crosses involving two genes simultaneously  Mendel’s peas: seed color and seed shape are on different chromosomes.  Y = yellow seed color; y = green seed color; R = smooth seeds; r = wrinkled seeds  Cross between two double heterozygote parents: YyRr x YyRr  The following Punnett square shows expected numbers of genotypes and phenotypes:

Copyright © 2010 Pearson Education, Inc. 7.2 Dihybrid Crosses - Punnett Square Figure 7.1 Possible types of pollen Possible types of ovules Phenotype RrYy RRYY round, yellow RRYy round, yellow RrYY round, yellow RrYy round, yellow RRYy round, yellow Rryy round, green RrYy round, yellow Rryy round, green RrYY round, yellow RrYy round, yellow rrYY wrinkled, yellow rrYy wrinkled, yellow RrYy round, yellow Rryy round, green rrYy wrinkled, yellow Rryy wrinkled, green Genotype Round, yellow Round, green Wrinkled, yellow Wrinkled, green RRYY, RrYY, RRYy, RrYy Rryy, Rryy rrYY, rrYy rryy

Copyright © 2010 Pearson Education, Inc. 7.2 Dihybrid Crosses  The Tsar and Tsarina were heterozygotes for eye color (Dd).  For hair texture, the Tsar was homozygous recessive (cc) and Tsarina were heterozygous (Cc)  Due to random alignment of chromosomes and independent assortment, they could form the following gametes:

Copyright © 2010 Pearson Education, Inc. 7.2 Dihybrid Crosses Figure 7.2a–b Meiosis Two types of gametes Two other types of gametes Tsarina CcDd Wavy hair Dark eyes Tsarina CcDd (b) Another possible Metaphase I alignment Wavy hair Dark eyes (a) One possible Metaphase I alignment

Copyright © 2010 Pearson Education, Inc. 7.2 Dihybrid Crosses  Their gametes could then potentially produce the following offspring: Figure 7.2c Tsar ccDd (straight hair, dark eyes) Tsarina CcDd (wavy hair, dark eyes) ccDd Straight hair Dark eyes cD cd Possible types of sperm Possible types of eggs CcDd Wavy hair Dark eyes ccDd Straight hair Dark eyes ccdd Straight hair Blue eyes CcDd Wavy hair Dark eyes Ccdd Wavy hair Blue eyes ccDD Straight hair Dark eyes (c) Punnett square for the mating of the Tsar and the Tsarina CcDD Wavy hair Dark eyes

Copyright © 2010 Pearson Education, Inc. Chapter 7 End Section 1 – Forensic Science End Section 2 – Dihybrid Crosses

Copyright © 2010 Pearson Education, Inc. Chapter 7 Section 3 Extensions to Mendelian Genetics

Copyright © 2010 Pearson Education, Inc. 7.3 Extensions of Mendelian Genetics Extensions of Mendelian Genetics  More complex patterns of inheritance  Incomplete dominance: two copies of the dominant allele are required to see the full phenotype; heterozygote phenotype is intermediate to the homozygotes (e.g., flower color in snapdragons) Figure 7.3 x= Flower color in snapdragons Red = RRWhite = rrPink = Rr

Copyright © 2010 Pearson Education, Inc. 7.3 Extensions of Mendelian Genetics  Codominance: neither allele is dominant to the other; heterozygote shows both traits at once (e.g., coat color in cattle)  Polygenic Traits = affected by multiple genes and the environment  Height, weight, etc Figure 7.4

Copyright © 2010 Pearson Education, Inc. 7.3 Extensions of Mendelian Genetics  Blood typing can be used to exclude potential parents.  ABO blood group has three alleles of one gene:  Multiple allelism  I A and I B are codominant to each other; i is recessive to both other alleles.  An individual will have two of these alleles.

Copyright © 2010 Pearson Education, Inc. 7.3 Extensions of Mendelian Genetics  Blood typing with Rh factor  A RBC membrane protein  Simple mendelian two gene complete dominance  Indicated as + or – after ABO blood type

Copyright © 2010 Pearson Education, Inc. 7.3 Extensions of Mendelian Genetics  Blood Transfusions  O - is universal donor  AB + is universal receiver

Copyright © 2010 Pearson Education, Inc. End Chapter 7 Section 3 Extensions to Mendelian Genetics

Copyright © 2010 Pearson Education, Inc. Chapter 7 Section 4 Sex Determination and Sex Linkage

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage  Prince Alexis suffered from hemophilia, the inability to clot blood normally due to the absence of a clotting factor.  Gene for this clotting factor is on the X chromosome.  Alexis inherited the hemophilia allele from his mother.

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Sex Determination and Sex Linkage  Humans have 22 pairs of autosomes and one pair of sex chromosomes  Women: two X chromosomes  Men: one X and one Y chromosome Figure 7.6 Male XY Female XX Meiosis Fertilization Possible spermPossible eggs XYXX XYXX This zygote will develop into a male. This zygote will develop into a female.

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Sex-linked genes: genes located on the sex chromosomes  X-linked: located on the X chromosome  Y-linked: located on the Y chromosome  Males always inherit their X from their mother  Males are more likely to express recessive X-linked traits than females  Only females can be carriers of X-linked recessive traits.

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Figure 7.8 Crosses of carriers for hemophilia

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Figure 7.8 Other X-linked recessive traits Red-Green Color Blindness Duchenne muscular dystrophy

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage X Inactivation  Early female embryos randomly inactivate one of the X chromosomes in each cell.  Inactivation is irreversible and inherited during mitotic cell division.  It is caused by RNA wrapping around the X chromosome. Figure 7.9

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Tortoiseshell Cats  Result is patches of tissue in adult female with different X chromosomes active. Figure 7.10 (a) Genotype Orange maleBlack femaleTortoise shell female (b) Random X chromosome inactivation Tortoiseshell cat with patches of orange and black Mitosis Inactive X chromosome Active X chromosome Allele for orange fur Allele for black fur x= Early embryo Phenotype X inactivation

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Y-Link Genes  Passed only from father to son  But few genes on Y-chromosome  SRY gene

Copyright © 2010 Pearson Education, Inc. 7.4 Sex Determination and Sex Linkage Figure 7.10 Animation—X-Linked Recessive Traits PLAY

Copyright © 2010 Pearson Education, Inc. End Chapter 7 Section 4 Sex Determination and Sex Linkage

Copyright © 2010 Pearson Education, Inc. Chapter 7 Section 5 Pedigrees

Copyright © 2010 Pearson Education, Inc. 7.5 Pedigrees Pedigree: a family tree, showing the inheritance of traits through several generations  Pedigrees reveal modes of inheritance  Symbols commonly used in pedigrees: Figure 7.11 Female Male Marriage or mating Offspring in birth order (from left to right) Affected individuals Known or presumed carriers or Pedigree analysis symbols

Copyright © 2010 Pearson Education, Inc. 7.5 Pedigrees Pedigree for an autosomal dominant trait: Polydactyly Figure 7.12a (a) Dominant trait: Polydactyly Two unaffected individuals cannot have affected offspring. Two affected parents can have unaffected offspring. pp Pp pp Pp pp Pp

Copyright © 2010 Pearson Education, Inc. 7.5 Pedigrees Pedigree for an autosomal recessive trait: Attached earlobes Figure 7.12b

Copyright © 2010 Pearson Education, Inc. 7.5 Pedigrees Pedigree for an X-linked trait: Muscular dystrophy Figure 7.12c

Copyright © 2010 Pearson Education, Inc. 7.5 Pedigrees Romanov Pedigree  Pedigree analysis reveals that Queen Victoria’s mother must have had a mutation for the hemophilia allele, which was ultimately passed on to Prince Alexis Romanov. Figure 7.13

Copyright © 2010 Pearson Education, Inc. End Chapter 7 Section 5 Pedigrees

Copyright © 2010 Pearson Education, Inc. Chapter 7 Section 6 DNA Fingerprinting

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting DNA Fingerprinting  No two individuals are genetically identical (except for MonoZygotic twins)  Therefore, individuals have small differences in nucleotide sequences of their DNA  This is the basis for DNA fingerprinting  Unambiguous identification of people

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Steps in DNA fingerprinting: overview 1.DNA isolated from tissue sample  Small samples can be amplified using another technique called “PCR” 2.DNA cut into fragments with enzymes  DNAs of different sequences produce fragments of different sizes 3.Fragments separated on basis of size and visualized 4.Each person’s set of fragments is unique

Copyright © 2010 Pearson Education, Inc. 7.6 Polymerase Chain Reaction DNA Fingerprinting: using small samples 1.Small amounts of DNA can be amplified using PCR (polymerase chain reaction) 2.DNA is mixed with nucleotides, specific primers, Taq polymerase, and then is heated 3.Heating splits the DNA molecules into two complementary strands 4.As solution cools, Taq polymerase builds a new complementary strand 5.DNA is heated again, splitting the DNA and starting a new cycle.

Copyright © 2010 Pearson Education, Inc. 7.6 Polymerase Chain Reaction  In each cycle of PCR, the DNA doubles. Figure Primer Double stranded DNA Primer Polymerase PCR is used to amplify, or make copies of, DNA. During a PCR reaction, primers (free nucleotides) and DNA are mixed with heat-tolerant polymerase. As the mixture cools, the primers bond to the DNA template and the two polymerase use the primers to initiate synthesis. A copy of the DNA template is assembled. The mixture is heated again. The process is repeated many times, doubling the DNA amount each time. The DNA is heated to separate, or denature, the two strands.

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Animation—Polymerase Chain Reaction (PCR) PLAY

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Cut DNA into fragments  DNA is cut into fragments using restriction enzymes, which cut around DNA sequences called VNTRs (variable number tandem repeats) Figure 7.15 Variable number tandem repeat (VNTR) 4 VNTRs 5 VNTRs Student 1 6 VNTRs 3 VNTRs Homologous chromosomes Student 2 =

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting DNA Fingerprint  Gel electrophoresis separates DNA fragments on basis of their sizes  Each person will have a unique pattern of bands. Figure 7.17

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Romanovs DNA fingerprinting analysis  DNA fingerprinting showed that 9 persons were buried in the Ekaterinburg grave.  Romanovs would be more similar in pattern to each other than to nonrelatives.  All of a child’s bands must be present in one or both of the parents.

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Figure 7.18 Hypothetical DNA pattern from Romanov graves

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Figure 7.18 Pretenders to the Romanov throne

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting But were remains in grave really Romanovs?  To see if parents and their children were Romanovs, DNA fingerprints were prepared for relatives of tsar and tsarina.

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting Pedigree of Romanov family Figure 7.20 Tsar’s brother George Tsar Tsarina Carrier of hemophilia allele Tsarina’s sister Not a carrier of hemophilia allele Tsarina’s niece Alice Tsarina’s grandnephew Prince Philip Queen Elizabeth II Lady Diana Charles Olga TatianaMariaAnastasia Alexis Hemophilia WilliamHenry DNA evidence Members of Romanov family executed in 1918 DNA evidence Anne Timothy Lawrence PeterZara AndrewSarah Ferguson Beatrice LouiseEugenie EdwardSophie Rhys-Jones

Copyright © 2010 Pearson Education, Inc. 7.6 DNA Fingerprinting But were remains in grave really Romanovs?  Adult male skeleton (related to the children) was related to George, the tsar’s brother.  Adult female skeleton (related to the children) was related to Prince Philip, the tsarina’s grand-nephew.  Conclusion: the grave contained the tsar, tsarina, three of their children, and four servants.

Copyright © 2010 Pearson Education, Inc. End Chapter 7 Section 6 DNA Fingerprinting

Copyright © 2010 Pearson Education, Inc. End Chapter 7