Human Genetics Chapter 11

11-1 Basic Patterns in Human Inheritance Objectives 1.Analyze genetic patterns to determine dominant or recessive inheritance patterns 2.Summarize examples of dominant and recessive disorders 3.Construct human pedigrees from genetic information

11.1 Basic Patterns of Human Inheritance Complex Inheritance and Human Heredity Chapter 11 Recessive Genetic Disorders  A recessive trait is expressed when the individual is homozygous recessive for the trait.

Complex Inheritance and Human Heredity 11.1 Basic Patterns of Human Inheritance Chapter 11 A dominant genetic disorder is expressed with ONE dominant allele present

Complex Inheritance and Human Heredity Pedigrees  A diagram that traces the inheritance of a particular trait through several generations 11.1 Basic Patterns of Human Inheritance Chapter 11

Pedigrees can have the following inheritance patterns: Autosomal dominant Autosomal recessive X-Linked

A = the trait (a genetic disease or abnormality, dominant) a = normal (recessive) Can we determine the Genotypes of all the individuals?

A = the trait (a genetic disease or abnormality, dominant) a = normal (recessive) What are the genotypes? What is the inheritance pattern?

What are the genotypes? What is the inheritance pattern?

What are the genotypes? What is the inheritance pattern?

What are the genotypes? What is the inheritance pattern?

11-2 Complex Patterns of Inheritance Objectives 1.Distinguish between various complex inheritance patterns 2.Analyze sex-linked and sex-limited inheritance patterns 3.Explain how the environment can influence the phenotype of an organism

11.2 Complex Patterns of Inheritance Complex Inheritance and Human Heredity Incomplete Dominance  The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes. Chapter 11

Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while cream-colored mice are heterozygous. If two cream-colored mice mate, what phenotypic ratio can we expect of their offspring? Show the Punnett Square?

In radishes, red and white are pure-breeding colors, while hybrids are purple. If a red radish is crossed with a white radish, what will be the phenotype of the F 2 generation (assuming the F 1 generation self-pollinates)? Show the Punnett Square.

Complex Inheritance and Human Heredity Codominance  Both alleles are expressed in the heterozygous condition Complex Patterns of Inheritance Chapter 11

Complex Inheritance and Human Heredity Sickle-cell Disease – an example of codominance  Changes in hemoglobin cause red blood cells to change to a sickle shape.  People who are heterozygous for the trait have both normal and sickle-shaped cells. Sickle cell Normal red blood cell 7766x 11.2 Complex Patterns of Inheritance Chapter 11

Sickle cell disease vs sickle cell trait -SCD, child inherits trait from both parents stroke, acute chest syndrome (a condition that lowers the level of oxygen in the blood), organ damage, other disabilities, and in some cases premature death -SCT, child inherits one trait Rarely, extreme conditions such as severe dehydration and high- intensity physical activity can lead to serious health issues, including sudden death

In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW), all the offspring are roan—a spotted, red and white or milky red color. What offspring are expected from mating a roan bull and a roan cow? Show the Punnett Square

Complex Inheritance and Human Heredity Multiple Alleles  Blood groups in humans  ABO blood groups have three forms of alleles.  AB are codominant to each other also! 11.2 Complex Patterns of Inheritance Chapter 11

Pretend that Brad Pitt is homozygous for the type B allele, and Angelina Jolie is type “O.” What are all the possible blood types of their babies

Two parents think their baby was switched at the hospital. Its 1968, so DNA fingerprinting technology does not exist yet. The mother has blood type “O,” the father has blood type “AB,” and the baby has blood type “B.” – Mother’s genotype: _______ – Father’s genotype: _______ – Baby’s genotype: ______ or ________ – Punnett square showing all possible genotypes for children produced by this couple – Was the baby switched?

Complex Inheritance and Human Heredity Sex Determination  Sex chromosomes determine an individual’s gender.  Humans have 2 sex chromosomes.  The other 22 pairs of chromosomes are called autosomes  SO who determines the sex of a child?????? 11.2 Complex Patterns of Inheritance Chapter 11

Complex Inheritance and Human Heredity Sex-Linked Traits  Genes located on the X chromosome  Red-green color blindness  Hemophilia 11.2 Complex Patterns of Inheritance Chapter 11

In fruit flies, the gene for white eyes is sex-linked recessive. (R) is red and (r) is white. Cross a white-eyed female with a normal red-eyed male

Hemophilia

In humans, hemophilia is a sex-linked recessive trait. If a female who is a carrier for hemophilia marries a male with normal blood clotting, answer the following questions What fraction of the female children will have hemophilia? What fraction of the female children will be carriers? What fraction of the male children will have normal blood clotting? What fraction of the male children will be carriers? What fraction of the male children will have hemophilia?

Complex Inheritance and Human Heredity Polygenic Traits  Polygenic traits arise from the interaction of multiple pairs of genes.  Skin color, height, eye color, fingerprint patterns 11.2 Complex Patterns of Inheritance Chapter 11

Complex Inheritance and Human Heredity Environmental Influences  Environmental factors  Diet and exercise  Sunlight and water  Temperature 11.2 Complex Patterns of Inheritance Chapter 11

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11-3 Chromosomes and Human Heredity Objectives 1.Distinguish normal karyotypes from those with abnormal numbers of chromosomes 2.Define and describe the role of telomeres 3.Relate the effect of nondisjunction to Down Syndrome and other abnormal chromosomes numbers

 Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size Chromosomes and Human Heredity Complex Inheritance and Human Heredity Karyotype Studies Chapter 11

Complex Inheritance and Human Heredity Nondisjunction  Cell division during which sister chromatids fail to separate properly  Ex. Disease-Down syndrome 11.3 Chromosomes and Human Heredity Chapter 11

Chromosomes Don’t Separate Properly during Meiosis

Chromosome mutations Chromosome mutations- changes in the structure of a chromosome or the loss of a chromosome. Often occur during cell division. – Deletion- loss of a piece of a chromosome due to breakage. Information carried by the missing piece is lost. – Inversion- a chromosomal segment breaks off and reattaches in the reverse orientation on the same chromosome.

Chromosome mutations cont. – Translocation- a chromosomal segment breaks off and attaches to another, non-homologous chromosome.

Patterns of Inheritance – Monosomy- and individual is missing one of a pair of particular chromosomes (the total number would be 45 for humans)

Nondisjunction Also Can Change the Number of Sex Chromosomes Turner syndrome – Missing an X chromosome; XO – Female; webbed neck; no secondary sexual traits at puberty; sterile; may age prematurely XXX females – May develop normally or may have developmental delays – 1 out 1000 females have it

In Downs Syndrome There Are Three Copies of Chromosome 21

Nondisjunction Also Can Change the Number of Sex Chromosomes Trisomy- an individual has 3 of a particular chromosome. (total number would be 47 for humans) Down syndrome- extra chromosome at number 21- individual has mental deficiencies, folded skin above the eyes, weak muscles Klinefelter syndrome (XXY) – Low fertility; mental retardation; small testes; sparse body hair; enlarged breasts – Testosterone injections may reverse the phenotype – intellectual disability, distinctive facial features, skeletal abnormalities, poor coordination, and severe problems with speech XYY condition Some develop normally increased risk of learning disabilities and delayed development of speech and language skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), hand tremors or other involuntary movements (motor tics), and behavioral and emotional difficulties are also possible Some develop autistic spectrum disorders, which are developmental conditions that affect communication and social interaction.

Turner Syndrome

Kleinfelter’s Syndrome