The Living Environment Unit 3 Genetics Unit 11 Complex Inheritance and Human Heredity-class key. Name: Class key. Period:

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1 Name: Class key Period:

2 Chapter 11 assignments Pages/Sections Date Assigned Date Due

3 Topic: Recessive Genetic Disorders Objective: Describe some recessive human genetic disorders. _recessive_ alleles are NOT shown in the _phenotype_ if a _DOMINANT_ allele for the same trait exists in the genotype. A person with a _recessive_ and _DOMINANT_ allele for a trait is called a carrier.

4 Topic: Dominant Genetic Disorders Objective: Describe some dominant human genetic disorders. _DOMINANT_ genetic disorders are not shown by individuals _homozygous recessive_ for the trait. While dominant, _breeding_ has _reduced_ the prevalence of the trait in the population.

5 Topic: Genetic Pedigrees Objective: Describe genetic pedigrees and genetic patterns. Genetic _pedigrees_ show a _relationship_ between phenotype and genotype. Pedigrees match offspring to parents and show which offspring are carriers (recessive) or affected (dominant).

6 Topic: Abnormal Chromosomes Objective: Describe how incorrect chromosomes are harmful. Chromosomal abnormalities o Incorrect number of chromosomes _Nondisjunction_ chromosomes don t _separate_ properly during meiosis breakage of chromosomes _deletion_ _duplication_ _inversion_ _translocation_

7 Topic: Chromosome Disorders Objective: Describe some human chromosome disorders. high frequency in humans o most embryos are lost to _miscarriage_ o alterations are too _disastrous_ o _developmental_ problems result from biochemical problems Certain conditions are _tolerated_ o upset the balance less = _survivable_ o characteristic set of symptoms = _syndrome_

8 Topic: Down syndrome (Tri-23) Objective: Describe Down syndrome and its probability. _Trisomy_ 21 o 3 copies of chromosome 21 o _1 in 700_ children born in U.S. Chromosome 21 is the smallest human chromosome o but still severe effects _frequency_ of Down syndrome is related to the age of the mother Down syndrome & age of mother

9 Topic: Nondisjunction Objective: Describe nondisjunction and separation failures. The failure of homologous chromosomes to _separate_ properly during meiosis is called _nondisjunction_. Problems in meiosis cause problems in _daughter_ cells o chromosome pairs do not separate properly during Meiosis 1 o sister chromatids fail to separate during Meiosis 2 o too many or too few chromosomes

10 Topic: Nondisjunction Objective: Describe nondisjunction and syndromes. Although organisms with extra chromosomes often survive, organisms missing one or more chromosomes usually do not. When a gamete with a missing chromosome fuses with a normal gamete during fertilization, the resulting zygote lacks a _chromosome_. This condition is called _monosomy_. o A woman with Turner syndrome lacks an _X_ chromosome (_XO_). o A male with _Klinefelter s_ syndrome has an extra X chromosome (_XXY_).

11 Topic: Turner syndrome Objective: Describe nondisjunction in Turner syndrome. _monosomy_ X or X0 female o 1 in every 5000 births o varied degree of effects o webbed neck o short stature o sterile

12 Topic: Klinefelter s syndrome Objective: Describe nondisjunction in Klinefelter s syndrome. XXY male o one in every 2000 live births o have male sex organs, but are sterile o feminine characteristics o some breast development o lack of facial hair o tall o normal intelligence

13 Topic: Nondisjunction affects Objective: Describe nondisjunction effects on organisms. When a gamete with an extra set of _chromosomes_ is _fertilized_ by a normal _haploid_ gamete, the offspring has three sets of chromosomes and is _triploid_. (3n) The fusion of two gametes, each with an extra set of _chromosomes_, produces offspring with four sets of chromosomes a _tetraploid_. (4n) This is _polyploidy_. o FATAL in most animals and plants. o some animals (earthworms); some plants (strawberries)

14 Notes page:

15 Name: Period: Carefully remove this sheet from your packet to hand in. Work silently and alone to complete this graded exercise. Check for Understanding 1. Name a recessive or dominant genetic disorder and the cure. 2. Describe the basic concept of nondisjunction. 3. The human 21 st chromosome is the smallest, so it is of no importance in reproduction. Is this true or false, and explain. 4. Explain why in your own ideas why polyploidy is most often fatal to complex organisms.

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