1. Chapter 11: Complex Inheritance and Human Heredity
Section 11.1: Basic Patterns of Human Inheritance
Section 11.2: Complex Patterns of Inheritance
Section 11.3: Chromosomes and Human Heredity

2. Section 11.1: Basic Patterns of Human Inheritance
Main idea: The inheritance of a trait over several generations can be shown in a pedigree
Objectives
Analyze generic patterns to determine dominant or recessive inheritance patterns
Summarize examples of dominant and recessive disorders
Construct human pedigrees from generic information
Review Vocabulary
Genes: segments of DNA that control the production of proteins
New Vocabulary
Carrier
Pedigree

3. Recessive Genetic Disorders
Mendel’s work was ignored for more than 30 years
During the early 1900’s scientists began to take an interest in heredity and Mendel’s work was rediscovered
Dr. Archibald Garrod, an English physician, became interested in a disorder linked to an enzyme deficiency called alkaptonuria, which results in black urine and runs in families.
A recessive trait is expressed when the individual is homozygous recessive for the trait.
Therefore, those with at least one dominant allele will not express the recessive trait.
An individual who is heterozygous for a recessive disorder is called a carrier

4. Recessive Genetic Disorders

5. Cystic Fibrosis
Affects the mucus-producing glands, digestive enzymes, and sweat glands
Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat.
Without sufficient chloride ions in the cells, a thick mucous is secreted.

6. Albinism
Caused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes
White hair
Very pale skin
Pink pupils

7. Tay-Sachs Disease
Caused by the absence of the enzymes responsible for breaking down fatty acids called gangliosides.
Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration.

8. Galactosemia
Recessive genetic disorder characterized by the inability of the body to digest galactose.
Severity of condition varies.

9. Dominant Genetic Disorders
Caused by dominant alleles
Those who do not have the disorder are homozygous recessive.
Huntington’s disease affects the nervous system.
Achondroplasia is a genetic condition that causes small body size and limbs that are comparatively short

10. Dominant Genetic Disorders

11. Pedigrees
A diagram that traces the inheritance of a particular trait through several generations.

12. Pedigrees Inferring Genotypes Predicting Disorders
Knowing physical traits can determine what genes an individual is most likely to have.
Predicting Disorders
Record keeping helps scientists use pedigree analysis to study inheritance patterns, determine phenotypes, and ascertain genotypes.

13. 11.2 Complex Patterns of Inheritance
Main idea-Complex inheritance of traits does not follow inheritance patterns described by Mendel
Objectives
Distinguish between various complex inheritance patterns
Analyze sex-linked and sex-limited inheritance patterns
Explain how the environment can influence the phenotype of an organism
Review Vocabulary
Gamete: a mature sex cell (sperm or egg) with a haploid number of chromosomes
New Vocabulary
Incomplete dominance - Codominance
Multiple alleles - Epistasis
Sex chromosome - Autosome
Sex-linked trait - Polygenic trait

14. Incomplete Dominance
The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

15. Codominance Both alleles are expressed in the heterozygous condition
Example
Sickle-cell Disease
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

16. Multiple Alleles Blood groups in humans
ABO blood groups have three forms of alleles

17. Multiple Alleles Coat Color of Rabbits
Multiple alleles can demonstrate a hierarchy of dominance
In rabbits, four alleles code for color: C, cch, cc, and c.

18. Epistasis
Variety is the result of one allele hiding the effects of another allele.
eebb eeB_ E_bb E_B_
No dark pigment present Dark pigment present

19. Sex Determination
Sex chromosomes determine an individual’s gender

20. Dosage Compensation
The X chromosome carries a variety of genes that are necessary for the development of both females and males
The Y chromosome mainly has genes that relate to the development of male characteristics
Chromosome inactivation
Barr bodies

21. Sex-linked Traits Genes located on the X chromosome
Since males have only one chromosome, they are affected by recessive X-linked traits more often than are females
Red-green color blindness
Hemophilia

22. Polygenic Traits
Polygenic traits arise from the interaction of multiple pairs of genes
Skin color, height, eye color, and fingerprint pattern

23. Environmental Influences
Environmental factors affect phenotype
Diet and exercise
Sunlight and water
Temperature

24. Twin Studies
Helps scientists separate genetic contributions from environmental contributions.
Traits that appear frequently in identical twins are at least partially controlled by heredity.
Traits expressed differently in identical twins are strongly influenced by environment

25. 11.3 Chromosomes and Human Heredity
Main idea – Chromosomes can be studied using karyotypes.
Objectives
Distinguish normal karyotypes from those with abnormal numbers of chromosomes.
Define and describe the role of telomeres.
Relate the effect of nondisjunction to Down syndrome and other abnormal chromosome numbers.
Assess the benefits and risks of diagnostic fetal testing
Review Vocabulary
Mitosis- a process in the nucleus of a dividing cell, including prophase, metaphase, anaphase, and telophase
New Vocabulary
Karyotype
Telomere
Nondisjunction

26. Karyotype Studies
Karyotype-micrograph in which the pairs of homologous chromosomes are arranged in decreasing size
Images of chromosomes stained during metaphase
Chromosomes are arranged in decreasing size to produce a micrograph
22 autosomes are matched together with one pair of nonmatching sex chromosomes

27. Telomeres Protective caps consist of DNA associated with proteins
Serves a protective function for the sttructure of the chromosome
Might be involved in both aging and cancer

28. Nondisjunction
Cell division during which sister chromatids fail to separate properly
Results in extra copy of chromosome or only one copy of a chromosome
Having a set of three chromosomes of one kind is trisomy
Having only one copy of a chromosome is monosomy
Down Syndrome – Trisomy 21
Distinctive facial features, short stature, heart defects, and mental disability

29. Nondisjunction Sex Chromosomes XX – Normal female
XO – Female with Turner’s Syndrome
XXX – Nearly normal female
XY – Normal male
XXY – Male with Klinefelter’s Syndrome
XYY – Normal or nearly normal male
OY – Results in death

30. Fetal Testing Used to diagnosis genetic disorders before birth
Amniocentesis
Benefits-diagnosis of chromosome abnormalities and other defects
Risks-discomfort for expectant mother, slight risk of infection, and risk of miscarriage
Chorionic villus sampling
Benefits-diagnosis of chromosome abnormalities and certain genetic defects
Risks-miscarriage, infection, and newborn limb defects
Fetal blood sampling
Benefits-diagnosis of genetic or chromosomal abnormality, checks for fetal problems and oxygen levels, and medications can be given to the fetus before birth
Risks-bleeding from sample site, infection, amniotic fluid might leak, and fetal death