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Chapter 12 Inheritance Patterns & Human Genetics Developed By: R. LeBlanc Biology Teacher Mountain Pointe High School 11/’06 Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Inheritance Patterns & Human Genetics Francis Collins and his lab group discovered the gene responsible for cystic fibrosis (CF). In this chapter, you will learn how diseases, such as CF, and characteristics, such as eye color, are inherited and expressed. Cystic fibrosis (CF) is the most common fatal genetic disease in the US today. It causes the body to produce a thick, sticky mucus that clogs the lungs, leading to infection, and blocks the pancreas, stopping digestive enzymes from reaching the intestines where they are required to digest food. CF is caused by a defective gene, which codes for a sodium and chloride (salt) transporter found on the surface of the epithelial cells that line the lungs and other organs. Several hundred mutations have been found in this gene, all of which result in defective transport of sodium and chloride by epithelial cells. The severity of the disease symptoms of CF is directly related to the characteristic effects of the particular mutation(s) that have been inherited by the sufferer. CF research has accelerated sharply since the discovery of CFTR in 1989. In 1990, scientists successfully cloned the normal gene and added it to CF cells in the laboratory, which corrected the defective sodium chloride transport mechanism. This technique - gene therapy was then tried on a limited number of CF patients. However this treatment may not be as successful as originally hoped. Further research will be required before gene therapy, and other experimental treatments, prove useful in combating CF. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Cystic Fibrosis • What do you notice about the airway of a normal person with one with cystic fibrosis? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Chromosomes •How many chromosomes does a human cell have? • Genes reside on chromosomes. 23 pairs or 46 •How many chromosomes does a sex cell have? 23 •What are genes? Genes are short segments of DNA that contains the instructions for a single trait. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Karyotypes: Male and Female Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Inheritance Patterns and Human Genetics Table of Contents Section 1 Chromosomes and Inheritance Section 2 Human Genetics Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Objectives • Distinguish between sex chromosomes and autosomes. • Explain the role of sex chromosomes in sex determination. • Describe how an X- or Y-linked gene affects the inheritance of traits. • Explain the effect of crossing-over on the inheritance of genes in linkage groups. • Distinguish between chromosome mutations and gene mutations. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Chromosomes, continued • Sex Chromosomes and Autosomes – Sex chromosomes contain genes that determine an organism’s sex (gender). – The remaining chromosomes that are not directly involved in determining the sex of an individual are called autosomes. • https://www.google.com/search?q=trisomy&rls=com.microsoft:e n-us:IE-SearchBox&oe=UTF-8&rlz=1I7SUNA_en&um=1&ie=UTF8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=YB4XT5eyEq HbiALth6jsDw&biw=1024&bih=563&sei=Yx4XT5C7AcqoiQKts6iq Dw •What is wrong with the karyotyping above? •What should it be? •This causes birth defects and is known as Trisomy 13. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Chromosomes, continued • Sex Determination – In mammals, an individual carrying two X chromosomes is female. – An individual carrying an X and a Y chromosome is male. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Sex Determination; con’t • In humans there are 22 pairs of autosome (exact) chromosomes • The 23rd pair are the sex X chromosomes. • Indicated by the letters X Y and Y. • Ex. Female = XX Male = XY X X XX XX Female Female XY Male Chapter menu XY Male Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Effects of Gene Location • Sex-Linked Genes and Traits – Genes found on the X chromosome are Xlinked genes. – A sex-linked trait is a trait whose allele is located on a sex chromosome. – Because males have only one X chromosome, a male who carries a recessive allele on the X chromosome will exhibit the sex-linked trait. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Sex Linked Traits; con’t • Examples: – Eye color in fruit flies – Hemophilia in humans - Unable to clot blood (recessive trait on the X chromosome) – Color Blindness in humans - Unable to see red and green – PROBLEM: If a man with hemophilia married and his wife was a carrier of hemophilia, what would the probability of their children of having this disease? Just the male child? Female child? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Example of Sex-Linked Crosses H = Normal blood clotting XH Xh h = hemophiliac Xh XHXh XhXh Female Carrier Female Hemophiliac XhY = Male Hemophiliac XhY XHY Y Male Normal Male Hemophiliac Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Sex Linked Traits; con’t • People with red-green color blindness can not differentiate between these two colors • Color blindness is also a X Linked Trait that is recessive. • PROBLEM: A mother who carries the trait for color blindness wants to know what the probability would be that her children would be color blind if her husband has normal vision? R = Normal vision r = color blindness Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Sex Linked Traits; con’t Color blindness solution •25% chance in all her children. Female Carrier XR Xr •50% chance that a male will be color blind.. •0% chance female will XR XR XR XR Xr be, but 50% chance they will be a carrier. Y Chapter menu XR Y Xr Y Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Effects of Gene Location, continued • Linked Genes – Pairs of genes that tend to be inherited together are called linked genes. – Why are these genes inherited together? • They are inherited together because they are found on the same chromosome. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Effects of Gene Location, continued • Chromosome Mapping – The farther apart two genes are located on a chromosome, the more likely a cross-over will occur. • Example: If 2 genes are 2 times further apart than 2 other genes, what is the chances a cross-over will occur? • TWICE AS LIKELY – Researchers use recombinant percentages to construct chromosome maps showing relative gene positions. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Mutations • Germ-cell mutations occur in gametes and can be passed on to offspring. – Example: Colorblindness. • Somatic-cell mutations occur in body that affect only the individual organism. – Example: skin cancer; cause by ?????? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Mutations, continued • Chromosome Mutations – Chromosome mutations are changes in the structure of a chromosome or the loss or gain of an entire chromosome. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Chromosomal Mutations Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Mutations, continued • Gene Mutations – Gene mutations are changes in one or more of the nucleotides in a gene. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 1 Chromosomes and Inheritance Gene Mutations Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Inheritance of Traits • Pedigrees – Geneticists use pedigrees to trace diseases or traits through families. – Pedigrees are diagrams that reveal inheritance patterns of genes. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Pedigree for Cystic Fibrosis Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Some Important Genetic Disorders Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Traits and Disorders • Polygenic Inheritance – Polygenic characters, such as skin color, are controlled by two or more genes. • Melanin: a protein that determines how much skin color is going to be deposited in a skin cell. More melanin produced, more color is deposited. • Other polygenic characteristics: eye color, height, and hair color. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Traits and Disorders, continued • Complex Characters – Many human conditions are complex characters, such as polygenic traits, are influenced by both genes and environment. – How can your skin color be influence by the environment? Height? – In diseases: breast cancer, diabetes, heart disease, stroke, etc. – Are there ways you can control disease factors to control your ability to contract a disease? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Traits and Disorders, continued • Multiple Alleles – Multiple-allele characters, such as ABO blood groups, are controlled by three or more alleles of a gene. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Comparing Single Allele, Multiple Allele, and Polygenic Traits Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Comparing Complete, Incomplete, and Co-Dominance Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. INCOMPLETE DOMINANCE • A cross where one allele does not completely hide or mask the other producing a blended appearance in the phenotype. • Example: In snapdragons, pure red crossed with pure white produce pink! Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. CODOMINANCE • Two non-identical alleles of a pair specify two different phenotypes yet one cannot mask the other and both are expressed . Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Traits and Disorders, continued • X-Linked Traits – The gene for colorblindness, an X-linked recessive gene, is found on the X chromosome. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Traits and Disorders, continued • Sex-influenced Trait – A sex-influenced trait, such as pattern baldness, is expressed differently in men than in women even if it is on an autosome and both sexes have the same genotype. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Comparing X-Linked and Sex-Influenced Traits Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Detecting Genetic Disease • Genetic screening examines a person’s genetic makeup and potential risks of passing disorders to offspring. • Amniocentesis and chorionic villi sampling help physicians test a fetus for the presence of genetic disorders. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Detecting Genetic Disease, continued • Genetic Counseling – Genetic counseling informs screened individuals about problems that might affect their offspring. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Treating Genetic Disease • Genetic disorders are treated in various ways. • Among the treatments are symptom-relieving treatments and symptom-prevention measures, such as insulin injections for diabetes. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Genetic Disorder Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Section 2 Human Genetics Treating Genetic Disease, continued • Gene Therapy – In gene therapy, a defective gene is replaced with a copy of a healthy gene. – Somatic cell gene therapy alters only body cells. – Germ cell gene therapy attempts to alter eggs or sperm. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice 1. Which can a chromosomal map show? A. the sex of the individual B. the presence of mutant alleles C. the positions of genes on a chromosome D. whether a gene is autosomal or recessive Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 1. Which can a chromosomal map show? A. the sex of the individual B. the presence of mutant alleles C. the positions of genes on a chromosome D. whether a gene is autosomal or recessive Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 2. Which can result from the deletion of a single nucleotide? F. trisomy G. a translocation H. nondisjunction J. a frameshift mutation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 2. Which can result from the deletion of a single nucleotide? F. trisomy G. a translocation H. nondisjunction J. a frameshift mutation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 3. At the present time amniocentesis cannot reveal which of the following? A. eye color B. genetic disease C. sex of the fetus D. chromosomal abnormalities Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 3. At the present time amniocentesis cannot reveal which of the following? A. eye color B. genetic disease C. sex of the fetus D. chromosomal abnormalities Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 4. A geneticist working with the fruit fly Drosophila melanogaster discovers a mutant phenotype that appears only in males who are offspring of males of the same phenotype. What does this information suggest about the mutant phenotype? F. The trait is X-linked. G. The trait is Y-linked. H. The trait is autosomal dominant. J. The trait is autosomal recessive. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 4. A geneticist working with the fruit fly Drosophila melanogaster discovers a mutant phenotype that appears only in males who are offspring of males of the same phenotype. What does this information suggest about the mutant phenotype? F. The trait is X-linked. G. The trait is Y-linked. H. The trait is autosomal dominant. J. The trait is autosomal recessive. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued The table below shows 5. Which statement best the genotypes and phenotypes of explains why men and pattern baldness. women express the Bb Use the table to answer the genotype differently? question that follows. A. The trait is polygenic. B. The trait has multiple alleles. C. Pattern baldness is a sex-linked trait. D. Pattern baldness is a sex-influenced trait. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued The table below shows 5. Which statement best the genotypes and phenotypes of explains why men and pattern baldness. women express the Bb Use the table to answer the genotype differently? question that follows. A. The trait is polygenic. B. The trait has multiple alleles. C. Pattern baldness is a sex-linked trait. D. Pattern baldness is a sex-influenced trait. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 6. translocation : chromosome mutation :: substitution F. gene mutation G. point mutation H. germ-cell mutation J. somatic-cell mutation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued 6. translocation : chromosome mutation :: substitution F. gene mutation G. point mutation H. germ-cell mutation J. somatic-cell mutation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued The image below is a 7. Which type of inheritance pedigree showing the pattern is associated with inheritance of hemophilia in a hemophilia? family. Use the pedigree to answer the question that A. autosomal recessive follows. B. sex-linked dominant C. sex-linked recessive D. autosomal dominant Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Multiple Choice, continued The image below is a 7. Which type of inheritance pedigree showing the pattern is associated with inheritance of hemophilia in a hemophilia? family. Use the pedigree to answer the question that A. autosomal recessive follows. B. sex-linked dominant C. sex-linked recessive D. autosomal dominant Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Short Response Consider a couple about to get married. The woman has cystic fibrosis, but the man does not. What benefit would they gain by seeing a genetic counselor? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Short Response, continued Consider a couple about to get married. The woman has cystic fibrosis, but the man does not. What benefit would they gain by seeing a genetic counselor? Answer: Genetic counseling will tell them the likelihood of each of their children having cystic fibrosis or carrying the cystic fibrosis gene. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Extended Response Colorblindness is a recessive, sex-linked trait. A woman and a man, both with normal vision, have three daughters with normal vision. One of the daughters marries a man with normal vision, and they have a son who is colorblind. Part A Which parent of the son is the carrier of the trait? Explain your answer. Part B What is the likelihood that the children of a woman heterozygous for colorblindness and colorblind man will express the trait? Explain your answer. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 12 Standardized Test Prep Extended Response, continued Answer: Part A The son’s mother carries the trait. The gene for colorblindness is carried on the X chromosome. Part B Given: X-linked recessive: heterozygous female = XB (normal)Xb (colorblind); colorblind male = Xb (colorblind)Y. This Punnett square predicts that 50 percent of the children will be male and 50 percent of the children will be female. 50 percent will be colorblind and 50 percent will have normal vision. 25 percent will be males with normal vision and will not be carriers. 25 percent will be female carriers with normal vision. 25 percent will be colorblind females. 25 percent will be colorblind males. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.