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Modern Genetics
Human Inheritance
Human Genetic Disorders
Advances in Genetics
Table of Contents
Modern Genetics
Patterns of Human Inheritance
1. Single genes with two alleles
Ex: widow’s pick
Figure 2 Punnett Square
Modern Genetics - Human Inheritance
Patterns of Human Inheritance• Single genes with multiple alleles
Ex: Inheritance of Blood Type
Blood type is determined by a single gene with three alleles.fig3/146
Modern Genetics
Patterns of Human Inheritance• Traits controlled by many genes• Ex: human height• Discovery activity/p144
Modern Genetics - Human Inheritance
The Sex Chromosomes
The sex chromosomes carry genes that determine whether a person is male or female. They also carry genes that determine other traits.
Modern Genetics
The Sex chromosomes
Sex-linked genes- genes on the X and Y chromosomes• not always the same• Can have dominant and recessive alleles• Because males have only one X chromosome, male are
more likely to have a sex linked trait that is controlled by recessive alleles.
Female -2X
Male 1X, 1Y
Modern Genetics - Human Inheritance
Colorblindness Punnett Square
Red-green colorblindness is a sex-linked trait. A girl who receives only one recessive allele (written Xc) for red-green colorblindness will not have the trait. However, a boy who receives one recessive allele will be colorblind.
Modern Genetics
Main Idea
Detail Detail Detail
Identifying Main IdeasAs you read the section “Patterns of Human Inheritance,” write the main idea in a graphic organizer. Then write three supporting details that further explain the main idea.
Human traits are controlled by single genes with two alleles, single genes with multiple alleles, and multiple genes.
Human traits controlled by single
genes with two alleles have two
distinctly different phenotypes.
Though a single gene can have
multiple alleles, a person can carry only two of these
alleles.
Multiple genes that control a trait act
together to produce a single trait with a
large number of phenotypes.
- Human Inheritance
Modern Genetics
The effect of environment• Many of a person’s characteristics are determined by an
interaction between genes and the environment
Modern Genetics
Links on Genetics
Click the SciLinks button for links on genetics.
- Human Inheritance
Modern Genetics
End of Section:Human
Inheritance
Modern Genetics
Human Genetic Disorders
Genetic disorder- abnormal condition that a person inherits through genes or chromosomes
Causes:• Mutations in the DNA of genes• Changes in the structure of chromosoms• Changes in the number of chromosomes
Modern Genetics
Human Genetic Disorders• Cystic Fibrosis- body produces abnormally thick mucus in
the lungs or intestines• Cause by a recessive allele on one chromosome as a
result of a mutation in which three bases are removed from a DNA molecule
Modern Genetics
Human Genetic Disorders
Sickle –Cell Disease• Affects hemoglobin, a protein in the red blood cells that
carries oxygen; cells clog blood vessels• The allele is codominant with normal allele• A person with two sickle cell alleles will have the disease
Modern Genetics
Human Genetic Disorders
Hemophilia• Person’s blood clots very slowly or nor at all• Caused by a recessive allele on the X chromosome• Sex-linked disorder/occurs more in male than in females
Modern Genetics
Human Genetic Disorders
Down Syndrome• A person’s cell have an extra copy of chromosome 21 ( 3
chromosomes)• Occurs when chromosomes fail to separate properly
during meiosis• Effect: some degree of mental retardation; heart defects
Modern Genetics - Human Genetic Disorders
A Pedigree
A pedigree is a chart or “family tree” that tracks which members of a family have a particular trait.
Modern Genetics - Human Genetic Disorders
A Hemophilia Pedigree
The pedigree shows the inheritance of hemophilia, a sex-linked disorder in a family.
Modern Genetics
Managing Genetic Disorders• Karyotypes- picture of all the chromosomes in a cell• Genetic counseling- understand the chances of having a
child with a particular genetic disorder• Dealing with genetic disorders
Modern Genetics
Pedigree Activity
Click the Active Art button to open a browser window and access Active Art about pedigrees.
- Human Genetic Disorders
Modern Genetics
Comparing and ContrastingAs you read, compare and contrast the types of genetic disorders by completing a table like the one below.
Cystic fibrosis Body produces abnormally thick mucus.
Recessive allele due to removal of three DNA bases
Disorder Description Cause
Sickle-cell diseaseRed blood cells are sickle-shaped and have reduced ability to hold oxygen.
Codominant allele
Hemophilia Blood clots slowly or not at all.
Recessive allele on X chromosome
Down Syndrome Mental retardation and heart defects
An extra copy of chromosome 21
- Human Genetic Disorders
Modern Genetics
Sickle-Cell Disease
Click the Video button to watch a movie aboutsickle-cell disease.
- Human Genetic Disorders
Modern Genetics
End of Section:Human Genetic
Disorders
Modern Genetics
Advances in Genetics• Selective Breeding: selecting organisms with desired traits
to be parents of the next generation• Inbreeding: crossing two individuals that have the similar
Characteristics
Hybridization: crossing two genetically different individuals;
the offspring will have the best traits from both parents
Modern Genetics
Changing Rice Production
The graph shows how worldwide rice production changed between 1965 and 2000. New, hybrid varieties of rice plants are one factor that has affected the amount of rice produced.
- Advances in Genetics
Modern Genetics
Changing Rice Production
Rice production increased.
Reading Graphs:
According to the graph, how did rice production change between 1965 and 2000?
- Advances in Genetics
Modern Genetics
Changing Rice Production
2 in 1965; 4 in 2000
Reading Graphs:
How many metric tons of rice per hectare were produced in 1965? How many were produced in 2000?
- Advances in Genetics
Modern Genetics
Changing Rice Production
2 metric tons/hectare
Calculating:
Calculate the approximate difference between rice production in 1965 and 2000.
- Advances in Genetics
Modern Genetics
Changing Rice Production
Possible answer: fertilizers and improved harvesting methods
Developing Hypotheses:
What factors besides new varieties of plants might help account for the difference in rice production between 1965 and 2000?
- Advances in Genetics
Modern Genetics
Cloning
• Organism that have the exact genes as the organism from which it was produced
• Is cloning ethical?
Modern Genetics - Advances in Genetics
Genetic Engineering
Scientists use genetic engineering to create bacterial cells that produce important human proteins such as insulin.
Modern Genetics
Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a question for each heading. As you read, write answers to your questions.
Questions AnswersWhat is selective breeding? Selective breeding is the process of
selecting organisms with desired traits to be parents of the next generation.
Why are organisms cloned? To produce offspring with desired traits
What is genetic engineering? A process in which genes from one organism are transferred into the DNA of another organism
What advance has helped us learn about human genetics?
The Human Genome Project
- Advances in Genetics
Modern Genetics
Links on Genetic Engineering
Click the SciLinks button for links on genetic engineering.
- Advances in Genetics
Modern Genetics
Selective Breeding
Click the Video button to watch a movie aboutselective breeding.
- Advances in Genetics
Modern Genetics
End of Section:Advances in
Genetics
Modern Genetics
Human traits
controlled by
such as such as such as such as
Graphic Organizer
Multiple alleles
Single genes Sex-linked genes
Widow's peak Height
Many genes
Blood type Colorblindness
Modern Genetics
End of Section:Graphic Organizer
