chapter: heredity table of contents section 3: biotechnologybiotechnology section 1: genetics...
TRANSCRIPT
Chapter: Heredity
Table of ContentsTable of Contents
Section 3: Biotechnology
Section 1: Genetics
Section 2: Genetics Since Mendel
Inheriting Traits
• Traits are inherited from parents
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• Heredity - the passing of traits from parent to offspring.
What is genetics?• Alleles - different
forms of a trait that a gene may have
• Alleles for each trait separate into different sex cells during meiosis
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What is genetics?• Genetics - study of how traits are inherited
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Mendel—The Father of Genetics• Mendel (1856) –
studied genes of pea plants
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• First to:
• trace one trait through several generations
• use probability to explain heredity
• Purebred - always produces the same traits generation after generation
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• Hybrids – receive different alleles for a trait from each parent
Dominant and Recessive Factors
• Cross-pollination - using pollen from one flower to pollinate others
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Dominant and Recessive Factors
• Dominant - factor expressed if there is only one allele for the trait
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• Recessive – factor expressed only when there are 2 alleles for the trait
Click image to view movie.
Punnett Squares 11
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• Punnett square -tool used to predict results
Click image to view movie.
• Studied > 30,000 pea plants over 8 yrs
Punnett Squares 11
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• Uppercase - dominant allele
• Lowercase - recessive allele
• Genotype - genetic makeup11GeneticsGenetics
• Phenotype - way an organism looks and behaves
• Homozygous - two alleles that are the same
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• Heterozygous - two different alleles for a trait
Making a Punnett Square 11
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11Section CheckSection Check
Question 1
How did Gregor Mendel use his knowledge of mathematics in his study of heredity in pea plants?
11Answer
Mendel was the first person to use the mathematics of probability to explain heredity. Probability is the branch of mathematics that helps you predict the chance that something will happen.
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11Question 2
According to this diagram, if meiosis proceeds correctly, how many alleles of a particular gene can a female pass on to her offspring?
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11Answer
Although she has two alleles of each gene, a mother can pass only one allele to her offspring. Meiosis separates alleles so that eggs have only one allele for each gene. The new individual then gets one allele from the mother and the other from the father.
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11Question 3
Mendel crossed pea plants that were pure-bred for yellow seeds with plants that were pure-bred for green seeds. All the offspring of this cross had yellow seeds. Based on these results, which form of color was recessive and which was dominant?
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11Answer
Green seed color was recessive and yellow seed color was dominant. Mendel called the form that seemed to disappear (green in this case) recessive and the form that covered up (yellow in this case) dominant.
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Incomplete Dominance• Incomplete dominance – results in an
intermediate phenotype
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• Multiple alleles - trait that is controlled by more than two alleles
• Produce more than three phenotypes
Multiple Alleles 22
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• Alleles for blood types
• A, B, and O.
Polygenic Inheritance• Polygenic inheritance - a group of gene
pairs acts together to produce a trait.
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• Produces a wide variety of phenotypes.
Click image to view movie.
Polygenic Inheritance• Examples:
• Height
• Eye color
• Skin color
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Impact of the Environment
• Environment plays a role in how some genes are expressed
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Human Genes and Mutations22
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• Mutations – errors when DNA copies
• Can be harmful or helpful
• Chromosome Disorders - error in the number of chromosomes
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Recessive Genetic Disorders - caused by recessive genes.
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Sex Determination
• Egg - 1 X chromosome
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• Sperm - 1 X or 1 Y chromosome
• Male XY• Female XX
Sex-Linked Disorders • Sex-linked
gene - allele inherited on a sex chromosome
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• Color blindness is sex-linked
Pedigrees Trace Traits
• Pedigree - visual tool for following a trait through generations
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• Males – squares
• Females – circles
Pedigrees Trace Traits
• Filled circle or square - shows trait
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• Half-colored - carriers
• Empty - do not have the trait and are not carriers.
22Section CheckSection Check
Question 1
Why is color blindness a sex-linked trait?
22Answer
This trait is sex-linked because the alleles for this trait are carried on the X-chromosome, one of the sex chromosomes. Color-blindness is caused by a recessive allele and because males get only one X-chromosome, they are more likely to be color-blind than females.
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22Question 2
In Himalayan rabbits, dark-colored fur is only found on cooler parts of the rabbits’ bodies. This is an example of _______.
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A. how sex-linked conditions change coat colorB. the risk of cancer in rabbits with light furC. the impact of internal environment on gene expressionD. what hybrid rabbits look like
22Answer
The correct answer is C. The alleles for dark fur color are controlled by the internal temperature of the rabbits. These alleles are expressed only at lower temperatures.
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22Question 3
If an individual has three copies of chromosome 21, what condition will result?
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A. color blindnessB. cystic fibrosisC. Down’s syndromeD. Hemophilia
22Answer
The correct answer is C. Down’s syndrome occurs when there are three copies of chromosome 21 instead of the usual two.
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• Genetic engineering - scientists are experimenting to change the arrangement of DNA that makes up a gene.
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• Recombinant DNA - made by inserting a useful segment of DNA from one organism into a bacterium.
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• Used to produce
• human insulin,
• human growth hormone
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Gene Therapy
• Normal allele is placed in a virus.
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• The virus then delivers the normal allele and replaces the defective one
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Genetically Engineered Plants • Selective breeding - selecting plants with the
most desired traits to breed
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Genetically Engineered Plants 33
• Find genes that produce desired traits in one plant and then insert them into a different plant
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33Section CheckSection Check
Question 1
What is it called when scientists use biological and chemical methods to change the arrangement of DNA in a gene?
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Answer
This is called genetic engineering. This process has been used to make large volumes of medicines and research is being conducted to find many other ways to use these techniques.
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Question 2What does this diagram illustrate?
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A. Bacteria cells can produce human insulin.B. Bacteria genes are put in human cells.
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C. People with diabetes are given the gene for insulin.D. The insulin gene is inserted in people with diabetes.
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The correct answer is A. Genetic engineering can be used to insert the human gene for insulin into bacterial cells. The bacterial cells then produce human insulin. This insulin can be used to treat people who have diabetes.
Answer
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Using genetic engineering to replace defective alleles in people with genetic diseases is called _______.
Question 3
A. gene therapyB. Mendelian genetics C. pedigree analysisD. recombinant DNA
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The correct answer is A. Often; a virus is used to deliver the normal allele to the patient. Scientists have been conducting experiments to cure many different genetic diseases, including cystic fibrosis, in this way.
Answer
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