Chapter: Heredity

Table of Contents Chapter: Heredity Section 1: Genetics Section 2: Genetics Since Mendel Section 3: Biotechnology

Genetics 1 Inheriting Traits • Traits are inherited from parents • Heredity - the passing of traits from parent to offspring.

Genetics 1 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

Genetics 1 What is genetics? • Genetics - study of how traits are inherited

Genetics 1 Mendel—The Father of Genetics • Mendel (1856) – studied genes of pea plants • First to: • trace one trait through several generations • use probability to explain heredity

Genetics 1 • Purebred - always produces the same traits generation after generation • Hybrids – receive different alleles for a trait from each parent

Genetics 1 Dominant and Recessive Factors • Cross-pollination - using pollen from one flower to pollinate others

Genetics 1 Dominant and Recessive Factors • Dominant - factor expressed if there is only one allele for the trait • Recessive – factor expressed only when there are 2 alleles for the trait Click image to view movie.

Genetics 1 Punnett Squares • Studied > 30,000 pea plants over 8 yrs • Punnettsquare -tool used to predict results Click image to view movie.

Genetics 1 Punnett Squares • Uppercase - dominant allele • Lowercase - recessive allele

Genetics 1 • Genotype - genetic makeup • Phenotype - way an organism looks and behaves

Genetics 1 • Homozygous - two alleles that are the same • Heterozygous - two different alleles for a trait

Genetics 1 Making a Punnett Square

Section Check 1 Question 1 How did Gregor Mendel use his knowledge of mathematics in his study of heredity in pea plants?

Section Check 1 Answer 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.

Section Check 1 Question 2 According to this diagram, if meiosis proceeds correctly, how many alleles of a particular gene can a female pass on to her offspring?

Section Check 1 Answer 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.

Section Check 1 Question 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?

Section Check 1 Answer 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.

Genetics Since Mendel 2 Incomplete Dominance • Incomplete dominance – results in an intermediate phenotype

Genetics Since Mendel 2 • Multiple alleles - trait that is controlled by more than two alleles • Produce more than three phenotypes

Genetics Since Mendel 2 Multiple Alleles • Alleles for blood types • A, B, and O.

Genetics Since Mendel 2 Polygenic Inheritance • Polygenicinheritance - a group of gene pairs acts together to produce a trait. • Produces a wide variety of phenotypes. Click image to view movie.

Genetics Since Mendel 2 Polygenic Inheritance • Examples: • Height • Eye color • Skin color

Genetics Since Mendel 2 Impact of the Environment • Environment plays a role in how some genes are expressed

Genetics Since Mendel 2 Human Genes and Mutations • Mutations – errors when DNA copies • Can be harmful or helpful

Genetics Since Mendel 2 • Chromosome Disorders - error in the number of chromosomes

Genetics Since Mendel 2 Recessive Genetic Disorders- caused by recessive genes.

Genetics Since Mendel 2 Sex Determination • Egg - 1 X chromosome • Sperm - 1 X or 1 Y chromosome • Male XY • Female XX

Genetics Since Mendel 2 Sex-Linked Disorders • Sex-linked gene - allele inherited on a sex chromosome • Color blindness is sex-linked

Genetics Since Mendel 2 Pedigrees Trace Traits • Pedigree - visual tool for following a trait through generations • Males – squares • Females – circles

Genetics Since Mendel 2 Pedigrees Trace Traits • Filled circle or square - shows trait • Half-colored - carriers • Empty - do not have the trait and are not carriers.

Section Check 2 Question 1 Why is color blindness a sex-linked trait?

Section Check 2 Answer 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.

Section Check 2 Question 2 In Himalayan rabbits, dark-colored fur is only found on cooler parts of the rabbits’ bodies. This is an example of _______. A. how sex-linked conditions change coat color B. the risk of cancer in rabbits with light fur C. the impact of internal environment on gene expression D. what hybrid rabbits look like

Section Check 2 Answer 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.

Section Check 2 Question 3 If an individual has three copies of chromosome 21, what condition will result? A. color blindness B. cystic fibrosis C. Down’s syndrome D. Hemophilia

Section Check 2 Answer The correct answer is C. Down’s syndrome occurs when there are three copies of chromosome 21 instead of the usual two.

Biotechnology 3 • Genetic engineering - scientists are experimenting to change the arrangement of DNA that makes up a gene.

Biotechnology 3 • Recombinant DNA - made by inserting a useful segment of DNA from one organism into a bacterium. • Used to produce • human insulin, • human growth hormone

Biotechnology 3 Gene Therapy • Normal allele is placed in a virus. • The virus then delivers the normal allele and replaces the defective one

Biotechnology 3 Genetically Engineered Plants • Selective breeding - selecting plants with the most desired traits to breed

Biotechnology 3 Genetically Engineered Plants • Find genes that produce desired traits in one plant and then insert them into a different plant

Section Check 3 Question 1 What is it called when scientists use biological and chemical methods to change the arrangement of DNA in a gene?

Section Check 3 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.

Section Check 3 Question 2 What does this diagram illustrate?

Section Check 3 A. Bacteria cells can produce human insulin. B. Bacteria genes are put in human cells.

Section Check 3 C. People with diabetes are given the gene for insulin. D. The insulin gene is inserted in people with diabetes.

Section Check 3 Answer 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.

Chapter: Heredity