DNA and Genetics

Genetics and Heredity See what you remember.  Directions: Fill in the blanks with vocabulary terms from the list below. All organisms reproduce, or make more organisms that are similar to themselves. ______________________ also involves the passing of traits from one parent to offspring. The passing of traits from parents to offspring is called _____________________________. A _____________ is a set of instructions for an inherited trait. For example, a gene may contain the instructions that determine the color of a person’s eyes. The genes are located on structures inside a cell called _____________________________. After scientists recognized that chromosomes store the genetic information, they began an intensive search to learn more about the structure and chemical composition of chromosomes. Chromosomes are made from a chemical compound called ______________________ ___________, abbreviated as ______________________. The genes that are passed from generation to the next are made of DNA. Knowing the structure of DNA would help scientists understand how DNA functions to control the development of traits in an individual. This is exactly what James Watson and Francis Crick were trying to do in the early 1950’s. Watson and Crick used data that other scientists obtained about the chemical composition of DNA to figure out its three-dimensional ___________.

Vocabulary Terms Chromosomes Deoxyribonucleic acid DNA Gene Heredity Reproduction Structure

Answer KEY All organisms reproduce, or make more organisms that are similar to themselves. REPRODUCTION also involves the passing of traits from one parent to offspring. The passing of traits from parents to offspring is called HEREDITY. Heredity is controlled by genes. A GENE is a set of instructions for an inherited trait. For example, a gene may contain the instructions that determine the color of a person’s eyes. The genes are located on structures inside a cell called CHROMOSOMES. After scientists recognized that chromosomes store the genetic information, they began an intensive search to learn more about the structure and chemical composition of chromosomes. Chromosomes are made from a chemical compound called DEOXYRIBONUCLEIC ACID abbreviated as DNA. The genes that are passed from generation to the next are made of DNA. Knowing the structure of DNA would help scientists understand how DNA functions to control the development of traits in an individual. This is exactly what James Watson and Francis Crick were trying to do in the early 1950’s. Watson and Crick used data that other scientists obtained about the chemical composition of DNA to figure out its three-dimensional STRUCTURE.

Reproduction-113 The process of making more of one’s own kind Each species reproduces only its own kind. Reproduction is essential for the survival of the species. There are two types of reproduction: Sexual Asexual

Sexual Reproduction-114

Asexual Reproduction Reproduction without sperm and egg. It involves only one parent organism.

Plants Egg cells form in the ovary. A long tube, or pistil, grows out from the ovary. Surrounding the pistil are stamens. Stamen produce pollen, a dust-like material that contains sperm cells.

The Structure of DNA Chromosomes are made of DNA. Each chromosome contains thousands of genes. The sequence of bases in a gene forms a code that tells the cell what protein to produce.

A Complex Molecule The shape of the molecule is like a twisted zipper. It is called a double helix. The scientist that discovered DNA and its shape realized that smaller molecules of DNA bond together and form this double helix shape.

The Genetic Code Genes and DNA: A gene is a section of DNA molecule that contains the information to code for one specific protein. Order of the Bases: The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced. Adenine (A) Cytosine (C) Thymine (T) Guanine (G)

The Human Genome-117 Humans have thousands of different genes. They are located on 23 pairs of chromosomes.

Twins and Cloning Identical twins are two individuals that formed from one egg fertilized by one sperm. Fraternal twins are offspring formed when two different egg cells are fertilized by different sperm cells at the same time. Cloning can be used to produce offspring hat are genetically identical to their parent.

Gregor Mendel A 19th century priest who revolutionize the study of heredity. HEREDITY is the passing of physical characteristics from parents to offspring. This is why we “look” the way we do. Why we have certain characteristics from one parent and other characteristics from the other parent.

Dominant and Recessive Alleles Mendel reached several conclusions on the basis of his experimental results. He reasoned that individual factors, or sets of genetic “information,” must control the inheritance of traits in peas. The factors that control each trait exist in pairs. The female parent contributes one factor, while the male parent contributes the other factor. Finally, one factor in a pair can mask, or hide, the other factor. The tallness factor, for example, masked the shortness factor.

An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive. A dominant allele is one whose trait always shows up in the organism when the allele is present. A recessive allele , on the other hand, is hidden whenever the dominant allele is present. A trait controlled by a recessive allele will only show up if the organism does not have the dominant allele.

Symbols for Alleles: Geneotypes Geneticists use letters to represent alleles. A dominant allele is represented by a capital letter. For example, the allele for tall stems is represented by T. A recessive allele is represented by the lowercase version of the letter. So, the allele for short stems would be represented by t. When a plant inherits two dominant alleles for tall stems, its alleles are written as TT. When a plant inherits two recessive alleles for short stems, its alleles are written as tt. When a plant inherits one allele for tall stems and one allele for short stems, its alleles are written as Tt and is a hybrid. A hybrid organism has two different alleles for a trait.

Punnett Squares-123 B=dominant for brown eyes b=recessive for blue eyes

Here are some practice sites: Traits Activities http://learn.genetics.utah.edu/content/inheritance/activities/ Learn. Genetics, Genetic Science Learning Center: The Basics and Beyond http://learn.genetics.utah.edu/content/begin/tour/ Science Kids at Home: Genetics–What are Genes? (tutorial for students) www.sciencekidsathome.com/science_topics/genetics-a.html Genetics for Kids Mini-lecture and Punnett’s Square Activity http://exploringnature.org/db/detail.php?dbID=22&detID=2290 The Wonderful World of Genetics. WebQuest. www.uni.edu/schneidj/webquests/spring05/genetics/index.html Gregor Mendel (1822–1884) www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.php Mendel’s Genetic Laws http://anthro.palomar.edu/mendel/mendel_1.htm