Genetics Georgia High School Graduation Test: Science Review Mrs. Kirby

Introduction From the key vocabulary, circle the words that you can already define or use in a sentence.From the key vocabulary, circle the words that you can already define or use in a sentence. Write down two or three things that you think are important for you to know today.Write down two or three things that you think are important for you to know today.

Genetics The study of the inheritance of traits and how genes pass on these traits from parents to offspringThe study of the inheritance of traits and how genes pass on these traits from parents to offspring

Important Genetic Vocabulary trait: a characteristic of an organism that is inherited (examples: eye color, hair type, etc.)trait: a characteristic of an organism that is inherited (examples: eye color, hair type, etc.) gene: basic unit of heredity made of DNA that determines the characteristics of a traitgene: basic unit of heredity made of DNA that determines the characteristics of a trait allele: the two different versions of a gene for a particular trait (one received from each parent)allele: the two different versions of a gene for a particular trait (one received from each parent)

Genotype versus Phenotype GENOTYPE an organism’s genetic makeupan organism’s genetic makeup includes the two allelesincludes the two alleles represented with two letters (example: Bb)represented with two letters (example: Bb) PHENOTYPE the physical appearance of a trait expressed by the organisms genes represented by description (example: brown eyes)

Dominant versus Recessive DOMINANT an allele that expresses itself while hiding the effects of another allelean allele that expresses itself while hiding the effects of another allele represented with a capital letterrepresented with a capital letter example: Bb (dominant brown eyes dominates over recessive blue)example: Bb (dominant brown eyes dominates over recessive blue) RECESSIVE An allele whose effects are hidden by a dominant allele Represented with a lower-case letter example: Bb (dominant brown eyes dominates over recessive blue)

Homozygous versus Heterozygous HOMOZYGOUS “homo-” means the same“homo-” means the same the pairing of alleles that are the samethe pairing of alleles that are the same examples:examples: BB is dominant homozygous brownBB is dominant homozygous brown bb is recessive homozygous bluebb is recessive homozygous blue HETEROZYGOUS “hetero-” means different the pairing of unlike alleles example: Bb is heterozygous brown

Sample Question 1.Explain how traits are passed from generation to generation.

Gregor Mendel Mendel Father of GeneticsFather of Genetics experimented with pea plantsexperimented with pea plants established a method for predicting how traits are inheritedestablished a method for predicting how traits are inherited

Mendel’s Laws The Law of Dominance: a recessive trait will only be expressed when the organism’s genotype is recessive homozygous (bb)The Law of Dominance: a recessive trait will only be expressed when the organism’s genotype is recessive homozygous (bb) The Law of Segregation: during fertilization, new alleles are randomly formed; one can only predict offspring (using Punnett squares)The Law of Segregation: during fertilization, new alleles are randomly formed; one can only predict offspring (using Punnett squares) The Law of Independent Assortment: each trait is inherited independently of other traitsThe Law of Independent Assortment: each trait is inherited independently of other traits

PPPP rrrr oooo bbbb aaaa bbbb iiii llll iiii tttt yyyy and Punnett Squares Probability is the likelihood an event will occurProbability is the likelihood an event will occur Geneticists use Punnett squares to predict the probability of genetic combinationsGeneticists use Punnett squares to predict the probability of genetic combinations Example: When two heterozygous brown eyes mate...Example: When two heterozygous brown eyes mate... Bb BBBBb bBbbb

Theory of Inheritance Chromosomes are the physical basis of inheritance (carry DNA).Chromosomes are the physical basis of inheritance (carry DNA).Chromosomes Variability results from dominant and recessive alleles.Variability results from dominant and recessive alleles. The chromosomes in the male gamete and female gamete join together during fertilization to form a zygote.The chromosomes in the male gamete and female gamete join together during fertilization to form a zygote. gamete = sex cellgamete = sex cell zygote = fertilized eggzygote = fertilized egg

Sample Question 2.Explain the role of DNA and RNA in heredity.

DNA deoxyribonucleic aciddeoxyribonucleic acid found in chromosomes in the nucleusfound in chromosomes in the nucleus determines the hereditary traits of an organismdetermines the hereditary traits of an organism contains all the information needed for the production of proteinscontains all the information needed for the production of proteins protein sequences determine traitsprotein sequences determine traits

RNA ribose nucleic acid aids in protein synthesis in the ribosome 3 types: messenger RNA: mRNA carries the DNA nucleotide sequence for a protein from the nucleus to the ribosome transfer RNA: tRNA transports amino acids (building blocks of proteins) to the ribosome ribosomal RNA: rRNA makes up the structure of the ribosome

Sample Question 3.Diagram and explain DNA replication.

DNA replication see figure 8-5 on p.149see figure 8-5 on p.149 self-duplication of the genetic materialself-duplication of the genetic material results in two new DNA moleculesresults in two new DNA molecules occurs during interphase (just before cell divides)occurs during interphase (just before cell divides) proteins unwind the DNA helix and each strand acts as a template for a new strandproteins unwind the DNA helix and each strand acts as a template for a new strand unbound nucleotides attach...unbound nucleotides attach... A-T (adenine binds with thymine)A-T (adenine binds with thymine) C-G (cytosine binds with guanine)C-G (cytosine binds with guanine)

Sample Question 4.Diagram and explain transcription.

DNA transcription transcription to “transcribe” is to copyto “transcribe” is to copy mRNA is synthesized in the cell nucleus from the DNA moleculemRNA is synthesized in the cell nucleus from the DNA molecule Just as in replication, the helix unwinds and free nucleotides attach to make mRNA...Just as in replication, the helix unwinds and free nucleotides attach to make mRNA... C-G (cytosine binds with guanine)C-G (cytosine binds with guanine) U-A (uracil binds with adenine)U-A (uracil binds with adenine) Only DNA has thymineOnly DNA has thymine mRNA separates and moves out of the nucleusmRNA separates and moves out of the nucleus DNA double helix reformsDNA double helix reforms

Sample Question 5.Diagram and explain translation.

DNA translation process of translating the genetic code to the amino acid sequenceprocess of translating the genetic code to the amino acid sequence tRNA decodes the mRNA to read the DNA in order to make the correct proteintRNA decodes the mRNA to read the DNA in order to make the correct protein

Mutations A mutation is any change in the DNA sequence.A mutation is any change in the DNA sequence.mutation A change in one nucleotide may cause a change in the structure of the protein.A change in one nucleotide may cause a change in the structure of the protein. During pregnancy, observing a karyotype (a chromosome picture) can detect chromosomal defects.During pregnancy, observing a karyotype (a chromosome picture) can detect chromosomal defects.

Discussion If you needed to get precise information from one person to another, what would you need to do? How would you structure the information? How would you store that information so that it could be easily retrieved?If you needed to get precise information from one person to another, what would you need to do? How would you structure the information? How would you store that information so that it could be easily retrieved?

Lesson Summarized Write a sentence that explains the system discussed. Draw a graphic organizer that shows the relationship of the parts of the gene system to the whole system.

Short Quiz Answers 1.A gene is the basic unit of heredity made of DNA. 2.Homozygous means the pair of alleles are the same. 3.DNA determine the hereditary traits of an organism and contains all the information needed for the production of proteins. RNA aids in protein synthesis in the ribosome by transcribing and translating DNA. 4.Inheritance depends on the pair of alleles from the parent chromosome, and variability depends on the dominant and recessive alleles. 5.replication = self-copy of DNA (in nucleus) transcription = production of mRNA from DNA (in nucleus) translation = production of protein with interaction of mRNA and tRNA (in ribosome)