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Home , Classical genetics

Chapter Outline

• Classical Classical and • DNA and the Birth of Molecular Modern Genetics Genetics •The Chapter 23

Great Idea: All living things use the same genetic code to guide the chemical reactions in

every cell. 1 2

Genetics of Inheritance iClicker Question

• Classical or Mendelian genetics (Gregory Mendel) • If you were to cross rabbits that • Competing hypotheses – Blended inheritance were black with rabbits that were – Particulate inheritance white and the offspring were either • Testing the hypotheses white or black, this outcome would – Flower color in peas (1 parent with red flowers and 2nd parent with white flowers) support the theory of – Results: two classes of flowers ______. • Red (300 seedlings) • White (100 seedlings) – A particulate inheritance • Conclusion: – B conspicuous inheritance – Support for particulate theory; reject blended theory – Specific quantitative data: 3:1 ratio – C Lamarckian inheritance – D blended inheritance 3 – E none of the above 4

iClicker Question Mendelian Genetics (1860’s)

• The studies of in the mid • – trait determined by a sequence of DNA 1860’s provide data in support of the • - alternative versions of the same gene theory of particulate theory of inheritance. (e.g., normal hemoglobin versus sickle cell The other notable observation of Mendel hemoglobin) was the quantitative data showing a ratio • Dominant allele (e.g., red flower color; brown of ____ in the offspring of pea plant flower eyes) color. • Recessive allele (e.g., white flower color; blue •A.blended eyes) •B.3:1 • – physical packaging of in •C.1:1 nucleus • D. 50:50 • Pairs of chromosomes (homologous pair) 5 • – all of the genes of an organism in the 6 • E. 1:4.632 nucleus

1 Classical Genetics

•Mendel – Basic laws of inheritance – Classic pea plant experiments •Purebred •Hybrid •Results –First generation – Second generation •Gene –Dominant – Recessive

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Qualitative versus Rules of Classical Genetics

• Traits (genes) are passed from • Qualitative parent to offspring –observational – mechanism unknown • Quantitative • Two genes for each trait –Predictive model – One from each parent – Used to trace genetic • There are dominant and recessive disease genes – Dominant expressed

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iClicker Question iClicker Question

• The study of ways in which • The offspring of two different biological information is passed strains are called: from one generation to the next is –A hybrids called –B purebred – A ancestry –C mutants – B husbandry – D Mendelian populations – C paleontology –D genetics

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2 iClicker Question iClicker Question

• The “unit of inheritance”, invented • In human beings, dark hair and eye by Mendel, is now called the: color are dominant over light. –A hybrid –A True – B parental strain –B False –C gene – D dominant characteristic –E Mendel

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iClicker Question

• Each offspring has only one gene for each trait. DNA and the Birth of –A True –B False

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Nucleotides: The Building Blocks of Nucleic Acids DNA Structure • • Join – Three molecules – Alternating •Sugar phosphate and sugar – DNA: deoxyribose •DNA – RNA: ribose • Phosphate ion –2 strands of •Base nucleotides – Adenine (A) – Joined by base pairs – Guanine (G) – Cytosine (C) • Bonding pattern – Thymine (T) – Adenine:Thymine – Cytosine:Guanine 17 18

3 DNA Structure RNA Structure

•Differences – One string of nucleotides –Sugar is ribose – Thymine replaced by uracil • Uracil (U) bonds with adenine

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The Replication of DNA iClicker Question • DNA replication – Occurs before • produces sex cells with half mitosis & the usual number of chromosomes. meiosis These cells are called • Process –A gametes –DNA double – B nucleic acids helix splits – New bases bond – C nucleotides to exposed bases –Result

• Two identical 21 22 DNA strands

iClicker Question iClicker Question

• Nucleic acids such as DNA and RNA • What three small molecules are polymers of combine to form a nucleotide? – A amino acids – A a sugar, a lipid, and an acid – B monosaccharides – B a sugar, a phosphate and a base – C nucleotides – C a lipid, a base and an amino acid – D lipids – D a nucleus, a sugar and a base – E a nucleus, a leonid and a tide

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4 iClicker Question Gene

• What structural feature gives DNA its helical shape (double helix)? – A the phosphates can form ionic bonds – B the sugars have covalent bonds – C the bases can form hydrogen bonds – D the strong force between bases

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DNA to Genes to Chromosomes Chromosomes and

Gene

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Genetics of Humans - Sex Transcription of DNA

• Sex determination associated with • Transcription one pair of chromosomes (Pair No. – Information transport 21) – x – Uses RNA – y chromosome • Female: 2 x chromosomes (X + X) • Process • Male: 1 x and 1 y chromosome (X + –Unzip DNA Y) • Female produces x chromosome – RNA binds to exposed bases eggs – RNA moves out of nucleus (mRNA) • Male produces both x and y chromosome sperm • Who determines the sex of offspring?

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5 The Synthesis of Proteins

•tRNA – Reads message – Structure •Amino acid • 3 bases • Process –mRNA moves to ribosome – rRNA aligns mRNA and tRNA – tRNA matches codon on mRNA – Amino acid chain forms • Basis for protein

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Protein synthesis cont.

• One gene codes for one protein

• Protein drives chemical process in cell •DNA –Introns –Exons • All living things on Earth use the same genetic 33 code 34

Mutations and DNA Repair Why Are Genes Expressed?

• •Gene control – Change in DNA of parent – Turning genes on and off –Causes – Each cell contains same genes • Nuclear radiation – Not all cells have same function •X-rays • UV light – Certain genes activated •DNA Repair • Scientists currently studying how – 10,000 ‘hits’ per day – Cells repair damage

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6 Genetics of Humans: Sex-Linked Human Genome and Genetic Differences Traits

• Some traits more common in one sex •Examples – Color blindness: males –Baldness: males – Hemophilia: males

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Viruses HIV

•Virus •Human – Not alive Immunodeficiency Virus – No metabolism (HIV) – Cannot reproduce on own –Contains RNA • Structure –Short DNA or RNA – Codes back to DNA – Protein coating – DNA incorporated into cell •How it works –Makes new viruses – Taken into cell – Cell dies – Takes over cell •Complex – Produces more copies – Kills cell –Two protein coats • Outer coat fits T cell receptors 39 • Inner coat encloses RNA 40

Viral Epidemics iClicker Question

•Viruses • RNA is different from DNA in that – Cannot use uracil (U) replaces which base? medication –A adenine – Use vaccination –B guanine •Viruses evolve –C cytosine rapidly –D thymine –HIV –Influenza – SARS

–Bird flu 41 42

7 iClicker Question iClicker Question

• Making a copy of DNA is called: • Forming a strand of RNA, using the –A replication code on a segment of DNA is called: –B transcription –A replication – C translation –B transcription – C translation

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iClicker Question iClicker Question

• Converting the code on a strand of • All living things on Earth use the RNA into a protein is called: same genetic code. –A replication –A True –B transcription –B False – C translation

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iClicker Question iClicker Question

• The sequence of all the base pairs • If it were possible to determine in all the chromosomes is known as which genetic diseases you might an organism’s develop by having your DNA –A DNA map sequence analyzed, would you do –B phagocyte this? –C genome –A Yes –B No

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8 iClicker Question iClicker Question

• The number of chromosomes in any • In genetic crosses, the re-current cell of your body (except for quantitative ratio of 3:1 among gametes) is _____. offspring supports the presence of A16 ____ copy/copies of each gene in B32 an organism. C41 –A four D46 –B three E None of the above –C two –D one

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Molecular Genetics iClicker Question

• In the following figure, the information process linking the • Structure of DNA and RNA – information DNA to RNA (see white arrow) storage, transmission and expression is called ______. A replication • Replication of the information – B transcription copying/duplication Ctranslation • Transcription of the information – D gene splicing transcribing • Translation of the information – expressing as proteins

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Molecular Genetics: Structure of DNA and RNA

• DNA – Deoxyribonucleic acid (nucleus) • RNA – Ribonucleic acid (protoplasm) • Monomer – nucleotides (N=5) – Guanine (always binds to Cytosine - G:C) – Adenine (always binds to Thymine - A:T) – Cytosine (always binds to Guanine - C:G) – Thymine (always binds to Adenine - A:T) – Uracil (T replacement in RNA) • Polymer – polynucleotide (DNA & RNA)

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9 Relating Chromosomes to the DNA Helix Sequence of Nucleotides and Genes

• Linear sequences of nucleotides

1150 1225 431 653

1580 102 954

• Gene: sequence of nucleotides responsible for a specific traits (e.g., eye color; hemoglobin and sickle cell anemia)

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Molecular Genetics: A Single Gene iClicker Question

• Exact sequence of nucleotides is important In a DNA polynucleotide, the base sequence is T-A-A-G-C-T. Which A T T A G C G G T A T G C C G G T T A A G A T C C G base sequence would be bonded to this section of a complementary strand of DNA polynucleotide? A T T A G C G G T A C G C C G G T T A A G A T C C G A A-C-G-T-A-A B A-C-G-U-U-A • Any change in sequence changes the information C A-G-C-T-T-A (“RAT to CAT”) and constitutes a D U-G-C-A-A-U E A-T-T-C-G-A 57 58

iClicker Question Molecular Genetics: Replication

• An mRNA sequence is 300 • Replication: nucleotides in length. The number process of of amino acids in the protein duplicating translated from this mRNA is DNA to ______. produce a • A. 50 new and exact copy •B. 100 with fidelity •C.150 –includes •D.200 “spell checking” •E. 600 59 60

10 Compartmentation: Ribosome Molecular Genetics: Transcription

• Process whereby information in DNA is “transcribed” into another type of message called mRNA (message RNA) • mRNA made in nucleus and subsequently shuttled to protoplasm • In protoplasm, mRNA finds its way to the ribosome (where protein synthesis occurs) 61 62

Molecular Genetics: Translation Translation and the Genetic Code Sequence of Amino Acids: Polypeptide • Process whereby information in mRNA is “transcribed” into proteins Genetic Code (polypeptides) – Monomer: amino acids (e.g., lab exercise) – Location: ribosome for protein synthesis • Genetic code: specificity and fidelity mRNA – Three consecutive nucleotides of mRNA Ribosome used to “call in” unique amino acid

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Genetic Code and Genetics “on the Cutting Edge”

• Fidelity in copying information • Genetic Counseling (probability of offspring with • Specificity in information particular traits) • Expression of gene via manufacturing of • Forensic (e.g., CSI TV series) polypeptide leading to protein (e.g., enzyme) • (e.g., “starlight” strain of corn) • Genetic Code is conserved in evolution – all – GMO’s (Genetically Modified Organisms) organisms use the exact same coding process • Genetic “Sleuthing •Example of Genetic Code: laboratory exercise – Human applications (e.g., ice man in the Alps + 5,000 using hemoglobin across multiple species years) •Pharmaceuticals – Toxicology of drugs and chemicals (e.g., Celebrex)

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11 Genetic Counseling Genetic Counseling using “Gene Chips”

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Forensic Sciences GMO’s

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Genetic Sleuthing: Ice Man of the Alps Take-Home Messages

• Inheritance of traits is best explained by the hypothesis that traits are not blended but expressed as distinct units called genes and alleles; this is the particulate theory of inheritance • The following two sequences underpin all of molecular genetics

DNA Transcription mRNA Translation Polypeptide Protein

DNA Replication DNA • Genetic code is a process common to all organisms and is prima facia evidence for evolution • Application of molecular techniques is substantial and will affect dramatically your lives and that of your children

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