1 Classical and Modern Genetics Chapter 23 Great Idea: All living things use the same genetic code to guide the chemical reactions in every cell.
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Classical and Modern Genetics
Chapter 23
Great Idea:All living things use the same genetic code to guide the chemical reactions in
every cell.
2
Chapter Outline
• Classical Genetics• DNA and the Birth of Molecular
Genetics• The Genetic Code
3
Genetics of Inheritance• Classical or Mendelian genetics (Gregory Mendel)• Competing hypotheses
– Blended inheritance– Particulate inheritance
• Testing the hypotheses– Flower color in peas (1 parent with red flowers and 2nd
parent with white flowers)– Results: two classes of flowers
• Red (300 seedlings)• White (100 seedlings)
• Conclusion: – Support for particulate theory; reject blended theory– Specific quantitative data: 3:1 ratio
4
iClicker Question
• If you were to cross rabbits that were black with rabbits that were white and the offspring were either white or black, this outcome would support the theory of ___________.
– A particulate inheritance– B conspicuous inheritance– C Lamarckian inheritance– D blended inheritance– E none of the above
5
iClicker Question
• The studies of Gregor Mendel in the mid 1860’s provide data in support of the theory of particulate theory of inheritance. The other notable observation of Mendel was the quantitative data showing a ratio of ____ in the offspring of pea plant flower color.
• A. blended• B. 3:1• C. 1:1• D. 50:50• E. 1:4.632
6
Mendelian Genetics (1860’s)
• Gene – trait determined by a sequence of DNA• Allele - alternative versions of the same gene
(e.g., normal hemoglobin versus sickle cell hemoglobin)
• Dominant allele (e.g., red flower color; brown eyes)
• Recessive allele (e.g., white flower color; blue eyes)
• Chromosomes – physical packaging of genes in nucleus
• Pairs of chromosomes (homologous pair)• Genome – all of the genes of an organism in the
nucleus
7
Classical Genetics
• Mendel– Basic laws of inheritance– Classic pea plant experiments
• Purebred• Hybrid
• Results– First generation– Second generation
• Gene– Dominant– Recessive
8
9
Rules of Classical Genetics
• Traits (genes) are passed from parent to offspring –mechanism unknown
• Two genes for each trait–One from each parent
• There are dominant and recessive genes–Dominant expressed
10
Qualitative versus Quantitative Genetics
• Qualitative–observational
• Quantitative–Predictive model–Used to trace genetic
disease
11
iClicker Question
• The study of ways in which biological information is passed from one generation to the next is called
– A ancestry– B husbandry– C paleontology– D genetics
12
iClicker Question
• The offspring of two different strains are called:
– A hybrids– B purebred– C mutants– D Mendelian populations
13
iClicker Question
• The “unit of inheritance”, invented by Mendel, is now called the:
– A hybrid– B parental strain– C gene– D dominant characteristic– E Mendel
14
iClicker Question
• In human beings, dark hair and eye color are dominant over light.
– A True– B False
15
iClicker Question
• Each offspring has only one gene for each trait.
– A True– B False
16
DNA and the Birth of Molecular Genetics
17
Nucleotides: The Building Blocks of Nucleic Acids
• Nucleotide–Three molecules
• Sugar– DNA: deoxyribose– RNA: ribose
• Phosphate ion• Base
– Adenine (A)– Guanine (G)– Cytosine (C)– Thymine (T)
18
DNA Structure
• Join nucleotides–Alternating
phosphate and sugar• DNA
–2 strands of nucleotides
– Joined by base pairs• Bonding pattern
–Adenine:Thymine–Cytosine:Guanine
19
DNA Structure
20
RNA Structure
• Differences–One string of nucleotides–Sugar is ribose–Thymine replaced by uracil
• Uracil (U) bonds with adenine
21
The Replication of DNA• DNA replication
–Occurs before mitosis & meiosis
• Process–DNA double
helix splits–New bases bond
to exposed bases
–Result• Two identical
DNA strands
22
iClicker Question
• Meiosis produces sex cells with half the usual number of chromosomes. These cells are called
– A gametes– B nucleic acids– C nucleotides
23
iClicker Question
• Nucleic acids such as DNA and RNA are polymers of
– A amino acids– B monosaccharides– C nucleotides– D lipids
24
iClicker Question
• What three small molecules combine to form a nucleotide?
– A a sugar, a lipid, and an acid– B a sugar, a phosphate and a base– C a lipid, a base and an amino acid– D a nucleus, a sugar and a base– E a nucleus, a leonid and a tide
25
iClicker Question
• 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
26
Gene
27
DNA to Genes to Chromosomes
Gene
28
Chromosomes and Alleles
29
Genetics of Humans - Sex• Sex determination associated with
one pair of chromosomes (Pair No. 21)– x chromosome– y chromosome
• Female: 2 x chromosomes (X + X)• Male: 1 x and 1 y chromosome (X +
Y)• Female produces x chromosome
eggs• Male produces both x and y
chromosome sperm• Who determines the sex of offspring?
30
Transcription of DNA• Transcription
– Information transport–Uses RNA
• Process–Unzip DNA–RNA binds to exposed bases–RNA moves out of nucleus (mRNA)
31
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
32
33
34
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 code
35
Mutations and DNA Repair
• Mutations–Change in DNA of parent–Causes
• Nuclear radiation• X-rays• UV light
• DNA Repair–10,000 ‘hits’ per day–Cells repair damage
36
Why Are Genes Expressed?
• Gene control–Turning genes on and off–Each cell contains same genes–Not all cells have same function–Certain genes activated
• Scientists currently studying how
37
Genetics of Humans: Sex-Linked Traits
• Some traits more common in one sex
• Examples–Color blindness:
males–Baldness: males–Hemophilia: males
38
Human Genome and Genetic Differences
39
Viruses
• Virus– Not alive– No metabolism– Cannot reproduce on own
• Structure– Short DNA or RNA– Protein coating
• How it works– Taken into cell– Takes over cell– Produces more copies– Kills cell
40
HIV
• Human Immunodeficiency Virus (HIV)– Contains RNA– Codes back to DNA– DNA incorporated into cell– Makes new viruses– Cell dies
• Complex– Two protein coats
• Outer coat fits T cell receptors
• Inner coat encloses RNA
41
Viral Epidemics• Viruses
–Cannot use medication
–Use vaccination
• Viruses evolve rapidly–HIV– Influenza –SARS–Bird flu
42
iClicker Question
• RNA is different from DNA in that uracil (U) replaces which base?
– A adenine– B guanine– C cytosine– D thymine
43
iClicker Question
• Making a copy of DNA is called:– A replication– B transcription– C translation
44
iClicker Question
• Forming a strand of RNA, using the code on a segment of DNA is called:
– A replication– B transcription– C translation
45
iClicker Question
• Converting the code on a strand of RNA into a protein is called:
– A replication– B transcription– C translation
46
iClicker Question
• All living things on Earth use the same genetic code.
– A True– B False
47
iClicker Question
• The sequence of all the base pairs in all the chromosomes is known as an organism’s
– A DNA map– B phagocyte– C genome
48
iClicker Question
• If it were possible to determine which genetic diseases you might develop by having your DNA sequence analyzed, would you do this?
– A Yes– B No
49
iClicker Question
• The number of chromosomes in any cell of your body (except for gametes) is _____.
A 16B 32C 41D 46E None of the above
50
iClicker Question
• In genetic crosses, the re-current quantitative ratio of 3:1 among offspring supports the presence of ____ copy/copies of each gene in an organism.
– A four– B three– C two – D one
51
Molecular Genetics
• Structure of DNA and RNA – information storage, transmission and expression
• Replication of the information –copying/duplication
• Transcription of the information –transcribing
• Translation of the information –expressing as proteins
52
iClicker Question• In the following figure, the
information process linking the DNA to RNA (see white arrow) is called _______.
A replicationB transcriptionC translationD gene splicing
53
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)
54
55
Relating Chromosomes to the DNA Helix
56
Sequence of Nucleotides and Genes
• Linear sequences of nucleotides
• Gene: sequence of nucleotides responsible for a specific traits (e.g., eye color; hemoglobin and sickle cell anemia)
1150
102
1225
954
431
1580
653
57
Molecular Genetics: A Single Gene
• Exact sequence of nucleotides is important
• Any change in sequence changes the information (“RAT to CAT”) and constitutes a mutation
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
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
58
iClicker Question
In a DNA polynucleotide, the base sequence is T-A-A-G-C-T. Which base sequence would be bonded to this section of a complementary strand of DNA polynucleotide?
A A-C-G-T-A-AB A-C-G-U-U-AC A-G-C-T-T-AD U-G-C-A-A-UE A-T-T-C-G-A
59
iClicker Question
• An mRNA sequence is 300 nucleotides in length. The number of amino acids in the protein translated from this mRNA is _________.
• A. 50 • B. 100• C. 150• D. 200• E. 600
60
Molecular Genetics: Replication
• Replication: process of duplicating DNA to produce a new and exact copy with fidelity– includes
“spell checking”
61
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)
62
Compartmentation: Ribosome
63
Molecular Genetics: Translation
• Process whereby information in mRNA is “transcribed” into proteins (polypeptides)–Monomer: amino acids (e.g., lab
exercise)–Location: ribosome for protein synthesis
• Genetic code: specificity and fidelity–Three consecutive nucleotides of mRNA
used to “call in” unique amino acid
64
Translation and the Genetic CodeSequence of Amino Acids: Polypeptide
Ribosome
mRNA
Genetic Code
65
Genetic Code and Evolution
• Fidelity in copying information• Specificity in information• Expression of gene via manufacturing of
polypeptide leading to protein (e.g., enzyme)• Genetic Code is conserved in evolution – all
organisms use the exact same coding process• Example of Genetic Code: laboratory exercise
using hemoglobin across multiple species
66
Genetics “on the Cutting Edge”
• Genetic Counseling (probability of offspring with particular traits)
• Forensic Sciences (e.g., CSI TV series)• Genetic Engineering (e.g., “starlight” strain of corn)
– GMO’s (Genetically Modified Organisms)
• Genetic “Sleuthing– Human applications (e.g., ice man in the Alps + 5,000
years)
• Pharmaceuticals– Toxicology of drugs and chemicals (e.g., Celebrex)
67
Genetic Counseling
68
Genetic Counseling using “Gene Chips”
69
Forensic Sciences
70
GMO’s
71
Genetic Sleuthing: Ice Man of the Alps
72
Take-Home Messages• Inheritance of traits is best explained by the hypothesis that traits
are not blended but expressed as distinct units called genes andalleles; 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
Related Documents
