Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are...
-
Upload
ashley-spencer -
Category
Documents
-
view
221 -
download
3
Transcript of Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are...
![Page 1: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/1.jpg)
Gene Expression and Control
Chapter 7
Part 2
![Page 2: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/2.jpg)
7.6 Mutated Genes and Their Products
Mutations are permanent changes in the nucleotide sequence of DNA, which may alter a gene product
A mutation that changes a gene’s product may have harmful effects• Example: Mutations that affect the proteins in
hemoglobin reduce blood’s ability to carry oxygen
![Page 3: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/3.jpg)
Types of Mutations
Deletion • Mutation in which one or more base pairs are lost
Insertion • Mutation in which one or more base pairs
become inserted into DNA
Base-pair substitution • Type of mutation in which a single base-pair
changes
![Page 4: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/4.jpg)
Two Common Mutations in Hemoglobin
![Page 5: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/5.jpg)
Fig. 7-9a, p. 125
A Hemoglobin, an oxygen-transport protein in red blood cells. This protein consists of four globin chains: two alpha chains (blue) and two beta chains (green). Each globin chain folds up to form a pocket that cradles a type of cofactor called a heme (red). Oxygen binds to the iron atom at the center of each heme group.
![Page 6: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/6.jpg)
Fig. 7-9b, p. 125
part of DNA
mRNA transcribed from DNA
threonine (thr)
proline (pro)
glutamic acid (glu)
glutamic acid (glu)
lysine (lys)
resulting amino acid sequence
B Part of the DNA, mRNA, and amino acid sequence of the beta chain of a normal hemoglobin molecule.
![Page 7: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/7.jpg)
Fig. 7-9c, p. 125
deletion in DNA
altered mRNA
threonine (thr)
proline (pro)
glycine (gly)
arginine (arg)
threonine (thr)
altered amino acid sequence
C A single base-pair deletion causes the reading frame for the rest of the mRNA to shift, so a completely different protein product forms. This mutation results in a defective globin chain. The outcome is thalassemia, a genetic disorder in which a person has an abnormally low amount of hemoglobin.
![Page 8: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/8.jpg)
Fig. 7-9d, p. 125
base-pair substitution in DNA
altered mRNA
threonine (thr)
proline (pro)
valine (val)
glutamic acid (glu)
lysine (lys)
altered amino acid sequence
D A base-pair substitution in DNA replaces a thymine with an adenine. When the altered mRNA is translated, valine replaces glutamate as the sixth amino acid of the new polypeptide chain. Hemoglobin with this chain is called HbS, or sickle hemoglobin.
![Page 9: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/9.jpg)
Base-pair substitution
![Page 10: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/10.jpg)
Fig. 7-10a, p. 126
valine (val)
histidine (his)
leucine (leu)
threonine (thr)
proline (pro)
glutamic acid (glu)
glutamic acid (glu)
1 Normal amino acid sequence at the start of the hemoglobin beta chain.
valine (val)
histidine (his)
leucine (leu)
threonine (thr)
proline (pro)
valine (val)
glutamic acid (glu)
2 One amino acid substitution results in the abnormal beta chain of sickle hemoglobin (HbS). The sixth amino acid in such chains is valine, not glutamic acid.
sickled cell
3 Glutamic acid carries an overall negative charge; valine carries no charge. This difference causes the protein to behave differently. At low oxygen levels, HbS molecules stick together and form rod-shaped clumps that distort normally round red blood cells into sickle shapes. (A sickle is a farm tool with a crescent-shaped blade.)
normal cell
4 Tionne “T-Boz” Watkins of the music group TLC is a celebrity spokesperson for the Sickle Cell Disease Association of America. She was diagnosed with sickle-cell anemia as a child.
Sickle-Cell Anemia: A Base-Pair Substitution
![Page 11: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/11.jpg)
Fig. 7-10b, p. 126
![Page 12: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/12.jpg)
What Causes Mutations?
Most mutations result from unrepaired DNA polymerase errors during DNA replication
Some result from transposable element activity, or from exposure to radiation or chemicals
Transposable element • Small segment of DNA that can spontaneously
move to a new location in a chromosome
![Page 13: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/13.jpg)
Ionizing Radiation Damage
Ionizing radiation (x-rays) breaks chromosomes and produces free radicals
![Page 14: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/14.jpg)
Nonionizing Radiation Damage
Nonionizing radiation (UV light) results in thymine dimers, which lead to skin cancer
![Page 15: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/15.jpg)
Fig. 7-11b, p. 127
thymine dimer
![Page 16: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/16.jpg)
Environmental Damage
Some natural and synthetic chemicals cause mutations in DNA
Example: Cigarette smoke transfers small hydrocarbon groups to bases in DNA, causing mispairing during replication
![Page 17: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/17.jpg)
Frameshift mutation
![Page 18: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/18.jpg)
Duplication
![Page 19: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/19.jpg)
Deletion
![Page 20: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/20.jpg)
Inversion
![Page 21: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/21.jpg)
Translocation
![Page 22: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/22.jpg)
Sickle-cell anemia
![Page 23: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/23.jpg)
7.7 Examples of Eukaryotic Gene Controls
All cells in your body carry the same DNA
Some genes are transcribed by all cells, but most cells are specialized (differentiated) to use only certain genes
Which genes are expressed at a given time depends on the type of cell and conditions
![Page 24: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/24.jpg)
Cell Differentiation
Cells differentiate when they start expressing a unique subset of their genes – controls over gene expression are the basis of differentiation
Differentiation • The process by which cells become specialized• Occurs as different cell lineages begin to express
different subsets of their genes
![Page 25: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/25.jpg)
Controlling Gene Expression
Controlling gene expression is critical for normal development and function of a eukaryotic body
All steps between transcription and delivery of gene product are regulated
Transcription factor • Protein that influences transcription by binding to
DNA
![Page 26: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/26.jpg)
Homeotic Genes
Homeotic gene • Type of master gene that controls formation of
specific body parts during development
Master gene • Gene encoding a product that affects the
expression of many other genes• Controls an intricate task such as eye formation
![Page 27: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/27.jpg)
Homeodomains
All homeotic genes encode transcription factors with a homeodomain – a region of about 60 amino acids that can bind to a promoter or some other DNA sequence
![Page 28: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/28.jpg)
Identifying Homeotic Genes and Their Functions
Researchers study the function of a homeotic gene by altering its expression – by introducing a mutation or deleting it entirely• Examples: eyeless, dunce, tinman, groucho
Gene knockout • A gene that has been inactivated in an organism
![Page 29: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/29.jpg)
Gene Knockout Experiment: Eyeless
![Page 30: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/30.jpg)
Fig. 7-12a, p. 128
![Page 31: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/31.jpg)
Fig. 7-12b, p. 128
![Page 32: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/32.jpg)
Fig. 7-12c, p. 128
![Page 33: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/33.jpg)
PAX6 Gene Function
Many master genes are interchangeable among species; in humans and many other animals, the PAX6 gene affects eye formation
![Page 34: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/34.jpg)
Sex Chromosome Genes
In mammals, males have only one X chromosome – females have two, but one is tightly condensed into a Barr body and inactive
Dosage compensation • Theory that X chromosome inactivation equalizes
gene expression between males and females
![Page 35: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/35.jpg)
X Chromosome Inactivation
Female cells have Barr bodies, male cells do not
![Page 36: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/36.jpg)
The Y Chromosome
The SRY gene, found on the Y chromosome, is the master gene for male sex determination• Triggers formation of testes• Testosterone produced by testes controls
formation of male secondary traits
Absence of SRY gene in females triggers development of ovaries, female characteristics
![Page 37: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/37.jpg)
Fig. 7-14, p. 129
Structures that will give rise to external genitalia appear
at seven weeks
SRY expressed no SRY present
penis
vaginal opening
birth approaching
Development of Human Reproductive Organs
![Page 38: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/38.jpg)
Cancer: Gene Expression Out of Control
Many gene expression controls regulate cell growth and division – mutations that disrupt normal controls can cause cancer
Cancer • Disease that occurs when a malignant neoplasm
physically and metabolically disrupts body tissues
![Page 39: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/39.jpg)
Tumors
Tumor • Abnormally growing and dividing mass of cells
Metastasis• A process of cancer in which tumor cells lose
membrane recognition proteins, break free, and establish themselves in other parts of the body
![Page 40: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/40.jpg)
Cancer and Mutations
Cancer begins with a mutation in a gene whose product controls cell growth and division
A mutation that causes cancer may be inherited or be caused by environmental agents
Tumors are more likely to occur when mutations occur in tumor suppressor genes, such as BRCA1 and BRCA2
![Page 41: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/41.jpg)
BRCA Genes and Cancer
![Page 42: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/42.jpg)
Fig. 7-15b, p. 130
normal cells in organized clusters
irregular clusters of cancer cells
![Page 43: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/43.jpg)
Controls of eukaryotic gene expression
![Page 44: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/44.jpg)
Fate map
![Page 45: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/45.jpg)
X-chromosome inactivation
![Page 46: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/46.jpg)
Protein synthesis summary
![Page 47: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/47.jpg)
7.8 Impacts/Issues Revisited
Ricin causes ribosomes to stop working – protein synthesis stops, and the cell quickly dies
Researchers are trying to kill cancer cells without harming normal cells by attaching ricin to an antibody that can find cancer cells in the body
![Page 48: Gene Expression and Control Chapter 7 Part 2. 7.6 Mutated Genes and Their Products Mutations are permanent changes in the nucleotide sequence of DNA,](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649ceb5503460f949b5f62/html5/thumbnails/48.jpg)
Digging Into Data: BRCA Mutations in Women Diagnosed with Breast Cancer