Ch 5:Cancer types
Carcinoma - epithelial tissue, - metastasize
Leukemia - bone marrow stem cells that produce white blood cells
Sarcoma - connective tissue, muscle, bone, cartilage
Lymphoma - lymph tissue, Hodgkins
Adenocarcinoma - glandular epithelia, liver, salivary, breast
Cancer Is Uncontrolled Cell Division What Is Cancer?
Cell division is the process through which a cell copies itself
Cancer begins when the a cell divides although it should not
Unregulated cell division leads to a tumor, a mass of cells with no apparent function in the body
Benign tumors do not affect surrounding structures
Malignant tumors invade surrounding structures and are cancerous
Malignant tumors can break away and start new cancers elsewhere through the process of metastasis
What Is Cancer?
Cancer cells differ from normal cells:
Divide when they should not
Invade surrounding tissue
Move to other locations in the body
What Is Cancer?
All tissues that undergo cell division, such as ovarian tissue, are susceptible to cancer Cancer Risk Factors
Known risk factors are linked to particular cancers…
Not all exposures to chemicals and radiation causes cancers Cell Division Overview
Cell division produces new cells in order to:
Heal wounds
Replace damaged cells
For growth
Also for reproduction
Cell Division Overview
DNA is organized into structures called chromosomes which can carry hundreds of genes along their length
The number of in each cell depends on the organism: humans have 46
Cell Division Overview
The “rungs” of the molecule are the bases:
A (adenine)
T (thymine)
G (guanine)
C (cytosine)
Cell Division Overview
The bases across the “ladder” are connected in a specific way:
A always bonds with T
C always bonds with G
The connection is a hydrogen bond
Cell Division Overview
James Watson and Francis Crick:
Determined the structure of the DNA molecule
Published in Nature in 1953 The Cell Cycle and Mitosis
Mitosis is an asexual division
Is part of the cell cycle – the life cycle of the cell
Makes new cells that are exactly the same as the original cells
Cytokinesis
Animal cells produce a band of filaments that divide the cell in half
Cancer Begins with a Single Cell
Controls in the Cell Cycle
Checkpoints exist in the cell cycle
Cell determines if cell is ready to enter next part of cell cycle
Controls in the Cell Cycle
When the proteins that regulate the cell cycle don’t work, the cell divides uncontrollably
This results in a tumor
Controls in the Cell Cycle
Mutations in the DNA can produce nonfunctioning proteins
Mutations can be inherited or induced by exposure to carcinogens that damage DNA and chromosomes
Mutations to Cell-Cycle
Control Genes
Mutations in the DNA can produce nonfunctioning proteins
Mutations can be in cell control proteins called proto-oncogenes proto-: before
-onco: cancer
Mutations to Cell-Cycle
Control Genes
Proto-oncogenes:
Normal genes on many different chromosomes
Regulate cell division
When mutated, they become oncogenes
There Are Several Ways to Diagnose Cancer
Mutations to Cell-Cycle
Control Genes
Proto-oncogenes carry instructions for building growth factors
Stimulate
cell division when needed
Oncogenes overstimulate cell division
Mutations to Cell-Cycle
Control Genes
Receptor proteins on the surface of a cell recognize and bind to a specific chemical signal
Tumor suppressors are genes that carry instructions for producing proteins that stop cell division if necessary
Cancer Begins with a Single Cell
From Benign to Malignant
Angiogenesis – growth of blood cells caused by secretions from cancer cells
Increases the blood supply to cancer cells: more oxygen and nutrients
Cancer cells can divide more
Tumors develop, sometimes filling entire organs
Cancer Begins with a Single Cell
From Benign to Malignant
Most cells divide a set number (60-70) of times, then they stop dividing
This usually limits benign tumors to small sizes
Cancer cells can divide indefinitely, as they are immortal through the manipulation of the enzyme telomerase
Detection Methods: Biopsy
Under a microscope, benign tumors appear orderly and resemble other cells in the same tissue
Malignant tumors do not resemble normal tissue Meiosis
Another form of cell division, meiosis, occurs within gonads, or sex organs
Male gonads are testes and female gonads are ovaries
Meiosis produces sex cells – gametes:
Male gametes: sperm cells
Female gametes: egg cells
Meiosis
Gametes have half the chromosomes (23) that somatic cells do (46)
Meiosis reduces the number of chromosomes by one-half
Fertilization of the male and female gamete will result in 46 chromosomes
Meiosis
Which 23 chromosomes end up in a gamete?
One of each kind
Chromosomes come in pairs
Each somatic cell has two of every chromosome
Each gamete has one chromosome from each homologous pair
Crossing Over, Random Alignment, Segregation
There are millions of possible combinations of genes that each parent can produce because of:
Crossing over
Random alignment of homologous pairs
Segregation
Fertilization of two gametes
Crossing Over
When the homologous pairs are in prophase I of meiosis, they can exchange genetic information in the process of crossing over
This occurs between chromatids among the homologous pair
Random Alignment
When the homologous pairs line up during metaphase I of meiosis, the way the homologs place themselves is random alignment
This is also known as independent assortment
Mitosis and Meiosis
Both are types of cell division
Occur in different types of cells
Produce very different products
Ch6: 6.1 The Inheritance of Traits
Offspring resemble their parents, but not exactly.
Siblings resemble each other, but not exactly.
How much is because of environment?
How much is inherited?
Genes
Most genes are segments of DNA that carry information about how to make proteins
Structural proteins – for things like hair
Functional proteins – for things like breaking down lactose
Genes Are on Chromosomes
The genes are located on the chromosomes
The number of chromosomes depends on the organism
Bacteria – one circular chromosome
Humans – 23 homologous pairs of linear chromosomes
Gene Variation Is Caused by Mutation
Genes on a homologous pair are the same, but the exact information may not be the same
Mutations in gene copies can cause somewhat different proteins to be produced
Different gene versions are called alleles
Segregation
When a gamete is formed, the homologous pairs are separated and segregated into separate gametes (this is called the law of segregation)
This results in gametes with only 23 chromosomes
1 of each homologous pair
Independent Assortment
Due to independent assortment, parents contribute a unique subset of alleles to each of their non-identical twin offspring
Diversity in Offspring
There are 223 combinations for the way the homologous chromosomes could line up and separate
This is more than 8 million combinations
Crossing Over
In addition, crossing over in meiosis can increase diversity
The chromosomes trade information, creating new combinations of information
Random Fertilization
Gametes combine randomly—without regard to the alleles they carry in a process known as random fertilization
You are one out of 64 trillion genetically different children that your parents could produce
Diversity in Offspring
Mutation, segregation, independent assortment, crossing over, and random fertilization result in unique combinations of alleles
These processes produce the diversity of individuals found in humans and all other sexually reproducing biological populations
Twins
Fraternal (non-identical) dizygotic – two separate fertilized eggs not genetically the same
Identical
develop from one zygote
6.1 Producing Diversity in Offspring
Random fertilization produces more diversity: 64 trillion possibilities!
No two humans are genetically identical, except for monozygotic twins.
Gregor Mendel
Determined how traits were inherited
Used pea plants and analyzed traits of parents and offspring
Genotype and Phenotype
Genotype – combination of alleles homozygous: two of the same allele heterozygous: two different alleles
Phenotype
the physical outcome of the genotype depends on nature of alleles Mendelian Genetics
Phenotype: physical traits of an individual
Genotype: description of the alleles for a particular gene in an individual
Homozygous (-ote): both alleles for a gene are identical
Heterozygous (-ote): the gene has two different alleles
Recessive: the phenotype of an allele is seen only when homozygous
Dominant: the phenotype is seen when homozygous or heterozygous
Genetic Diseases in Humans
Most alleles do not cause diseases in humans
There are some diseases that are genetic:
Recessive, such as cystic fibrosis
Dominant, such as Huntington’s Disease
Codominant, such as sickle-cell anemia
Genetic Diseases:
Cystic Fibrosis
Affects 1 in 2500 individuals in European populations
Recessive condition: individuals have 2 copies of cystic fibrosis allele
Genetic Diseases:
Cystic Fibrosis
Produces nonfunctioning proteins
Normal protein transports chloride ion in and out of cells in lungs and other organs
Result – thick mucus layer that is difficult to clear out of lungs and interferes with absorption of nutrients in intestines
Huntington’s Disease
Dominant condition
Fatal condition
Only one Huntington’s allele needed
Produces abnormal protein that clumps up in cell nuclei – especially nerve cells in the brain
Results in the death of brain cells
Sickle-Cell Anemia
Codominant – both alleles are expressed
One allele codes for normal hemoglobin and the other codes for sickle-cell hemoglobin
6.3 Why Traits Are Quantitative
Quantitative traits, with continuous variation, are polygenic traits.
Result of several genes
Each with more than one allele
Interaction of multiple genes with multiple alleles results in many phenotypes.
Example: human eye color
Mean: sum up all the phenotypic values and divide by the number of individuals; same as the average.
Variance: a measure of how much variability there is in the population
The amount an individual varies from the mean, on average
Ch7: 7.3 Extensions of Mendelian Genetics
Codominance: neither allele is dominant to the other; heterozygote shows both traits at once (e.g., coat color in cattle)
7.3 Extensions of Mendelian Genetics
7.2 Dihybrid Crosses
Their gametes could then potentially produce the following offspring:
Meiosis and Sex Chromosomes
Sometimes the homologous pairs do not separate during meiosis
This is called nondisjunction and can occur in either meiosis I or meiosis II
Meiosis and Sex Chromosomes
Having an incorrect number of chromosomes is usually detrimental to the organism
One example is trisomy 21 (Down Syndrome)
One extra chromosome #21
X-Linked Genes
Males inherit their X chromosomes from their mothers
Males get the Y chromosome from their fathers
Since males only have one X chromosome, they are more likely to suffer from X-linked diseases, like hemophilia
X-Linked Genes
Since females get one X chromosome from each parent, and have two copies, they are less likely to suffer from X-linked diseases
X inactivation allows some female organisms to shut off their X chromosomes
Females can be carriers and pass the disease on to offspring, especially sons Pedigrees
A pedigree is a chart showing inheritance patterns in a family DNA Fingerprinting
Unless they are identical twins, individuals have unique DNA
The name used for the unambiguous identifying technique that takes advantage of differences in DNA sequence is DNA fingerprinting
DNA Fingerprinting
The process of DNA fingerprinting begins by isolating DNA from blood, semen, vaginal fluids, hair roots, skin, skeletal remains, or elsewhere
Polymerase Chain Reaction (PCR)
If there is only a small amount of DNA available, scientists can augment the amount using a technique called PCR (polymerase chainreaction)
DNA Fingerprinting
Treat the DNA with restriction enzymes
These enzymes cut DNA at specific sequences
This results in different sized fragments, since individuals have unique DNA patterns
RFLP Analysis
The different sized fragments are called restriction fragment length polymorphisms, or RFLPs
The RFLP patterns can be analyzed
RFLP Analysis
Everyone has genetic sequences called variable number tandem repeats, or VNTRs
Everyone has different amounts of VNTRs
The VNTRs make the different sized RFLPs
Gel Electrophoresis
Fragments of DNA from restriction enzyme cleavage are separated from each other when they migrate through a support called agarose gel
An electric current is applied so the gel will impede the larger DNA fragments more than the smaller ones
Meiosis and DNA Fingerprinting
DNA fingerprints of children should be similar to the DNA fingerprints of parents
The VNTRs occur on chromosomes and the chromosomes are put into gametes and inherited by offspring
7.6 DNA Fingerprinting
Pedigree of Romanov family