Test 2 Flashcards
Nucleotides
-Molecules that make up DNA
- For DNA: Thymine, Adenine, Guanine, Cytosine
- Thymine and Adenine go together (double strand)
- Guanine and Cytosine go together (triple strand)
- For RNA: Uracil, Adenine, Guanine, Cytosine
- Adenine → Uracil go together
- Thymine → Adenine
- Guanine and Cytosine go together
-Held together by hydrogen bonds
DNA
- Deoxyribonucleic Acid
- Long polymer made up of a sequence of nucleotides
- Nucleotides are building blocks
- Sequence of nucleotides (bases) are “blue prints” for proteins
- Gene - specific segment of DNA that determines a specific protein
DNA vs. RNA
-RNA:
Single strand
Has U rather than T
-DNA:
Double Strand
Has TProtein
- Made up of amino acids (sequence)
- Associated with transport, speed up processes (enzymes), help with physical structure, and act as messenger
Gene
- Specific segment of DNA that determines a specific protein
- 20,000-25,000
- Occurs sequentially on DNA (thus on chromosomes)
- Each gene occurs as two homologous copies
Transcription
- DNA transcribes (codes) to RNA (ribonucleic acid)
- Enzyme aligns RNA nucleotides (A, C, G, U) with complementary bases on one strand of the DNA
- Stops when enzyme reaches a termination (“stop”) sequence
- Result: Messenger RNA (mRNA)
- Uses RNA polymerase and promoter
Translation
- 3-base code of RNA - RNA translates information from DNA into a sequence of amino acids using a 3-base
- Converting the coded information in RNA into a protein
Structure of DNA
- DNA molecule is tightly coiled with proteins, called histones (histones provide packaging and control, forming nucleosomes)
- Includes chromatin, chromosomes (look at their definitions)
- During DNA synthesis, chromatin is is replicated producing “sister chromatids”
- Genes are arranged in sequence (kinda sorta)
- Sister chromatids are joined by a centromere
- Watson and Crick
- Made up of nucleotides (which carry genetic information)
- A polymer, a molecule, made up of a phosphate group, nitrogen base, and sugar
- Double helix
Chromatin
DNA when is loosely structured in the nucleus and is active
Before cells divide, chromatin condense
During DNA synthesis, chromatin is replicated, producing “sister chromatids” (still attached)
Chromosomes
- Individual strands of DNA
- human diploid cells have 46 chromosomes (give or take) in homologous pairs
Centromere
Attachment point for spindle fibers that pull chromatids apart during cell division
Mitosis. Products?
- Division that results in identical cells
- Result: Two daughter cells, each containing a full, identical set of genetic information
Cell Cycle and Division (Mitosis): Why cells divide?
1) Development and Growth
- Zygote
2) Replacement and Repair
3) Sex
Zygote
- Single cell formed by union of sperm and egg
- By adulthood, we have trillions of cells
Cell Cycle and Division (Mitosis): Two Main Phases?
- Interphase: Active growth and function
2. M-Phase: Mitosis - actual cell division
Interphase
- Active growth and function
- Gap 1 (G-1) = Rapid growth of cell and structures; cell is metabolically active
- S = DNA synthesis, chromatin is (chromatids are) replicated; cell is metabolically active
- Gap 2 (G-2) = Proteins for mitosis is synthesized, centrioles replicated; cell is metabolically active
M-Phase
-Mitosis – Actual cell division
- Four Phases + Cytokinesis:
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
- Chromatin condenses
- Replication stops
- Nuclear membrane breaks down
- Mitotic spindles grow from centrioles
Metaphase
- Spindles attach to chromosomes
- Chromosomes positioned along center of cell
Anaphase
- Sister chromatids pulled apart to form separate identical chromosomes
- Chromosomes pulled to opposite poles
Telophase and Cytokinesis
- Nuclear envelope forms
- Mitotic spindles disassemble
- Cytokinesis
Human Chromosomes
- Homologous Pairs - a pair of chromosomes that carry the same genes, but potential different versions (alleles)
- Sister Chromatids - identical, attached copy of chromosome
- Numbers in ‘Diploid cells’
- Sex Chromosomes
Alleles
- Different forms (versions) of a specific gene
- Different alleles may produce the same resulting protein
- OR produce differences in resulting proteins and differences in physical traits
- Represent differences in nucleotides of the gene
- Differences may or may not produce differences in the resulting protein
- Can be homozygous or heterozygous
- Can be dominant or recessive
Sister Chromatids
Result of DNA replication
Identical and attached at centromere
Meiosis
-Sex! But not in a fun way
- Brief Overview:
- resulting in genetically different cells
- these cells have ½ the # of chromosomes (haploid cells)
- male or female gametes
Purpose of Meiosis?
1) Meiosis selectively reduces the number of chromosomes in gametes (if it didn’t do this, there’d be too many chromosomes; selective reduction in the number of chromosomes in gametes
2) Genetic recombination to increase genetic diversity of offspring
Meiosis
- Cell division associated with sex
- Haploid cells: carry half the number of chromosomes
- Result in genetically different cells
- Male or female gametes
- Has two cell divisions; the process is a lot like Mitosis, but it has two cell divisions (Meiosis I and Meiosis II)
- Remember spermatogenesis and oogenesis!
Meiosis I (first cell division)
- Starts after the end of Interphase
- Like Mitosis, but the homologous chromosome pairs separate; homologues chromosome pairs are pulled apart (not the same chromatids as in mitosis); not the sister chromatids
- Crossing-over: exchange of genetic information between non-sister chromatids; specific genes have been switched (exchanged) on the homologous chromosomes
- Results in only 23 chromosomes in each cell
- Semi-random segregation of maternal and paternal chromosomes
Crossing-Over
- Exchange of genetic information between non-sister chromatids
- Specific genes have been switched (exchanged) on the homologous chromosomes
- LOOK IN MEIOSIS PACKET
Meiosis II (second cell division)
- Like in mitosis, sister chromatids are pulled apart
- Chromatids are selectively pulled apart
- Results in 4 haploid cells that are highly genetically diverse, containing 23 chromosomes each
Independent assortment of chromosomes
-It’s another way that meiosis generates genetic variation
Nondisjunction
- Problem with meiosis
- It is when during anaphase I, homologues pairs do not separate, or during anaphase II, sister chromatids do not separate
- Results in sperm or egg cells with abnormal chromosome numbers
Imbalance in chromosome number causes what?
- Abnormality in development
- Most result in death of fetus (miscarriage)
- Includes many syndromes
Syndromes
- Down
- Turner
- Klinefelter
- Triple-X
- Jacob
Down Syndrome
- Extra chromosome 21
- Limits in mental development
- Abnormal skeletal growth - short stature and body parts
- Facial features: flattened nose, protruding tongue that forces mouth open, folded skin at corner of eyes
- Heart and digestive defects are common
- Risk of down syndrome increases with mother’s age; increase rapidly after 30; by age 45, the mother is 45x more likely than at age 20
Turner Syndrome
- XO
- Infertile
- Reduced stature
Klinefelter Syndrome
- XXY
- Limited testosterone
- Often sterile
Triple-X Syndrome
- XXX
- Fertile, but occasional learning disabilities
Jacob Syndrome
- XYY
- Often taller
- Often lower than normal intelligence
- He says good example is: prisoners
Gene Expression
-Basic Model (aka Dogma of gene expression):
DNA (gene) → RNA → Protein → Phenotype
- Physical expression of proteins determines the “traits” (characteristics) of the organism
- Phenotype: phenotypic expression; physical expression of genes
Phenotype
Physical expression of genes
Physical expression of genotype
Genotype
The two alleles that represent a gene
Homozygous
- Individuals with identical copies of an allele
- AA or aa
Heterozygous
- Individuals with different alleles
- Aa
Dominant
-An allele that determines phenotype regardless of the other allele present
Recessive
-An allele whose effect is masked by the dominant allele
Incomplete Dominance
- Each copy of a dominant allele provides some expression
- Heterozygotes: thus a heterozygous individual only produces half the expression of a homozygous individual (one functioning protein, one nonfunctioning protein)
- Ex: pink flower
Sickle Cell Anemia
- Heterozygous individuals suffer from sickling and clumping of cells under prolonged drops in blood level oxygen
- Homozygous individuals suffer from multiple problems and often have shortened life expectancy
- Malaria parasite gets into bloodstream, and people with sickle cell anemia in Africa can use sickle cell to defend against Malaria
Can you have 3 different types of alleles?
Yes.
Multiple Alleles
- Most genes have more than two alleles
- Alleles are population parameters; we are a population, not individual
- Different alleles, maybe just not in you
- Ex: Multiple blood types
Blood Types
-Determined by polysaccharides on the surface of blood cells
-Phenotypes: Type A Type B Type AB Type O (=neither)
-Genotypes:
AA, Ao
BB, Bo
AB (codominance)
Oo
-LOOK IN INHERITANCE PACKET
Codominance
-Ex: AB blood type
Polytypic Inheritance. Polygenic Inheritance?
- Most traits are governed (produced) by multiple genes, each with multiple alleles
- In such cases, phenotypic expression of the trait is a continuum from when viewed in a population
- Ex: Height
- Determined by multiple genes, each with its own alleles
- Phenotype strongly influenced by environment
-Results in lots of phenotypic variation in a population – which often manifests as a continuum of characteristics
Sequences of bases in DNA is transcribed to ____?
RNA
The 3-base-pair code of RNA translates to ______?
Amino Acids
Within ribosomes, amino acids strung together produce _____?
Proteins
Proteins are molecules that facilitate/regulate chemical reactions, providing ____?
Movement/Transport
What other functions are nucleotides associated with? Related to chromosomes how?
- ATP! (energy used to run biochemical machinery)
- Genes carry chromosomes
RNA Polymerase
-An enzyme that moves along the DNA, unwinding and unzipping the strands
Promoter
-Sequence of bases that indicates where transcription should start
mRNA Editing
- Exon = “coding” segments that provide instructions for proteins
- Intron = noncoding segments
- Before leaving nucleus, specific enzymes modify mRNA by removing introns and splicing together exons
- DNA contains a lot of sequence that does not translate into proteins*
Alternative Splicing
- 20,000 - 25,000 genes, but less than 100,000 proteins are produced
- Primary transcript can be edited in different ways to yield multiple mRNAs and multiple proteins
Translation requires which types of RNA?
- mRNA
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
mRNA
Carries instructions for proteins out of the nucleus
rRNA
- Ribosomal RNA
- Combines with proteins to form ribosomes
tRNA
- Transfer RNA
- Bonds to an amino acid, then ferries the amino acid to sites on mRNA (reading the three-base code)
- Like nucleic acid enzyme (not protein)
- He said looks like seahorse
- There’s at least one type of tRNA for each amino acid
Translation Process
- LOOK AT PIC IN TEXT
- Anti-codons are linking amino acids through dehydration synthesis
Ways by which gene activity is affected and controlled? A.k.a. Regulating gene activity
-Ex: regulator segments of DNA
Promoters
Enhancers:
- Transcription Factors
- Methylation
Enhancers?
- (enhancer segments)
- Increase transcription of particular genes (thus proteins), affects timing of expression
Transcription Factors
- Proteins that increase transcription
- Switching genes “on”
Methylation
- An epigenetic process that keeps genes from being transcribed
- Like switching turning off genes (ex: big boobs on 7-year-old girl)
DNA Replication
- Process by which DNA makes a copy of itself
- Important step in cell division
- DNA is a stable molecule, and the process of replication is highly precise, but sometimes errors occur
Gene Mutation
- Change in DNA sequence caused by faulty replication
- In body (somatic) cells, mutations affect cell function and subsequently function of daughter cells
- In cells destined to become gametes (sex cells), the mutation can be passed on to your offspring
Point Mutations
- Change in one or a few nucleotides (bases)
- Can be helped by repair enzymes (sometimes repair original nucleotide instead of mRNA)
- LOOK IN DNA (PART II) PACKET
Other Mutation Types
-Insertions - addition of one or more bases
- Deletions - loss of one or more bases
- These two types of mutations are more serious, causing “reading frameshifts” in codon
- Inversions - flipping of nucleotide position
- Duplications - complete copies of genes
Silent Mutation
- Change does not affect amino acid sequence
- Change in DNA sequence, but doesn’t affect amino acid sequence
Harmless Mutation
-Change amino acids in sequences, but the change does not affect protein function
Issues with Mutations
-Altered protein function - new protein structure does not work as well
-E.g. Sickle cell anemia, caused by a point mutation
DNA: CTC → CAC
Transcription
RNA: GAG → GUG
Translation
Amino Acids: Glutamic Acid (Hydrophilic) → Valine (hydrophobic)
- OR destruction of protein function
- Ex: Point mutation produces stop codon in the wrong place
- Mutation causes improper function
Cancer
- It’s uncontrolled mitosis (cell division)
- They form tumors
- Carcinoma in situ
- Malignant Tumor
- Metastasize
Carcinoma in situ
- ”Carcinoma” = tumor
- ”in situ” = in place
- Tumor remains at area of origin
- About size of bee-bee
- Easiest to deal with/ get rid of
Malignant Tumor
- Attracts blood supply
- Mutated cells can now enter blood and lymphatic systems
- 2nd hardest to get rid of
Metastasize
- Mutated cells have spread to distant sites
- Grown additional tumors
- Basically, you’re dead; very hard to deal with
How does cancer kill?
- Interferes with normal body cells
- Cancer cells and tumors are greedy and take up all resources possible
-Blocks… growing tumors can block vital pathways in organ systems
Benign Tumors
- Not all tumors are cancerous
- An abnormal growing mass, which remains at the area origin
- Harmful if it causes problems with neighboring organs or blocks important pathways
Cell Division Damage Control
-Cells self-regulate, checking for errors and initiating repairs or cell death
- Healthy cells follow sets of “controls” or “regulations”
- When to divide
- When to stay in place
- When to self-destruct (popotus)
Tumor-Suppressor Genes
- Detect DNA damage
- Stop cell division
- Assess damage
- Uses enzymes (or made up of them?)
- If repair fails = damage accumulates
- If repair is successful = cell cycle continues
- If too damaged to repair = programs for death
What causes cancer?
-Gene mutations that produce proteins that malfunction
- Mutation of tumor suppressor genes
- Fail to detect or repair damaged DNA
- Fail to suppress cell division
- Mutation of proto-oncogenes producing oncogenes
- Normally stimulate cell division (before cancer genes)
- Become oncogenes when they are mutated
- Tumor-suppressor gene p53 - a protein that regulates another gene that produces a protein that keeps cells from dividing
- Mutation of p53 has been linked to more than half of all cancers
-LOOK IN DNA (PART II) PACKET
BRCA1 & BRCA2 Genes
- Breast Cancer 1 gene and Breast Cancer 2 gene
- Mutations in these two genes have been linked to breast cancer (in men and women) and ovarian cancer
- Broken genes inherited from parents
- Tumor-suppressor genes that initiate DNA repair
Body Defenses
-Apoptosis - programmed cell death
-Cells that can detect and destroy cancerous cells:
E.g. Killer Cells, Cytotoxic T Cells: defensive cells that recognize changes to identification proteins on cell membranes when they become cancerous
Risk Factors for Cancer
- Tobacco (use-smoking)
- Chemical Carcinogens (lots of these besides tobacco)
- Sunlight (UV radiation) and other forms of radiation
- Viruses (and even some bacteria) ex: through sex, like anal cancer
- Hormones and synthetic hormones
- Poor diet, lack of physical activity
- Genetics
- Age (most important factor)
Limiting the Potential for Cancer
- Avoid or limit exposures to known chemical carcinogens
- Limit exposure to known cancer-causing viruses
- Limit exposure to UV radiation
- Maintain an effective immune system (eat well, exercise, limit stress, sleep)
When did earth form?
4.6 billion years ago (bya)
When did life first form/evolve?
- Shortly after
- About 3.8 billion years ago
When did life emerge from water?
½ million years ago
When did human emerge?
About 20 million years ago (just a handful of years ago)
Common Descent with Modification
- A principle of the theory of evolution
- Species undergo modification through successive generations
- Changes in species can lead to formation of new, separate species
Species
In its simplest sense, they are different kinds of organisms
- Individual of the same species share genetic similarity and can (potentially) interbreed
- there is no good species concept
Population
-All individuals of the same species occupying a specific area over a particular time
All species have…
- Descended from other species
- A common ancestor lies at the base of evolutionary tree
What is the meaning of life?
Fitness (a measure of the number of successful offspring you leave in the next generation
-Successful reproduction (leaving behind copies of yourself, or more specifically your genes)
Natural Selection
- Darwin
- An agent of evolution (“agent” means “something that causes”)
- Another basic principle in the theory of evolution
- Process through which a trait (or character) that confers reproductive advantage to an individual spreads in a population over successive generations
Biotic Potential
- Most populations are capable of producing more offspring that can be supported by the environment
- Exponential growth
Which type of cell division is responsible for the repair of your skin following a sunburn?
Mitosis
During what period of the cell cycle does a cell spend most of its time?
Interphase
What are sister chromatids?
Replicate copies of a strand of DNA in chromosome form that are held together by a centromere.
During which phase of mitosis do spindle fibers pull the sister chromatids apart, thus sending chemical copies of the chromosome to opposite poles of the dividing cell?
Anaphase.
Chromosomes are structures composed of DNA, and thus they must also have the genes that direct protein synthesis. True or false?
True.
A normal human cell has how many chromosomes? Arranged in how many pairs?
46
23
What does crossing over result in?
New genetic recombination (increased genetic diversity)
Which of the following processes results in only one of the haploid cells being viable?
Oogenesis
What is immediately produced by fertilization?
A zygote.
DNA synthesis is associated with which type of cell division?
Both mitosis and meiosis.
During meiosis, chromosome number is reduced by half. During which step of this process does the reduction in chromosome number actually occur?
Anaphase I
How many nuclear divisions occur during meiosis?
2
During which phase of the cycle does DNA synthesis occur?
Interphase
What is not associated with mitosis?
Production of egg and sperm.
Differences between mitosis and meiosis?
Mitosis:
-associated with body growth and repair
- involves one cell division
- results in genetically similar (identical) daughter cells
Meiosis:
-results in production of gametes (egg or sperm)
- involves two cell divisions
- results in genetically dissimilar cells
Chromosomes are structures composed of DNA, and thus they must also have the genes that direct protein synthesis. True or false?
True.
An individual with two copies of the same allele for a particular gene is said to be?
Homozygous
When a heterozygous individual exhibits the trait associated with the dominant allele but not that of the recessive allele, this is said to be complete dominance. Complete dominance, however, is not the only possibility for a heterozygous genotype. What are the other possibilities?
Codominance
Pleiotrophy
Incomplete Dominance
Variation in the expression of a trait that results from involvement of two or more genes is best defined as?
Polygenetic Inheritance
What are different forms of a particular gene called?
Allele.
An individual that has two of the same alleles, but does not express the dominant trait is said to be?
Homozygous Recessive.
All chromosomes that are not sex chromosomes (not X or Y) are called?
Autosomal.
When a heterozygous individual shows a phenotype for a trait that is somewhere between the phenotypes expressed by a homozygous dominant individual and a homozygous recessive individual, the trait is said to show?
Incomplete Dominance.
What does the “t” in tRNA stand for?
Transfer
What monomers (or simple building block molecules) are proteins composed of?
Amino Acids
When does protein synthesis stop?
When a stop codon on the mRNA is reached.
What is a codon?
A sequence of three nucleotides on mRNA that specifies a particular amino acid.
What best describes transcription?
DNA –> RNA
How many amino acids are there?
20
When is gene expression complete?
When protein is produced.
What molecule transports amino acids to the ribosome during protein synthesis?
tRNA.
DNA is composed of which type of monomers?
4 different nucleotides.
Which type of RNA carries the information in the DNA from the nucleus (where DNA occurs) to the cytoplasm (where protein synthesis can occur)?
mRNA
During translation, what determines the sequence of amino acids in a protein?
The sequence of nucleotides in the mRNA.
What happens during translation?
Codons on mRNA are read and translated into a chain of amino acids (eventually to form a protein).
Process of Natural Selection
-More offspring reproduced than can be supported by the environment
- Within populations, there is variation of traits between individuals – some of this variation is heritable
- variation in physical, psychological (or physiological), or behavioral traits with a genetic basis that can be passed onto offspring
- Because of their particular traits, some individuals have higher fitness (leave behind more offspring) than other individuals lacking the traits
- Overtime, beneficial traits passed through the population
Natural selection requires what?
- Competition!
- During competition for resources, some individuals will have an advantage because of physical, physiological, or behavioral traits
- Genetic traits that provided an advantage will be spread within a population, but those than do not will be lost from the population
- Selection through this process will change a population’s phenotype over time
- Individuals do not evolve, populations do!
Evolution
-Any genetically-based change of phenotype in a population over successive generations
What is it that evolves?
-Populations!
Example of allele changes in frog populations
- In original environment, it’s one large population, so they could interbreed
- In environment where species are separated, then they eventually can’t interbreed anymore
Importance of evolutionary thinking?
- Species are not fixed entities, but instead are constantly undergoing modification and change
- Organism today descended from other varieties that existed before them
- Humans have descended from other organisms that existed before them
Author and information of author of natural selection book?
- Charles Darwin
- Book is on the origin of species by means of natural selection (1859)
- Developed existing ideas about descent with modification
- Acquired a large body of supporting evidence
-Perceived natural selection as the primary force driving descent with modification
Other guy who isn’t Darwin and info on him?
-Jean-Baptiste de Lamarck (1809, before Darwin)
- Evolution of acquired characters
- Believed over time, an organism could acquire enough changes that one species could diverge into two, but also believed organisms change form over generations through inheritance of acquired characteristics (which is very wrong; examples of gauges, giraffes, etc.)
*REMEMBER: ON TEST, HE WILL HAVE QUESTION LIKE THE ONE ON GIRAFFES, AND THE ANSWER WILL (MOST LIKELY) BE DARWIN’S THEORY
Five Agents of Evolution?
- Natural Selection
- Sexual Selection
- Gene Flow
- Genetic Drift
- Mutation
- (Believed by Jean-Baptiste, or everybody?)
Where do traits come from?
Mutations!
Mutation (in terms of traits and evolution)
- It’s a change in DNA sequence
- The only means by which new genetic information is generated
- Most are detrimental or harmless, but rare few are beneficial to organisms’ fitness
- Beneficial mutations are the building blocks of evolutionary change
