Biology Exam 3
What did Gregor Mendel contribute to today's understanding of inheritance?
"Father of Modern Genetics", he conducted the genetic crosses (controlled mating experiments) that determined how traits are inherited -Discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.
What 4 events are included in cell division?
1. A reproduction signal 2. Replication of DNA 3. Equal segregation of replicated DNA into each daughter cell 4. Cytokinesis (splitting of cytoplasm)
Interphase:
1. G1 Phase: Cell grows, makes required proteins for DNA Replication, 1st phase in a newly divided cell (usually the longest) Checkpoint: make sure cell is good to go for cell division 2. S Phase: (synthesis) during which DNA is replicated-cell now has 2x as much DNA 3. G2: Cell grows, after S Phase but before cell division Checkpoint: make sure DNA Replication is complete
What are uses of PCR?
1. Identify a wide variety of biomolecules 2. Crime scene analysis 3. Tissue typing 4. Disease outbreak 5. Detection of the presence/absence of genes
Steps of DNA replication
1. Unwinding: Helicase splits double helix, single strand binding proteins hold unwound strands apart 2. Replication: Dna polymerase makes the new strand of DNA and primase guides DNA Polymerase, Primers are RNA bases
How many pairs of homologous chromosomes do humans have?
22 pairs
Be able to label DNA
A Phosphate Group, Five Carbon Sugar, and Cyclic Nitrogen Containing Compound (Base),
What is a dihybrid cross?
A mating between 2 individuals that are each heterozygous for the same 2 genes
Describe the structure of DNA: what makes up a base? What holds the bases together? Think of the DNA modeling. Where are the covalent bonds? Where are the hydrogen bonds?
Adenine, Thymine, Guanine and Cytosine make up the bases, the pyrmidines are Cytosine, Thymine and Uracil and the Purines are Guanine and Adenine, hydrogen bonds hold the bases together, the covalent bonds hold the phosphate to the sugar
What is gene regulation? When can it occur?
Allows cells to change which genes are expressed, down regulate-slow down and up regulate-speed up, it occurs to conserve energy
What is a genetic trait?
Any inherited characteristic of any organism that can be observed or detected
What is the name for chromosomes not involved in determining gender?
Autosomes
How can bacteria share their genes? What is the importance of this?
Bacteria share genes when a plasmid is taken and placed in the cell, which then gives the daughter cells the resistance gene. This is important because it makes transgenic organisms
Why is cell division more complex in eukaryotes?
Because the cells have organelles, usually large amounts of cells and there is more DNA
heterozygous:
Carrying 1 dominant allele and 1 recessive allele, phenotype displays dominant allele (Bb)
Homozygous dominant:
Carrying 2 copies of the dominant allele (BB)
Homozygous recessive:
Carrying 2 copies of the recessive allele (bb)
homozygous:
Carrying 2 copies of the same allele
What is binary fission? What is produced?
Cell division in prokaryotes, 2 new cells are produced, genetically identical
What is independent assortment?
Chromosomes randomly line up during metaphase, the segregation of alleles for one gene does not influence the segregation for alleles for another gene
What are Mendelian traits? Examples?
Controlled by a single gene and unaffected by the environment ex. attached earlobes, freckles, dimples etc..
What is an allele?
Different versions of a given gene for a genetic trait
What is the difference between diploid and haploid?
Diploid cells are identical and have as much DNA as parent cells, 2 sets of chromosomes Haploid cells have half as much DNA as parent cells, 1 set of chromosomes
What is the difference between dominant and recessive alleles?
Dominant alleles are expressed whether there are 2 copies of it or 1 of it and 1 copy of the recessive variety in the genotype and Recessive alleles are expressed only when their are 2 identical copies of it in the genotype
Compare and contrast dominant and recessive traits
Dominant traits are expressed whether there are 1 or 2 copies (BB) or (Bb), and Recessive traits are only expressed if there are 2 copies (bb)
What is the chromosome theory?
Explains the mechanism underlying Mendel's 2 laws, chromosomes are exchanged in meiosis, fertilization, and crossing over -states that genes are found at specific locations on chromosomes, and that the behavior of chromosomes during meiosis can explain Mendel's laws of inheritance.
G and C have how many hydrogen bonds? A and T have how many hydrogen bonds?
G&C=3 A&T=2
What is the difference between genotype and phenotype?
Genotype is entire setup of genetic information the individual carries (set of alleles) and Phenotype is the physical expression of the genetic makeup
What are 2 events that occur to make a cell divide?
Growth and Repair
Give an example of environmental effects on phenotype
In siamese cats, if the temperature is cold the cat will have more white hair and when the temperature is warm the cat will have more black hair, in humans : skin color (exposure to sunlight), height (nutrition), intelligence (nutrition, mental exercises)
Compare and contrast incomplete dominance and codominance
Incomplete dominance is when neither allele is able to exert its full effect, so a heterozygote displays an intermediate phenotype ex. tall dog (BB), medium dog (Bb), small dog (bb) Codominance is when both alleles are equally visible in the phenotype of the heterozygote, see both alleles ex. brown chicken (BB), brown chicken with white spots (Bb), white chicken (bb)
What are the complex traits?
Incomplete dominance, Codominance, Pleitropy, Polygenic traits, Epistasis
What are the 2 stages of cell division?
Interphase and Cell Division (mitosis/meiosis)
Describe the stages of the cell cycle
Interphase: is 90% of a cells life, when the cell does what it normally does, DNA is replicated Cell Division: Last stage of a cell's life when the DNA is divided into daughter cells
What gets cut out and what gets expressed? (RNA slicing)
Introns get cut out exons get expressed
What is the Law of Segregation?
It says the individual can only donate the genotype it has, each gamete only gets 1 allele per gene
What is the difference between the leading and the lagging strand?
Leading strand grows continually to form 1 DNA molecule 5'-3' and the Lagging strand forms okazaki fragments 3'-5'
List the stages of meiosis and what occurs in each step
Meiosis (Sperm or germ cells) 1. Prophase I: homologous chromosomes are fully paired, crossing over occurs 2. Metaphase I: tetrads align on metaphase plate, independent assortment occurs 3. Anaphase I: Chromosomes separate, sister chromatids remain attached at the kinetchores 4. Telophase I: Nuclear envelope forms, spindle disappears 5. Cytokinesis: divides cell into 2 6. Prophase II: chromosomes attach to spindle, nuclear envelope disappears 7. Metaphase II: Chromosomes line up in 1 row 8. Anaphase II: chromatids separate to opposite poles 9. Telophase II: nuclear envelope reforms 10. Cytokinesis: cell splits into 2 Making 4 gamete cells
What gets split in Meiosis I and Meiosis II?
Meiosis I: Chromosomes split Meiosis II: Chromatids split
What are the ways chromosomes are exchanged?
Meiosis, Fertilization, and Crossing Over
What occurs during each stage of cell division?
Mitosis (Meiosis) = replicated DNA is divided 1. Prophase: Nuclear envelope disappears and chromatin condenses, DNA condenses 2. Metaphase: Chromosomes meet in the middle 3. Anaphase: Chromosomes pull away towards opposite ends of cell 4. Telophase: Nuclear envelope reforms, cell starts to pinch in half 5. Cytokinesis: cytoplasm slits (animal cells are fully separated when split, and plant cells create a plate between each cell and are still attached)
List the steps of mitosis and what occurs during each step
Mitosis (somatic cells) = replicated DNA is divided 1. Prophase: Nuclear envelope disappears and chromatin condenses, DNA condenses 2. Metaphase: Chromosomes meet in the middle 3. Anaphase: Chromosomes pull away towards opposite ends of cell 4. Telophase: Nuclear envelope reforms, cell starts to pinch in half 5. Cytokinesis: cytoplasm slits (animal cells are fully separated when split, and plant cells create a plate between each cell and are still attached)
Are all substitutions, insertions, and deletions only point mutations?
No; they are only point mutations if only one base is involved
What are the different types of generations?
P=parents, F1=result of P gen cross, F2=result of F1 cross
What is gene expression?
Protein Synthesis
What is involved in transcription and translation?
RNA polymerase, 1. Initiation: start 2. Elongation: Building 3. Termination: End
Complementary bases in RNA and in DNA
RNA: GCAU DNA: GCAT
DNA is ____________________.
Semi-conservative
What is the SRY gene?
Sex Determining Region of Y, the "Master sex switch" determines that embryo will be male, otherwise its female
What is epistasis?
The allele of 1 gene affects the expression of an independently inherited gene ex. Labrador coat color (only "ee" affects the coat color)
After transcription and translation what happens to the mRNA, and the proteins?
The mRNA gets degraded and the proteins get folded
How does PCR work?
The scientists artificially "replicate" the DNA by mimicking the natural DNA replication
What is the purpose of the 5' cap and the 3' poly A tail?
To protect DNA from degeneration
What are Polygenic traits, and some examples?
Traits governed by more than 1 gene, many genes controlling 1 allele ex. hair color, eye color and skin color
Where does transcription take place? Where does translation take place? What happens in each step?
Transcription takes place in the nucleus of eukaryotes and in the nucleoid space of prokaryotes, Translation takes place in the ribosomes in the cytoplasm, in transcription the RNA synthesizes and in Translation the Protein synthesizes
What are sister chromatids? What are they held together by?
Two identical copies of a single replicated chromosome They are held together by a centromere
What does semi-conservative mean?
Two new DNA helices, each having 1 original strand and 1 new strand
What is pleiotropy?
When a single gene influences a number of different traits, one gene and many traits
Why and when are a Cap and Poly A tail added to the RNA strand?
When the RNA is processed in the Nucleus to protect it from degeneration, the Cap goes on the 5' end and the Poly A tail is added to the 3' end
What is an origin of replication? How many does a prokaryote have? Eukaryotes?
Where DNA replication starts, prokaryotes have 1 and eukaryotes have have multiple
Compare and contrast inheritance of recessive, dominant, and sex-linked disorders
X-linked dominant disorders are less severe in female, X-linked recessive disorders affect more males than female
What is an allele???
an alternative form a gene
What is the main use of PCR?
artificial replication of DNA
Chromosomes that are NOT involved in determining gender are known as.....
autosomes
quantitative characters:
characters that exhibit a range, or continuum of variation
What is a pedigree?
chart showing family relationships and phenotypes
What is a chromosome and chromatid?
chromosome = forms when DNA wraps around proteins chromatid = DNA that is already wrapped around proteins
Qualitative characters:
discrete characters that are either present, or not present
Two copies of the same gene on a single chromosome would indicate a(n) ________ had occurred.
duplication
nondisjunction:
failure to separate, occurs during anaphase I or II, extra chromosome in 1 zygote and not enough in the other, results in down syndrome
Dizygotic twins:
fraternal twins
What is a frameshift?
genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read
monozygotic twins:
genetically identical, identical DNA but different fingerprints, zygot splits into 2 embryos
Know what can/cannot be passed from parent to child
ie a mutation in a skin cell
A karyotype shows a chromosomal abnormality that does not change the length of any of the chromosomes. Which abnormality is indicated?
inversion
What is an Okazaki fragment? Which strand does these occur on?
newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication
What is the purpose of the G0 non-replication phase?
non-replicating phase is for specialized cells to enter and not replicate, most of our cells are currently in this phase, lack of nutrients, cancerous cells, lack correct replication organelles ex. neurons
conditional probability:
occurs when information about the problem changes the probability of events
linked genes:
on same chromosome, need to be close together and on same chromosome, law of independent assortment does not apply to linked genes
A ________ is a chart that shows genetic relationships within a family over several generations.
pedigree
What are the different genetic traits?
physical, biochemical, behavorial
What is the purpose of a cell cycle checkpoint?
to make sure cell is ready for cell division and to make sure DNA replication is complete
invariant trait:
traits that are the same in all individuals of a species ex. 2 eyes, 2 ears, nose, mouth in humans etc.
variant trait:
traits that differ among individuals of the same species ex. eye color
On chromosomes within an individual, there are ________ alleles for a given gene found on ________ chromosomes.
two; homologous
