BIOL 111 Exam 3 Flashcards
Gregor Mendel
“Father of Genetics” ; independent assortment and law of segregation
Fredrick Meischer
First scientist to successfully isolate DNA molecule and show that the dominant molecule in the nucleus was not the protein
Pheobus Levene
Determined structure/composition of nucleotides and how they were linked together
Frederick Griffith
Utilize an in vivo experiment to provide evidence that transformation occurs; determined how living “R” bacteria transformed into pathogenic “s” bacteria
Avery, McLeod, and McCarthy
Performed an in vitro study to identify DNA as the transforming principle; Determined that DNA is substance that is transmitted from one generation to the next
Erwin Chargaff
Analyzed base composition for DNA; saw that composition of DNA nucleotides are different between differing species, but within a species % of A and T are roughly the same and the % of G and C are roughly the same
Wilkins and Franklin
Developed method of x-ray imaging that could detect and visualize molecular structure of DNA; found double-helical structure; responsible for famous “photo 51”
Hershey and Chase
Utilized bacteriophages to provide evidence that DNA is inherited from one generation to the next
Watson and Crick
Interpreted “photo 51” and developed a working double-helical model of DNA; concluded specific pairing in nucleotides and how base pairs differ the number of hydrogen pairs formed
Meselson and Stahl
Tested possible models of DNA replication; found that semi-conservative hypothesis was correct
What is complimentary strand for the sequence 5’ AAACGCTT 3’
5’ AAGCGTTT 3’
What strand would be the same as 5’ AAACGCTT 3’
3’ TTCGCAAA 5’
You discover a new organism and analyze its DNA. If you find 17% of nucleotides are adenine, which of the following is true:
33% are guanine ; Remember % A roughly equals % T in a species/organism and % G roughly equals % C.
Methylation
Used to decrease expression of genes by causing increase compaction of the DNA around its histones
Acetylation
Increases the expression of genes because it reduces the compaction of DNA by decreasing the interaction of the histone proteins
Heterochromatin
Function is to silence euchromatic gene expression to protect chromosome integrity; consists of repetitive DNA sequences; gene poor; highly condensed; transcriptionally silent; unexpressed genes; telomeres and centromeres
Euchromatin
Participates in active transcription of DNA to mRNA products; loosely packed; enriched in genes; under active transcription; easily translated; distal arms of chromosome
Correct order of cell cycle
G1, S, G2, Mitosis, Cytokinesis
Diploid plant with 16 pairs of chromosomes. How many chromatids after S phase?
64 ; diploid plant, so 16x2 chromosomes and 32x2 chromatids
Which of the following is a major difference between Binary Fission and Mitosis?
Binary Fission does not have a nucleus to break down and reform as part of its process, while mitosis uses Prophase and Telophase to break down and reform the nucleus.
The typical human body cells contains 46 chromosomes. How many does a typical human egg cell contain?
23
Mitosis has
2n to 2n cell division; divide DNA so each daughter cell receives the correct amount of DNA and number of chromosomes; single round of cell division resulting in diploid daughter cells; used my somatic cells
Meiosis has
2n to 1n cell division; divide DNA so each daughter cell receives the correct amount of DNA and number of chromosomes; double round of cell division resulting in haploid daughter cells; produces gametes
If a parent cell of a certain organism has 16 chromosomes total in each somatic cell and it undergoes meiosis, the resulting daughter cells will have ____ chromosomes
8
Homologous chromosomes may differ from each other in terms of _____________
types of alleles
Which of these lead to genetic diversity in a population?
Mutations, crossing over, independent assortment, recombination
After a certain meiotic division in a human male, 4 gametes were obtained with the following number of chromosomes: 22, 22, 24, 24. In which stage of meiosis did nondisjunction take place?
Anaphase I
What is the correct order of the steps of DNA replication?
I. New nucleotides are added to the template strand by DNA polymerase III.
II. The DNA helix is unzipped by helicase.
III. Topoisomerase creates nicks in the DNA.
IV. Primase adds a RNA primer to the template strand in a 5’ to 3’ direction.
V. RNA nucleotides are replaced with DNA nucleotides by DNA polymerase I.
VI. DNA ligase forms covalent bonds between fragments in the backbone of the newly synthesized DNA strand.
III, II, IV, I, V, VI
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only towards the 3′ end of a pre-existing strand, and the strands are antiparallel
_______ is responsible for proofreading the DNA and fixing errors during DNA replication, while errors detected outside of DNA replication occurring are fixed through the combined effort of ________, __________, and __________.
DNA polymerase III; Nuclease, DNA polymerase, DNA ligase
Ultraviolet exposure can commonly result in which of the following forms of DNA damage?
Thymine dimer formation
Which of these poses a challenge for DNA replication that must be overcome to allow progression of replication?
Antiparallel Orientation of DNA, Torsion, Priming
Topoisomerase
An enzyme that breaks a covalent bond in both strands of DNA periodically ahead of the replication fork to prevent supercoiling of the DNA replication
Helicase
An enzyme responsible for breaking the hydrogen bonds between nucleotide base pairs in order to open the replication fork
Primase
An enzyme that bonds RNA nucleotides to the parent DNA strand in order to provide a primer for a subsequent enzyme
DNA Polymerase II
An enzyme that bonds DNA nucleotides based on complementary base pairing in a 5’ to 3’ direction
DNA Ligase
An enzyme that covalently bonds the 3’ end of one fragment of DNA to the 5’ end of the neighboring fragment of DNA
Single-stranded binding proteins
Proteins that bind to the unwound DNA and stabilize it, preventing hydrogen bonds from reforming between the base pairs.
DNA polymerase I
An enzyme that breaks the bonds attaching the RNA nucleotides of the primer in a 5’ to 3’ direction and replaces the RNA nucleotides with DNA nucleotides
Nitrogenous base pair hydrogen bonds
A with T = 2 hydrogen bonds
C with G = 3 hydrogen bonds
Pyrimidines
C U T
Purines
A G
3’ carbon attached to
hydroxyl group
R - O - H
5’ carbon attached to
phosphate group
O = P - OOO
Where does DNA stay?
Chromosomes
Chromosome
Consists of DNA and proteins; Humans have 23 pairs or sets of chromosomes
Centromere
Joining point for replicated chromosomes
Telomere
Nucleotides at both ends of chromosomes
Chromatid
Sister chromatids when replicated; can be 1 chromatid = 1 chromosome or 2 chromatids = 1 chromosome
Somatic cell
Body cell, not a sperm or egg cell; Diploid (2n); 2 copies of each chromosome (1 from maternal and 1 from paternal); each pair of chromosomes are homologous
Gamete cell
Sperm and egg cells; 1 copy of each chromosome; Haploid (n)
Karyotype
An image of an individuals complete collection of chromosomes
Genome
a cells entire DNA library
DNA package in increasing density
DNA strand < nucleosome < 30nm fiber < looped domain < chromatid
4 fiber levels of chromosomes
Histones + DNA < nucleosome interactions < looped domains < chromatid
Histone
Proteins that provide structural support and regulatory sites; 10nm DNA fiber winds around histones to form nucleosome
Epigenetics
Does not do genetic modifications but can still alter changes; does not change DNA but changes how body reads a DNA sequence
Cell division
A single cell splits into two new daughter cells; cell needs to replicate DNA before division
Interphase
Time for normal growth and preparation for cell division; includes G1, S, G2 phases; majority of cell cycle is spent in interphase
Mitotic phase
Replicated DNA and cytoplasm are split and the cell divides
G1 phase
Cell goes through normal growth and metabolic activity; primary growth period; organelles are duplicated
S phase
DNA is copied forming sister chromatids; sister chromatids are joined at centromere; centromeres produce mitotic spindles
G2
DNA is checked for damage and completeness and cellular reserves replenished; organelles reproduce; if there is physical damage to helix or incomplete replication, the cell will try to fix/ trigger cell death; MUTATION OF DNA IS NOT CHECKED OR FIXED
G0
Resting phase; can be permanent or temporary depending on cell type and/or environment; cells are kicked into G0 if cell type isnt needed or the cell did not grow big enough, or have enough protein, etc.; would lose genes without this stage due to loss of telomeres; causes higher lifespan; not all cells enter this phase
Karyokinesis and Cytokinesis in mitosis
Division of nucleus and cytoplasm; mutation is the only way these daughter cells are not identical to each other and the parent
Prophase
Organelles disperse toward edges of cell; Nucleus disappears; Centromeres begin migration to poles; Microtubules form; DNA is still duplicated and attached at centromeres; centromeres still represented as sister chromatids
Prometaphase
Sister chromatids develop protein kinetochore at centromere; mitotic spindle arises from centromeres and attach to kinetochores; DNA is still duplicated and attached to centromeres; chromosomes still represented as sister chromatids
Metaphase
Chromosomes line up along metaphase plate (or middle of cell); DNA is still replicated and attached to chromosomes; chromosomes still represented as sister chromatids
Anaphase
Cohesion proteins degenerate; separated sister chromatids move in opposite directions toward chromosomes; cell elongates; ONLY PART OF CELL CYCLE WHERE 92 AND 92 CHROMOSOMES; no longer duplicated by end of anaphase
Telophase
Chromosomes reach opposite poles and begin to unravel; nuclear envelopes form around each set of chromosomes; no sister chromatids, only chromosomes; DNA is no longer duplicated
Cytokinesis
Division of cytoplasm; formation of cleavage furrow in animal cells (outside to inside); formation of cell plate in plant cells (inside to outside)
Conservative replication
Original parent DNA double strand remains intact; 2 completely new double helix strands are synthesized
Semi-conservative replication
The 2 strands of the parent DNA come apart; each act as a template for synthesis of a new complementary strand
