Test 2: Compare and Contrast Flashcards
Nullisomic/disomic
Both refer to abnormal gametes due to non-disjunction and are characterized by aneuploidy.
Nullisomic - gametes that lack a complete chromosome from the haploid compliment. Nullisomic gametes lead to monosomic zygote that usually doesn’t survive.
Disomic – gametes that posses 2 copies of a chromosome from the compliment haploid, when they should only have one. Disomic gametes lead to trisomic zygotes that result in abnormal offspring who typically don’t survive that long.
Monosomy/trisomy
Both are forms of aneuploidy that refer to chromosomal abnormality where an individual doesn’t have the normal diploid number. Both can occur due to a meiotic mal-assortment.
Monosomy - having only one out of a particular pair of chromosomes, monosomic zygotes usually die shortly after formation (except Turner’s syndrome)
Trisomy – having 3 copies of the same chromosome instead of 2. Lead to abnormal individuals who survive for differing amounts of time depending on severity of their deformities.
Primary non-disjunction/secondary non-disjunction
Both of these terms refer to spindle malfunction which leads to the failure of homolog separation during meiosis.
Primary non-disjunction – occurs in 1st meiotic division. Results in 2 disomic gametes & 2 nullisomic gametes
Secondary non-disjunction – occurs in 2nd meiotic division. Results in 2 normal gametes, 1 disomic gamete, and 1 nullisomic gamete.
Patau’s/Downs
Both of these are tri-somic conditions resulting from autosomal aneuploidy, characterized by meiotic mal-assortments.
Patau’s – trisomy on chromosome 13, most don’t make it past 6 months (100% fatality in 1st year). All systems are abnormal including incomplete formation of: retina, inner ear, & cranial facial closure.
Downs – trisomy on chromosome 21, extremely variable in expression. Can express short/stocky build, epicanthic fold, thick tongue, palm crease, or CNS abnormality.
Edward’s/Patau’s
Both of these are tri-somic conditions resulting from autosomal aneuploidy, characterized by meiotic mal-assortments.
Edward’s – 3 copies of chromosome 18, high mortality rate in 1st year, but can survive to pre-teen
Patau’s – 3 copies of chromosome 13, slightly more rare. Results in failure of formation of retinas, inner ears, and cranio-facial closure. Complete mortality by first year of life.
Klinefelter’s/Turner’s
Both are conditions resulting from sex aneuploidy and display CNS abnormalities.
Turner’s – only viable monosomic condition in humans, diploid number of 45, contains only 1 sex chromosome (X0). Females that have normal X chromosome and a Barr body.
Klinefelter’s – has diploid number of 47 and has normal X & Y chromosomes along with a Barr body (XXY). Males that are sterile and display secondary female sex characteristics.
Patau’s/Klinefelter’s
Both are aneuploidy conditions and both have a diploid number of 2n=47.
Patau’s – autosomal tri-somic aneuploidy that have 3 copies of chromosome 13. Failure in formation in retinas, inner ears, & cranio-facial closure. Die within 1st year, can occur in males & females
Klinefelter’s – sex aneuploidy (XXY) who are always male, but display secondary female characteristics and live to adulthood. Have normal X & Y chromosome, but also have a Barr body
Aneuploidy/Euploidy
Aneuploidy – segregational mistake where organism gains/loses one or more chromosomes but not a complete set (2n+/- X) resulting in trisomic or monosomic zygotes. More common in animals.
Euploidy – results from a cold shock followed by chromosomal doubling as the S-phase of DNA replication is repeated. Organisms gains or loses an entire set of chromosomes (2n+/- Xn), results in doubling, tripling, etc. of chromosomes. More common in plants
Autopolyploidy/Allopolyploidy
Both are forms of euploidy and occur more commonly in plants. Both require a cold shock during cell division in which the spindles are disrupted and the cells revert to Interphase where an S-phase DNA replication occurs again.
Autopolyploidy – involves 1 species and results in a sterile offspring. B/c of the doubling of DNA (2n–>4n), leaves, fruits, flowers, etc. will appear larger in size but will be sterile.
Allopolyploidy – involves hybridization of 2 different species prior to cold shock and results in viable offspring that are usually reproductively isolated. If process produces a mate = instantaneous speciation.
Hershey and Chase/Avery et al
Both of these groups were researchers who were attempting to find out whether protein or nucleic acid was responsible for carrying genetic information.
Avery, McLeod, and McCarthy - expanded on Griffiths transforming principal research and used selective destroyer enzymes and bacterial cultures to show only when DNA was destroyed causing transformation to shut down.
Hershey/Chase – used viruses to show DNA is the important layer in transferring of genetic material. Used radiolabeled sulfur/phosphate along with electron microscopy to show viruses insert nucleic acids into host cell.
Purines/pyrimidines
Both of these are types of nitrogenous bases found in nucleotides that have nitrogen substitutions in the rings. Are always paired together and both capable of hydrogen bonding, total # of purines = pyrimidines.
Purines – Adenine & Guanine and both present in DNA/RNA. Made up of one 6 membered ring & one 5 membered ring.
Pyrimidines – Cytosine & Thymine in DNA, Cytosine & Uracil in RNA. Made up of one 6 membered ring
Z-DNA/E-DNA
Both forms of DNA are anti-parallel and complementary, and both have a hydrophilic outer wall and hydrophobic core.
Z-DNA – more compact than E-DNA, 12 bp/turn of its left handed double helix, has zig zag appearance and functions in gene inactivation
E-DNA – 7.5 bp/turn of its right handed double helix, more A-T rich than Z-DNA which results in lower stability, enhances gene expression.
B-DNA/E-DNA
Both of these forms of DNA are anti-parallel and complementary, and both have a hydrophilic outer wall and a hydrophobic core.
B – most common DNA form in human genome & was structure described by Watson/Crick. 10 bases/turn and doesn’t play a role in enhancing gene expression.
E – 7.5 bases/turn, typically more A-T rich which makes E-DNA less stable and plays role in enhancing gene expression.
Nearest neighbor analysis/triplet-binding assay
Both sets of experiments used radiolabeling to isolate products & interpret results and both experiments were successful and supported their respective hypothesis.
Nearest Neighbor – conducted by Kornberg to demonstrate high fidelity copying of DNA during replication. He used 4 reactions based on 4 different nitrogenous bases in DNA and radio labeled phosphate. Used splenic phosphodiesterase to digest nucleotide chains.
Triplet Binding – conducted by Nirenburg to determine which codon sequences coded for which specific amino acids. Used 20 different reactions based on 20 different amino acids coded for in DNA. Radiolabeled tRNA molecules and passed through a filter which didn’t allow ribosomes to pass through.
Semi-conservative/conservative
Both semi-conservative and conservative are hypotheses that were put forward to explain the method of DNA replication.
Semi-conservative – states that a single strand of DNA is used as a template to synthesize a new complimentary strand. After replication, the 2 DNA molecules both contain one old & one new strand. This was proven to be the correct method.
Conservative – proposed that the new strands are separated after replication and joined back together. After replication, one DNA molecule will be completely new, other will be original. This method is incorrect.
