Nondisjunction
Where chromosomes do not separate properly during meiosis; you’ll end up with a wrong number of chromosomes in a particular gamete
Can occur during Meiosis I (homologous chromosomes do not separate, end up with too few or too many chromosomes)
Can occur during Meiosis II (sister chromatids do not separate)
Aneuploidy: abnormal number of chromosomes is found in a cell
Trisomy: 3 copies of a chromosome instead of 2 in a cell
Monosomic: 1 copy of chromosome instead of 2 in a cell
Polyploidy:
More than 2 complete sets of chromosomes
Triploidy: 3 sets of chromosomes
Tetraploidy: 4 sets of chromosomes (particularly lilies)
Polyploidy occurs in some plants
Alterations of Chromosome Structure (during meiosis)
Chromosomes can break and reform
Changes in the chromosome structure
Changes can be:
Lethal: which means that the embryo is not going to be able to develop normally and will die
Sub-lethal, cause serious problems to the organism but it doesn’t actually kill the developing embryo
Not serious, but phenotype of cell changes
Mutation by Base Substitution (animation)
A mutation occurs by base substitution when an incorrect base is incorporated into DNA. Some base substitutions occur because purines and pyrimidines exist in 2 structural forms
The most common form results in base-pairing between adenine and thymine and between guanine and cytosine
However, the hydrogen atoms can move to form a base with altered hydrogen bonding properties, creating a tautomeric shift. When a tautomeric shift occurs in adenine, the adenine can bond to cytosine
A tautomeric shift in thyme allows it to bond to guanine
The error in DNA replication is passed on to the cell’s progeny. The change in a single nucleotide in the DNA results in a change in the corresponding nucleotide in messenger RNA
The change in the codon can result in a different amino acid being incorporated into the protein
Figure 15.14 Alteration of chromosome structure
A deletion removes a chromosomal segment
A duplication repeats a segment
An inversion reverses a segment within a chromosome
A translocation moves a segment from one chromosome to another, nonhomologous one. In a reciprocal translocation, the most common type, nonhomologous chromosomes exchange fragments. Nonreciprocal translocations also occur, in which a chromosome transfers a fragment without receiving a fragment in return
Extranuclear Inheritance
Not all of the cellular genetic material is found in the cell nucleus
Mitochondria and some plant plastids contain DNA
In humans,
Contributions of Watson, Crick, Wilkins, and Franklin on the structure of DNA ○ ii. Avery-MacLeod-McCarty experiments ○ iii. Hershey-Chase experiment ● DNA replication ensures continuity of hereditary information. ○ i. Replication is a semiconservative process; that is, one strand serves as the template for a new, complementary strand. ○ ii. Replication requires DNA polymerase plus many other essential cellular enzymes, occurs bidirectionally, and differs in the production of the leading and lagging strands…
Chapter 20: Altering the genetic message – Summary All of the DNA within a cell originated from other DNA via multitudes of replications, not an error-free process. Eukaryotes may have evolved meiosis to help correct serious replication errors. Any change in a cell’s genetic information is a mutation. There are three basic kinds: point mutations, transpositions, and chromosomal rearrangement. DNA may be damaged as a result of ionizing or ultraviolet radiation, or chemical mutagens. Damage also results…
genetic abnormality is passed to offspring from parents, and it is a condition that is a deviation from the usual or average but is not life threatening, a genetic disorder is passed to offspring from parents, and it is a condition that causes medical problems, and a syndrome is a set of symptoms that characterize a particular disorder. 22. An example of a trait that is autosomal recessively inherited is…
strung together – instructions used in building proteins – DNA replicates and makes copies of itself to pass onto other cells – Mutates: Genetic Diversity – Replication of DNA, Transcription mRNA, Translation Protein DNA Replication 1) 2 strands of DNA become “ladder like” 2) Enzyme hilicase breaks H-Bonds and unzips – DNA is opened at “Replication origin” 3) Free floating nucleotides in the nucleoplasm move to appropriate position via complementary base pairing – The enzyme DNA polymerase facilitates…
pairing rules – rule that describes how nucleotides form bonds in DNA; adenine (A) always bonds with thymine (T), and guanine (G) always bonds with cytosine (C) Chapter 8.3 Replication – process by which DNA is copied DNA polymerase – enzyme that makes bonds between nucleotides, forming an identical strand of DNA during replication Chapter 8.4 Central dogma – theory that states that, in cells, information only flows from DNA to RNA to proteins RNA – nucleic acid molecule that allows for the transmission…
1. The process of DNA replication requires that each of the parental DNA strands be used as a to produce a duplicate of the opposing strand. A) catalyst B) template 2. DNA replication is accomplished by employing a mechanism. A) semiconservative B) conservative 3. allows the flawless repair of DNA double-strand breaks. A) Homologous recombination B) Nonhomologous end-joining 4. In a double stranded DNA helix, . A) adenine always base pairs with guanine B) purines…
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is mainly divided into three phases: G1 phase, S phase and G2 phase. S phase is the period of replication. G1 and G2 are the two gap phases during which the cell grows, producing proteins and preparing the cells. These phases also have certain check points and the whole cell cycle is strictly regulated. M phase of the cell cycle stands for Mitosis or nuclear division. In eukaryotes, DNA replication is followed by a process called mitosis which separates the chromosomes in its cell nucleus into…
Bipolar Disorder Psychology Northwood University What I found interesting is how the brain reacts to bipolar individuals. What is bipolar disorder, also known as manic- depressive illness? According to the institute of psychiatry at Kings college London Bipolar disorder causes dramatic mood swings—from feeling overly “high” and/or irritable to sad and hopeless, and then back again, often with periods of normal mood in between. Severe changes in energy and…
DNA and Genes Study Guide DNA 1. Nucleotides 2. Nitrogen bases, phosphate groups, and sugar 3. Deoxyribose and phosphate 4. DNA Replication 5. A complimentary strand is paired with a DNA strand 6. In the cell’s nucleus 7. Adenine, Thymine, Cytosine, and Guanine 8. Adenine pairs with Thymine and Cytosine pairs with Guanine 9. Double helix 10. Nucleus RNA 11. Nucleotides 12. Ribose sugar, phosphate groups, and nitrogen bases 13. Adenine, Uracil, Cytosine and Guanine 14. Adenine pairs with Uracil and…