Module 2 Flashcards
Nondisjunction?
Failure of chromosomes to separate properly during meiosis.
Aneuploidy?
Abnormal number of a particular chromosome
Deletion?
removal of a chromosomal segment
Inversion?
Reverses a segment within a chromosome
Duplication>
Repeated segment within a chromosome
Translocation?
Removal of a segment from one chromosome to a non-homologous chromosome
Polyploidy?
possession of multiples sets of chromosomes
Disease resulting from nondisjunction?
Down Syndrome, 95% of DS babies have 2 maternal chromosome 21
Diseases resulting from Aneuploidy?
Klinefelter syndrome (XXY) and Turner Syndrom (XO)
Disease resulting from Deletion?
Lejeune Syndrome, tip or short arm of chromosome are deleted
Diseases resulting from translocation?
Myeloid Leukemia, TK overexpression, Familial Down Syndrome
How do chromosome abnormalities and rearrangements occur.
Mutations & Nondisjunction
Explain the effects of odd numbers of chromosomes in meiotic segregation?
An odd number of chromosomes will mean the organism is sterile/infertile as they can not produce viable gametes
Outline the concept of X-inactivation?
X-inactivation occurs in females because they have two copies of the X chromosome, one from each parent. One X chromosome is compacted into a structure calle Barr Body which contains mostly inactive genes. Whether it is the paternal or maternal X chromosome varies randomly from cell to cell. This process happens during embryonic development and is also referred to a lysonization.
What are the birth defects of chromosome abnormalities and rearrangements.?
EMbryo will often die early or have physical abnormalities and a decreased life expectancy
What is gene expression>
The process by which information from a gene is used to synthesis a functional gene product: Protein or non-coding RNA
Define a gene?
A define region of DNA that produces a type of RNA that has some function.
What are gene (DNA) sequences responsible for?
Regulation of the synthesis of RNA
producing RNA
Future processing of RNA
What is the central Dogma of molecular biology?
The process by which DNA is converted to RNA to protein
Transcription?
The synthesis of RNA using a DNA template (MRNA is transcribed from the template strand)
Which DNA strand is transcribed?
Template strand = strand running in the 3-5 prime direction
What occurs during Initiation?
Transcription factors bind to TATA box and other regions of the promotor,
RN pol II binds, forming a transcriptional initiation complex together with the transcription factors,
The two DNA strands seperate and RNA pol II starts mRNA synthesis without the need of a primer.
What occurs during Elongation?
RNA pol II uses the template strand as a template and inserts complementary RNA nucleotides in the 5-3 direction.
Where does Transcription. occur?
In the Nucleus
Where does Translocation occur?
In the cytoplasm
What is a coding sequence?
Portion of a genes DNA that is translated into a protein
What is the proimotor?
DNA segment recognised by RNA polymerase to initiate transcription
What is the genetic code?
The instructions in a gene that tell a cell how to make a specific protein. Each gene’s code combines the four chemicals in various ways to spell out three-letter “words” that specify which amino acid is needed at every step in making a protein.
What is a codon?
A triplet that encodes one amino acid
What are the key features of the genetic code>
61 of a possible 64 codons code for an amino acid,
Most amino acids have more than one codon,
(UAG, UAG, UGA) codons specify stop
(AUG) codon specifies start as well as methionine.
Structure of tRNA?
Transfer RNA is a single strand of RNA, there is at least one tRNA for each amino acid. Each tRNA has a region which can bind an amino acid AND a region which can interact with mRNA
Role of tRNA in RNA synthesis?
tRNA acts as the adaptor. An enzyme (aminoacyl tRNA synthetase),recognises both a specific amino acid and the correct tRNA for this amino acid and joins them together
What is Translation?
The synthesis of proteins by ribosomes using mRNA as a set of instructions
Role of ribosomes in protein synthesis?
Ribosomes translate the genetic code transcribed in mRNA into an amino acid sequence
Outline the relationship between genetic and phenotypic variation.
what happens at the DNA level is reflected at the protein level, and that genetic variation commonly leads to phenotypic variation
Define allele?
Different form of a gene
Describe the difference between genotype and phenotype?
Genotype is a set of genes and/or DNA
combinations that are responsible for a particular trait.
Phenotype is the physical expression, or characteristics of a genotype, i.e. are traits or characteristics of an organism that can be observed.
What is Mendel’s 1st Law?
Segregation:
Genes segregate at meiosis so that each gamete contains only one of the two possessed by the parent
What is Mendel’s 2nd Law?
Independent Assortment:
Alleles of different genes assort independently during gamete formation
What is the sum rule?
the probability of the occurrence of one event or the other event, of two mutually exclusive events, is the sum of their individual probabilities
What is the product rule?
the probability of two independent events occurring together can be calculated by multiplying the individual probabilities of each event occurring alone
Polymorphic?
One gene that has many different alleles
Co-dominance?
Both parental phenotypes are present in F!
Incomplete dominance?
Both alleles of a gene are partially expressed, resulting in an intermediate phenotype.
How do environmental factors effect phenotype?
Examples: Nutrition - height and weight, disease - life expectancy.
What are sex linked trauts?
Involves genes on the sex chromosomes, their inherritanc epatterns differ between males and females.
What are linked genes?
Genes that do not sort independently, and therefore are linked on the same chromosome.
How does recombination occur for linked genes?
Crossing over during meiosis
What is recombination frequency?
The proportion of recombinant gametes
What is random genetic drift?
A random change in allele frequencies due to sampling
error over generation
What is a population bottleneck?
Occurs when a species experiences an event that suddenly and significantly reduces it’s population
What is the Founder Effect?
reduction in genetic variation that results when a small subset of a large population is used to establish a new colony.
What is the effect of stabalising selection?
reduces variation but does NOT change the mean
What is the Effect of Dissruptive selection?
favours the two extremes producing two peaks
What is the effect of directional selection?
changes the mean value towards one extreme
What is sexual selection?
Animals that express desired phenotypes for producing fit offspring will have better mating success.
What is cline?
The gradual geographic change in genetic/phenotypic composition
