SEARCH
You are in browse mode. You must login to use MEMORY

   Log in to start

level: Level 1

Questions and Answers List

level questions: Level 1

QuestionAnswer
Locuslocation of a gene/ position of the allene on the chromosome
Allelealternate DNA sequence at same locus and gene (gives traits like eye colour)
Genotypecombination of genetic information
Phenotypephysical appearance of genotype
Hetrochromatiddensely packaged chromosome
Euchromatinloosely packaged chromosome
Chromatidone strand of duplicated chromosome joined by centromere to it’s sister chromatid.
Sister chromatids2 chromatids joined by centromeres. Each carries identical genetic information.
CentromereHeterochromatic region of a chromosome to which microtubule fibres attach.
Interphaseincludes the S-phase- DNA is synthesised. Period of growth in between cell division. Up to 90% of the cells time in the cell cycle is spent in interphase. It appears dormant but the activity level is high.
G0a point in G1 of interphase where cells are non-dividing (leave the cell cycle) but still metabolically functioning. Cells like Heart cells are always in G0.
G1period prior to synthesis of DNA. For most cells this is where their major cell growth occurs. DNA in this phase is diploid (2n, 2 copies of the chromosomes) the genetic material is in the loose chromatin form.
G1 Restriction (R) pointpresent at the end of G1. Dependant of levels of nutrients and energy it decides if cells will enter the cell cycle or move to G0.
S-PhasePeriod where DNA is synthesised, creates 2 identical semi conservative condensed chromosomes (2 sets of chromosomes in this phase)
G2final subphase of interphase. Right before mitosis. Microtubule formation, organelles produced, cytoplasmic volume increased. Replicated chromosomes are indistinct and nuclear envelope is intact.
G2 Restriction (R) pointfinal check point before mitosis. Prevents cells from entering mitosis with DNA damage.
Mitosisone diploid cell divides into 2 diploid cells with the same genetic information.
Prophasechanges in nucleus, nucleosome disappears, chromosomes densify, spindle fibres begin to form, centrosome attaches to spindles and pull across forming an early form of the spindle bridge.
Prometaphasenuclear membrane breaks apart, spindle fibres attach to condensed chromosomes, begin to pull chromosomes to centre. Microtubules make contact with each other from opposite polls. Some microtubules attach to kinetochore. Spindle proteins pull chromosomes to centre.
MetaphaseHighly condensed chromosomes align in middle (Centromeres converge on the metaphase plate). Fully formed spindle fibres.
Spindle checkpointmonitors interaction between improperly connected kinetochores and tension.
AnaphaseChromosomes move to opposite polls of cell. Initiated by protease which cleaves cohesion pulling sister chromatids apart.
Telophase2 daughter nuclei form in the cell, the chromosomes unwind back into loose chromatin, nucleus reforms. Daughter nuclear envelope are formed.
Cytokinesisseparate phase to mitosis, cytoplasm divides into 2 daughter cells, contractive ring formed by actin and myosin tightens around cytoplasm of cell and they are pinched apart.
Meiosismakes 4 haploid cells containing only one copy of each chromosome.
Meiosis 1membranes of a pair of homologous chromosomes physically associate. Goes through same stages as mitosis for round 1.
Prophase 1crossing over occurs sharing genetic information from 2 parent cells.
Metaphase 2unpaired chromosomes align at cells middle. No synthesis has occurred. So only 1 replicated chromosome remains so in anaphase sister chromatids have separated.
Law of independent assortmentwhen one trait is concerned a 3:1 ratio is observed if 2 traits are concerned a 9:3:3:1 ratio is observed.
Autosomal recessivefor rare traits, most affective individuals will have unaffected parents, all children of an affected parent are affected, risk of an affected child with homozygous parents for the trait is 25%
Autosomal dominantevery affected personal has at least one affected parent. 2 affected individuals can have an unaffected child.
X linked recessiveaffected males receive mutant allele form their mother and transmit it to ALL daughters but no sons. Daughters of affected makes are usually heterozygous. Sons of heterozygous females have 50% change of being affected. Effect males more than females.
X linked dominantaffected males produce ALL affected daughters and NO affected sons. A heterozygous female will transmit the trait to ½ her children. On average 2x as many daughters are affected.
Dominant lethal allelesrarely detected because they are rapidly killed. E.g. Manx cat.
Incomplete dominanceboth alleles blend effects together.
Codominanceboth alleles show effects but do not blend. Neither are dominant both expressed.
Epistasisa form of gene interaction where one gene masks the phenotypic expression of another.
Pleiotropyone gene influences multiple phenotypic traits
Genetic heterogeneitywhen a single phenotype is caused by any one of multiple alleles or loci
Allelic heterogeneitydifferent mutations with a single gene locus
Germline mosaicismpresence of 2 or more populations of cells with different genotypes in one individual who has developed form a single fertilised egg.
Linkage2 or more genes located on the same chromosome that do not show independent assortment and tend to be inherited together.
X chromosomehumans use X Y sex chromosomes, only one X chromosome can be expressed at a time. Any other X chromosomes are inactivated.
Karyotypea complete set of chromosomes from a cell that has be photographed during cell division (usually at metaphase)
Centromere locationsMetacentric- centrally placed. Submetacentric- a but uneven. Acrocentric- close to one end. Telocentric- at one end of the chromatid.
Polyploidya chromosomal number that is multiple of the normal haploid number. More than one full chromosome set.
Aneuploidychromosomal number not exact multiple of haploid.
Triploploidy3 times copy of autosomes
Tetraploidyfour times copy of the autosomes.
Autoploidyeach set is identical to parent set. Diploid genome. 2 sperms fertilising one egg.
Allotetraploidpolyploid contains 4 haploid genes derived from separate species
AmphidiploidAllotetraploid, where both original species are known
DNAa right-handed double helix structure turning every 10 bases. With a phosphate group, a pentose sugar deoxyribose and a nitrogen containing base. A paring unstably with T and G pairing stably with C. 2 polynucleotides chains held together by hydrogen bonds.
Purinethe bases A and G
PyrimidineBases C and T
Nucleosidea nitrogen base and a sugar without a phosphate.
Nucleotidea nucleoside plus a phosphate.
Polynucleotidesnucleotides are joined together to make a chain. Are directional. Work form the 5 prime end to the 3 prime end with the hydroxyl group.
Telomeresequences at the end of chromosomes that play a critical role in chromosome replication. They keep chromosomes protected and prevent them from fusing into rings.
Aneuploidychange in number of individual chromosomes. Can lead to reproductive failure and birth defects.
Monosomyone member of the chromosome pair is missing. Is lethal in humans.
Trisomyone chromosome is present in 3 copies. Relatively common, most autosomal are lethal (50%). Down-syndrome is trisomy of chromosome 21.
Nondisjunctionfailure of homologues chromosomes to separate in meiosis, giving rise to aneuploidy.