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level: chromosomes and karyotypes

Questions and Answers List

level questions: chromosomes and karyotypes

QuestionAnswer
what are chromosomes-Structure containing single DNA molecule and associated proteins - they carry genes
what do chromosomes look likeVarious shapes and sizes – appearance changes over life of organism - when condensed they are depicted as long oval shapes - when uncondensed they are just floating strings
what types of chromosomes do eukaryotic cells havelinear chromosomes
where are chromosomes found in eukaryotic cellsnucleus
what does each chromosome possessEach chromosome has a set of genes – passed on to daughter cells in mitosis and germ cell in meiosis
what chromosomes do prokaryotes haveProkaryotes have a single circular chromosome – may also contain small circular DNA called plasmids which can move between cells
what is histone proteinshistone proteins are the substance that DNA is wrapped around
what is a nucleosomethey are sections of DNA which is wrapped around histone proteins nucleosomes are particles, so they give DNA the appearance of string beads
what is the main function of nucleosomesserve to package DNA efficiently and protect it from enzymatic degradation
what happens to nucleosomes when chromosomes are condensedwhen chromosomes are condensed nucleosomes fold producing supercoils
what is a centromereChromosomes have a constriction point called a centromere which divides the chromosome in to two sections called chromosome arms
what are chromosome armsthey are the two sides of a chromosome separated by a centromere
what are the names for the two types of chromosome armsthe shorter arm is the p arm and the longer the q arm – p arm is always on top
what are the names for the four positions centromeres can be inmetacentric, submetacentric, acrocentric and telocentric
where is the centromere if a chromosome is metacentriccentromere is in the centre - p and q are equal
where is the centromere if a chromosome is submetacentriccentromere closer to one side making q almost double the length of p
where is the centromere if the chromosome acrocentriccentromere is very close to one end
where is the centromere is the chromosome is telocentriccentromere is at the tip of the arm
how many genes does each DNA molecule haveEach DNA molecule has many genes
what is a locusEach gene has a particular position called a locus on a specific chromosome
what is spacer DNA and what does it do- Genes of each DNA molecule are separated by regions called spacer DNA → spacer DNA doesn’t code for a protein product → they space genes far enough apart that it enables enzymes and other molecules to interact with genes easily
what is a ploidy levelThe number of sets of chromosomes in a cell
what is gametes ploidy level and how many sets of chromosomes do they haveGametes have one set of chromosomes and are haploid (n)
what are somatic cells ploidy level and how many sets of chromosomes do they haveSomatic cells are diploid (2n) – two sets of chromosomes (1 from each parent) -> Humans have a diploid number of 46
what are homologous chromosomestwo chromosomes in a matching pair - have the same genes found in the same location -> same genes but different DNA (different variations of each gene - one maternal and one paternal)
what is another name for homologous chromosomehomologues
what are sister chromatidsthey are two chromosomes that are genetically identical and are created when DNA is duplicated
what are sex chromosomeschromosomes involved in the determination of a person’s sex
what are allosomessex chromosomes
what is an autosomechromosomes not involved in sex determination
what are mating typessome organisms (fungi and algae) don’t have allosomes and therefore don’t have sexes instead they have mating types
what are organisms called is they have two similar allosomesindividuals with two similar allosomes are of the homogametic sex
what are organisms called is they have two different allosomesindividuals with 2 different allosomes are of the heterogametic sex
what is haplodiploidyin some species sex is determined by haplodiploidy – males develop from unfertilised eggs so are haploid and females are derived from fertilised eggs hence they are diploid (bees and wasps)
what are some environmental factors that can determine a species sexsome species sex is determined by environmental factors such as temperature (turtles and crocodiles), day length (some types of shrimp) or richness and availability of food resources (types of worms) → when sea turtles lay their eggs if the temperature is between 32 and 34 degrees there will only be females but if the temp is between 26 and 18 degrees, they will all be male
what is chromosome bandingChromosome banding refers to alternating light and dark regions along the length of a chromosome, produced after staining with a dye. A band is defined as the part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter
what are banding types used forbanding types are specific and consistent in each species hence they can be used to distinguish between chromosomes and to identify changes in chromosome structure which may be associated with genetic abnormality
what is a karyotypea karyotype is the image or picture of the full set of chromosomes from an organism’s cell – represented by chromosomes arranged in pairs according to length and centromere position
what are karyotypes used forkaryotypes allow scientists to compare chromosomes of related species and allows them to identify changes associated with genetic abnormalities such as changes in chromosome number or structure
what is the human karyotypethe human karyotype is made up of 22 pairs of autosomes and 1 set of allosomes → the autosomes are numbered 1-22 and are order largest to smallest → allosomes are usually shown after autosomes