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level: Sexual reproduction and Meiosis

Questions and Answers List

level questions: Sexual reproduction and Meiosis

QuestionAnswer
What is meiosisIt is a type of cell division that happens in the reproductive organs to produce gametes
Define gametesHaploid sex cells produced by meiosis in organisms that reproduce sexually (sperm and eggs)
Define somatic cellAny cell of a living organism but reproductive cells
Define zygoteThe diploid cell produced by fertilisation (fertilised eggs)
What is a homologous chromosomePairs of matching chromosomes
Difference between haploid and diploid cellsHaploid = half the normal chromosomes number Diploid = normal number of chromosomes
What is the importance od meiosisProduces genetic variation during sexual reproduction by independent assortment and crossing over.
What are the main stages of meisosInterphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase II, metaphase II, anaphase II, telophase II
Describe interphase- Cell's DNA unravels and replicates to produce double armed chromosomes called sister chromatids
Describe prophase 1- Chromosomes condense - homologous chromosomes pair up and crossing over occurs - centrioles move to opposite poles of the cell forming spindle - nuclear envelope breaks down
Describe metaphase 1- homologous pairs line up across the equator of the cell and attach to the spindle by their centromeres
Describe anaphase 1- spindles contract, pulling pairs apart
Describe telophase 1- a nuclear envelope forms around each group of chromosomes - cytokinesis occurs and 2 haploid daughter cells are produced
Describe prophase II- chromosomes condense - nuclear envelop breaks and spindle forms
Describe metaphase II- chromosomes line up at the equator - independent assortment occurs
Describe anaphase II- sister chromatids are separated randomly
Describe telophase II- chromatids assemble at poles - cytokinesis occurs - 4 daughter haploid cells are produced
Define bivalenthomologous chromatids referred to after crossing over
Explain crossing over- occurs during prophase 1 - homologous pairs of chromosomes come together and pair up - the chromatids twist around each other and bits of the chromatids swap over
How does crossing over create variationThe chromatids still contain the same genes but now have different combinations of alleles
Explain independent assortment- Of chromosomes happen during metaphase 1 - Of chromatids happen during metaphase II - homologous pairs line up and are separated. It's completely random which chromosome or chromatid from each pair end up in the daughter cells
How does independent assortment create variationThe 4 daughter cells produced have completely different combinations of those maternal and paternal chromosomes.