Lesson 1 - Sexual reproduction and meiosis Flashcards
meaning diploid (2n)
signifies a cell with a nucleus containing 2 full sets of chromosomes
meaning haploid (n)
signifies a cell with a nucleus containing 1 full set of chromosomes
meaning zygote
the cell formed when 2 haploid gametes fuse during fertilisation
meaning fertilisation
the fusing of the haploid nuclei from 2 gametes to form a diploid zygote in sexual reproduction
meaning polypoidy
when a cell or organism has more than 2 sets of chromosomes
meaning gonads
the sex organs in animals
meaning anthers
male sex organs in plants
meaning ovaries
the female sex organs in plants and animal
meaning pollen
produced in the anthers, contains the haploid female gametes in plants
meaning ovules
formed in the ovaries, containing haploid female gametes in plants
meaning testes
male sex organs in animals
meaning spermatozoa
haploid male gametes in animals
meaning ova
haploid female gametes in animals
meaning microspores
the result of meiosis in plants that produce the male gametes, pollen
meaning megaspores
the result of meiosis in plants that produce female gametes, ovules
meaning homologous chromosomes
a set of maternal chromosome and 1 paternal chromosome that pair up during meiotic cell division
meaning crossing over (recombination)
the process by which large multi-enzyme complexes cut and rejoin parts of the maternal and paternal chromatids at the end of prophase 1
meaning independent assortment (random assortment)
the process by which the chromosomes derived from the male and female parent are distributed into the gametes at random
meaning chaismata
the points where the chromatids break during recombination
state 3 differences between asexual and sexual reproduction
- asexual reproduction requires 1 parent, whilst sexual reproduction requires 2 parents
- sexual reproduction introduces genetic variance, asexual doesn’t
- asexual reproduction is completed faster than sexual reproduction
what would happen if 2 diploid chromosomes would fuse to form a new individual
the offspring would have 4 sets of chromosomes, losing the characteristic number of the species. Each new generation would become more heavily loaded with genetic material until the cells break down and fail to function
how many daughter cells does meiosis produce
4
how many daughter cells does mitosis produce
2
name the 8 stages of meiosis
- prophase 1
- metaphase 1
- anaphase 1
- telophase 1
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
what happens during prophase 1
each chromosome appears in the condensed form with 2 chromatids. Homologous pairs of chromosomes associate with each other. Crossing over occurs
what happens during metaphase 1
the spindle forms and the pairs of chromosomes line up on the metaphase plate
what happens during anaphase 1
the centromeres do not divide. One chromosome from each homologous pair moves to each end of the cell. As a result, the chromosome number in each cell is half that of the original
what happens during telophase 1
the nuclear membrane reforms and the cell begin to divide. There is no further replication of the DNA
what happens during prophase 2
new spindle are formed
what happens during metaphase 2
the chromosomes, still made up of pairs of chromatids, line up on the metaphase plate
what happens during anaphase 2
the centromeres now divide and the chromatids move to the opposite ends of the cell
what happens during telophase 2
the nuclear envelope reforms, the chromosomes return to their interphase state and cytokinesis occurs, giving 4 daughter cells, each with half the chromosome number of the original diploid cell
