Lab 4 Flashcards
Meiosis 1
The first division when homologous chromosomes are separated into two different cells, halves the number of chromosomes ( diploid- haploid )
G0
G1
S
G2
M
Meiosis 2
Second division of meiosis when replicated chromosomes are separated into single chromosomes
Gamete
Gamete a haploid reproductive cell which combines with another gamete during sexual reproduction; eg
Spore
In plants, a haploid reproductive cell produced by meiosis
Ploidy
A number of sets of chromosomes in a cell; haploid = 1 n diploid = 2n
Diploid
A cell or organism that has two sets of chromosomes ( pair of homologous chromosomes)
Haploid
A cell or organism which only has one set of chromosomes
Homologous chromosomes
Chromosomes that have the same size, shape, centromere position and linear sequence of genes; pair up during prophase 1 to form tetrads
Locus
a physical site or location within a genome (such as a gene or another DNA segment of interest), like a street address
Gene
A unit of hereditary information that contributes to the inherited characteristics or traits of an organisms; composed of a specific organized sequence of DNA
Allele
Alternative version of gene ( either dominate or recessive)
Capital letter for dominate gene
Lowercase for recessive gene
Dominant
An allele that is expressed in both the heterozygous and homologous condition
Recessive
An allele that is not expressed phenotypically in the heterozygous condition
Genotype
The genetic makeup makeup of an organism ( Aa or AABB)
Cross-over
Exchange of segments of the non-sister chromatids of homologous chromosomes when they are in tetrads during prophase 1 of meiosis
Tetrad
Paired set of homologous chromosomes, each made up of two sister chromatids, closely associated at the centromeres, formed during prophase 1 of meiosis
Sporangium
In plants, a diploid structure in which haploid spores are produced by meiosis
Alternations of generations
In life cycle with distinct multicellular haploid and diploid stages found in some plants (ferns)
gameotype
Multicellular haploid generation in the life cycle of a plant that produces gametes by meiosis
Sporophyte
Multicellular, diploid generation in the life cycle of a plant; produces haploid spores by meiosis
Rhizomes
Horizontal stem that grows below ground
Sorus
In most ferns, a cluster of sporangia which develops on the undersides of mature leaves
Rhizoids
In some plants, hair-like structure involved in water absorption and in anchoring the plant
Prothallus
In ferns, refers to the small-heart shaped gametophyte
Antheridium
Male reproductive organ on the fern gametophyte in which flagellated sperm cells are formed
Archegonium
Female reproductive organ on the fern gametophyte in which egg cell is formed
Zygote
Diploid cell formed when toe gametes fuse
Chiasma
Site of crossing over between the non-sister chromatids of tow homologous chromosomes
Ovary
One pair of female glands in which the eggs form and the female hormones estrogen are produced
Egg
Haploid cell
Sperm
Haploid cell
Prophase 1
Diploid cell contains 4 chromosomes (2n=4)
Replicated chromosomes condense
Spindle microtubules begin to pair up (Synapsis) to form tetrads
Genetic exchange occurs between homologous chromosomes during a process called crossing over
Prometaphase 1
Nuclear envelope disintegrates
Spindle microtubules attach to centromeres of each replicated chromosome
Metaphase 1
Tetrads are lined up along the mid region of the cell
Anaphase 1
The homologous chromosomes separate from each other and are moved to opposite poles of the cell by the spindle apparatus
Telophase 1
Replicated chromosomes arrive at poles and begin to disappear
Spindle apparatus disappears
Nuclear envelope starts to reform
Cytokinesis begins
At the end of telophase 1 there is a haploid number of replicated chromosomes
Prophase 2
Replicated chromosomes condense again
New spindle apparatus forms
Prometaphase 2
Nuclear envelope disintegrates again
Spindle microtubules attach to the centromeres of each replicated chromosome
2 cells
Metaphase 2
Replicated chromosomes line up individually along the metaphase plate of daughter cells
2 cells
Anaphase 2
Centromeres of each replicated chromosome seperate and the resulting single chromosomes are moved to opposite poles by the spindle apparatus
2 cells
Telophase 2
Single chromosomes arrive at opposite poles and start to uncoil
Spindle apparatus disappears nuclear envelope will reform
Cytokinesis begins
Appears like the beginning of 4 cells
At the end there will be 4 daughter cells each containing a haploid number of chromosomes
Meiosis in plants : where does it occur
In plants meiosis occurs in diploid cells called sporophytes within reproductive organs called sporangia to form haploid spores
Plant life cycle
Plants have a complex life cycle called an alternation of generations; meaning that they have distinct haploid and diploid stages
The diploid generation called sporophyte, produces haploid spores by meiosis within structures called sporangia. These spores undergo mitosis to produce the multicellular haploid gametophyte
Sporangia experiment
Sporangium
Sporangial stalk
Spores
Rhizoids help absorb food water
Sporophyte tissues water
Chiasma
Crossed over chromosomes
Animal life cycle and meiosis
