T5M2- Meiosis Flashcards
what does asexual reproduction produce
exact copy of the parent cell
what are the only cells not produced in mitosis
gametes
where are gametes derived from
specialized germ cells from ovaries and testes
how many haploid sperm cells are produced for one sex cell
4
is meiosis diploid to haploid or haploid to diploid?
diploid to haploid
what do females produce?
-one large egg cell with higher cytoplasmic volume
-3 non gametic polar bodies
what happens during prophase 1?
-homologous recombination and the crossover at chiasmata (adds to variation)
-nuclear envelope breaks down
what characterizes prophase 1?
condensation and synapsis
-centromere duplication
-spindle formation
what pairs the homologous chromosomes?
synaptonemal complex
what types of alleles do homologous chromosomes during prophase 1 have?
different
where is the evidence of crossing over in prophase 1?
chiasma
define crossover
a random process that can happen anywhere along chromosome and allow for production of recombinant chromatids
describe metaphase 1
pairs of homologous chromosomes randomly arranged at metaphase plate
what arranges chromosomes at metaphase plate and why
microtubules of spindle apparatus- to increase diversity
what occurs during anaphase 1
Synaptonemal complex breaks down, allowing for separation of homologue to opposite side of cell
do sister chromatids separate during anaphase 1?
no- only homologues
what marks the end of meiosis 1
telophase 1
what is there during beginning of telophase 1
each end of cell has haploid set of duplicated chromosomes
what occurs in telophase 1
chromosomes uncoil, envelope reforms and cytokinesis follows
what is meiosis 1 also called and why
reductional division- due to reduced number of chromosomes
what immediately follows telophase 1?
prophase 2 and meiosis 2
what is meiosis 2 referred to as? why?
equational division- parent cells have same number of gametes produced at the end of meiosis 2
what causes equational division?
separation of sister chromatids
what occurs in prophase 2
- nuclear envelope breaks down
- spindle apparatus reforms
- chromosomes condense
what occurs during metaphase 2
chromosomes positioned at plate
are sister chromatids genetically identical in meiosis 2?
no because crossover occurred in meiosis 1
what happens to the proteins holding together chromatids during anaphase 2?
break down
what happens to chromatids during anaphase 2
move to opposite sides of cell
what happens during telophase 2
end of meiosis 2
- reforming of nuclear envelope and chromosomal decondensing
- followed by cytokinesis
what is produced at the end of meiosis 1 and 2
4 haploid daughter cells
what causes abnormal variation chromosome number
homologous chromosomes do not separate properly during meiosis 1 and 2
define nondisjunction
too many or too few chromosomes
what was the idea of heredity during the 1800s
blending hypothesis- genetic material was mixed to form the visible traits of offspring
who is the father of genetics
gregor mendel- used pea plants to identify two laws of inheritence
what type of pea plants did mendel start with and what did he differentiate
true breeding plants- differentiated dominant and recessive genes
what did Mendel find in his first generation
all f1 offspring were yellow seed in colour- trait was not lost
what ratio did mendel’s breed occur in
3:1
what happens for the inherited factor for a recessive gene?
masked by dominant gene
what is mendel’s first law
the law of segregation- two alleles of gene segregate into different gametes during gamete formation in both parents
define monohybrid crossing
crossing between true breeding parents
