MEIOSIS L11 Flashcards
I. Intro to Heredity - CC sexual and asexual reproduction II. Life cycles - SEQ, CC sexual life cycles III. Four stages of meiosis - SEQ, CC, HD process of meiosis
1
Q
heredity
A
- transmission of traits from one generation to the next
2
Q
variation
A
- differences between individuals
3
Q
genetics
A
- the study of heredity and hereditary variation
4
Q
gametes
A
- reproductive cells that transmit genes from one generation to the next
5
Q
advantages of asexual
A
- fast
- low E required
- safe
- lots of offspring
6
Q
advantages of sexual
A
- genetic variation
- offspring represent novel combinations of parents genes
- better able to respond to change or stress
7
Q
why meiosis is good
A
- cell divides twice
- 1 diploid – 4 haploid
- if gametes have same chromosome number as parents, chromosome number doubles when the fuse
8
Q
karyotype
A
- orderly display of chromosomes
9
Q
life cycles
A
- sequence of stages from generation to generation
10
Q
what do fertilization and meiosis have in common
A
- occur in all sexual life cycles
- alternate
- timing varies
11
Q
human life cycle
A
- meiosis – haploid gametes – fertilization – diploid zygote – mitosis
12
Q
what cells can undergo mitosis
A
- n
- 2n
13
Q
what cells can undergo meiosis
A
- 2n
14
Q
meiosis
A
- reduction division
- 4 stages
- 2 cell divisions
- interphase
- meiosis 1
- interkinesis
- meiosis 2
15
Q
interphase
A
- like before mitosis
- chromosomes and centrioles duplicate
- each chromosome is now 2 sister chromatids
16
Q
meiosis 1
A
- prophase 1
- metaphase 1
- anaphase 1
- telophase 1
17
Q
prophase 1
A
- crossing over
- genes in chromosomes align
- synaptonemal complex forms - protein structure
- results in tetrad: 2 homologous chromosomes (4 chromatids) held together
- chromatin condenses
- centromeres and kinetochores of homologous chromosomes separate
- sister chromatids still attached
- chiasmata form
- nuclear envelope breaks down, spindle forms
18
Q
metaphase 1
A
- tetrads align at metaphase plate
- homologous chromosomes orient towards opposite poles
- both sister kinetochores of one chromosome – spindle for same pole
- kinetochores of homologous chromosomes – spindle for opposite pole
19
Q
anaphase 1
A
- sister chromatids still connected
- chromosomes act independently
- direction depends on orientation of tetrad
20
Q
telophase 1
A
- chromosomes may decondense
- nuclear envelope reforms
- cytokinesis occurs
- results in 2 haploid cells
21
Q
meiosis 1 summary
A
- start: 1 cell, 2n, duplicated chromosomes
- end: 2 cells, n, duplicated chromosomes
- diploid – haploid
- homologous pairs line up at metaphase plate
22
Q
interkinesis
A
- time between 1st and 2nd meiotic divisions
- no S phase
- no DNA synthesis
23
Q
meiosis 2
A
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
- similar to mitosis
- chromatids separate in daughter cells
24
Q
meiosis 2 summary
A
- start: 2 cells, n, duplicated chromosomes
- end: 4 cells, n, unduplicated chromosomes
- each daughter cell is genetically unique
- no crossing over
- amount of DNA per cell is reduced
- ploidy does not change
