Order of events in cell cycle
Interphase: G1, S, G2, mitosis: Prophase, metaphase, anaphase, telophase, cytokinesis
haploid vs diploid
one set of chromosomes vs two sets of chromosomes;
n/2n
n-Haploid (gamete)
2n-Diploid (somatic)
Duplicated vs unduplicated chromosomes
Unduplicated chromosomes are single linear strands, whereas duplicated chromosomes contain two identical copies (called chromatids or sister chromatids) joined by a centromere.
homologous chromosomes
Chromosomes that have the same sequence of genes and the same structure
Alleles
different versions of a gene
Gametes
sex cells
germ cells
cells that undergo meiosis; is still a body cell
somatic cells
body cells
Prophase I
- Nucleus breaks down
- duplicated chromosomes condense and homologous pairs pair up
- crossing over occurs
crossing over
the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring; increased genetic variability
Metaphase I
homologous pairs line up along the center of the cell
Anaphase I
homologous pairs separate and sister chromatids are still intact
Telophase I
- cells separated by cytokinesis
- each cell only contains one of each pair of chromosomes
- cells are now haploid
Prophase II
- no interphase between Telophase and Prophase II
- each of the cells divide again in Meiosis II
- Meiosis II looks just like Mitosis
Metaphase II
chromosomes line up in the center
Anaphase II
sister chromatids separate
Telophase II
- cytokinesis occurs
- 4 haploid cells form with a combination of chromosomes from both father and the mother
- will go to become sex cells
when do cells first become haploid
telophase 1
xx
female
xy
male
Spermatogenesis
process of male gamete production; occurs in testes; produces 4 gametes (sperm cells) QUANTITY OVER QUALITY
oogenesis
process of female gamete production; occurs in the ovary; produces one gamete (ovum or egg) and 3 polar bodies; one of the four cells produced in Meiosis becomes really big because of the cytoplasm given by other 3 cells and those 3 cells end up becoming
nondisjunction
- failure of chromosomes to separate during Anaphase I or II in meiosis
- resulting in aneuploidy
Aneuploidy
cells do not have the correct number of chromosomes
Down syndrome
- Trisomy 21
- Clinical features: flattened face, poor muscle tone, short stature, protruding tongue
- intellectual disability: mild to moderate
- higher risk for development of other health problems
Trisomy
3 copies of a chromosome
Klinefelter Syndrome
- XXY (extra x chromosome)
- Affects only males
- Clinical features: breast development, small testes, low testosterone, sterile
Turner syndrome
- XO: monosomy X
- affects females
-clinical features: short stature, broad chest, usually sterile, webbed neck
monosomy
missing a chromosome
karytope
A picture of all the chromosomes found in the somatic cells of a particular person.
What does nondisjunction result in?
aneuploidy