topic 7 chromosomes and cell division

chromosome

one length of double stranded DNA

what does DNA contain?

the genes

haploid state (1n)

• 4 genes

• 4 loci

• genotype Abcd

• gametes

diploid state (2n)

• 4 genes

• 4 loci

• genotype AABbccdd

• somatic cells

human chromosomes

23 homologous pairs

monkey chromosomes

24 pairs

fission

one to two

fusion

two to one

klinefelters syndrome

2x and 1y

down syndrome

3 on pair 21

interphase

duplicates chromosomes

prophase

nuclear envelope condenses

metaphase

chromosomes line up in the middle

anaphase

daughter chromatids separate

telophase

two nucleolus form, nuclear envelope returns

cytokinesis

animal cells- cleavage furrow

plant cells- cell wall reforms

order of mitosis

1. interphase

2. prophase

3. metaphase

4. anaphase

5. telophase

6. cytokinesis

steps of meiosis

1. interphase

2. meiosis 1

   1. prophase

   2. metaphase

   3. anaphase

   4. telophase

3. cytokinesis

4. meiosis 2

   1. everything repeats from meiosis 1

why is sex good

• genetic recombination has adaptative value

• outcrossing adds to adaptive value

• crossing over during prophase 1

• diversity