Bio Skills Check 6

Metaphase 1

Metaphase 1

Paired homologous chromosomes line up across the center of the cell

Crossing Over

Increases genetic diversity; process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Prophase 1

Crossing over occurs

Anaphase 1

Homologous chromosomes separate

Anaphase II

sister chromatids separate

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Gamete

sex cell; haploid; humans 23 chromosomes; made during meiosis

Somatic cell

body cell; diploid; made during mitosis

Meiosis purpose

reduce the amount of DNA by half so that traits can be passed on

S phase

DNA replication; happens first in both meiosis and mitosis

Which phase of meiosis is most like mitosis?

Meiosis II; sister chromatids separate

Which process is how a zygote is developed into a baby?

mitosis

Zygote

fertilized egg

Autosomes

1- 22

Sex chromosomes

X and Y chromosomes

Chromosomes of male

XY

Chromosomes of female

XX

Trisomy 21

Down syndrome; three of the 21st chromosome

Karyotype

A picture of all the chromosomes in a cell arranged in pairs

Homozygous

Having two identical alleles for a particular gene

Heterozygous

having two different alleles for a trait

Diploid

2 sets of chromosomes; body/ somatic cells

Haploid

having a single set of unpaired chromosomes; gamete/ sex cell

Homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure