unit 8 bio

DNA replication

DNA making a copy of itself prior to cell division; semi-conservative process: the two new DNA molecules each contain half of the original molecule as well as new nucleotides

DNA helicase

enzyme that unzips the double helix

leading strand

DNA polymerase enzyme continually builds the new DNA strand built toward the replication fork in 5’ —> 3’ direction

lagging strand

constructed in Okazaki fragments by the DNA polymerase (5’ —> 3’ direction) away from the replication fork and joined together by DNA ligase to create a final strand

G1 stage

cell volume increases; cell differentiation/growth completed; cell begins to function

G0 stage

stage outside the cell cycle in which cells do not copy their DNA and do not prepare to divide; may last weeks or indefinitely

S stage

DNA Replication occurs; all cell activity ceases as replication is completed; the onset of the S stage is triggered by a buildup of the hormone “S-Cyclin”

G2 stage

cell function resumes; cell increases in volume as all cell contents double in preparation for cell division

M-stage

cell division occurs; mitosis followed cytokinesis; triggered by the buildup of the hormone “M-Cyclin”

Mitosis

specifically the formation and segregation of chromosomes and division of the nucleus; occurs in 4 stages: prophase, metaphase, anaphase, telophase

cytokinesis

the physical division of the cell membrane and cell contents into 2 cells

chromosomes

tightly coiled DNA found in the nucleus of a dividing cell during M-Phase

• each chromosome represents one highly coiled DNA molecule; visible in cell

• chromosomes are rod-shaped or X shaped depending on when they are observed

chromatin

DNA in a non-dividing cell that is not tightly coiled; not visible

• allows transcription/translation to occur in the cell between cell divisions

centromere

structure which holds together the sister chromatids in a doubled chromosome

histone

proteins that help organize DNA; DNA is wound around histone “spools”

nucleosome

group of 8 histones; nucleosome wind into helix; helix condenses into visible chromosome

homologous chromosome

chromosome pairs that contain the same genes

sister chromatids

result of DNA replication, genetically identical duplicate DNA molecule making two halves of a doubled chromosome

sex chromosomes

determine gender; known as X and Y

autosomes

chromosome #1 - #22

diploid cell

contains both halves of each homologous pair of chromosomes

contains a full set of genetic information (2N)

haploid cell

contains ½ of the full set of genetic information

contains only one chromosome from each homologous pair (1N)

testes

male gonads

sperm

male gametes

ovaries

female gonads

egg cell (ova)

female gametes

karyotype

an image taken of chromosomes during mitosis used to identify both biological gender and possible chromosomal mutations

chromosomal mutations

occur during DNA replication or meiosis, mutations include partial chromosomal mutations and whole chromosome mutations

trisomy

karyotype shows an entire extra chromosome

• whole chromosomal mutation

monosomy

karyotype shows a missing chromosome

• whole chromosomal mutation

deletion

a section of a chromosome is missing; chromosome appears small

• partial chromosome mutation

duplication

a section of a chromosome is repeated; chromosome appears oversized

• partial chromosome mutation

translocation

a section of a chromosome detached and reattached to a different chromosome

• partial chromosome mutation

inversion

a section of a chromosome detached and reattached in the wrong direction

• partial chromosome mutation