Bio 101-DNA replication, mitosis, and Cell cycle (part 1)

Chief characteristic of life

Chief characteristic of life

Life reproduces

• (cells die and are replaced by other cells through cell reproduction)

binary fission

asexual reproduction that bacteria go through

Meiosis

formation of sex cells (gametes)

• produces sperm and ova

Fertilization

Union of the sperm and ova

• produces zygote (fusion of gametes)

mitosis

results in duplicated DNA being transferred from one to two cells

• how children develop into adults

• produces new cells → new organisms

Apoptosis

shapes organisms by cells dying, necessary for development of organisms and necessary for cell division/reproduction

• life is about balance between cell death and cell reproduction (mitosis)

2 steps to cell reproduction

1. DNA replication

2. replicated DNA being moved to each cell

When does DNA become replicated?

when it is opened up (unzipped) & new nucleotides are added to each old strand of DNA

• 1 piece of DNA becomes 2—each with a copy of old and new material

Position of Carbon atoms in sugar molecule

plays a big factor in the formation of DNA molecules

antiparallel

strands are parallel but opposite and oriented in different directions

• 5’ carbon points upward on the right side and 3’ carbon points upwards on the left side. They are antiparallel.

Helicase

first enzyme which unzips DNA molecule

binding proteins

put into stabilizing the separation

Primase

adds short RNA primer to each strand of unzipped DNA to facilitate/influence DNA polymerase which is going to add the new nucleotides

DNA polymerase

enzyme which assembles/adds nucleotides during DNA replication

• facilitated/smoothed by primase

• proofreading mechanism

5’ → 3’ direction

new nucleotides get added by DNA polymerase with the 5’ side oriented downwards while new nucleotides added to 3’

• down the left strand & up the right

• proofread

Leading strand

DNA polymerase just works its way up continuously, following helicase

• no problems, DNA polymerase follows the helicase and replicates old strand

Lagging strand

DNA polymerase works its way down (discontinuously)

• does NOT start at the beginning

• when unwinds more, new primer added and DNA polymerase start anew

Okazaki Fragments

the fragments that develop on the lagging strand when RNA primers are lost.

• with Okazaki fragments, come gaps

Ligase

enzyme that fixes gaps in fragments by putting nucleotides in and finishing DNA construction

Substitution Mutation

when the wrong nucleotide is substituted for another

• purine for a purine or pyrimidine for a pyrimidine

• purine for a pyrimidine or pyrimidine for a purine

Deletion

dna nucleotide skipped and not added

• frameshift, changes entire DNA seq

Insertion

DNA nucleotide squeezed in between two nucleotides which are bound to old strand

chromosome

polymer of DNA and its associated by proteins which organize the DNA molecule

• carries genetic info

• found in nucleus

• most humans have 46

chromatin

-collective amount of DNA (chromosomes) and proteins (enzymes)

• building, repairing, and using DNA molecules

• compose chromosomes

• contains subunits: Nucleosomes

nucleosomes

proteins that organize human cells. (2 meters)

subunit/collections of chromatin organized around proteins called histones

histones

proteins that organize nucleosomes/bind and hold DNA; structural support for chromosome

• each nucleosomes consists of 8 histones

semi conservative

one strand is old/ancient while the other is newly produced