Unit 4 Bio 120

Eukaryotic Cell Cycle

1. Mphase: division of mitosis and cytokinesis

2. Interphase: cell grows and prepares for division

   1. G: cell growth and normal metabolism

   2. S: cell divides (synthesis)

   3. G2: preparation for mitosis

Structure of DNA

a nucleotide has 3 parts

phosphate group: bonds to sugar of the next nucleotide thought a phosphodiester bond, forming sugar phosphate backbones

deoxyribose sugar:

nitrogenous base: A-T, C-G (2 polynucleotides pair up by HB b/w their complementary base)

Overview

Parental DNA molecules starts as a double helix

-HB between complementary bases are broken, causing 2 strands to separated

-Each strand serves a as a template for making a new complementary strand

-Enzymes bonds the new nucleotides together forming sugar-phosphate backbone

-HB reform between complementary bases, creating 2 identical DNA molecules

Origin of Replication

A specific site on a DNA molecule where replication begins

• The replication bubbles expand latterally, as DNA replication proceed in oth direction

• The replication bubbles meet as the parental DNA completely unwinds and separates

  • synthesis of the daughter strands or new complementary strands is completed = 2 daughter DNA molecules

Helicase

unwinds the parental double helix at the replication fork, so a single strand of DNA is available for complementary nucleotide to be added by DNA polymerase

Single-stranded binding proteins

Binds to the single-stranded regions of the parental strands and prevents them from coming back together, stabilizes the single strands

Topoisomerases

Works upstream of the replication fork to relieve the stress caused by unwinding the double helix at the replication fork

RNA primase

synthesizes a short piece of RNA that is complementary to a region of the DNA parental strand so that DNA polymerase can ad DNA nucleotides

DNA polymerase

adds nucleotides to the newly forming complementary strand. it can only add bases to another nucleotide, either those of the RNA primer or the DNA nucleotides of the new complementary strand

How do we read DNA

5’ —> 3’

or

3’ —> 5’

Helicase

Unwinds the strands

Primase

Places primers

DNA polymerase - leading strands

Builds new strands (only in 5’ —> 3’) (leading strand)

DNA polymerase - lagging strand

Builds new strands (3’ —> 5’) primers have to keep being places

Okazaki Fragments

Each fragment has their own RNA primer, which provides 3’ end for DNA polymerase II to add nucleotides

Ligas

Gluing enzymes, seals Okazaki enzymes

DNA Ligase - to generate a single strand of lagging DNA: what must occur?

The RNA primers are removed by DNA polymerase I and replaced with nucleotides that are complementary to the code of parental DNA strands

DNA ligase joins the DNA fragments together by completing the sugar-phosphate backbone

Telomeres

are repetitive, non-coding nucleotide sequences found at the ends of eukaryotic chromosomes.

• Their main function is to protect important genes from being lost during DNA replication.

Somatic cell

non-sex cell

• 46 chromosomes in a human somatic cell

• 2 of each type

2 types of somatic cell

Genome: complete set of genetic material (all the DNA) in an organism.

Chromosome: long, coiled molecule of DNA that contains many genes and associated proteins.

• un-replicated: A single, continuous DNA double helix with its associated proteins

• replicated: A chromosome that has been copied during DNA replication

Gene

A unit of hereditary information made up of a specific sequence of nucleotides in DNA

Character v. Trait

Hand-folding can place right or left thumb on top

Allele

Variation of a gene

Mitosis

cells produce 2 genetically identical daughter nuclei

Cell division

the process by which cells make more cell

Meiosis

cell divisions that results in 4 daughter cells each with half the numebr of chromosomes of the parent cell