DNA structure replication

What is the goal of DNA replication

Create new DNA strands that are complementary to the original strands, leading to two full copies of DNA

In which way is DNA replicated

From 5’ to 3’

How do you tell the difference between a 5’ and 3’

What is bonded at the number, count from base clockwise

5’ Carbon

Sticks upwards and attached to phosphate group

3’ carbon

Attached to the OH group

DNA replication enzymes in order

Helicase

Topoisomerase

Primase

DNA Polymerase III

DNA Polymerase I

Ligase

Helicase

Unzips DNA, allows for other enzymes to access DNA

What does the Helicase create after unzipping the DNA

Replication Fork

Topoisomerase

Will bind to DNA to keep it from over-coiling as replication begins

Primase

Creates primers that bind to the open strands, tells DNA polymerase III where to start building

Primers

Small chunks of complimentary DNA, both strands need this

DNA Polymerase III

Responsible for placing complimentary bases along the new strand of DNA, always in the 5’ to 3’ direction

DNA Polymerase I

Comes through and removes the leftover primers at the end of replication

DNA polymerase II

Used for DNA repair

Okazaki Fragments

Small fragments of DNA that get synthesized in chunks to create the complement of the lagging strand

Ligase

Reforms the bonds between the phosphate sugar backbones (phosphodiester bonds)

Step 1 of DNA replication

DNA Helicase unzips your genes

Step 2 of DNA replication

Primase creates primers to bind to DNA.

Step 3 of DNA replication

DNA polymerase III binds to the primer and begins replication.

Step 4 of DNA replication

The lagging strand gets synthesized using Okazaki fragments.

Step 5 of DNA Replication

DNA Ligase glues DNA back together.

Differences in eukaryotic and prokaryotic DNA replication

The general process is the same, prokaryotes have more DNA polymerases.

Ori

Origin of replication for prokaryotes

Telomeres

Unpaired, repetitive sequences of DNA that do not code for genes, get shorter with each cell division.

Telomeres and Okazaki fragments

Primers for Okazaki fragments need something to bind to. As more cell cycles occur, the more
DNA they use up

What do telomeres do

Protect genes from getting deleted as cells continue to divide segments of DNA that get
shorter as cells continue to divide

What are the two ways mutations can occur

Induced

Spontaneous

Induced Mutations

Caused by exposure to chemicals, UV, x-rays

Spontaneous Mutations

Happen in response to natural reactions in the body (aging, change in ph, issues with replication)

What are the two types of single-nucleotide polymorphisms(SNPs)

Transition and Transversion Substitutions

Transition Substitution

Substitute purine for the wrong purine OR sub pyrimidine for the wrong pyrimidine

Transversion Substitution

sub a purine for a pyrimidine OR sub a pyrimidine for a purine

What are the 3 frameshift mutations

Insertions

Deletions

Duplications

Insertion

Insert an additional base that is NOT supposed to be there

Deletion

Delete a base that is supposed to be there.

Duplication

Duplicate base, gene, or chromosome region by mistake.

Genotype

Different genes on the chromosomes

Alleles can be what

Dominant or Recessive, does not necessarily mean better or worse

Dominant (A)

Only needs one copy of the allele to be expressed

Recessive (a)

Needs two copies of the allele to be expressed

Homozygous

AA or aa

Heterozygous

Aa, will always express the dominant gene.