Bio - Molecular Genetics

What is DNA

genetic material that carries hereditary info in cells

what is DNA made out of

nucleotides (deoxyribose, phosphate group, nitrogenous base)

What are the 4 nitrogen bases?

Adenine (A) , Thymine (T), Guanine (G), Cytosine (C)

How is DNA structured

double helix

What is the double helix structure?

2 strands of nucleotides wrapped around each other, sugar phosphate backbone, nitrogenous bases on the inside

What does it mean that DNA strands are antiparallel?

run in opposite directions

Complimentary base pairing

A-T and G-C

How are the bases held together?

hydrogen bonds (A and T have 2, C and G have 3)

Chargaff's Rule

In any DNA molecule A=T and G=C

What is the semi-conservative model?

Each new DNA molecule contains one original strand and one newly synthesized strand

When does DNA replication occur?

S phase of the cell cycle

Where does DNA replication begin

origins of replication

What are replication forks

Sites where DNA unwinds

What does DNA polymerase do

Adds nucleotides to the newly formed strand

DNA replication in prokaryotes

single origin of replication, circular DNA

DNA replication in eukaryotes

multiple origins of replication, linear DNA

what are telomeres

DNA at the tips of chromosomes

what do telomeres do

protect coding DNA from being lost during replication

How does RNA differ from DNA

ribose sugar instead of deoxyribose, single stranded, U instead of T

What are the three types of RNA

mRNA, tRNA, rRNA

what does mRNA do

carries genetic info from DNA out of the cytoplasm to ribosomes

what does rRNA do

makes up ribosomes

what does tRNA do

carries amino acids to ribosomes during protein synthesis

What is transcription?

The process of creating an RNA copy of a DNA sequence

steps of transcription

1. RNA polymerase bonds to DNA

2. DNA strands separate

3. RNA polymerase adds complementary RNA nucleotides

4. RNA transcript is released

what are introns

non coding regions of RNA (removed)

what are exons

coding regions of RNA (kept and put together)

what is translation

the process of protein synthesis using the genetic code in mRNA

mRNA during translation

binds to ribosome and carries the message

tRNA during translation

bring amino acids to ribosome and pairs with codons on mRNA

when does translation stop

When it reaches a stop codon

what are codons

3 nucleotides that specify amino acids

what are (gene) mutations

changes in DNA sequence

substitution mutation

one base is replaced by another (little or no change)

insertion mutation

addition of one or more nucleotides

deletion mutation

loss of one or more nucleotides

silent mutation

no change in amino acid (substitution)

missense mutation

changes one amino acid (substitution)

nonsense mutation

creates a premature stop codon

frameshift mutation

alter the reading frame (insertion or deletion)

what causes mutations

errors during DNA replication or mutagens (chemical/physical agents that increase mutation rate)