Ch. 10 Vocab - Bio

Molecular biology

Molecular biology

• the field of biology that studies the composition, structure and interactions of cellular molecules – such as nucleic acids and proteins – that carry out the biological processes essential for the cell's functions and maintenance

Nucleotide

• monomer of nucleic acids

• structure:

  • 5 carbon sugar

  • Phosphate group

  • Nitrogenous base

Polynucleotide

• polymer

• several nucleotides in a chain

• DNA or RNA

Sugar-phosphate backbone

• The “backbones” of DNA are made of a sugar (deoxyribose) covalently bonded to a phosphate

• backbones connected to each other via nitro. bases in btwn

DNA

• carries genetic info

Thymine

• nitrogenous base T

• bonds w A

  • 2 hydrogen bonds

• single ring

Cytosine

• nitrogenous base C

• bonds w G

  • 3 hydrogen bonds

• single ring

Adenine

• nitrogenous base A

• bonds w T

  • 2 hydrogen bonds

• double ring

Guanine

• nitrogenous base G

• bonds w C

  • 3 hydrogen bonds

• double ring

Uracil

• nitrogenous base U for RNA

  • Would replace T

Double helix

• form of native DNA

• 2 adjacent polynucleotide strands interwound into a spiral shape

• antiparallel

Semiconservative model

• type of DNA replication in which the replicated double helix consists of 1 old strand (derived from the old molecule) and 1 newly made strand

DNA polymerase

• the builder

• large molecular complex that assembles DNA nucleotides into polynucleotides using a pre-exisiting strand of DNA as a template

• can only add nucleotides to the 3' end of a DNA strand

• Slides:

  • DNA builds the missing backbone using the bases on the old backbone as a template

  • proofreader

DNA ligase

• gluer

• an enzyme in DNA replication that catalyzes the covalent bonding of adjacent DNA strands

• joins Okazaki fragments together

purine

• 2 rings

• A + G

pyrimidine

• 1 ring

• T + C

Helicase

• unzipper

• breaks the H-bonds between the nitrogenous bases

Origin of replication

• sites where replication begins

  • Euk have multiple, pro have 1

Okazaki fragment

• short segment of DNA synthesized discontinuously in small segments in the 3’ direction to 5’ direction by DNA polymerase

• on the lagging strand

Leading strand

• the new DNA strand continuously synthesized along template strand toward the replication fork

• because the DNA polymerase is moving in the same direction as the replication fork (5’ → 3’)

Lagging strand

• discontinuously synthesized

• away from replication fork

  • on a 5’ to 3’ direction

3’ end

• hydroxyl group

5’ end

• phosphate group

transcription

• the transfer of genetic information from DNA into an RNA molecule 

  • DNA → RNA

Steps:

• Occurs in the cell’s nucleus

  • Enzymes unzip the molecule of DNA by breaking hydrogen bonds

  • Free RNA nucleotides base pair with 1 side of the DNA strand

  • EX: DNA strand ATGCTAG

  • The RNA nucleotides are linked together by the transcription enzyme, RNA polymerase

  • This mRNA (messenger RNA) breaks away as the DNA strands rejoin.

  • mRNA leaves the nucleus via nuclear pores and enters the cytoplasm

translation

• the transfer of information in the RNA into a protein

  • RNA → Protein

• Occurs in the ribosomes in the cytoplasm

Steps

• The strand of mRNA attaches to the ribosome

•  A tRNA molecule brings the first amino acid to the mRNA strand that is attached to the ribosome

• A tRNA anticodon pairs with the first mRNA codon temporarily

• AUG signals the start of protein production

• The ribosome slides along the mRNA to the next codon

• A new tRNA carrying an amino acid pairs with the second mRNA codon

• The first and second amino acids bond together in a peptide bond

• This process continues- joining amino acids until the ribosome reaches a stop codon on the mRNA strand

• The amino acid strand (now a protein) is released from the ribosome

Next…

• The chain of amino acids (polypeptide) folds in on itself and makes its 3D protein shape

• Now it’s a protein!

codon

• Set of 3 nucleotides that represent or code for 1 amino acid

  • ex. UUU, CUU, AAG

• 64 possible

• Stop codons = code for stopping the production of the protein

• Start codon = code for starting the production of the protein (AUG is the only start codon!!!!)

• More than 1 codon can code for the same amino acid BUT for any 1 codon, there can only be 1 amino acid

• This is a UNIVERSAL genetic code

genetic code

• The code for how a sequence of bases in DNA or RNA translates into the sequence of amino acids in a protein

RNA polymerase

• connect complimentary RNA bases to the DNA

  • these RNA bases are bonded together to form mRNA

    • (Single stranded)

mRNA

• Messenger RNA

• encodes genetic info from DNA and conveys it to ribosomes, where the info is translated into amino acid sequences

Intron

• noncoding region of DNA

exon

• coding region of DNA

RNA splicing

• removal of introns by enzymes in the mRNA (occurs in the nucleus)

tRNA

• Transfer RNA

• carry amino acid on them

• bring amino acids together to make proteins

  • in ribosome

• mRNA will direct which tRNAs come in/which amino acids are transferred

• looking for complimentary bases → find on mRNA → transfer amino acid

• reads codons. contains anticodon!

  • then transfers the amino acid it carries!

anticodon

• set of 3 nucleotides on tRNA that base pair with the codon

ribosome

• makes proteins

• reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins

start codon

• code for starting the production of the protein (AUG is the only start codon!!!!)

stop codon

• code for stopping the production of the protein

mutation

• somatic

  • Not passed on

• sex cell

  • passed on

• any change in DNA sequence of a protein

  • Types: point mutations, deletions, insertions

silent mutation

• the mutation doesn’t result in a change in the amino acid sequence

• typically in last letter of codon

missense mutation

• 1 amino acid in a protein sequence is changed to another one

nonsense mutation

• a mutation that results in a stop codon where there there used to be a codon for an amino acid

  • → translation stopped before the primary structure of the protein is complete

frameshift

• a mutation caused by an insertion or deletion

• → shifts the reading frame of the mRNA, resulting in a series of changed amino acids

  • better to happen near the end of a sequence!

point mutation

• a change in any single nucleotide of a DNA sequence

insertion

• 1+ nucleotides added to DNA sequence

deletion

• 1+ nucleotides removed from DNA sequence