rDNA, protein synthesis, and gene mutation

DNA function

• Stores genetic info and transmits genetic info

• Protein synthesis

• DNA replication

• Gene mutation

DNA structure

• double helix, unwinds like a ladder

• Monomer is a nucleotide

• sugar phosphate back bone→ deoxyribose

• Double stranded

• Parts of a nucleotide

• 5 carbon sugar, nitrogenous base, phosphate group

Types of nitrogenous bases in DNA

• Adenine- 2 rings

• Guanine- 2 rings

• Cytosine- 1 ring

• Thymine- 1 ring

RNA nitrogenous bases

-Adenine

-Guanine

-Cytosine

-Uracil

RNA structure

• single stranded

• No helix

• Sugar phosphate backbone→ ribose

• Monomer is nucleotide

Adenosine triphosphate

• Adenosine = ribose + adenine

• Cells main form of energy

• Made in the mitochondria

  • Chemical rxn turning chemicals from food into useable energy (ATP)

Complimentary base pairing

• Each nitrogenous base has its respected pair; hydrogen bonded

• In DNA replication, free roaming nucleotides form H-bonds w/ the template strands nitrogenous bases

DNA

A-T

C-G

RNA

C-G

A-U

DNA replication stages

1. unzipping the double helix

2. Complimentary base pairing

3. Joining adjacent nucleotides

Unzipping double helix

Stage 1 of DNA replication

• The helix unwinds into a ladder

• DNA helicase moves the molecule along to continue unzipping while it breaks H-bonds between nitrogenous bases

joining adjacent nucleotides

Stage 3 of DNA replication

• DNA polymerase catalyzes the formation of the sugar phosphate backbone of the NEW strand through dehydration synthesis

Semi conservative DNA replication

When DNA is replicated, one strand of DNA is new and the other comes from the original/parental strand

Gene mutations

• Change in the DNA sequence that makes a gene that differs than what found in most people

• There are 2 types of gene mutation

  • Frameshift mutations

  • Point mutations

• 300+ diseases due to the change/error in one

Frameshift mutation

• most common type of mutation

• A nucleotide is either added to or deleted from DNA causing a shift in the sequence

  • Ex. Original: THE CAT BIT THE DOG→A gets removed→THE CTB ITT HED OG

Point mutations

• a change in a single nucleotide resulting in a change in a codon

• 3 types of mutations:

  • Silent mutation: one base is substituted for another but doesn’t change the result

  • Nonsense mutation: one base is substituted for another resulting in a premature stop codon

  • Mis-sense mutation: one base is substituted for another resulting in a completely different amino acid→changes the shape and function of the protein

Sickle cell anemia

Blood disorder due to a mis-sense mutation where valine (GUG) appears in a sequence of hemoglobin instead of glutamate (GAG) causing hemoglobin to pile up in a sickle shape which clogs vessels

• Hemorrhaging→pain of internal organs and joints

• Punctuated periodic attacks

Sickle cell disease is resistant to malaria

Mutagens

Physical or chemical agents that change DNA and increases the chances of a gene mutation

• Radiation and x-rays

• UV rays

• Organic factors (smoke and pesticides)

• Radioactive elements

Prevention of gene mutations (cancer)

• Don’t sunbathe- exposure to UV rays which may cause skin cancer

• Avoid obesity- colon, breast, and uterine cancer

• Get regular check ups- ensures that you know of your bodies current state and allows you to catch risks and disease early on

• Have foods high in vit. A and C- prevents formations of free radicals which can affect DNA

• Beware of hormone therapy- estrogen therapy to control menopausal symptoms increases chances of endometrial cancer

BRCA gene

gene that everyone has that is used to protect you from breast and ovarian cancer

BRCA gene mutation

• when the BRCA gene gets mutated, you risk of breast cancer goes up to about 65%

• Ovarian cancer risk from 1% to as high as 40%

• We can prevent breast cancer with a mastectomy

Mastectomy

• breast cancer prevention procedure

• cuts off the breast (tissue) removing the breast cancer removing the breast cancer

• With this procedure and the BRCA gene mutation, the risk goes down to less that 5%

Gene

• segment of DNA that determines amino acids

• Doesn’t directly control protein synthesis but transfers genetic information to RNA which then passes on the info to make proteins

• DNA→RNA→Protein

classes of RNA

1. Messenger RNA- mRNA

2. Ribosomal RNA- rRNA

3. Transfer RNA- tRNA

Phenotype

Traits that are observable and expressed because of the interaction between the genotype and the environment

Transcription and translation

What is needed for a gene to be expressed

Essential in creating proteins

Transcription

• process that results in the production of mRNA

• DNA helix unzips and unwinds

• Complementary RNA nucleotides pair with the template DNA strand and are connected by RNA polymerase

• DNA→RNA

mRNA

• Complimentary to strand of DNA→sequence of codons complimentary to DNA triplet code

  • If DNA has “ATG” mRNA has “UAC”

• Transfers genetic information

• Sequence of mRNA specifies the order of amino acids in protein and determines which tRNA-amino acid complex attaches

Introns vs exons

Introns: DNA sequences that do not code for a gene and aren’t needed when a mRNA copy is made

Exons: portions of DNA sequences that are expressed and result in proteins

Ribozymes

organic catalysts made of RNA that splice introns from mRNA so that only exons remain

• Ex. jdhwidbetableidejejdojdwi

Translation

• RNA→ Protein

• Occurs in ribosome

• tRNA drops of an amino acid one at a time

3 main steps:

1. Chain initiation

2. Chain elongation

3. Chain termination

tRNA

• Single stranded nucleic acid that folds around itself

• Transfers amino acids to ribosomes

• When the tRNA attached to an amino acid arrives at the ribosome, the anticodon pairs with the mRNA codon

  • If the codon was GAA, the anticodon on the tRNA would be CUU

Anticodon

Group of the bases complimentary rona codon of mRNA

Chain initiation

• mRNA and tRNA come together

• Small ribosomal unit attaches to the initiator tRNA

• tRNA anticodon brings in methionine and complimentary base pairs with the mRNA codon which is between the subunits of the ribosome

Chain elongation

The ribosome moves along the mRNA while complimentary base pairing with each codon it comes across, thus is called translocation

Chain termination

The ribosome reaches a stop codon on the mRNA and the mRNA strand detaches through hydrolysis

Chromosome vs gene

A gene is a section of DNA that codes for specific proteins and RNA while chromosomes are thread like structure that are made up of DNA and proteins that carries the genes

Cystic fibrosis

A gene mutation that is inherited causing a thick mucus the be produced and affect the lungs, digestive system, and other organs

Importance of mutation

Mutation are important because the allow diversity and evolution. If we didn’t have mutations, everyone would look the same and we would have no variations. Mutations also allow us to continue to evolve so we can keep adapting to our environments which is essential for survival (palmaris longus). If we didn’t have mutations, we would also all die from the same disease, because if we were all exact copies of each other, if one of us had a gene mutation like the BRCA gene mutation, that would mean everyone else does as well increasing everyone chance of breast cancer and women’s chances of ovarian cancer

Protein synthesis

Protein synthesis is the process of building proteins which follows 2 main steps, transcription and translation.

rRNA

• Ribosomal RNA found in the nucleus used to create ribosomes

• Joined with proteins in the nucleolus to form 2 ribosomal subunits

• After subunits are made, they exit the nucleus and go into the cytoplasm

  • The ribosome has b8ndung sites for 2 tRNA molecules and an mRNA strand