Summary Biochemistry Module Review notes

BIOCHEMISTRY REVIEW MODULE 1 2021 SOLUTIONS
DNA-

1. Located in nucleus
2. Double helix
3. Nucleic acid
4. Adenine/Guanine/Cytosine/Thymine
5. A-T/C-G pairing
6. Duplicates itself and passes on to generation to generation
7. Contains 46 chromosomes (23 pairs from mother and father)
8. Stores and transmits-chemicals and traits
RNA-

1. Carries important info from DNA to the body (Transcription)
2. Used to make proteins (Translation)
3. Single stranded
4. 3 types of RNA (mRNA- messenger contains codons, rRNA-ribosomal contains 2 subunits and
tRNA- transfer amino acid with end codon)
5. mRNA- Adenine/Guanine/Cytosine/Uracil
6. A-U/C-G pairing
Central Dogma- replication of DNA process= DNA- transcription- RNA- translation- Protein
Steps of DNA replication-
1. DNA must be separated


individual nucleotides and matches them up to the parental sequences to ensure a correct
pair.
• DNA polymerase does not start synthesis of a new strand, it must bind with a RNA primer
• RNA primer is synthesized by RNA polymerase

Genes- encoded with information/ small segment of DNA

1. Gene Expression- the ability to turn genes on and off
2. Epigenetics- packaging of DNA: DNA wrapped around histones to make nucleosomes
Wide spread nucleosomes=genes ON (i.e. a dance floor-more space you can get your
dance ON)
• Tightly packed nucleosomes = genes OFF
• Environment can change genetics in generations

,Genetic sequence- 5’(phosphate)- 3’ (sugar)
Non-Complementary
Coding Strand: non-template
Coding Strand: mRNA (identical)

Complementary
mRNA: tRNA/non-coding strand:mRNA
Ex: 5’ ATG AGT CTC TCT 3’
Template strand: 3’ TAC TCA GAG AGA 5’
mRNA sequence: 5’ AUG AGU CUC UCU 3’
Protein Sequence-

1. Used in mRNA form only from 5’ – 3’ for the chart
2. Mutations are found from the protein sequence
Splicing- introns are cut out and the remainging exons are joined together
Protein Mutations-

POINT MUTATIONS

Nonsense- 1. change in 1 nucleotide produces a STOP (found on the mRNA amino acid chart)
Silent- 2. Change in 1 nucleotide but does not change amino acid
3. Missense- Change in 1 nucleotide leads to coding a new amino acid
DOUBLE STRANDED BREAKS
1. Environmental (i.e. x-rays) discontinuity through both strands (double strand break)
FRAMESHIFT MUTATIONS- nucleotide-codon pattern gets “out of sync “

1. Insertion- changes in the amino acid and can lead to formation of STOP (chain can be longer)
2. Deletion- deletion of nucleotide (chain is shorter) #’s not divisible by 3 (ATG CGC CG)
Mutation Repairs-

1. Base excision repair (BER): Chemical damage to a single nucleotide. The single nucleotide is
removed (excised) by enzymes and replaced by DNA polymerase.
Example of damage: Rogue oxygen attaches to a nucleotide; this is what antioxidants try to
protect us from. Eat your blueberries!

1 Nucleotide excision repair (NER): Chemical or radiation damage to two or more nucleotides. A
large section of nucleotides is removed, including the damage and nucleotides around it, and
replaced by DNA polymerase. Example of damage: UV radiation causes two thymines (T’s) to
clump together. These are called thymine-thymine (T-T) dimers.

1 Mismatch repair (MMR): During replication, DNA polymerase can usually proofread to make
sure it has the made the correct match, but sometimes a mismatch
still gets through. When this happens, mismatch repair removes a large section of

, nucleotides, including the mismatch, from the newly replicated DNA, and then DNA
polymerase tries again. Example of damage: A

C is put across from T instead of A.

1 Homologous recombination (HR): This is one of two types of repair for double-strand breaks
(DNA is literally cut in half). The break is repaired by using the replicated copy of the DNA (the
homologous DNA) to “recombine” with the broken copy so that the DNA is copied back
correctly. Example of damage: Cosmic radiation can cause double-strand breaks in
astronaut’s DNA.

1 Non-homologous end-joining (NHEJ): This is the second type of repair for double-strand
breaks. If a break occurs before the DNA is replicated, the break is pasted back together
instead. Because the break can be uneven, nucleotides may be removed (deleted) to make
the ends even so they can be stuck together. A deletion can result in a frameshift mutation,
but that is a risk our cells are willing to take because the damage from a break is a lot worse.

Inheritance- Genotype- pair of genes Phenotype- physical characteristics
Inheritance patterns- Using Punnett Square

1. Complete Dominance- 3/4 (i.e black and white puppies make 3 black puppies and 1 white)
2. Incomplete Dominance- grey area (i.e. black and white puppies makes grey puppy)
3. Co-Dominance- 2/2 (i.e. black and white puppies make 2 black puppies and 2 white puppies)
4. Sex-Linked- X-linked traits-largely in males
Pedigree-

1. Carrier parents- Recessive trait (2 parents unaffected with affected offspring)
2. Autosomal - Males and females equally affected
3. Sex-Linked- Males affected >females affected
4. Non-carrier parents- Dominate trait
PCR- Polymerase Chain Reaction (occurs in the lab- copies a chosen segment of DNA)
PCR can be used for genetic testing or forensic testing
PCR reaction:

1. Template DNA (patient cells)
2. dNTPs (nucleotides)
3. DNA polymerase- works well at 70 degrees Celsius
4. DNA primer
5. TAQ polymerase-stable at high temps
3 Major Stage of PCR

1. Denaturation- heat DNA to 95 degrees Celsius to separate DNA strands
2. Annealing- cooled to 50 degrees Celsius (Primers will stick to area to copy on DNA to provide 3’-
end of DNA polymerase)