Ch. 12 Flashcards
When does DNA replicate?
S phase
DNA replication
When the DNA in the chromosomes is copied
What direction do the phosphate/sugar backbones go?
Anti-parallel, p=5 s=3
How are hydrogen bonds broken?
Enzymes
Why does the replication go in a different direction than the original strand?
The new strand starts at 5’, but it is a the 3’ of the old strand
Leading strand
Strand that DNA is copied on (natural flow)
Lagging strand
Unnatural flow of DNA that has to be copied in fragments
What are the lagging fragments called?
Okazaki fragments
DNA polymerase
Attaches the new nucleotides to its complementary base by hydrogen bonds
What contains the info in DNA?
The sequence of nucleotides
How is the information put to work?
Through the production of proteins
What controls all the chemical reactions of an organism?
Enzymes
What controls us?
DNA
What do amino acids create?
Proteins
Proteins
Long polymers
Polymers
Chains composed of amino acids
What determines the shape of proteins?
The order of the amino acids
What determines the action of the proteins?
The shape of the proteins
What is the sequence of DNA?
DNA, RNA, protein
What is RNA?
Nucleic acid
How does RNA differ from DNA?
- Different sugars
- Single stranded
- Contains uracil
What kind of sugar does DNA have?
Deoxyribose
ATGC
What contains the instructions for making proteins?
DNA
Is DNA allowed to leave the nucleus?
NO
How many proteins do ribosomes make at a time?
One
How do we get specific directions to the ribosomes outside the nucleus?
mRNA
What does mRNA take from DNA?
Instructions on how the protein should be assembled
When can the ribosomes assemble the protein?
When the ribosome has the mRNA instructions
What are the three types of RNA?
- mRNA
- rRNA
- tRNA
mRNA
Brings instructions from the DNA in the nucleus to the cytoplasm
rRNA
Binds to the mRNA and uses the instructions to assemble the amino acids in the correct order (does the work)
tRNA
Delivers amino acids to the ribosome to be assembled into a protein (the supplier)
Transcription
When enzymes make an RNA copy of a portion of a DNA strand
What is the difference between transcription and DNA replication?
Transcription=one strand RNA molecule
DNA molecule=double stranded
Introns
Long non coding nucleotide sequences
Exons
Regions that contain info
When mRNA is transcribed what happens to the introns/exons?
They are copied
What must happen to the introns before it can function to make a protein?
They must be removed
What are proteins?
Chain of amino acids
Codon
Group of 3 nitrogenous bases
How many different combinations of codons are there?
64
Translation
The process of converting the information in a sequence of nitrogenous bases in mRNA into amino acids
Where does translation take place?
Ribosomes
During translation what do ribosomes attach to?
mRNA
How are proteins built?
The amino acids must be brought to the proteins
What does tRNA molecules attach to?
One type of amino acids
What is the first codon in mRNA?
AUG
What does AUG do?
Signals the start of protein synthesis
After bonding the first tRNA what does the ribosome do?
Slides to the next codon
Peptide bond
Holds the amino acids together
When is the ribosomes job done?
When it reaches the stop codon
What are the chains called that will become proteins?
Polypeptide
Mutations
Changes in the DNA sequence that affect genetic information
Gene mutations
Affect a single gene
What are the two types of gene mutations?
- Gene mutations
2. Chromosomal mutations
Chromosomal mutation
Affect a whole chromosome
What are gene mutations usually called?
Point mutations
What do point mutations consist of?
- Substitution
- Insertions/additions
- Deletions
Substitution
One base is changed to another base
Will a substitution always result in the wrong amino acid?
NO
Do different amino acids result in a different protein?
Not always, it depends on the chemical properties
What do addition or deletion mutations result in?
Frame shift mutations
Are frame shift mutations drajstic?
YES
What are the 4 chromosomal mutations?
- Deletion
- Duplication
- Inversion
- Translocation
Inversion
Reverses the direction
Translocation
Part of one chromosome breaks off and reattaches to another chromosome
Nondisjunction
A homologous pair fails to separate during meiosis, where two cells have one less chromosome and two have one more chromosome
What is an example of nondisjunction?
- Down syndrome
2. Kinfelter syndrome
Kinfelter syndrome
2x chromosomes, male with feminine qualities
How do we get mutations?
- Spontaneous
2. The environment
Mutagens
Any agent that can cause a change in DNA
What are some mutagens?
- Radiation
- Chemicals
- High temperatures
- Infectious agents
What usually causes substitution mutations?
Chemical mutagens
The breaking and reforming of a double stranded DNA molecule can lead to what?
Deletions
What proofreads DNA and replace incorrect nucleotides with correct nucleotides?
Enzymes