chapter 16 & 17 Flashcards
what is the molecule of heredity?
DNA
when does DNA replication occurs?
During S-phase of the cell cycle
what enzymes are involved in DNA replication?
DNA polymerase, Helicase
where in the cell does DNA replication occur?
in the nucleus
what is RNA splicing?
introns removed; exons spliced together
What is an intron?
non coding regions
what is an exon?
coding regions
what is a mutation?
a change in the DNA
what is a point mutation?
change in single nucleotide pair in a gene
how are mutations caused?
spontaneously or by radiation / chemical substances (mutagens)
silent mutation
the amino acid that the wild type coded for is the same amino acid that resulted from the mutation, therefore the mutation is silent
missense mutation
a mutation that causes an amino acid to be changed to a different amino acid
ex: Met-Ser-Lys-His
Met-Leu-Lys-His
nonsense mutation
a mutation in DNA that replaces a codon that codes for an amino acid with a codon that codes for a stop codon
insertion mutation
this mutation adds a nucleotide in the genetic sequence changed the genetic code for all the triplets following after that
deletion mutation
this mutation causes the deletion of a nucleotide in the genetic sequence therefore changed the genetic code for all the triplets following after that
frameshift mutation
the addition or deletion of one or more bases(nucleotides) that changes the genetic code for all triplets following after that
what type of mutation causes sickle-cell disease?
Point mutation: Missense mutation
Describe transcription in eukaryotic cells
-transcription is taking DNA to make RNA
transcription steps
1. Initiation:
- Transcription factors and an RNA polymerase binds to the TATA box AKA the promoter
- RNA transcript starts at the template strand (3’ to 5’ AKA bottom strand of DNA)
- the RNA polymerase reads the DNA and makes mRNA
- Elongation:
-The two DNA starts separating due to the RNA polymerase
- As the RNA polymerase starts reading the DNA strand it starts adding nucleotides to the template strand making an RNA strand (makes a copy of the non-template strand) - Termination:
- Polyadenylation signal (row of adenine signal sequence) causes the RNA transcripted to be cut free from RNA polymerase
How do eukaryotic cells process RNAs after transcription?
By RNA splicing:
-meaning introns are removed (non-coding regions) and exons (coding regions) are spliced together
-and the end result is a RNA with a 5’ cap (sequence of guanine added to the start), the coding segments (exons), and the poly-A tail (50-250 adenines added to the end)
What are some characteristics of the genetic code?
- its redundant AKA repetitive
- no ambiguity; two or more codons could code for the same thing. alone 4 codons are truly unique (start and stop codons)
- nearly universal; almost every organism uses the same code
What are the three types of RNA?
-mRNA: Messenger RNA
-tRNA:
-rRNA:
What are the steps of Initiation in translation?
Initiation:
-translation occurs in ribosomes on the cytoplasm
-the mRNA the ribosome at the binding site, and then later attaches an initiator tRNA codon to the small subunit that scans for the start codon (AUG)
-Large subunit then binds forming translation initiation complex
- GTP hydrolysis provides the energy for assembly
what are the steps of elongation in translation?
-There’re 3 steps cycle
1. Codon recognition:
- we start with a polypeptide already attached to the tRNA on the P site of the enzyme complex
- Anticodon of incoming tRNA binds with mRNA codon in A site
2. Peptide bond formation:
-Amino acids connected by peptide bond- catalyzed by tRNA of large subunit
- polypeptide chain moves from P sit to A site
3. Translocation:
-ribosome moves:
-A site: becomes empty
-P site: growing chain
-E site: used tRNA exits and reloaded
What are the steps of termination in translation?
- ribosome reaches a stop codon on mRNA. A site accepts release factor
- Release factor promotes hydrolysis, freeing polypeptide
- ribosomal subunits and other components dissociate
