Biology written exam part 2 Flashcards
(50 cards)
Hows does DNA replication start?
It starts by the uncoiling of the DNA double helix by the enzyme helicase, which breakes the hydrogen bonds between the nuclotides (seperates the 2 template strands)
Whats the function of RNA primase in DNA replication?
RNA primase adds after the 2 template strands are separated short sequences of RNA to the template strands. These short short sequences are primers which allows the DNA polymerase III to bind to the strands and start the replication process. Then DNA polymerase III adds nucleotides to each template strand in a 5’ -> 3’ direction
Whats the function of DNA polymerase III in DNA replication?
DNA polymerase III to bind to the strands and start the replication process (occurs afterRNA primase). Then DNA polymerase III adds nucleotides to each template strand in a 5’ -> 3’ direction
The work tasks of polymerase III of the leasing and lagging strand in DNA replication?
Leading strand only need one primer and DNA polymerase III. While the lagging strand, forms small fragments, called Okazaki fragments (in Eukaryotes).
Whats the function of DNA polymerase I in DNA replication?
DNA polymerase I will remove the RNA primers, and replace them with DNA, the enzyme DNA ligase then joins the Okazaki fragments together to form a continuous strand (in Eukaryotes).
Describe an RNA
- only one strans
- composed of adenine, cytosine, guanina and urasil
- the sugar is ribose
Coding amino acids in DNA: what does it depend on? Codon? translation?
- The coding for amino acids depend on the sequence of the nucleotides
- The nucleotide arrangement determines the codon of the t-rna in translation.
- 3 nucleotides form one codon
- Depending on in which arrangement the nucleotides are place, different amino acids can be formed when the mRNA sequence is translated.
What is produced during transcription?
mRNA
What is the promoto in transcription?
The promoter basically “tells” the RNA polymerase where to start the transcription process.
How is transcription initiated?
Transcription is initiated with the binding of RNA polymerase to the promoter site. The RNA polymerase then uncoils the DNA and separates the two strands. One of the strands is used as the template strand for transcription.
How are the free nucleotides bond to the template strand in transcription?
by complementary base pairing
Is thymine used as a nucleotide in transcription?
No, urasil is used cause you are producing a mRNA
What are the steps of translation?
Initiation, Elongation, Translocation and Termination
In which part of the cell occurs replication?
In the nucleus
In which art of the cell occurs transcription?
In the nucleus
In which art of the cell occurs translation?
In the cytoplasm
How does translation start?
It starts off with the tRNA containing the matching anticodon for the start codon AUG binding to the small subunit of the ribosome. This tRNA carries the amino acid methionine and is always the first tRNA to bind to the P site.
Outline the structure of the ribosome in translation
They have 2 subunits, one large and one small. On the surface of the ribosome there are 3 sites which tRNA can bind to. However, not more than 2 tRNA molecules can bind to the ribosome at one time. Also there is a site on the surface of the ribosome to which mRNA can bind to.
What kind of bond is formed between the amino acids in translation?
peptide bond
How does translation end?
Once the ribosome reaches the stop codon on the mRNA translation will end as no tRNA will have a matching anticodon to the stop codon.
What is formed in translation?
A polypeptide
What are polysomes?
Many ribosomes can translate the same mRNA at the same time. They will all move along the mRNA in a 5’→3’ direction. These groups of ribosomes on a single mRNA are called polysomes.
What is spermatogenisis?
the process of the production of spermatozoa (sperm) in seminiferous tubules of the testes
What does the first stage of spermatogenesis requitre?
the division of germline epithelium by mitosis
