DNA EXAM PT. 4 Flashcards
Describe histones and supercoiling, and how their processes work.
Histones are small and simple proteins that are strongly positively charged.
This means that the negatively charged backbone of DNA is attracted to them, so the DNA wraps around histone after histone and is arranged in a tight ‘hairpin’ arrangement.
This is then arranged in a larger arrangement, in a process called supercoiling, effectively packaging the DNA into chromosomes.
Why are histones so important for gene expression?
It is the histone package that allows the transcription factors involved to access the DNA, so this directly affects the expression of genes.
Normally, the DNA is supercoiled, but at times, mainly during cell replication by mitosis or meiosis, it is necessary for the coiled strands of DNA to be even more tightly coiled, forming the bunched up chromosomes that are then easier e for cell division.
What are telomeres?
Each chromosome is a single long chain of DNA with the histones that support this double strand. Each chromosome is tipped by telomeres, which help prevent degradation of the chromosome but forming ‘caps’ on the DNA strands.
What is transcription?
Transcription occurs when the two DNA strands in a gene that codes for a protein, unzip from each other.
Similar to the way DNA replicates itself, a single strand of mRNA is then made by pairing up mRNA bases with the exposed DNA nucleotide bases, using the enzyme RNA polymerase.
The completed mRNA molecule detaches from the DNA strand and moves out of the nucleus through the nuclear pores into the cytoplasm of the cell.
What is translation?
After transcription, in the cytoplasm, ribosomes now attach themselves to the mRNA.
In the ribosome, the mRNA code is translated into tRNA code which is then transferred into a protein sequence.
In this process, each set of 3 mRNA bases (called a codon) will pair with a complimentary tRNA base triplet (called an anticodon).
Each tRNA is specific to an amino acid. As tRNAs are added to the sequence, amino acids are linked together by peptide bonds, eventually forming a protein that is later release by the tRNA.
After the process of transcription and translation are complete, we are let with a protein that consists of the chain:
Aspartic acid - Leucine
What is a codon?
A set of 3 mRNA bases that pair up with a complimentary tRNA base triplet
What is an anticodon?
A complimentary tRNA base triplet that pairs up with a codon
In terms of an error in genetic code, what can cause sickle cell anaemia?
An alteration of one nucleotide in the gene for the synthesis of the beta chain of the protein haemoglobin.
The beta chain consists of 147 amino acids and the alteration to the nucleotide only affects one of these amino acids, but that is enough.
The error cause red blood cells to become deformed and rigid. These cells do not carry oxygen effectively and lack the flexibility needed for red blood cells to flow through capillaries. This can clog and cut off blood flow to different tissues, inflicting intense pain.
The average cell is around …….. across, but that cell contains DNA that is over a …… In length
The average cell is around 6 micrometres across, but that cell contains DNA that is over a metre In length
Describe histones and supercoiling, and how their processes work.
Histones are small and simple proteins that are strongly positively charged.
This means that the negatively charged backbone of DNA is attracted to them, so the DNA wraps around histone after histone and is arranged in a tight ‘hairpin’ arrangement.
This is then arranged in a larger arrangement, in a process called supercoiling, effectively packaging the DNA into chromosomes.
Why are histones so important for gene expression?
It is the histone package that allows the transcription factors involved to access the DNA, so this directly affects the expression of genes.
Normally, the DNA is supercoiled, but at times, mainly during cell replication by mitosis or meiosis, it is necessary for the coiled strands of DNA to be even more tightly coiled, forming the bunched up chromosomes that are then easier e for cell division.
What are telomeres?
Each chromosome is a single long chain of DNA with the histones that support this double strand. Each chromosome is tipped by telomeres, which help prevent degradation of the chromosome but forming ‘caps’ on the DNA strands.
What is transcription?
Transcription occurs when the two DNA strands in a gene that codes for a protein, unzip from each other.
Similar to the way DNA replicates itself, a single strand of mRNA is then made by pairing up mRNA bases with the exposed DNA nucleotide bases, using the enzyme RNA polymerase.
The completed mRNA molecule detaches from the DNA strand and moves out of the nucleus through the nuclear pores into the cytoplasm of the cell.
What is translation?
After transcription, in the cytoplasm, ribosomes now attach themselves to the mRNA.
In the ribosome, the mRNA code is translated into tRNA code which is then transferred into a protein sequence.
In this process, each set of 3 mRNA bases (called a codon) will pair with a complimentary tRNA base triplet (called an anticodon).
Each tRNA is specific to an amino acid. As tRNAs are added to the sequence, amino acids are linked together by peptide bonds, eventually forming a protein that is later release by the tRNA.
After the process of transcription and translation are complete, we are let with a protein that consists of the chain:
Aspartic acid - Leucine
What is a codon?
A set of 3 mRNA bases that pair up with a complimentary tRNA base triplet
