Chapter 13 - The Code For Life Flashcards
What is DNA short for?
DNA is short for Deoxyribonucleic Acid
How many DNA molecules are found in the nuclei of human cells?
46 DNA molecules
Explain the structure of DNA
- DNA strands are bound to special proteins called histones
- In a cell that is NOT dividing, the coiled DNA forms a tangled network called Chromatin.
- When a cell is about to divide, the coiled chromatin becomes even more coiled to become chromosomes (X,Y).
- Sections of the DNA strands make up genes.
- Genes contain the genetic code which is stored information that determines the structure and activities of the cell.
What is a Nucleotide?
There are two strands of alternating nucleotides that make up the double helix structure of DNA. These nucleotides have cross-links that correspond with the nucleotide directly opposite them.
- Phosphate group
- sugar molecule (deoxyribose)
- Nitrogenous base
There are four different nitrogen bases ;
1. Adenine & thymine
2. Guanine & cytosine
There is a weak hydrogen bond that connects the of the pairs.
The average length of the DNA molecule that makes up a human chromosome is about 140 billion base pairs.
Why is replication of DNA so important?
So that inherited information that is passed on remains unchanged when the cell reproduces. This is possible because the two strands of DNA are separated by easily broken bonds between corresponding nucleotides.
What is protein synthesis
The genetic code in DNA provides the instructions for protein synthesis, which is the making of proteins within the cell. Some specific examples of proteins are ; - haemoglobin - actin & myosin - fibrin - collagen - amylase
What is a triplet?
A sequence of three bases (nucleotides) is the code for a particular amino acid.
What is transcription?
Transcription is the process by which the mRNA is formed using the code in a DNA molecule. The genetic instructions are copied (transcribed) from the DNA to the mRNA molecule.
Transcription is triggered by chemical messengers that enter the nucleus from the cytosol and bind to the DNA of the relevant gene. This causes an enzyme called RNA polymerase to make copies of the DNA to make a complimentary strand of mRNA.
Where is a T in DNA, there is a U in RNA.
At the end of the gene, a particular triplet of bases tells the RNA polymerase to stop copying, and as a result, gets released.
The strand that is copied is called the template strand. The mRNA strand is called the coding strand.
What is Translation?
The production of a protein using the information that is coded in the mRNA molecule.
The mRNA leaves the nucleus and enters the cytosol were it where a ribosome attaches to it and moves along the strand three bases (codons) at a time. The ribosome reads the strand and calls on tRNA to bring a particular amino acid. The amino acids join together by an energy bond to form a long line of polypeptides. A polypeptide can make up a protein.
The process of transcribing and translating the mRNA is called gene expression.
What is lipid and carbohydrate synthesis?
There are no genes that carry instructions for the manufacture of lipids or carbohydrates. However, the synthesis of these substances require the protein of enzyme. So indirectly, gene expression has a role in the synthesis of lipids and carbohydrates.
What are 2 important differences between nuclear DNA and mitochondrial DNA?
- Nuclear DNA is in the form of very long strands that bound to proteins, known as histones. mtDNA is in the form of small circular molecules that are not bound to proteins. There are about 5 to 10 of these molecules in each mitochondrion.
- Each molecule of mtDNA only has 37 genes, all of which are essential for the mitochondria. Rare diseases can be caused by mutations in mtDNA.
What are Epigenetics?
Epigenetics are changes in gene expression. That result from mechanisms other than changes in genes. This means that the environment someone is exposed to has a huge effect on gene expression and inherited factors.
What is the difference between a genome and an epigenome?
A genome is the hereditary information encoded in their DNA.
An epigenome is the sum of all factors that determine when, where and which genes are expressed.
