The structure of DNA, the four bases and how they pair, transcription and translation, and what mutations do. Mostly Biology only content.
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1.What is DNA?
The polymer that makes up chromosomes and carries the genetic code. It is made of two strands forming a double helix.
2.What is a gene?
A small section of DNA on a chromosome that codes for a particular sequence of amino acids, and so for a specific protein.
3.What is the genome of an organism?
The entire genetic material of that organism.
4.Give three reasons studying the human genome is important.
It helps in the search for genes linked to disease, in understanding and treating inherited disorders, and in tracing human migration patterns from the past.
5.What is DNA made of?
Repeating units called nucleotides, each made of a sugar, a phosphate group and one of four bases.
6.Name the four bases in DNA.
A, C, G and T.
7.How do the bases pair up?
A always pairs with T, and C always pairs with G. This is complementary base pairing.
8.How many bases code for one amino acid?
Three. A sequence of three bases is called a codon or triplet.
9.What determines which protein is made?
The order of the bases in the gene, which determines the order of the amino acids in the protein.
10.What is a polymer?
A large molecule made of many small repeating units joined together.
11.Where does transcription happen and what is produced?
In the nucleus. A template of the gene is copied to produce a molecule of mRNA.
12.Why is mRNA needed?
DNA cannot leave the nucleus, so a copy is made that can travel out to the ribosomes.
13.Where does translation happen?
At the ribosomes in the cytoplasm.
14.Describe translation.
The mRNA passes through the ribosome, carrier molecules bring the matching amino acids in the order coded for, and the amino acids are joined into a chain.
15.What happens to the chain of amino acids once complete?
It folds into a unique three dimensional shape, which determines how the protein works.
16.Name three types of protein and give their roles.
Enzymes act as catalysts, hormones act as chemical messengers, and structural proteins such as collagen give strength.
17.What is a mutation?
A random change in the sequence of bases in DNA.
18.Do all mutations change the protein?
No. Most have no effect at all, because several triplets code for the same amino acid.
19.When does a mutation have a significant effect?
When it changes the shape of the protein, for example altering the active site of an enzyme so the substrate no longer fits.
20.What effect can a mutation have in a non-coding region?
It can alter how genes are switched on and off, so it may change how much of a protein is produced.
21.What are the three types of mutation?
Insertion, deletion and substitution of a base.
22.Why is an insertion or deletion often more serious than a substitution?
It shifts every triplet after it, so all the amino acids from that point change, producing a very different protein.
23.How does a mutation in a structural protein cause problems?
It changes the shape and so the strength of the protein, for example weakening collagen in connective tissue.
24.What causes mutations?
They occur continuously and at random, and their frequency can be increased by radiation or by certain chemicals.
25.Why is complementary base pairing important?
It allows DNA to be copied accurately, because each strand acts as a template for the other.
26.If one strand reads ACGT, what does the complementary strand read?
TGCA.
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