Unit 2, Module 1 - Cellular Control Flashcards Preview

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Flashcards in Unit 2, Module 1 - Cellular Control Deck (16):

What do genes do?

They code for one or more polypeptides.


What are some examples of polypeptides that genes code for?

Structural proteins
Cell surface receptors


How many genes are there in the human genome?

About 25000.


Where are genes situated in humans?

Mostly on the linear chromosomes within the nucleus.
A few are in the mitochondria.


What characteristics does the genetic code have?

It is a triplet code.
It is a degenerate code.
Some codes don't correspond to an amino acid but for 'stop'.
It is widespread but not universal.


What is meant by triplet code?

A sequence of three nucleotide bases codes for an amino acid.


What is meant by degenerate code?

All amino acids except methionine have more that one code.


Why is the sequence of amino acids in a protein critical?

It forms the primary structure of the protein.
The primary structure determines the tertiary structure.
The tertiary structure is what allows a protein to function.
If the tertiary structure is altered, the protein can no longer function.


How does cyclic AMP activate some proteins?

It changes their 3D shape so that their shape is a better fit to their complementary molecules.


Where does translation happen in prokaryotes?

As soon as some mRNA has been made in the cytoplasm.


What are the main classes of DNA mutations?

Point mutations in which on base pair replaces another.
Insertion/deletion mutations in which one or more nucleotide pairs are inserted or deleted from a length of DNA. Causes a frameshift.


What can point mutations cause?

Missense - mutation causes change in amino acid.
Nonsense - mutation truncates polypeptide.
Silent mutation - still codes for same amino acid.
Frameshift - insertion/deletion changes from that point.


What are some genetic diseases caused by a DNA mutation?

Sickle-cell anaemia
Cystic fibrosis.


What mutation often causes cystic fibrosis?

Deletion of a triplet of base pairs


What mutation in sickle-cell anaemia caused by?

Point mutation on codon 6 of the gene for the beta-polypeptide chains of haemoglobin.


Why might a mutation cause no change to the organism?

The mutation is in a non-coding region of the DNA.
It is a silent mutation.