Topic 6 Flashcards
What is DNA
A polymer made of two strands colied making a double helix. The polymers are made up of lots of repeating units called nucleotides
What is a gene
A small section of DNA found on chromosomes, each codes for a particular sequence (what order) of amino acids which are put together to make a specific protein. Only 20 amino acid are used.
What is a genome
Entire set of genetic material in an organism.
Hhy is understanding the human genome important
Allows scientists to identify links to different diseases (which ones are inherited). It can also trace migration
What does each nucleotide consist of
A sugar, a phosphate group and one ‘base’. These form a backbone to the DNA strands. They are complementary bases with C-G or A-T which decides the order of amino acids. Each amino acid is coded for by a sequence of three bases in the gene.
What is mRNA and ribosomes effect of protein synthesis
Molecule which gets code from DNA to ribosomes. Proteins are synthesised on ribosomes, according to a template. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.
Functions of protiens
Enzymes
Hormones
Structral Protiens
What do parts of DNA that don’t code protien effect
Some of these non-coding parts switch genes off and on so they control wether or not a gene is expresses.
What is the structure of a completed protin chain
When the protein chain is complete it folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body such as collagen.
How do mutations occur
Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.
How does mutations effect enzymes
A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
What are different types of mutations
Insertions - when a new base is inserted (may have a knock-on effect)
Deletions - random bases deleted from DNA base sequence
Substitutions - random base is changed
What does the father pordice is sexual reproduction
Gametes by meiosis
What is exual reproduction
Involves the fusion of male and female gametes. Because there are two parents, the offspring contain a mixture of their parent’s genes.
What does sexual reproduction lead to
sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
What does asexual reproduction involve
Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
What is mitosis
An ordinary cell makes a new cell by dividing in two
What are gametes
They only have one copy of each chromosome so that when gamete fusion takes place, you get the right amount of chromosomes agian.
how meiosis halves the number of chromosomes in gametes
- first the cell duplicates its genetic information forming two armed chromosomes (each arm being an exact copy of the other).
- after replication the chromosomes arrange into pairs.
- the first division the chromosomes pairs line up in the centre of the cell
- the pairs pull apart so each new cell only has one copy of each chromosome (father’s and mother’s)
- in second division the chromosmes line up again in the centre of the cell. The arms are pulled aprt.
- you get four gametes, each with single set of chromosomes in it. Each gamete is gentically different as the chromosomes are all shuffled up.
How does the cell produced by gamete fusion replicate itself
After two gametes fuse the resulting new cell divides by mitosis and repeates many times to form an embryo. The cells then diffrinciate and become specialised.
Some characteristics are controlled by a single gene, such as:
fur colour in mice; and red-green colour blindness in humans. Each gene may have different forms called alleles.
A dominant allele
A dominant allele is always expressed, even if only one copy is present.
A recessive allele
A recessive allele is only expressed if two copies are present (therefore no dominant allele present).
What do alleles presented/genotype do
The alleles present, or genotype, operate at a molecular level to develop characteristics that can be expressed as a phenotype.
