Section 7 - Reproduction and Inheritance P2 Flashcards
Where is FSH produced and what’s its function?
- produced in the pituitary gland
- causes ova to mature in one of the ovaries in a follicle
- stimulates the ovaries to produce oestrogen
- oestrogen then inhibits the release of FSH
Where is LH produced and what’s its function?
- produced by the pituitary gland
- stimulate the release of an egg on day 14
What is the shape of a DNA molecule?
- has two strands
- a double helix
What are the four bases in DNA?
adenine
cytosine
guanine
thymine
What are the two pairs of bases?
adenine - thymine
cytosine - guanine
What is the pair of bases of DNA called?
complementary-base pairing
What does DNA control?
the production of proteins in a cell (protein synthesis)
What makes up proteins?
chains of amino acids
What makes proteins unique?
each protein have its own number and order of amino acids
-amino acid chains fold up to give each protein a different specific shape
What is required for the coding of one amino acid?
a sequence of three bases in a gene (a codon)
How many possible codons are there?
since there are four bases:
there are 4 x 4 x 4 = 64 possible codons
How many amino acids are there?
20
What are non-coding regions of DNA?
- areas of DNA which don’t code for amino acids
- but they are still involved in protein synthesis
What are the two stages by which proteins are made?
Transcription
Translation
Where are proteins made and what by?
Proteins are made in the cell cytoplasm
They are made by Ribosomes
Why is the process of transcription needed?
DNA is found in the cell nucleus and can’t move out because it is really big
-but the cell needs information from the DNA to get to the ribosomes in the cytoplasm so this is why transcription is needed
What molecule does transcription use?
messenger RNA (mRNA)
- it is shorter and is only a single strand
- uses uracil (U) instead of thymine (T)
Describe the process of transcription:
- RNA polymerase binds to a region of non-coding DNA in front of a gene
- two DNA strands unzip and the RNA polymerase moves along one strand of DNA
- it uses the coding DNA in the gene as a template to make mRNA, base pairing between the DNA and RNA ensures that mRNA is complementary to that gene
- once made, the mRNA molecule moves out of the nucleus and joins with a ribosome
What is RNA polymerase?
the enzyme involved in joining together the base sequence to make mRNA
Describe the process of translation:
- amino acids are brought to the ribosome by transfer RNA (tRNA)
- the order which the amino acids are brought matches the order of the codons in mRNA
- part of tRNA’s structure is called an anticodon (complementary to the codon), the codon and anticodon are paired
- amino acids are joined together by the ribosome (this makes a protein)
What are codominant alleles?
Some characteristics are caused by codominant alleles
-when neither allele is recessive, so you show characteristics from both alleles
How do you draw genetic diagrams for codominant inheritance?
draw a punnet square
draw a grid (3 x 3)
-put the possible gametes from one parent down one side and the other across the top
-in each of the middle squares fill in the pairs of letters (one from the column and one from the row), this shows all the possible combinations of the gametes
What is an example of a codominant allele which determines a characteristic?
Blood type is determined by two codominant alleles (A and B) and one recessive one (O)
What do mutations do to DNA?
Mutations change the sequence of the DNA bases in a gene, producing a genetic variant
-the sequence of DNA bases codes for an amino acid to make a protein, mutations sometimes lead to a change in the protein it codes for
What is a genetic variant?
A different form of a gene
What are enzymes?
Enzymes are proteins which need an active site with a very specific shape to be able to work properly
What affect can genetic mutations have on enzymes?
A mutation could lead to a change in the shape of an enzyme’s active site, altering its function
A mutation could also stop the production of an enzyme all together
How can mutations increase variation?
By leading to a different phenotype
What do most mutations cause?
most have no affect on the phenotype, they are neutral
(if a mutation occurs in an unimportant region of DNA or a mutated codon still codes for the same amino acid or if the mutation occurs in the recessive allele)
What do some mutations cause?
Some mutations have a small affect on the phenotype
if a change in an amino acid only has a slight effect on a protein’s structure
What do very few mutations cause?
Very rarely, a mutation will have a significant effect on a phenotype
(can result in a very different protein that can no longer carry out its function (can be harmful and lead to cancer, or beneficial like getting a survival advantage))
What can increase the chance of a mutation?
- exposure to ionising radiation
- chemicals called mutagens (e.g. chemicals in tobacco)
