Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Kamali
F215: Control, Genome and the Environment
Module 1: Cellular Control and Variation
5.1.1: Cellular Control
(a) State that genes code for polypeptides, including enzymes
(b) Explain the meaning of the term `genetic code'
The genetic code is the sequence of base pairs on a length of DNA. It codes (contains the genetic
information) for the production of polypeptides (proteins), as well as containing non-coding lengths of
DNA.…read more

Page 3

Preview of page 3

Here's a taster:

Kamali
- A second molecule of tRNA, with an anticodon complementary to the second codon on the
mRNA strand, also binds to its specific amino acid, and also binds to the mRNA strand.
- Ribosomal enzymes cause a peptide bond to form between the two amino acids.…read more

Page 4

Preview of page 4

Here's a taster:

Kamali
Lactose present
Lactose is taken up by the bacterium, and then binds to the lac repressor, causing it to
change shape. This shape change causes the repressor protein to
dissociate from the operator region, which allows RNA polymerase to bind to the
promoter region, and hence transcribe the structural genes. These
structural genes code for the production of the enzymes necessary to
metabolise lactose.…read more

Page 5

Preview of page 5

Here's a taster:

Kamali
5.1.2: Meiosis and Variation
(a) Describe, with the aid of diagrams and photographs, the behaviour of chromosomes during meiosis, and the associated behaviour of the nuclear
envelope, cell membrane and centrioles (names of the main stages are expected, but not the subdivisions of prophase)
Meiosis is the process by which gametes (sex cells) are produced in the sexual organs.…read more

Page 6

Preview of page 6

Here's a taster:

Kamali
3. Anaphase II
The spindle fibres contract.
Sister chromatids are separated at the centromere and pulled to opposite poles of the
cell.
The chromatids randomly segregate (any combination of chromatids is possible in
each of the daughter cells).
4. Telophase II
Nuclear envelopes form around the daughter cells.
Cytokinesis (cell membrane separation) occurs in animals, to form a total of four
genetically dissimilar haploid daughter cells.
In plants, a tetrad of four haploid cells is formed.…read more

Page 7

Preview of page 7

Here's a taster:

Kamali
3. During metaphase II, the independent assortment and distribution of sister chromatids
means that any combination of chromatids could enter the daughter cells
4. Random mutations
Fertilisation:
1. Any female can mate with any male
2. Any sperm cell (male gamete) can fuse with any egg cell (female gamete)
(e) Use genetic diagrams to solve problems involving sex linkage and codominance
Sex linkage: (e.g.…read more

Page 8

Preview of page 8

Here's a taster:

Kamali
Codominance: (e.g.…read more

Page 9

Preview of page 9

Here's a taster:

Kamali
(f) Describe the interactions between loci (epistasis)
Many different alleles can have an effect upon the same characteristic. These alleles
interact to produce the phenotype. Epistasis is the interaction of different gene loci so that the phenotypic
expression of one gene locus masks or suppresses the effect of another gene locus.
Recessive epistasis:
Recessive epistasis occurs only when two copies of the dominant epistatic allele are
present (when the individual is homozygous for the epistatic allele).…read more

Page 10

Preview of page 10

Here's a taster:

Kamali
(j) Explain the basis of continuous and discontinuous variation by reference to the number of genes which influence variation
Continuous variation:
Most continuous variation is controlled by multiple genes (known as `polygenic'). Multiple gene
loci interact together to form a large range of possible phenotypes. Different alleles at the same
locus have small effects.
Different gene loci have the same, often additive, effect on the trait.
Discontinuous variation:
Most discontinuous variation is controlled by one, or very few, genes (known as
`monogenic').…read more

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »