Pages in this set

Page 1

Preview of page 1
Control, Genome and Environment
Cellular Control

(a) state that genes code for polypeptides, including enzymes

(b) explain the meaning of the term genetic code
The sequence of the bases on a gene is a code with instructions for the construction of proteins. It
has a number of characteristics:
It is…

Page 2

Preview of page 2
(h) explain genetic control of protein production in a prokaryote using the lac operon
This involves both regulatory and structural genes.
Regulatory genes make a repressor protein which is a transcription factor that switches a
structural gene on or off
Structural genes make enzymes, polypeptides or proteins
So the regulatory…

Page 3

Preview of page 3
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 I
Prophase I
1. The chromatin…

Page 4

Preview of page 4
Observable characteristics of an organism
genotype
The combination of alleles possessed by organism
dominant
Characteristic in which the allele responsible is expressed in the phenotype, even in those
with heterozygous genotypes
codominant
A characteristic where both alleles contribute to the phenotype




recessive
Characteristic in which the allele responsible is only…

Page 5

Preview of page 5
If both the A and the B alleles are present in the genotype, the phenotype will be AB they
are codominant. The O allele is recessive, so it will not be expressed in the phenotype
unless the alleles A or B are not present

(f) describe the interactions between loci…

Page 6

Preview of page 6
Continuous variation
Different alleles at the same gene locus have small effects
Different gene loci have the same, often additive effect on the trait
A large number of gene loci may have a combined effect on the trait

(k) explain that both genotype and environment contribute to phenotypic variation. (No…

Page 7

Preview of page 7
If two subpopulations are separated from each other, they will evolve differently as they have
different selection pressures, so different alleles will be eliminated or increased within each sub
population. Eventually the sub populations will not be able to interbreed and so will be different
species.
The sub populations may…

Page 8

Preview of page 8
(s) describe how artificial selection has been used to produce the modern dairy cow and to produce breed
wheat (Triticum aestivum)
Dairy cow
Characteristics selected for
large yield (volume) of milk
long lactation period
high milk quality
large udders or the correct udder shape (for milking machine)
resistance to disease…

Page 9

Preview of page 9
Biotechnology and Gene Technologies
Cloning in Plants and Animals

(a) outline the differences between reproductive and nonreproductive cloning
Reproductive cloning is the production of offspring which are genetically identical to either the
mother (nuclear transfer), or the other offspring (splitting embryos)
Nonreproductive cloning is the use of stem cells in…

Page 10

Preview of page 10
and the disease also spreads through the suckers it spread rapidly. The beetles only live on elm trees
and attempts at control contributed to spread. As more trees became diseased then more tree surgery
was necessary and as more trees became infected then more saws were contaminated.

(c) describe the…

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »