EduNinjaThe Indian muntjac deer, Muntiacus muntjak, is recorded as the mammal with the lowest number of chromosomes.
Fig. 2.1 is an image of the chromosomes in the nucleus of a diploid cell of a female muntjac deer.
Fig. 2.1
Another cause of variation is the formation of new alleles.
Describe how new alleles can be formed.
Carp are a type of fish. Researchers in Brazil measured the body lengths of a population of carp in a river in 1998 and again in 2008.
Histograms of their results are shown in Fig. 2.1.
Fig. 2.1
Describe the variation in body length of the carp population in 1998. Use the data in Fig. 2.1 to support your answer.
Body length is an example of continuous variation.
Suggest what causes the variation in body length in a population of fish.
Continuous variation is shown with a histogram.
Name the type of graph that should be used to show discontinuous variation.
A scientist investigated the inheritance of fur colour in cats.
The gene for coat colour is located on the X chromosome. The gene has two alleles:
- B black
- b orange.
The X chromosome with the allele for black is represented by .
The X chromosome with the allele for orange is .
A female cat can be a mixture of these colours, described as calico.
Fig. 3.1 shows the inheritance of this condition in a family of cats.
Fig. 3.1
Coat colour in cats is an example of discontinuous variation.
Explain why coat colour is an example of discontinuous variation.
The American writer Ernest Hemingway lived on the island of Key West in Florida, USA in the 1930s. During this time he was given a male cat by a sea captain.
The cat had more toes than usual. This inherited condition is called polydactyly. The allele for polydactyly is dominant.
Scientists published the results of an investigation into the DNA of cats with and without polydactyly. They compared the base sequence from a particular region of DNA that controls the development of the limbs.
Table 3.1 shows the base sequences.
Table 3.1
State the name of the process by which base sequences in DNA are changed.
The base sequences in Table 3.1 provide evidence that indicates which country the male cat given to Hemingway in the 1930s came from.
Suggest which country this cat came from and give a reason for your choice.
Explain why polydactyly is an example of discontinuous variation.
Characteristics of plants are controlled by genes. Alleles are alternative forms of a gene.
Explain how new alleles are formed.
A researcher investigated genetic variation in fruit flies, Drosophila melanogaster.
The bodies of fruit flies can be black or yellow. A yellow body colour is a recessive feature in fruit flies.
The ancestors of C. caeca had pigmented bodies.
The lack of a coloured pigment in C. caeca is called albinism and was caused by a mutation many thousands of years ago.
State two factors that can cause mutations.
1
2
Tobacco smoke is made up of over 7000 chemicals.
Nicotine is a component of tobacco smoke.
A study compared the percentages of men and women aged between 35 and 54 years who smoked cigarettes. The annual death rate caused by lung cancer was also recorded.
The results are shown in the two graphs in Fig. 4.1.
Fig. 4.1
Use the data shown in Fig. 4.1 to compare the percentages of men and women who smoked cigarettes between 1950 and 1998.
Scientists investigated the amount of genetic variation found within different crop plants. They grew large numbers of each crop and measured the genetic variation within the species of crop. The results are shown in the table.
Which crop or crops have been produced by sexual reproduction?
banana only
banana, pea and carrot
pea only
pea and carrot only
Seed banks are used to conserve endangered plant species.
Fig. 4.1 shows some of the steps involved in managing a seed bank.
Fig. 4.1
Seeds are X-rayed before they are stored to check that they contain an embryo.
State one possible consequence of using ionising radiation on seeds.
Yeast is an example of a single-celled fungus.
A small sample of yeast cells and 19 g per of sugar were added to a fermenter. The population size of live yeast cells and the concentration of the sugar in the fermenter were calculated every day for 10 days.
The results are shown in Fig. 4.2 and Fig. 4.3.
Fig. 4.2
Fig. 4.3
Draw an X on Fig. 4.3 to indicate the position of the lag phase.
Complete the line on Fig. 4.3 to show the expected change in the population size of live yeast cells from day 3 to day 10 .
Describe and explain the changes in the concentration of sugar in the fermenter over the 10-day period.