Topic 3 Genetics

Which statements are characteristics of alleles?

I. Alleles differ significantly in number of base pairs.

II. Alleles are specific forms of a gene.

III. New alleles are formed by mutation.

• I and II only

• I and III only

• II and III only

• I, II and III

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells.

What can be deduced from this information?

• The sex of the chimpanzee

• The number of genes in each chromosome

• Whether non-disjunction has occurred

• The number of autosomes in a diploid cell

Which statement correctly describes genome and proteome?

• Only the genome but not the proteome can be analysed using gel electrophoresis.

• The genome and the proteome are the same in all tissues in an organism.

• In cells of different tissues, the genome is the same while the proteome varies.

• Only mutations in the proteome but not in the genome cause any variability.

Some yeast genes can be replaced by human genes that then continue to produce the same human proteins in the yeast cells. Which statement helps to explain this evidence?

• The DNA of yeast and humans is identical.

• Yeast and humans have the same number of chromosomes.

• The genetic code is universal.

• Yeast and humans are both eukaryotes.

What determines the genomic size of a species?

• The total amount of DNA

• The total number of genes

• The total number of alleles

• The total number of chromosomes

What distinguishes an allele from a gene?

• An allele is made of RNA.

• An allele is shorter.

• An allele is a variety of a gene.

• An allele cannot be transferred during genetic modification.

What is the effect of dominant alleles?

I. They mask the effect of recessive alleles.

II. They become more frequent than recessive alleles in a population.

III. They have a joint effect with recessive alleles when characteristics are co-dominant.

• I only

• I and II only

• I and III only

• I, II and III

A pregnant woman had fetal cells removed by chorionic villus sampling and tested. The following karyogram was produced.

What does this show?

• The child is female with Down syndrome.

• The child is female without Down syndrome.

• The child is male with Down syndrome.

• The child is male without Down syndrome.

The image shows chromosomes from an insect (2 n = 8).

Which pair of chromosomes are the sex chromosomes of this insect species?

• c and e

• a and h

• f and h

• a and e

What is the same in all parts of homologous chromosomes?

• Base pair sequence

• Alleles

• Sequence of genes

• Deletions