IB Bio HL1 QUIZ: Genes and Genome

Which statement defines alleles?

• They are the different forms of a gene that have the same effect on the phenotype.

• They are the similar forms of a gene in different positions of a chromosome.

• They are the various forms of a gene with slight differences in their base sequences.

• They are the different forms of a gene coding for identical polypeptide chains.

The table shows the estimated total number of genes in several organisms.

• Throughout evolution, the number of genes increases.

• The domestic dog is more closely genetically related to the fruit fly than to the human.

• The number of genes does not determine evolutionary success.

• Humans produce about half as many proteins as rice.

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 is a difference between two alleles of a gene?

• Their positions on homologous chromosomes

• Their amino acid sequence

• The characteristic they influence

• Their base sequence

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 feature of eukaryotic chromosomes distinguishes them from the chromosomes of prokaryotes?

• Histone proteins

• Circular DNA

• Double-stranded DNA molecules

• Multiple genes along the length of each chromosome

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 micrograph shows two types of blood cell. What determines the differences between the two types of cell?

• Different number of mitotic cycles

• Different expression of some genes

• Reaction to oxygen of red blood cells

• Reaction to antigens of white blood cells

A short sequence of amino acids (represented by letters) in cytochrome c is shown for six vertebrates. Letters in bold indicate identical amino acids for all species. Which statement refers to this section of cytochrome c?

• The DNA base sequences for human and rhesus monkey are different.

• The most DNA base changes are between humans and snapping turtles.

• The largest number of amino acid differences is two.

• The amino acid at position 32 is the most variable.

Chromosome numbers vary between species. Which statement refers to humans?

• An egg cell has 22 autosomes.

• A sperm cell has 23 autosomes.

• An egg cell has two X chromosomes.

• A zygote has two autosomes.