Genetic diversity - Yr 1

Question 1

Gene Mutation

Answer 1

A change to one or more nucleotide bases in DNA that could result in a change in genotype which may be inherited

Question 2

Substitution mutation

Answer 2

If a nucleotide is changed in the DNA sequence

Question 3

Nonsense mutation

Answer 3

If the base change results in the formation of a stop codon

Question 4

Mis-sense mutation

Answer 4

If the base change results in a code for a different amino acid completely

Question 5

Silent mutation

Answer 5

If the base change still codes for the same amino acid as before (as code is degenerate)

Question 6

Deletion mutation

Answer 6

If a nucleotide is lost from the DNA sequence, resulting in a ‘frame shift’ in translation

Question 7

Mutagen (mutagenic agent)

Answer 7

A material or other factor which increases the normal mutation rate eg high energy radiation, chemicals

Question 8

Chromosome mutation

Answer 8

A change that occurs in a chromosome. These changes are most often brought on by problems that occur during meiosis and can result in changes in the number of chromosomes in a cell or changes in the structure of a chromosome.

Question 9

Polyploidy

Answer 9

The process of the genome doubling that gives rise to organisms with multiple sets of chromosomes.

Question 10

Non-disjunction

Answer 10

The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

Question 11

Meiosis

Answer 11

The type of nuclear division in which the number of chromosomes is halved.

Question 12

Gamete

Answer 12

Reproductive (sex) cell that fuses with another gamete during fertilisation

Question 13

Diploid

Answer 13

Cell or nucleus containing pairs of homologous chromosomes (two sets of chromosomes)

Question 14

Haploid

Answer 14

Cell or nucleus containing single, unpaired chromosomes (a single copy of each chromosome)

Question 15

Homologous chromosomes

Answer 15

A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. They are not necessarily identical as may have different alleles. They are capable of pairing during meiosis.

Question 16

Crossing over

Answer 16

The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged

Question 17

Chiasmata

Answer 17

A point at which paired chromosomes remain in contact during the first metaphase of meiosis and at which crossing over and exchange of genetic material occur between the strands.

Question 18

Recombination

Answer 18

The rearrangement of genetic material, especially by crossing over in chromosomes.

Question 19

Independent assortment

Answer 19

The alleles of two (or more) different genes get sorted into gametes independently of one another. The allele a gamete receives for one gene does not influence the allele received for another gene. This is because homologous chromosomes line up in random orientations at the middle of the cell at metaphase as they prepare to separate, meaning that the same parent cell can produce different combinations of chromosomes in the daughter cells.

Question 20

Independent segregation

Answer 20

During the formation of gametes, each gamete receives just one gene copy, which is selected randomly. Each pair of alleles segregates independently of the other pairs and all possible combinations of alleles can occur in the resulting gametes.

Question 21

Variation

Answer 21

Differences between individuals. It can be interspecific (between different species) or intraspecific variation (between individuals of the same species).