Inherited change - Yr 2

Question 1

Gene

Answer 1

Section of DNA on a chromosome that controls a feature by coding for formation of one or more specific polypeptides or a functional RNA (including rRNA and tRNA).

Question 2

Locus

Answer 2

The specific linear position of a particular gene on a certain chromosome

Question 3

Alleles

Answer 3

Alternative forms of a particular gene with different base sequences, and therefore different codes

Question 4

Homozygous

Answer 4

Situation or organism in which paired alleles are the same

Question 5

Heterozygous

Answer 5

Situation of organism in which paired alleles are different

Question 6

Dominant

Answer 6

An allele that expresses itself in the phenotype in heterozygous organisms

Question 7

Recessive

Answer 7

An allele that does not express itself in the phenotype in heterozygous organisms

Question 8

Co-dominant

Answer 8

Alleles which both contribute to the phenotype (i.e. produce a blended effect) in the heterozygous condition

Question 9

Multiple alleles

Answer 9

If there are more than two alleles for each gene in the gene pool. NB. Only 2 chromosomes in a homologous pair so only 2 of the three or more alleles can be present in a single organism

Question 10

Pure-breeding strain

Answer 10

Group of organisms in which a certain characteristic is unaltered for generations, indicating that organisms are homozygous for that feature

Question 11

Monohybrid

Answer 11

Inheritance of a single pair of alleles

Question 12

Dihybrid

Answer 12

Inheritance of two pairs of alleles

Question 13

Haploid (n)

Answer 13

Cell or nucleus containing single, unpaired chromosomes

Question 14

Diploid (2n)

Answer 14

Cell or nucleus containing pairs of homologous chromosomes

Question 15

Phenotype

Answer 15

The observable or biochemical characteristics of an organism, resulting from both its genotype and the effects of the environment

Question 16

Genotype

Answer 16

The combination of alleles present within the cells of an organism

Question 17

Heritable

Answer 17

Features determined by genes (rather than the environment) and therefore passed on to offspring

Question 18

Homologous chromosomes

Answer 18

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 19

Ratio

Answer 19

A measure of the relative size of two classes that is expressed as a proportion.

Question 20

Sex linked

Answer 20

Any gene that is carried on either the X or Y chromosome.

Question 21

Autosomal linkage

Answer 21

The situation where two or more genes are carried on the same autosome.

Question 22

Autosome

Answer 22

A chromosome which is not a sex chromosome

Question 23

Epistasis

Answer 23

This arises when the allele of one gene affects or masks the expression of another in the phenotype.