3.4 and 10.2 Inheritance

Question 1

Allele mask

Answer 1

when one allele covers the phenotypic expression of another allele at the same gene locus.

Question 2

Autosomal genes

Answer 2

chromosomes that do not determine sex.

Question 3

Co-dominant alleles

Answer 3

two alleles at a particular locus that have different effects and are distinguishable in a heterozygous individual (e.g. AB blood groups).

Question 4

Colour blindness

Answer 4

an abnormal condition caused by an X-linked recessive allele and characterized by the inability to clearly distinguish different colours of the visible light spectrum.

Question 5

Cystic fibrosis

Answer 5

a mutation in a gene that changes a protein that regulates the movement of salt in and out of cells; characterized by the production of thick and sticky mucus.

Question 6

Dominant alleles

Answer 6

the allele that is fully expressed in the phenotype of a heterozygote.

Question 7

Gametes

Answer 7

one of two haploid reproductive cells, egg or sperm, whose union is necessary in sexual reproduction to produce a diploid zygote.

Question 8

Gene

Answer 8

a hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism.

Question 9

Genotype

Answer 9

the genetic constitution of an organism.

Question 10

Haemophilia

Answer 10

a sex-linked inheritable disease characterized by loss or impairment of the normal clotting ability of blood, so that a minor wound may result in fatal bleeding.

Question 11

Haploid cells

Answer 11

have one chromosome of each pair (have one full set of the chromosomes that are found in its species).

Question 12

Huntington’s disease

Answer 12

caused by a genetic defect on chromosome 4; the defect causes a part of DNA, called a CAG repeat, to occur many more times than it is supposed to.

Question 13

Mutagen

Answer 13

a chemical or physical agent that interacts with DNA and causes a mutation.

Question 14

Phenotype

Answer 14

the physical and physiological traits of an organism.

Question 15

Punnett grid (or Punnett square)

Answer 15

a tool that helps to show all possible allelic combinations of gametes in a cross of parents with known genotypes in order to predict the probability of their offspring possessing certain sets of alleles.

Question 16

Recessive allele

Answer 16

an allele that has an effect on the phenotype only when present in the homozygous state.

Question 17

Sex-linked inheritance

Answer 17

traits controlled by genes located on one sex chromosome but not the other.

Question 18

Zygotes

Answer 18

the diploid product of the fusion of haploid gametes (a fertilized egg).

Question 19

chi-square test

Answer 19

A statistical method used to calculate whether the observed and expected genotype frequencies of a population are significantly different.

Question 20

continuous variation

Answer 20

An assemblage of measurements of a phenotypical characteristic which forms from a continuous spectrum of values, such as body height, skin color or hair curl

Question 21

dihybrid cross

Answer 21

A cross between two individuals, concentrating on two definable traits, for example pea color and height of pea plant

Question 22

discrete variation

Answer 22

Inherited characteristic that have a limited number of variations, such as the ability or inability to roll one’s tongue

Question 23

gene loci

Answer 23

specific locations of genes along the chromosome

Question 24

linked genes

Answer 24

Genes located on the same chromosome that tend to be inherited together in genetic crosses

Question 25

polygenic inheritance

Answer 25

An additive effect of two or more gene loci on a single phenotypic character

Question 26

recombinants

Answer 26

Offspring whose phenotype differs from that of the parents; also called recombinant types