genetic crosses key terms

Question 1

gene

Answer 1

base sequence of DNA that codes for the amino acid sequence in a polypeptide or functional RNA (including rRNA and tRNAs)

Question 2

allele

Answer 2

form of a gene

Question 3

gene loci

Answer 3

fixed position on particular DNA molecule/chromosome

Question 4

genotype

Answer 4

genetic constitution of an organism (combination of alleles of a particular gene)

AA aa Aa

Question 5

phenotype

Answer 5

expression of the genetic constitution and its interaction with the environment

Question 6

homozygous (pure breeding)

Answer 6

having 2 copies of the same allele of a gene

AA or aa

Question 7

heterozygous

Answer 7

having 2 different alleles of a gene

Aa

Question 8

dominant

Answer 8

expressed in both the homozygote and heterozygote

A

Question 9

recessive

Answer 9

only expressed in the homozygote, not the heterozygote

a

Question 10

haploid

Answer 10

gametes having one allele of each gene

A or a

Question 11

diploid

Answer 11

cells aside from gametes have 2 alleles of each gene

AA, Aa or aa

Question 12

monohybrid cross

Answer 12

inheritance of one characteristic

e.g. coat colour in mice

Question 13

dihybrid cross

Answer 13

inheritance of 2 characteristics

e.g. pea colour

Question 14

pedigree analysis

Answer 14

family tree of patterns of inheritance

Question 15

test cross/back cross

Answer 15

cross with the homozygous recessive individual to determine genotype of an individual

Question 16

codominance

Answer 16

alleles which are both expressed in the heterozygote

Question 17

multiple alleles

Answer 17

many alleles of a particular gene within the population

A, a…

Question 18

sex linkage

Answer 18

where the gene is carried on the x chromosome

Question 19

autosomal linkage

Answer 19

where the 2 genes are carried on the same chromosome

Question 20

epistasis

Answer 20

where 2 genes are on different chromosomes but interact in a biochemical pathway to produce phenotypes

e.g. Labrador dogs with black, chocolate & golden fur

Question 21

chi-squared test/ goodness of fit

Answer 21

way of comparing results (observed) to predicted (expected) results to decide whether linkage is occurring