3.7.1 Inheritance - definitions

Question 1

What is the definition of genotype?

Answer 1

the genetic constitution of an organism

Question 2

What is the definition of phenotype?

Answer 2

the characteristics of an organism, often visible, resulting from both its genotype and the effects of the environment

Question 3

What is the definition of allele?

Answer 3

an alternative form/ version of a gene
(e.g. gene for the shape of a pea has 2 alleles; one for round and one for wrinkled)

Question 4

What is the definition of gene?

Answer 4

base sequence of DNA that codes for the amino acid sequence of a polypeptide, occupying a fixed position (locus) on a DNA molecule
OR
section of DNA on a chromosome coding for one or more polypeptides

Question 5

What is the definition of dominant allele?

Answer 5

allele that is always expressed in the phenotype when it is present, even in heterozygote

Question 6

What is the definition of recessive allele?

Answer 6

allele that is only expressed in the phenotype when present in homozygous state (or in haploid organism)

Question 7

What is the definition of a locus?

Answer 7

the position of a gene on a chromosome/ DNA molecule

Question 8

What is the definition of an autosome?

Answer 8

a non-sex chromosome (chromosomes 1-22)

Question 9

What is the definition of heterozygous?

Answer 9

condition in which the alleles of a particular gene are different

Question 10

What is the definition of homozygous?

Answer 10

condition in which the alleles of a particular gene are identical

Question 11

What is autosomal linkage?

Answer 11

when 2 or more genes are located on the same non-sex chromosome, so they tend to be inherited together

Question 12

What is Epistasis?

Answer 12

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

Question 13

What is sex-linkage?

Answer 13

when a gene is located on a sex chromosome (usually the X chromosome) so its inheritance is linked to the sex of the individual

Question 14

What is a dihybrid cross?

Answer 14

genetic cross between 2 individuals that are heterozygous for 2 different genes, used to study inheritance of 2 characteristics at the same time

Question 15

What is a monohybrid cross?

Answer 15

genetic cross between 2 individuals that considers the inheritance of 1 gene (1 characteristic) often between 2 heterozygotes

Question 16

What is a chi-squared test used for?

Answer 16

• used to compare the observed phenotypic ratios from a genetic cross with the expected ratios
• to see if any difference is likely to be due to chance or if it is significant