6.2.1 Key Terms in Genetics

Question 1

Gene

Answer 1

Section of DNA coding for a particular protein

Question 2

Species Def

Answer 2

• Group of organisms with the same genes
• Same common ancestry
• Can reproduce to produce fertile offspring

Question 3

Loci

Answer 3

Position of gene on a chromosome

Question 4

Allele

Answer 4

Different forms of genes coding for the same characteristics (slightly different nucleotide positions but occupy same loci on chromosome)

Question 5

Genotype

Answer 5

All the different alleles in an organism

Question 6

Homozygous

Answer 6

When the 2 allele copies are identical

Question 7

Heterozygous

Answer 7

When the 2 allele copies are different

Question 8

Phenotype

Answer 8

Observable characteristics of an organism coded for by the organisms genotype

Question 9

Dominant Alleles

Answer 9

Always expressed in the phenotype

Question 10

Recessive Alleles

Answer 10

Only expressed in phenotype if no dominant allele is present (only expressed when present in a homozygous individual)

Question 11

What is codominance

Answer 11

Where both alleles are expressed in the phenotype at the same time

Question 12

What is the F1 generation

Answer 12

The generation produced when a homozygous dominant individual is crossed with a homozygous recessive individual

Question 13

What is the F2 individual

Answer 13

When 2 individuals from the F1 generation crossbreed, offspring produced are called the F2 generation

Question 14

How can the genotype of an unknown individual be deduced?

Answer 14

• Using a test cross
• Unknown individual must have a dominant phenotype
• Unknown individual crossed with an individual with a recessive phenotype
• Resulting phenotype of offspring provides sufficient information to suggest genotype of unknown individual
• If any offspring present with recessive phenotype then the unknown individual must be heterozygous

Question 15

What is sex linkage?

Answer 15

• 2 sex chromosomes X and Y
• Women have XX, men have XY
• Y chromosome is shorter than X
• Some genes are found on a region of a sex chromosome which is not present on the other sex chromosome
• So inheritance of these genes is dependendent on the sex of the individual, hence, sex linked genes

Question 16

What is an autosomal linkage

Answer 16

• Occurs on autosomes (any chromosome that isn’t a sex chromosome)
• 2 or more genes on same chromosome do not independently assort during meiosis
• So genes are linked and stay together in original parental combination