Genetics Key Terms

Question 1

Continuous Variation

Answer 1

There is no distinct categories, there are a range of values eg height weight etc

Question 2

Discontinuos variation

Answer 2

There are two or more distinct categories.

Eg blood group

Hair colour

Question 3

What is a gene?

Answer 3

The sequence of bases on a section of DNA that codes for a protein

Question 4

What is an allele?

Answer 4

Different versions of the same gene

Eg eye colour, same gene but different versions of

Question 5

What is the locus?

Answer 5

The fixed position of the allele of each gene on the chromosome

Question 6

What is genotype?

Answer 6

The combination of alleles an organism has

Eg combination for blue eyes is bb

Question 7

What is phenotype?

Answer 7

The characteristic the alleles produce eg blue eyes

Question 8

What does homozygous mean?

Answer 8

Two copies of the same allele

Question 9

What does heterozygous mean?

Answer 9

Two different alleles

Question 10

What does dominant mean?

Answer 10

One copy of a dominant allele is needed for the dominant characteristic to be seen. Represented by capital letters

Question 11

What does recessive mean?

Answer 11

Two copies are needed for the recessive characteristic to be seen

Shown by lower case letters

Question 12

What does codominant mean?

Answer 12

Both alleles expressed in the phenotype because neither one is recessive.

In between phenotypes

Question 13

What is a carrier?

Answer 13

When you are heterozygous you can carry an allele not seen in the phenotype, can be passed on to offspring

Question 14

What is a mono hybrid cross?

Answer 14

Crosses show inheritance pattern controlled by a single gene. You get a 3:1 ratio when crossing heterozygous parents

Question 15

Dihybrid cross?

Answer 15

These crosses show the inheritance of two characteristics controlled by different genes. Get a 9:3:3:1 phenotypic ratio when crossing 2 heterozygous parents

Question 16

What is an auto some?

Answer 16

Any chromosome that isn’t a sex chromosome

Question 17

What is autosomal linkage?

Answer 17

Genes on the same autos one are linked (found on same chromosome arm) their alleles will be passed onto offspring together, unless crossing over occurs during meiosis and splits the alleles up

Question 18

What is epistasis?

Answer 18

When the allele of one gene blocks or masks the expression of the alleles of other genes

Question 19

Recessive epistasic alleles?

Answer 19

Two copies of recessive allele is needed to mask the expression of another allele. You get a 9:3:4 phenotypic ratio in the f2 gen when crossing homozygous recessive and dominant parents

Question 20

Dominant epistatic alleles?

Answer 20

At least one copy of the dominant allele is needed to mask the expression of the other gene. You get a 12:3:1 ratio phenotypic ratio in the f2 gen when crossing homozygous recessive and dominant parents.

Question 21

What is the Critical value?

Answer 21

The value of chi squared that corresponds to a 0.05 (5%) level of probability that the difference between the observed and expected results is due to chance.