Inheritance

Question 1

What is monohybrid inheritance?

Answer 1

The inheritance pattern of one gene

Question 2

What is a gene?

Answer 2

Sort section of DNA found on a chromosome that codes for a particular trait

Question 3

What is a chromosome?

Answer 3

Long chain on DNA that contains genes

Question 4

What is an allele?

Answer 4

Different versions of a particular gene

Question 5

What is a genotype?

Answer 5

Description of the alleles an individual carries for a particular trait

Question 6

What is a phenotype?

Answer 6

The physical expression of an individual’s genotype for a particular trait

Question 7

What is a dominant allele?

Answer 7

The allele that only needs to be present at least once in the individual’s genotype in order to be expressed in their phenotype

Question 8

What is a recessive allele?

Answer 8

The allele that must be present twice in an individual’s genotype in order to be expressed in the phenotype

Question 9

What is a homozygous genotype?

Answer 9

The genotype for a particular trait contains two identical alleles

Question 10

What is a heterozygous genotype?

Answer 10

The genotype for a particular trait contains two different alleles

Question 11

What are the five types of monohybrid inheritance patterns that you have looked at this year?

Answer 11

Complete dominance
Incomplete dominance

Codominance
Multiple alleles
Lethal alleles

Question 12

Define complete dominance

Answer 12

When one allele is completely dominant over the other. If both are present in the genotype, only the dominant allele will be expressed in the phenotype

Question 13

Define incomplete dominance

Answer 13

When neither allele is dominant over the other. If both are present in the genotype, neither will be expressed solely in the phenotype and the phenotype is a blend of the two alleles

Question 14

Define codominance

Answer 14

When both alleles are equally dominant. If both are present in the genotype, both will be expressed in the phenotype

Question 15

Define multiple alleles

Answer 15

When there are more than two different alleles for a particular trait

Question 16

Define lethal alleles

Answer 16

When a certain combination of alleles leads to that individual not surviving

Question 17

Define dihybrid inheritance

Answer 17

The inheritance pattern of two genes

Question 18

Explain how you determine whether an individual is homozygous dominant or heterozygous for a particular trait

Answer 18

Carry out a test/back cross
Cross the individual with a homozygous recessive individual for that trait and have lots of offpsring

If any offspring display the recessive trait then the unknown parent must have been heterozygous for that trait
If none of the offspring display the recessive trait, then the unknown parent is most likely homozygous dominant

Question 19

What are unlinked genes?

Answer 19

Two different genes found on the same chromosome

Question 20

Identify whether linked or unlinked genes create more variation in the offspring and explain why

Answer 20

In unlinked genes, the two different genes can assort independently of each other in meiosis which creates more allele combinations in the gametes, which increases genetic variation. Linked genes stay together in meiosis and don’t assort independently of each other which produces less allele combinations and hence less genetic variation

Question 21

What would you expect to see if the offspring of linked genes compared to unlinked genes?

Answer 21

Linked genes tend to produce two phenotypes whereas unlinked produce four
The offspring of linked genes tend to reflect the parents phenotypes (3:1 ratio) whereas unlinked genes will have a 9:3:3:1 ratio if both parents are heterozygous for both genes

Question 22

Explain how you can work out if two genes are linked or unlinked if the individual is heterozygous for both genes?

Answer 22

Cross the individual with a homozygous recessive individual. If the offspring show four phenotypes typically a 1:1:1:1 ratio then they are unlinked. If the offspring show mainly two phenotypes at a ratio of 1:1 then the genes are linked

Question 23

What are linked genes?

Answer 23

Two different genes found on the same chromosome

Question 24

Explain how linked genes can produce the other two genotypes and hence phenotypes to increase variation

Answer 24

The linked genes are cross over and be recombined during meiosis which increases the allele combinations and hence variation. This happens randomly and so wouldn’t meet the expected ratios of unlinked genes