Inheritance

Question 1

What is a genotype ?

Answer 1

the genetic constitution (make-up) of an organism

It describes all the alleles that an organism has.

Question 2

What is the phenotype ?

Answer 2

expresssion/appearance due to the interaction between the genotype and the environment

OR the observable characteristics of an organism

Question 3

What is homozygous ?

Answer 3

two allele copies are identical

Question 4

What is heterozygous ?

Answer 4

two allele copies are different

Question 5

What does it mean if alleles are dominant ?

Answer 5

they are always expressed in the phenotype
This means they are expressed in both heterozygous and homozygous individuals

Question 6

What does it mean if alleles are recessive ?

Answer 6

they are only expressed in the phenotype if no dominant allele is present
This means that it is only expressed when present in a homozygous individual

Question 7

What is Co-dominance ?

Answer 7

Both alleles are expressed in the phenotype

Question 8

What is an example of Co-dominance in humans ?

Answer 8

Human blood types

Question 9

If both allele A and allele B are present in a heterozygous individual what will be their blood type ?

Answer 9

they will have blood type AB (IAIB)

Question 10

What genotypes result in blood type A ?

Answer 10

IAIA or IAIO

Question 11

What genotypes result in blood type B ?

Answer 11

IAIA or IAIO

Question 12

Is blood type O recessive or dominant to groups A and B ?

Answer 12

Blood type O (IOIO) is recessive to both group A and group B alleles

Question 13

What is the name of the offspring produced when a homozygous dominant individual is crossed with a homozygous recessive individual ?

Answer 13

the F1 generation which are all heterozygous

Question 14

What are the SEX chromosomes ?

Answer 14

X and Y

Question 15

What are the SEX chromosomes in females ?

Answer 15

XX

Question 16

What are the SEX chromosomes in males ?

Answer 16

XY (the y chromosome is shorter)

Question 17

What are the three genotypes for females for a genetic trait caused by a recessive allele ?

Answer 17

XAXA = unaffected
XAXa = carrier
XaXa = affected
Males have only two genotypes, e.g.
XAY = unaffected
XaY = affected

Question 18

Explain Sex Linkage

Question 19

What does monohybrid crosses look at ?

Answer 19

Monohybrid crosses look at how the alleles of one gene transfer across generations

Question 20

What does dihybrid crosses look at ?

Answer 20

Dihybrid crosses look at how the alleles of two genes transfer across generations

Question 21

What does pure bread mean ?

Answer 21

organisms are homozygous they have two alleles for the same gene