6.2 Patterns Of Inheritance & Variation

Question 1

Why does variation arise?

Answer 1

Due to random mutations

Question 2

Random mutations are essential for what to take place?

Answer 2

Natural selection

Evolution

Question 3

Variation within a species can arise from which factors?

Answer 3

Genetic

Environmental

Question 4

Give examples of variation arising from both genetic and environmental factors?

Answer 4

Chlorosis

Body mass

Question 5

Some plants suffer from chlorosis what does this affect?

Answer 5

A plants ability to photosynthesise
Don’t produce enough chlorophyll
Plants look pale and yellow

Question 6

Most plants have genes coding for chlorophyll so what causes chlorosis?

Answer 6

Environmental factors

Question 7

What 3 environmental factors can cause chlorosis?

Answer 7

Lack of light
Mineral deficiency
Virus infections

Question 8

How does chlorosis occur due to lack of light?

Answer 8

Plants turn off chlorophyll production to reserve resources

Question 9

How does chlorosis occur due to mineral deficiency?

Answer 9

Lack of iron which is needed as a cofactor to the enzymes making chlorophyll
Lack of magnesium to make chlorophyll

Question 10

How does chlorosis occur due to virus infections?

Answer 10

Interfere with metabolism of infected cells so they can no longer make chlorophyll

Question 11

what is body mass mostly determined by?

Answer 11

environmental factors - diet

Question 12

in some cases body mass is genetic, what happened to the obese mouse?

Answer 12

mutation in chromosome 8 caused it to deposit more fat

Question 13

genetic variation is caused by what?

Answer 13

the alleles you inherit resulting in different characteristics being displayed

Question 14

combination of alleles inherited are determined by what?

Answer 14

meiosis and random fusion of gametes at fertilisation

Question 15

what are alleles?

Answer 15

different versions of genes

Question 16

what is an organisms genotype?

Answer 16

the combination of alleles an organism inherits for a characteristic

Question 17

what is an organisms phenotype?

Answer 17

an organisms physical observable characteristics

Question 18

what is a dominant allele?

Answer 18

version of gene always expressed if present

Question 19

what is a recessive allele?

Answer 19

version of a gene only expressed if two copies are present in an organism

Question 20

what is homozygous?

Answer 20

two identical alleles for a characteristic

Question 21

what is heterozygous?

Answer 21

two different alleles for a characteristic

Question 22

what is continuous variation?

Answer 22

a characteristic that can take any value within a range

Question 23

what is discontinuous variation?

Answer 23

a characteristic which can only appear is specific discreet categories

Question 24

what factors cause continuous variation?

Answer 24

genetic and environmental

Question 25

what factors cause discontinuous variation?

Answer 25

mostly genetic

Question 26

what is continuous variation controlled by?

Answer 26

polygenes - a number of genes

Question 27

what is discontinuous variation controlled by?

Answer 27

one or two genes

Question 28

give examples of continuous variation:

Answer 28

leaf surface area
animal mass
skin colour
height 
mass
length of parts of the body

Question 29

give examples of discontinuous variation:

Answer 29

blood group 
albinism
round and wrinkled pea shape
tongue rolling
attached earlobes
eye colour

Question 30

is discontinuous variation qualitative or quantitative?

Answer 30

qualitative

Question 31

is continuous variation qualitative or quantitative?

Answer 31

quantitative

Question 32

what 4 things are genetic variation due to?

Answer 32

1. independent assortment of homologous chromosomes
2. crossing over in meiosis
3. random fertilisation of gametes
4. mutation