phenotypic variation

Question 1

what is a phenotype?

Answer 1

an observable characteristic

Question 2

what is phenotypic variation?

Answer 2

differences between observable characteristics of a group of organisms

Question 3

what is interspecific variation?

Answer 3

• differences between different species due to different genes
• code for different proteins so look and function differently
• not affected by environment

Question 4

what is a gene?

Answer 4

section of DNA that codes for a particular protein

Question 5

describe continuous variation

Answer 5

• takes any value on a scale
• caused by mostly genes with many alleles
• eg height
• polygenic
• histogram

Question 6

describe discontinuous variation

Answer 6

• variation that fits into distinct categories
• caused by genes with few/no alleles and the environment
• eg blood group
• monogenic
• bar chart

Question 7

what is a homologous pair?

Answer 7

a pair of chromosomes carrying the same genes but different alleles

Question 8

what is intraspecific variation?

Answer 8

• differences between organisms of the same species
• same genes, different alleles
• subtle differences
• polygenic traits are affected by the environment
• monogenic less likely

Question 9

what is an allele?

Answer 9

different versions of a gene with a slightly different base sequence
- slightly different proteins are produced

Question 10

what is genetic variation?

Answer 10

variation caused by differences in DNA base sequences
- different hair/eye colour

Question 11

what is environmental variation?

Answer 11

variation caused by the environment in which the organism lives

Question 12

what is a chromosome?

Answer 12

a long section of DNA made up of many genes

Question 13

what is a gene?

Answer 13

a section of DNA that codes for a particular polypeptide

Question 14

what is the genotype?

Answer 14

combination of alleles an organism has

Question 15

what is the phenotype?

Answer 15

observable characteristics resulting from the genotype

Question 16

describe environmental modification of a genetic trait

Answer 16

• phenotypes of genetic traits are often modified by the environment
• traits are usually polygenic
• eg weight

Question 17

what is chlorosis?

Answer 17

a condition where a plant doesn’t produce enough chlorophyll so leaves appear yellow

Question 18

what is chlorosis caused by?

Answer 18

the environment

Question 19

why does chlorosis occur?

Answer 19

• lack of light
• magnesium deficiency
• virus infection

Question 20

what is etiolation?

Answer 20

plants grown in the dark will be yellow and grow long and spindly

Question 21

why does etiolation occur?

Answer 21

they grow as long as possible to try and reach a light source

Question 22

which phenotypic characteristics are affected by what we eat?

Answer 22

height and weight

Question 23

what genetic and environmental factors influence weight?

Answer 23

• exercise
• presence of disease

Question 24

how does our diet affect our genes?

Answer 24

• obesity genes are triggered
• eating unhealthily from a young age can trigger the genes and make it harder to lose weight

Question 25

what is epigenetics?

Answer 25

- changes in gene expression that do not involve DNA sequence changes - environment and individual lifestyle interact with the genome to influence epigenetic change

Question 26

state the difference between a homozygous and heterozygous genotype (1)

Answer 26

homozygous = same alleles of same gene heterozygous = different alleles of same gene

Question 27

explain the difference between the phenotype and genotype of an oak tree (2)

Answer 27

phenotype = physical appearance eg height genotype = allele that determines the characteristic

Question 28

state and explain the difference between continous and discontinuous variation (6)

Answer 28

- continuous = variation that takes any value on a scale - eg height between 1-200cm - influenced by environment and genetics - discontinuous = variation that fits into distinct categories which you do or do not have - eg eye colour blue/green - mainly only influenced by genetics

Question 29

what graph would display data that is controlled by one or two genes and is influenced only by genes? (1)

Answer 29

bar chart - only genetic = discontinuous - few genes = monogenic

Question 30

state 3 phenotypic characteristics that show discontinuous variation (3)

Answer 30

- eye colour - hair colour - blood group

Question 31

state 3 phenotypic characteristics that show continuous variation (3)

Answer 31

- height - weight - hand span