patterns of inheritence🧬

Question 1

define homozygous

Answer 1

genotype with two identical alleles

Question 2

define gene locus

Answer 2

location of gene on chromosome

Question 3

if a behaviour is naturally performed, what type of behaviour is it and what is its characteristic

Answer 3

type: innate
characteristic: not learned

Question 4

suggest why the frequency of a trait in a population may decrease

Answer 4

• not selected for

- alleles not passed on

Question 5

why are physiological problems more common in bred animals

Answer 5

• less genetic variation/ decreased gene pool
• weaker selection against less healthy animals
• disease may be homozygous recessive
• breeders select for looks not health

Question 6

define genotype

Answer 6

combination of alleles possessed by organism

Question 7

define allele

Answer 7

alternative version of a gene

Question 8

List two factors that might cause allele frequencies to change from generation to generation
in a population that meets the Hardy-Weinberg criteria.

Answer 8

• natural selection
• genetic drift
• mutation
• migration

Question 9

what is linkage

Answer 9

if genes for multiple traits are on the same chromosome, they are inherited together

Question 10

what is epistasis

Answer 10

one gene affects expression of another via enzyme pathway

Question 11

what are the different types of isolating mechanism for natural selection

Answer 11

• geographical
• behavioural
• mechanical
• gamete incompatibility

Question 12

biological species concept vs phylogenetic species concept

Answer 12

bio- members of same species can interbreed to produce fertile offspring

phylo- common ancestry
-one species may have a lot of phenotypic variation

Question 13

Suggest a suitable technique by which the student might have collected his samples of ladybirds along this transect.

Answer 13

• sweep netting
• beating
• pooter

Question 14

define recessive

Answer 14

only expressed when homozygous

Question 15

Over time, the frequency of a new allele increased in the gene pool of the human populations whose diet included milk.
Name the process by which this increase occurred.

Answer 15

natural selection

Question 16

Distinguish between the terms ‘regulatory gene’ and ‘structural gene’.

Answer 16

regulatory- makes transcription factor to turn structural gene on/off

structural- makes polypeptide

Question 17

Describe how genes Z and Y (in lac operon) are switched on in bacteria that are moved to a nutrient medium
that contains lactose.

Answer 17

• lactose binds to repressor protein
• changes shape of protein
• stops it binding to operator
• RNA polymerase binds to promoter
• Z and Y are transcribed

Question 18

in eye colour epistasis, explain how the products coded for by the genes interact to give the different pigments

Answer 18

• gene products are enzymes
• multi enzyme pathway
• product of one reaction is substrate for next
• dominant allele gives functional enzyme
• recessive allele gives non-functional enzyme

Question 19

outline the main ways that human presence and activity has put some species at risk of extinction

Answer 19

• habitat destruction
• land for buildings or farming
• deforestation
• more pollution
• hunting

Question 20

Name the type of gene which, if mutated, gives rise to dramatic changes in body plan

Answer 20

homeotic/homeobox

Question 21

Describe how the information coded on genes is used to synthesise polypeptides and how these polypeptides control the physical development of an organism

Answer 21

• gene copied into mRNA
• transcription
• one strand copied
• complementary base pairing
• ribosome
• translation
• tRNA contains anticodon on one end and amino acid on opposite side
• enzymes
• hormones
• structural proteins
• cAMP
• receptor proteins
• apoptosis

Question 22

State two developments, other than selective breeding, that could account for the total increase in wheat yield per hectare

Answer 22

• new technology
• fertiliser
• pesticide

Question 23

State the term used to describe the random changes in allele frequency in a small population

Answer 23

genetic drift

Question 24

hypothesis: genes assort independently

the observed ratio is different to the expected. Suggest a genetic explanation for this difference.

Answer 24

• alleles are linked
• on same chromosome
• linked alleles inherited together
• crossing over produced rare recombinants
• tight linkage

Question 25

Give two reasons why it is not appropriate to use the Hardy-Weinberg principle to estimate the frequencies of alleles for a group of rabbits in the pet shop

Answer 25

• small population
• not all members of population are breeding
• mating is not random
• migration occuring