patterns of inheritance exam qs

Question 1

explain how selective breeding can lead to an increase in yield in wheat plants

Answer 1

• interbreed wheat plants that have alleles for high yield
• measure the yield
• interbreed the high yield offspring
• prevent unwanted cross pollination

Question 2

2 developments that increase wheat yield per hectare

Answer 2

• use of fertilizer
• use pesticide
• improved technology

Question 3

3 phenotypic traits selected for in dairy cows

Answer 3

• high yield of milk
• long lactation period
• high milk quality
• large udders
• resistance to disease
• calm temperament

Question 4

2 modern techniques used in selective breeding of cows

Answer 4

• IVF
• artificial insemination
• cloning
• DNA screening

Question 5

name an isolating mechanism that prevents interbreeding

Answer 5

geographical

Question 6

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

Answer 6

genetic drift

Question 7

explain how to answer a linkage question

Answer 7

1. genes are linked on the same chromosome
2. linked alleles inherited together
3. e.g (Ry and rY) on chromosomes
4. crossing over produces rare recombinants
5. 2 genes are close together on chromosome

Question 8

describe how modern cattle have been produced from less productive wild cattle ancestors

Answer 8

1. selective breeding
2. selection of desired characteristics (e.g. higher yield of milk)
3. crossbreed selected cattle
4. crossbreed selected offspring
5. over many generations

Question 9

reasons why hardy weinberg principle might be able to be used in ARTIFICAL POPULATION

Answer 9

1. small population
2. mating is not random
3. migration is occurring

Question 10

process that given rise to the modern domestic cat from its wild ancestor

Answer 10

selective breeding

Question 11

process that gave rise to coat colour variation in cats

Answer 11

gene mutation/ production of new alleles

Question 12

define homozygous

Answer 12

individual with 2 identical alleles

Question 13

define heterozygous

Answer 13

individual with w different alleles

Question 14

gene locus

Answer 14

position of gene on a chromosome

Question 15

define genotype

Answer 15

all of the alleles an individual has

Question 16

define allele

Answer 16

a different variant of a gene

Question 17

reasons why hardy weinberg principle cannot be used to predict frequencies of alleles in ARTIFICAL selection

Answer 17

1. small population
2. not randomly mating

Question 18

2 factors that can cause allele frequencies to change from generation to generation in pop that meats hardy weinberg

Answer 18

• mutations
• genetic drift
• artifical selection
• migration

Question 19

why are more females than males needed in selective breeding

Answer 19

• males can have as many babies as possible females can only bring pregnant once at a time
• so more needed to maintain numbers
• inbreeding causes genetic problems if population is too small

Question 20

define recessive

Answer 20

only expressed when homozygous

Question 21

define dominant

Answer 21

only expressed when homozygous or heterozygous

Question 22

define codominace

Answer 22

both alleles are equally dominant and are expressed in the phenotype of the organism

Question 23

explain how recessive epistasis produces different pigments

Answer 23

• the gene products are enzymes
• it is a multi step pathway
• the enzymes change ________ into _______ (start and end result)
• product of one reaction is substrate for next
• dominant allele gives functional enzyme
• recessive allele gives non functional

Question 24

explain why a collection of small islands remote from the mainland provides optimal conditions for speciation

Answer 24

• geographically isolated
• so they are reproductively isolated
• diff environments have diff selection pressures
• small populations are more effected by mutations
• they result in the founder effect
• resulting in greater genetic drift

Question 25

define phenotype

Answer 25

the physical characteristic of an organism due to the genotype and environment

Question 26

tigers evolved to form stripes to camouflage.
describe and explain how a tiger with striped fur may have evolved from a non-striped ancestor. (6 marks)

Answer 26

-Natural Selection
1. a mutation may have occurred in the DNA base sequence of the tigers
2. causing the formation of a new allele that codes for the colour/pigment for the stripes.
3. the mutation is beneficial as it allows the tigers to camouflage so they can hide from predators and find more prey.
4. allowing them to survive and reproduce so the allele for pigment will be passed on their offspring
5. this is called natural selection
- Gene Regulation + Epistasis
1. regulatory genes control the pigment produced/ expression of the genes
2. the genes are switched on and off during development
3. recessive epistasis prevents expression of pigment gene