Patterns of Inheritance

Question 1

What happens if alleles are autosomal linked

Answer 1

Higher proportion of heterozygous

Alleles not completely remixed

Question 2

Why might the observed results not match the predicted results

Answer 2

Random fertilisation

Question 3

How does dominant epistasis work

Answer 3

B, produces / codes for, repressor protein /
repressor polypeptide / enzyme / transcription
factor
(protein / polypeptide / product of B) binds to,
promoter (of A) / mRNA / ribosome
(product of allele B) stops, transcription /
translation (of allele A) / protein synthesis /
described
product of B inhibits the enzyme (encoded by
A)

Question 4

Autosomal linkage

Answer 4

(both) genes / alleles, occur on same,
chromosome / autosome / chromatid

no independent assortment

(so) alleles, inherited together / end up in
same gamete

(unless) crossing over occurs / chiasma forms
between gene loci

Question 5

Continuous

Answer 5

polymorphic
-Line graph

Question 6

Antibiotics

Answer 6

Antibiotic is selective pressure ./ bacteria gene pool has some variation some more resistant than others

When exposed to antibiotics most resistant survive. Surving bacteria continue to reproduce making a

resistant population (under continued antibiotic pressure) antibiotic becomes ineffective

Question 7

How can genetic diversity be measured

Answer 7

The number of polymorphic gene loci within a population

Question 8

Genetic bottleneck

Answer 8

-Alleles and gene pool significantly reduced
-Modern population descended from a few survivors

Question 9

Problems of genetic drift on an endangered population

Answer 9

idea that one individual or allele has
proportionally higher effect on small population

(more likely that) alleles will be lost from
population
(population) more vulnerable / likely to become
extinct due , to environmental change

Question 10

Rate

Answer 10

Product/ time

Question 11

Standard deviation - graph

Answer 11

If bars overlap there is not a significant difference between the means

Question 12

Cm3 to Dm3

Answer 12

/1000

Question 13

Pedigree diagrams

Answer 13

2 parents without the disease but have a child with the disease means that the carriers are on the recessive allele

If parents have the disease but the child does not then the disease is on the dominant allele

Question 14

How do you know if the disease is sex-linked and recessive

Answer 14

Male has the disease as they only need one recessive allele

Question 15

How do you know the disease is sex-linked and dominant

Answer 15

Any affected father will pass the disease to the daughter as daughter is xx and inherits one of the x chromosomes from the father

Question 16

How does dominant epistasis work

Answer 16

the dominant allele codes for the repressor which binds to the promoter and stops transcription

Question 17

Why is a genetic drift unlikely to affect a smaller population

Answer 17

One individual/ allele has proportionally higher effect on a smaller population
More likely alleles that will be lost from the population
Population more vulnerable to extinction/ environmental change

Question 18

What to look for in a graph that shows disruptive selection

Answer 18

Supports because: 1) two peaks 2) at (0) and 1.2/1.4
Does not support: The second peak is not much higher than background / second peak represents
a small number of birds / there could be other explanations for more birds between 1.2-1.4

Question 19

Explain the effects of stabilising pressure

Answer 19

Genetic variation: pre-existing ; sexual reproduction ; meiosis; mutation
Differential survival: overproduction of offspring; finches with extreme beak depth less likely to survive
inheritance: survivors possess alleles for average beak depth; alleles for average beak depth more likely to be inherited by offspring; increase frequency of these alleles from one generation to the next
Figures: Bell shaped

Question 20

Changes in body length

Answer 20

Ref. continuous variation

Question 21

Describe how DNA can be used to provide evidence to support the theory of evolution by natural selection

Answer 21

DNA found in all organsims - highly conserved ; compariosn of DNA between species ; similair
secquence indicates recent common ansesctor

Question 22

Selection used by farmers to exaggerate certain features

Answer 22

Artificial selection

Question 23

Explain, with reference to selective breeding, why it is important to maintain viable wild populations of crop plant species

Answer 23

genetic variation
* genetic resource / gene
bank
* source of useful alleles
* can be cross bred with
crop varieties
* allows introduction of
different traits
* unknown future
requirements
* potentially useful in
changing climate
* prevention of inbreeding
depression
* promotion of hybrid
vigour
* prevent dwindling gene
pool
* source of replacement if
cultivated population is in
danger
* plausible example(s) of
any of the above

Question 24

How does sexual reproduction make individuals genetically unique

Answer 24

Crossing over; allele swapping/shuffling; between non-sister chromatids; at prophase 1; of meiosis; independent assortment of chromosomes at metaphase/anaphase 1/independent assortment of chromatids at metaphase/anaphase 2; haploid gametes; genetically unique gametes; random fertilisation/gamete combination