Patterns of inheritance

Question 1

Monohybrid inheritance

Answer 1

inheritance of a charicteristic that is controlled by one single gene

Question 2

autosome

Answer 2

a non sex chromosome

Question 3

autosomal linkage

Answer 3

when two genes are located on the same autosome, so alleles are likely to be inherited together. not likely to be separated during crossing over.

Question 4

Dihybrid inheritance

Answer 4

The inheritance of a charicteristic is controlled by more than one gene.
parents that differ in two characteristics.

Question 5

sex linkage

Answer 5

a gene present on x chromosome but not Y chromosome. If an allele if this gene is recessive, it is more likely to be expressed in a male than a female. Female would have to be homozygous recessive wheras male only needs one recessive allele on the x chromosome to be expressed in phenotype.

Question 6

Epistasis

Answer 6

a gene at one locus prevents the expression of a gene at another

Question 7

gene being supressed

Answer 7

hypostatic gene

Question 8

the gene doing the supressing

Answer 8

epistatic gene

Question 9

Dominant Epistasis

Answer 9

expression of the dominant allele of the epistatic gene supresses the expression of the hypostatic gene.

Question 10

recessive epistasis

Answer 10

two copies of recessive allele al one position prevent the expression of another allele.

Question 11

complementary

Answer 11

two genes working together

Question 12

phenotypic variation

Answer 12

visible differences in characteristics
- can be genetic or environmental

Question 13

Causes of genetic variation (4)

Answer 13

• mutations
• recombination during prophase 1
• independent segregation ( different combinations of maternal and paternal chromosomes) during metaphase 1
• random fertalisation

Question 14

offstring ratio of cross between dihybrid heterozygotes (theyre heterozygous for both characteristics)

Answer 14

9:3:3:1

Question 15

co-dominance

Answer 15

both alleles simultaneously expressed

Question 16

codominant alleles are

Answer 16

neither of them are recessive

Question 17

example of co-dominance

Answer 17

sickle cell anaemia:
those with both Hn and Hs have both normal and sickle cells.

Question 18

Monohybrid crosses between 2 heterozygotes

Answer 18

3:1

Question 19

monohybrid crosses between 1 heterozygote and 1 homozygote

Answer 19

1:1

Question 20

Monohybrid crosses between 2 homozygotes

Answer 20

all same

Question 21

autosomal linkage is relevant to…

Answer 21

dihybrid crosses

Question 22

if a male inherits a recessive allele on the x chromosome…

Answer 22

the allele will always be expressed because because there is no other x chromosome containing a dominant allele.

Question 23

A disorder that is sex linked. who does it affect more?

Answer 23

haemophilia, affects men more because ots inherited via an allele on the x chromosome.

Question 24

hemizygosity

Answer 24

no role for dominance or recesiveness because a person only inherits one of these genes.

Question 25

dominance hierarchy

Answer 25

the hierarchy of alleles being expressed

Question 26

recessive epistasis

Answer 26

epistatic allele is recessive. two copies of this epistatic allele must be present to silence the hypoststic allele.

Question 27

dominant epistasis

Answer 27

only one copy of the epistatic allele must be present to mask the expression of the hypoststic allele.

Question 28

conclusion for statistically insignificant chi- squared test

Answer 28

There is no significant difference between observed and expected data, the difference is due to chance'.

Question 29

stabilising selection

Answer 29

mean is selected. selection pressures select against. occurs in non-changing environment

Question 30

directional selection

Answer 30

natural selection favours extreme phenotype. caused by a changed environment

Question 31

where does directional selection take place

Answer 31

in an environment that has seen change

Question 32

stabalising selection takes place

Answer 32

in environments that have not seen change

Question 33

disruptive selection

Answer 33

selection pressures select against the mean.

Question 34

decreases genetic diversity

Answer 34

- genetic drift - founders effect - genetic bottleneck (sudden reduction in genetic variation caused by a sudden event) - artificial selection

Question 35

increases genetic diversity

Answer 35

mutations gene flow

Question 36

gene pool

Answer 36

sum of all the alleles in a population

Question 37

allele frequency

Answer 37

frequency at which an allele appears in a population

Question 38

hardy weinburg equation

Answer 38

P² + Q² + 2PQ = 1 (for genotypes) P+Q = 1 (for proportions of each allele)

Question 39

assumptions about hardy weinburg

Answer 39

- no mutations - no migration or emigration

Question 40

processes involved in speciation

Answer 40

- reproductive isolation - accumulation of differences

Question 41

allopatric speciation

Answer 41

geographically isolated

Question 42

allopatric speciation and selection pressures

Answer 42

different selection pressures applied on the different isolated populations.

Question 43

sympatric speciation

Answer 43

reproductively isolated without geographical isolation

Question 44

Reproductive isolation mutations - that cause sympatric isolation

Answer 44

- polypliody - extra set of chromosomes - behavioural changes i.e mating behaviours and times. - alter reproductive organs

Question 45

sympatric isolation- prezygotic barriers

Answer 45

- any factors that prevent formation of a zygote i.e changes in reproductive organs, mating times, mating behaviour.

Question 46

sympatric isolation- postzygotic barriers

Answer 46

reduced viability or fertility of offspring

Question 47

Artificial selection other name

Answer 47

selective breeding

Question 48

Artificial selection

Answer 48

individuals with desired charicteristics interbred. offspring with desired characteristics are inbred

Question 49

disadvantages of artificial selection

Answer 49

- decreased genetic diversity - organisms closely related likely to have same recessive alleles so possibility of homozygous recessive genetic diseases.