Patterns of Inheritence

Question 1

define phenotype

Answer 1

expression of an organisms genetic constitution combined with interaction with the environment

Question 2

how can meiosis bring about genetic variation

Answer 2

random assortment of chromosomes during line up
crossing over in prophase 1

Question 3

how does random fertilisation bring about genetic variation

Answer 3

gametes are haploid cells (only contain half DNA)
every gamete contains different DNA same two individuals can produce genetically different offspring

Question 4

define monogenic inheritance

Answer 4

one phenotypic characteristic is controlled by a single gene

Question 5

define dihybrid inheritance

Answer 5

two phenotypic characteristics controlled by two different genes present on two different chromosomes at the same time

Question 6

what is meant by sex linkage

Answer 6

an allele is located on the sex chromosome-its expression depends on sex of the individual

Question 7

what is meant by multiple alleles

Answer 7

a gene that has more than two alleles

Question 8

what is meant by codominant alleles

Answer 8

two dominant alleles that both contribute to phenotype
either blend of characteristics or characteristics appearing together

Question 9

what is meant by autosomal linkage

Answer 9

two or more genes located on the same chromosome
only one homologous pair needed for all four alleles to be present
for genes not linked, two homologous pairs needed

Question 10

what is meant by epistasis

Answer 10

when two non linked genes interact
one gene masks or suppresses the other gene

Question 11

what is the chi squared test

Answer 11

a statistical test to find out whether difference between observed and expected data is due to chance

Question 12

how is a chi squared test performed

Answer 12

formula results in a number which is compared with critical value (for corresponding degrees of freedom)
if number greater than or equal to critical value-no significant difference and due to chance

Question 13

how can the number of genes coding for a characteristic influence variation

Answer 13

discontinuous variation-characteristic determined by one gene
continuous variation-characteristic determined by more than one gene

Question 14

what is stabilising selection

Answer 14

occurs when environmental conditions stay the same
Individuals closest to mean are favoured and new characteristics selected against
results in low diversity

Question 15

what is directional selection

Answer 15

when environmental conditions change
individuals with phenotypes suited for conditions will survive and pass on genes
mean of population will move towards these characteristics

Question 16

what is genetic drift

Answer 16

change in populations allele frequency
occurs due to chance not selective pressures

Question 17

what is meant by genetic bottle neck

Answer 17

catastrophic event dramatically reduces size of population
decreases variety of alleles in gene pool
causes large change in allele frequency

Question 18

what is meant by the founder effect

Answer 18

a small number of individuals become isolated forming a new population with limited gene pool
allele frequencies not reflective of original population

Question 19

what is the hardy weinberg principle

Answer 19

allows us to estimate frequency of alleles in population

Question 20

explain the hardy Weinberg equation for calculating allele frequency

Answer 20

frequencies of each allele must add up to 1
p+q=1
p=frequency of dominant allele
q=frequency of recessive allele

Question 21

explain the hardy Weinberg equation for calculating genotype frequency

Answer 21

p2+2pq+q2=1
p2=frequency of homozygous dominant
2pq=frequency of heterozygous
q2=frequency of homozygous recessive

Question 22

define speciation

Answer 22

when a population is split and isolated there are different selective pressures
if the genetic makeup changes to the extent they can no longer interbreed-become separate species

Question 23

what is meant by allopatric speciation

Answer 23

speciation resulting from physical barrier
environments are different so different alleles favoured

Question 24

what is meant by sympatric speciation

Answer 24

speciation resulting from non physical barrier
any changes in anatomy or behaviour may affect breeding

Question 25

what is artificial selection

Answer 25

humans choose particular organisms to breed together to produce a desired characteristic in the offspring

Question 26

why is it important to keep a resource of genetic material when selective breeding

Answer 26

allows traits that were accidentally bred out to be reintroduced
revert back to a point before any negative traits introduced

Question 27

what ethical issues surround artificial selection

Answer 27

anatomical changes in animals
higher susceptibility to disease