17: Inherited change and 18

Question 1

Phenotype

Answer 1

expression of the genes and its interaction with the environment

Question 2

homozygous

Answer 2

a pair of homologous chromosomes carrying the same alleles for a single gene

Question 3

heterozygous

Answer 3

a pair of homologous chromosomes carrying two different alleles for a single gene

Question 4

recessive allele

Answer 4

allele only expressed if no dominant allele present

Question 6

dominant allele

Answer 6

an allele that will always be expressed in the phenotype

Question 7

multiple alleles

Answer 7

more than two alleles for a single gene

Question 8

codominant

Answer 8

both alleles are equally dominant and expressed in the phenotype

Question 9

sex-linkage

Answer 9

a gene whose locus is on the x chromosome

Question 10

autosomal linkage

Answer 10

genes that are located on the same chromosome

Question 11

epistasis

Answer 11

when one gene modifies or mask the expression of a different gene at a different locus

Question 12

monohybrid

Answer 12

genetic inheritance cross of a characteristics determined by one gene

Question 13

dihybrid

Answer 13

genetic inheritance cross of a characterisic determined by two genes

Question 14

whats a cause of new combinations of gametes

Answer 14

• crossing over in meiosis

Question 15

chi squared

Answer 15

• category data
• investigating a difference between frequencies
• determines whether there is a significant difference between the frequency you expect and frequency you observe

Question 16

Hardy weinberg principle

Answer 16

used to predict the allele frequency within a population

Question 17

gene pool

Answer 17

all the alleles of all the genes within a population at one time

Question 18

population

Answer 18

all the individuals of one species in one area at one time

Question 19

allele frequency

Answer 19

the proportion of an allele within the gene pool

Question 20

variation

Answer 20

individuals within a population of a species may show a wide range of variation in phenotype, due to genetic and environmental factors

Question 21

cause of variation

Answer 21

• main source is mutation
• meiosis (crossing over and independent segragation) and the random fertilisation of gametes

Question 22

type of selection other than directional and stabilising

Answer 22

• disruptive
• individuals which contain the alleles coding for either extreme trait are more likely to survive and pass on their alleles.
• the allele frequency changes, more individuals possess the allele for extreme trait and middling trait allele becomes less frequent. continued disruptive selection can ultimately lead to speciation (creation of new species)

Question 23

Speciation

Answer 23

• creation of new species
• occurs when one original population of the same species becomes reproductively isolated.
• this isolation means there r now two populations of the same species, but cant breed together
• results in the accumulation of differences in their gene pools to the extent that the two populations would be unable to interbreed to make fertile offspring so classed as diff species

Question 24

allopatric speciation

Question 25

sympatric speciation

Answer 25

populations can become reproductively isolated due to differences in their behaviour
- individuals of the same species may not be separated by geographical barrier, but still unable to reproduce
- random mutation could impact reproductive behaviour. like diff courtship ritual, or fertile at diff times of the year
- no gene flow between populations
- accumulate more diff mutations, dna so diff cannot produce fertile offspring

Question 26

Genetic drift

Answer 26

change in allele frequency within a population between generations
- results in evolution
- smaller a population is the bigger impact allele freq changes have
- evolution more rapid in smaller populations